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Transcript of Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed. © 2008 by Pearson Education, Inc....
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Chapter 16The Digestive System
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Topics (1 of 2)IntroductionAn Overview of the Digestive TractThe Oral CavityThe PharynxThe EsophagusThe StomachThe Small Intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Topics (2 of 2)The PancreasThe LiverThe Gall bladderThe Large IntestineDigestion and AbsorptionAging and the Digestive SystemIntegration with Other Systems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Provides the fuel to keep all cells functioning
Provides the building blocks for cell growth and repair
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Components– Digestive tract
Muscular tube
– Accessory organsSalivary glands
Gallbladder
Liver
Pancreas
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Functions involve 6 related processes– Ingestion– Mechanical processing– Digestion– Secretion– Absorption– Excretion
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Ingestion– Food enters digestive tract through the
mouth
Mechanical processing– Physical manipulation of solid foods
Tongue and teeth
Swirling and mixing motions of the digestive tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Digestion– Chemical breakdown of food for
absorption
Secretion– Release of water, acids, enzymes, and
buffers
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Absorption– Movement of substances across
digestive epithelium into interstitial fluid of digestive tract
Excretion– Removal of waste products from body
fluids through defecation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Introduction
Defensive roles of the digestive tract– Protects surrounding tissues against
corrosive effects of digestive acids and enzymes
– Protects against bacteria using nonspecific defenses
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview ofthe Digestive Tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Begins at the oral cavity
Continues through the pharynx, esophagus, stomach, and small and large intestines
Ends at the rectum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Each subdivision– Functions overlap– Each has its own specialization
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Histological organization– 4 major layers
Mucosa
Submucosa
Muscularis externa
Serosa
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The mucosa– Inner lining of the
digestive tract– Consists of
Mucosal epitheliumMoistened by glandular secretions
Lamina propriaUnderlying layer of loose connective tissue
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive TractThe mucosa– Formed into folds
Folds increase surface area for absorption
Folds permit expansion after a large meal
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The mucosa– Features in the
small intestineForm fingerlike projections
Called villi
Further increase the area for absorption
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The mucosa– Stratified squamous epithelium
Allows for most severe mechanical stresses
Found in the oral cavity, pharynx, esophagus, and anus
– Simple columnar epitheliumLines the rest of the digestive tract
Contains various types of secretory cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive TractThe mucosa– Ducts open onto epithelial surfaces
Carry secretions of glands
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The mucosa– Muscularis mucosae
Narrow band of smooth muscle and elastic fibers
Located in most regions of the digestive tract
Move the mucosal folds and villi
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The submucosa– Second layer of
loose connective tissue
– Immediately deep to the muscularis mucosae
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The submucosa– Contains
Large blood vessels
Lymphatic vessels
Network of nerve fibers
Sensory neurons
Parasympathetic motor neurons
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The submucosa– Submucosal plexus
Neural tissue
Controls and coordinates contractions of the smooth muscle layers
Regulates secretion of digestive glands
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The muscularis externa– Band of smooth
muscle cellsInner circular layer
Outer longitudinal layer
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The muscularis externa– Muscle contractions
Autonomic reflexes
Agitate materials
Propel material along the digestive tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The muscularis externa– Myenteric plexus
Nerve network
Located between the smooth muscle layers
Controls autonomic reflexes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The muscularis externa– Autonomic control
Parasympathetic stimulationIncreases muscle tone and activity
Sympathetic stimulationPromotes muscle inhibition and relaxation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The serosa– Serous membrane– Covers the muscularis
externa within the peritoneal cavity
– Visceral peritoneum is continuous with the parietal peritoneum
– Parietal peritoneum lines the inner surface of the body wall
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The serosa– Mesenteries
Suspend portions of the digestive tract within the peritoneal cavity
Stabilize the positions of attached organs
Prevent entanglement of the intestines
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The serosa– Mesenteries
Double sheets of serous membraneComposed of the visceral and parietal peritoneum
Loose connective tissue between epithelial surfaces
Pathway for blood vessels, nerves, and lymphatic vessels
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The serosa– Not found in the oral cavity, pharynx,
esophagus, and rectum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Adventitia– Dense network of collagen fibers– Surrounds are the muscularis mucosae
in the absence of serosa– Firmly attaches components of the
digestive system to adjacent structures
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The movement of digestive materials– Pacesetter cells
Found in the smooth muscle of the digestive tract
Trigger waves of contractionResults in rhythmic cycles of activity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
The movement of digestive materials– Coordinated contractions important for 2
processesPeristalsis
The movement of material along the tract
SegmentationThe mechanical mixing of material
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Peristalsis– Waves of muscular contractions of the
muscularis externa– Propels food through the digestive tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Peristalsis– Circular muscles contract behind
contents– Longitudinal muscles contract
Contraction shortens adjacent segments of the tract
– Wave of contraction of the circular muscles
Forces material in the desired direction
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Peristalsis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
An Overview of the Digestive Tract
Segmentation– Movements that churn and fragment
digestive materials– Results in a thorough mixing of contents
with intestinal secretions– Does not propel material in any direction
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
The first part of the digestive tract to receive food
Lined by a mucous membrane of stratified squamous epithelium
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Senses and analyzes materials before swallowing
Mechanically processes material with the tongue and teeth
Lubricates material with mucous and salivary secretions
Begins digestion of carbohydrates and lipids with enzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Also referred to as the buccal cavity– Cheeks form the
lateral wallsAnteriorly
Continuous with the lips or labia
VestibuleSpace between the cheeks or lips and teeth
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Gums or gingivae– Pink ridges that
surround the base of the teeth
– Cover tooth-bearing surfaces of the upper and lower jaws
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Hard and soft palates– Form the roof of the oral cavity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity Tongue– Dominates the floor of the oral cavity– Free anterior portion connected to underlying
epitheliumThin fold of mucous membrane
Called the lingual frenulum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity Division between the oral cavity and oropharynx– Base of the tongue– Uvula
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
The tongue– Manipulates materials inside the mouth– Brings food into the oral cavity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
The tongue– Primary functions
Mechanical processing through compression, abrasion, and distortion
Manipulating to assist in chewing
Preparing materials for swallowing
Performing sensory analysis by touch, temperature, and taste receptors
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity The tongue– Lies mostly within the oral cavity– Base extends into the oropharynx
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity The tongue– Lingual tonsils
Prominent lateral swellings at the base of the tongue
Lymphoid nodules that help resist infection
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary glands– 3 pairs– Secrete into the
oral cavityParotid salivary glands
Sublingual salivary glands
Submandibular salivary glands
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parotid salivary glands– Lie under the skin– Located in the
lateral and posterior surfaces of the mandible
– Parotid ductEmpties into the vestibule at the level of the second molar
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Sublingual salivary glands– Located beneath
the mucus membrane
On the floor of the mouth
– Sublingual ductsNumerous ductsOpen along either side of the lingual frenulum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Submandibular salivary glands– Located in the floor
of the mouth– Along the inner
surfaces of the mandible
– DuctsOpen into the mouth behind the teethOn either side of the lingual frenulum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary glands– Produce 1–1.5 liters of saliva per day
99.4% water
Also contains mucins, ions, buffers, waste products, metabolites, and enzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary glands– Mucins
Absorb water
Form mucus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary glands– Saliva
Produced in large quantities at mealtimes
Lubricates the mouth
Dissolves chemicals that stimulate the taste buds
Reduces friction with food, enabling swallowing
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary glands– Saliva
Flushes and cleans oral surfaces
Contains IgA antibodies and lysozymesControl oral bacteria
Leads to recurring infections
Causes progressive erosion of the teeth and gums
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary secretions– Different kinds produced by different
glandsParotid glands
Secretion rich in salivary amylase
Breaks down starches into smaller molecules
Allows absorption in the digestive tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary secretions– Submandibular and sublingual gland
secretionsContain fewer enzymes
Contain more buffers and mucus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Salivary secretions– During meals
Submandibular glandsProduce 70% of secretions
pH rises from acidic to basic
Secretions controlled by autonomic nervous system
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Teeth– Perform chewing or mastication
Breaks down tough connective tissues in meat
Breaks down plant fibers in vegetables
Helps saturate materials with salivary secretions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity Parts of the tooth– Neck
Marks the boundary between the root and the crown
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Enamel
Covers the crownContains a crystalline form of calcium phosphate
Hardest biologically manufactured substance
Requires adequate amounts of calcium, phosphates, and vitamin D3 during childhood
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Dentin
Mineralized matrix similar to that of bone
Does not contain cells
Makes up the bulk of each tooth
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Pulp cavity
Contains cytoplasmic processes cells
Extend into the dentin
Receives blood vessels and nerves through the root canal
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Root
Base of the tooth
Sits within a bony socket
Called an alveolus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Periodontal
ligamentCollagen fibers
Extends from the dentin of the root to surrounding bone
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Cementum
Layer that covers the dentin of the root
Provides protection and firmly anchors the periodontal ligament
Similar in structure to bone
Softer
Does not undergo remodeling
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Parts of the tooth– Penetration of the gum surface
Epithelial cells form tight attachments to the tooth
Prevent bacterial access to the cementum or the root
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
4 types of teeth– Incisors– Cuspids or canines– Bicuspids or premolars– Molars
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Functions of teeth– Incisors
Blade-shaped teeth
Found at the front of the mouth
Used for clipping or cutting
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Functions of teeth– Cuspids
ConicalSharp ridgeline and a pointed tip
Used for tearing or slashing
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Functions of teeth– Bicuspids and
molarsFlattened crowns with prominent ridges
Used for crushing, mashing, and grinding
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Dental succession– 2 sets form during
developmentDeciduous teeth
First to appear
Also referred to as primary teeth, milk teeth, or baby teeth
Full set is 20
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Dental succession– Secondary dentition
Also referred to as permanent dentition
Permits processing of a wider variety of foods
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Dental succession– Periodontal ligaments and roots of
deciduous teeth erode– Deciduous teeth fall out or are pushed
aside– Secondary teeth erupt – Full set of 32 teeth
3 new teeth appear on each side of the upper and lower jaws
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Oral Cavity
Dental succession– Wisdom teeth
Third molars
Become impacted if eruption is not permittedMay form abscess
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pharynx
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pharynx
Common passageway– Allows for passage of solid food, liquids,
and air– 3 major subdivisions– Regions composed of stratified
squamous epithelium– Lamina propria
Contains mucous glands and tonsils
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pharynx
Pharyngeal muscles– Initiate swallowing process
Cooperate with muscles of the oral cavity and esophagus
– Force food into the esophagus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Muscular tube
25 cm long
2 cm in diameter
Conveys solid food and liquids to the stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Begins at the pharynx
Runs posterior to the trachea
Passes through the mediastinum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Enters the peritoneal cavity– Through the esophageal hiatus
Opening in the diaphragm
Empties into the stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Lined with stratified squamous epithelium– Resists abrasion– Resists hot or cold temperatures– Resists chemical attack
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Epithelial surface lubricated by mucous gland secretions– Prevent materials from sticking to the
esophagus during swallowing
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Muscularis externa– Upper third contains skeletal muscle– Middle third contains skeletal and
smooth muscle– Lower third contains smooth muscle
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Esophageal sphincter– Circular muscle– Located in the superior and inferior ends
Inferior sphincter normally in active contraction
Prevents backflow of material from the stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Swallowing– Deglutition– Complex process– Can be initiated voluntarily
Proceeds automatically
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Swallowing– Before swallowing
Food must have the proper consistency and texture
Tongue compacts debris into a small massReferred to as a bolus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Process of swallowing– Oral phase– Pharyngeal phase– Esophageal phase
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus Oral phase of swallowing– Begins with the
compression of the bolus against the hard palate
– Tongue retracts– Bolus forced into the
pharynxElevates the soft palate to prevent entrance into the nasopharynx
– Only phase that can be consciously controlled
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Pharyngeal phase of swallowing– Bolus contacts
sensory receptorsLocated around the pharynx and pharyngeal wall
Initiates the involuntary swallowing reflex
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Swallowing reflex– Larynx elevates– Epiglottis folds to protect the glottis
Directs food past the closed glottis
– Pharyngeal muscles contract– Bolus forced through the esophageal
entranceGuarded by the upper esophageal sphincter
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Esophageal phase of swallowing– Begins when the bolus enters
the esophagus– Peristaltic contractions push
the bolus toward the stomach– Bolus triggers the opening of
the lower esophageal sphincter
– Bolus enters the stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Esophagus
Swallowing– Typically takes about 9 seconds– Fluids move faster
Do not require peristaltic contractions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Located in the left upper quadrant of the abdominopelvic cavity
Receives food from the esophagus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
4 primary functions– Temporary storage of ingested food– Mechanical breakdown of ingested food– Breakdown of chemical bonds in foods
Through actions of acids and enzymes
– Production of intrinsic factorNecessary for the absorption of B12
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Chyme– Mixture of ingested material and
secretions from stomach glands– Viscous– Highly acidic
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Muscular, J-shaped organ
4 main regions– Cardia– Fundus– Body– Pylorus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach Cardia– Smallest part of the stomach– Connects with the esophagus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach Fundus– Superior bulge of the stomach– Extends above the cardia
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach Body– Large area– Located between the fundus and the
curve of the J
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach Pylorus– Distal part of the J– Connects the stomach with the small
intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Pyloric sphincter– Regulates flow of chyme between the
stomach and small intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Rugae– Prominent ridges and
folds of mucosa– Visible when the stomach
is emptyStomach resembles a muscular tube with a narrow lumen
– Flatten out as the stomach expands
Stomach can hold 1–1.5 liters of material when fully expanded
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Muscularis externa– 3 layers
Extra layer adds strength and assists in movement necessary to form chymeLongitudinal layerCircular layerInner oblique layer
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Visceral peritoneum– Covers the outer surface of the stomach– Is continuous with a pair of mesenteries
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Mesenteries– Greater omentum
Extends below the greater curvatureForms an enormous pouch
Hangs over and protects the abdominal viscera
– Lesser omentumExtends from the lesser curvature to the liver
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
The gastric wall– Lined by simple columnar epithelium
Dominated by mucous cellsProduces an alkaline mucus
Protects cells from acids, enzymes, and abrasive materials
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach The gastric wall– Gastric pits
Shallow depressions
Open onto the gastric surface
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach The gastric wall– Mucous cells located at the base, or neck, or
the gastric pitsActively divide
Replace superficial cells of the mucous epitheliumCells are shed into the chyme
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
The gastric wall– Fundus
Gastric pits communicate with gastric glandsGlands extend deep into lamina propria
Glands secrete 1.5 liters of gastric juice per day
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach The gastric wall– Gastric juice
Components produced by parietal cells and chief cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
The gastric wall– Pylorus
Gastric glands also contain endocrine cells
These walls regulate gastric activity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach Parietal cells– Secrete intrinsic factor
Facilitates absorption of B12 across intestinal lining
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Parietal cells– Secrete hydrochloric acid
Lowers the pH of gastric juicepH of 1.5–2
Kills microorganisms
Breaks down plant cell walls
Breaks down connective tissues in meat
Activates enzyme secretions of chief cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach Chief cells– Secrete pepsinogen into the stomach lining
Protein that converts to pepsin on contact with hydrochloric acid
A proteolytic enzyme
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Chief cells– In newborns
Produce reninCoagulates milk
Slows passage through the stomach
Allows more time for digestion
Produce gastric lipaseInitiates the digestion of milk fats
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
The regulation of gastric activity– Central nervous system controls acid
and enzyme productionRegulated by
Reflexes within the walls of the digestive tract
Hormones of the digestive tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
The regulation of gastric activity– 3 overlapping phases
Named according to the location of the control center
Cephalic phase
Gastric phase
Intestinal phase
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Cephalic phase of gastric regulation– Initiated by the smell,
sight, taste, or thought of food
– Directed by the CNS– Prepares the
stomach to receive food
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Cephalic phase of gastric regulation– Parasympathetic fibers innervate
mucous cells, parietal cells, chief cells, and endocrine cells
Fibers found in the submucosal plexus
Controlled by the vagus nerves
– Phase last only a few minutes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Gastric phase of gastric regulation– Begins with the
arrival of food in the stomach
– StimulatesStretch receptors in the stomach wallChemoreceptors in the mucosa
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Gastric phase of gastric regulation– Receptor stimulation triggers local
reflexes Reflexes controlled by submucosal and myenteric plexuses
Myenteric plexus stimulates mixing waves in stomach wall
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Gastric phase of gastric regulation– Submucosal plexus
Stimulates parietal cells and chief cells
Stimulates endocrine cellsRelease gastrin into circulatory system
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Gastric phase of gastric regulation– Gastrin
Stimulates parietal and chief cellsAccelerates secretory activities
Effect on parietal cells most pronounced
Drops the pH of gastric juice
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Gastric phase of gastric regulation– Phase continues for several hours– Gastrin stimulates stomach contractions
Swirl and churn gastric contents
Mix materials to form chyme
Contractions move chyme through the stomach
Pylorus contracts, pushing chyme through pyloric sphincter
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Begins when chyme
starts to enter the small intestine
– Regulatory controls are primarily inhibitory
Control the rate of gastric emptyingEnsure efficiency of small intestine
Secretory, digestive, and absorptive functions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Movement of chyme
Reduces stimulation of stretch receptors in the stomach
Increases stimulation of stretch receptors in the small intestine
Produces enterogastric reflex
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Enterogastric reflex
Inhibits neural stimulation Reduces gastrin production
Reduces gastric motility
Reduces further movement of chyme
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Chyme enters small intestine
Stimulates the release of intestinal hormones
Secretin
Cholecystokinin (CCK)
Gastric inhibitory peptide (GIP)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Stimulation of inhibitory reflexes that
depress gastric activityOccurs when the proximal portion of the small intestine
Becomes too full
Becomes too acidic
Is excessively irritated by chyme
Is filled with partially digested proteins, carbohydrates, or fats
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Rate of chyme movement
Highest with a distended stomach and little protein
Alcohol and caffeine stimulate gastric secretion and motility
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Digestion in the stomach– Pepsin performs the preliminary
digestion of proteins– Salivary amylase continues carbohydrate
digestionRemains active until pH falls below 4.5
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Digestion in the stomach– Pepsin
Becomes more active as contents become fluid and pH drops to 2.0
Begins protein disassemblyNot completed in the stomach
Breaks complex proteins into small peptide and polypeptide chains
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Stomach
Intestinal phase of gastric regulation– Nutrients not absorbed in stomach
Epithelial cells covered by alkaline mucusNot directly exposed to chyme
Epithelial cells lack specialized transport mechanisms
Gastric lining is impermeable to water
Digestion is incomplete when chyme exits the stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Responsible for 90% of nutrient absorption
Approximately 20 feet long
Diameter of 4 cm at the stomach– Reduces to 2.5 cm at the large intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Contains 3 segments– Duodenum– Jejunum– Ileum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Duodenum– 25 cm long– Closest
segment to the stomach
– Curves in a C-shape
Encloses the pancreas
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Duodenum– Receives chyme from the stomach– Receives digestive secretions from the
pancreas and liver– Lies outside the peritoneal cavity
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Jejunum– Connects to the
duodenum at a sharp bend
– 8 feet long– Supported by a sheet
of mesentery– Responsible for the
bulk of chemical digestion and nutrient absorption
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Ileum– Averages 12
feet in length– Ends at the
ileocecal valveSphincter
Controls material flow from the ileum to the cecum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Fills much of the peritoneal cavity
Stabilized by mesentery attached to dorsal body wall
Connective tissue in mesentery contains blood vessels, lymphatic vessels, and nerves
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Plicae
Also referred to as plicae circulares
Series of transverse folds in the intestinal wall
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Villi
Fingerlike projections on the intestinal liningCovered by simple columnar epithelium with microvilli
Resemble the bristles on a brushReferred to as a brush border
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Epithelium contains several plicae– Each plica contains many villi– Each villus covered by epithelium
blanketed in microvilli– Absorptive area roughly 2,200 ft²
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Villus
Contains a capillary network
Transports respiratory gases
Transports absorbed nutrients to hepatic portal circulation
Contains nerve endings
Contains a lymphatic capillary
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Lymphatic capillary
Called a lacteal
Transports materials that cannot enter blood capillaries
Example: protein-lipid packages of absorbed fatty acids
Called a chylomicron
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Intestinal glands
Entrances located at the base of the villi
Contain stem cells that divide continuously
Replenish intestinal epithelium
Contain endocrine cells that produce intestinal hormones
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
The intestinal wall– Duodenum
Contains duodenal glandsSubmucosal glands
Secrete alkaline mucus
Buffers the acids in chyme
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal movements– Chyme enters the small intestine– Segmentation contractions mix chyme,
mucous secretions, and enzymes– Weak peristaltic contractions slowly
move material
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal movements– Peristaltic contractions
Allow increased time for digestion and absorption
Local reflexes not under CNS controlLimited to a few centimeters from the stimulus site
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal movements– Stomach distention initiates the
gastroenteric reflexAccelerates glandular secretion and peristalsis
– Increased peristalsis moves material through the small intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal movements– Food entering the stomach triggers
gastrin release– Gastrin responsible for the gastroileal
reflexRelaxes the ileocecal valve
Allows food to enter the large intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal secretions– Intestinal juice
Arrives through osmosis
Secreted by intestinal glandsStimulated by touch and stretch receptors in the intestinal walls
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal secretions– Intestinal juice
Moistens intestinal contents
Helps buffer acids
Keeps digestive enzymes and products of digestion in solution
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal secretions– Regulated by hormonal and CNS
controls– Focused in the duodenum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Functions of intestinal secretions– Acid content of chyme must be
neutralized– Appropriate enzymes must be added
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal secretions– Duodenal glands
Protect the duodenal epithelium from gastric acids and enzymes
Increase secretions stimulated byLocal reflexes
Parasympathetic stimulation through the vagus nerve
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal secretions– Parasympathetic stimulation
Duodenal glands begin secreting during cephalic stage of gastric secretion
Before chyme reaches the pyloric sphincter
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal secretions– Sympathetic stimulation
Inhibits the activation of the duodenal glands
Duodenal lining unprepared for the acid chyme
Stress may result in duodenal ulcers
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Various peptide hormones produced by
duodenal endocrine cells– Coordinate the stomach, duodenum,
pancreas, and liver
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Gastrin– Secretin– Cholecystokinin (CCK)– Gastric inhibitory peptide (GIP)
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Gastrin
Secreted by duodenal cellsIn response to large quantities of incompletely digested proteins
Increases stomach motility
Stimulates production of acids and enzymes
Also secreted in the distal portion of the stomach
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Secretin
Released as pH of the duodenum fallsOccurs when acidic chyme arrives from the stomach
Increases the secretion of bile and buffersFrom the liver and pancreas
High concentration reduces gastric motility and secretion
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Cholecystokinin (CCK)
Secreted when chyme arrives in the duodenum
Especially with the presence of lipids and partially digested proteins
Also targets the pancreas and gall bladder
High concentration reduces gastric motility and secretion
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Cholecystokinin
PancreasAccelerates the production and secretion of all types of digestive enzymes
GallbladderCauses the ejection of bile into the duodenum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones– Gastric inhibitory peptide (GIP)
Released by the presence of fats and carbohydrates in the small intestine
Inhibits gastric activity
Causes insulin release from the pancreatic islets
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Intestinal hormones
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Digestion in the small intestine– Location of most of the important
components of digestionFinal products of digestion are absorbed
Simple sugars, fatty acids, and amino acids
Most of the water content is absorbed
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Small Intestine
Digestion in the small intestine– Enzymes and buffers for digestion
Only a few produced in the small intestine
Most are contributed by the liver and pancreas
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Lies behind the stomach
Extends from the duodenum toward the spleen
Roughly 6 inches long
Located retroperitoneal
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Surface– Pinkish-gray organ– Lumpy texture– Tissue is soft and
easily torn– Only anterior
surface covered by peritoneum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Histological organization– Pancreatic islets
Endocrine cells
Secrete insulin and glucagon
1% of the cellular population of the pancreas
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas Histological organization– Exocrine cells and ducts make up most
of the pancreasProduce pancreatic juice
Mixture of digestive enzymes and buffers
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas Histological organization– Exocrine ducts
Branch throughout the pancreas
End at the pancreatic aciniSaclike pouches
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Histological organization– Acinar cells
Located in the pancreatic acini
Secrete enzymes and buffersMix with enzymes and buffers produced by epithelial cells in the ducts
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Histological organization– Pancreatic duct
Collects secretions from all ducts in the pancreas
Carries secretions to the duodenum
Penetrates duodenal wall with the common bile duct
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
Histological organization– Pancreatic enzymes
Responsible for most of the digestion in the small intestine
Classified according to intended targetsCarbohydrases digest sugars and starches
Lipases break down lipids
Nucleases break down nucleic acids
Proteases break proteins apart
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Pancreas
The control of pancreatic secretion– 1000 ml of pancreatic juice produced
daily– Secretion controlled mainly by duodenal
hormonesSecretin released in duodenum
Triggers pancreas to secrete watery, alkaline fluid
pH between 7.5–8.8
Contains buffers, primarily sodium bicarbonate
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Largest visceral organ
Firm, reddish-brown
Roughly 2.5% of total body weight
Lies in the right hypochondriac and epigastric regions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Anatomy of the liver– Wrapped in a tough fibrous capsule– Covered by a layer of visceral peritoneum– Divided into 4 unequal lobes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Anatomy of the liver– Left and right lobes
Larger
– Caudate lobe– Quadrate lobe
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Anatomy of the liver– Falciform ligament
Tough connective tissue fold
Marks the division between the left and right lobes
Thickened posterior margin Referred to as the round ligament
Fibrous remnant of the umbilical vein
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Anatomy of the liver– Gallbladder
Located in a recess under the right lobe
Muscular sac
Stores and concentrates bile
Excretes bile into the small intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Histological organization of the liver– Lobes divided by connective tissue
Tissue forms 100,000 liver lobulesBasic functional unit of the liver
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Liver lobules
Contain hepatocytesLiver cells
Arranged into irregular plates
Resemble the spokes of a wheel
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Plates
Only 1 cell thick
Covered with microvilli where exposed
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Sinusoids
Specialized and highly permeable capillaries
Form passageways between adjacent plates
Empty into the central vein
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Kupffer cells
Phagocytic cells
Located in the sinusoidal lining
Part of the monocyte-macrophage system
Engulf pathogens, cell debris, and damaged blood cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Blood flow
Enters sinusoids From branches of the hepatic portal vein and hepatic artery
Forms the hepatic triad
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Histological organization of the liver– Blood flow
Hepatic triadPortal area
Includes a small branch of the bile duct, the hepatic portal vein, and the hepatic artery
Located at the 6 corners of each lobule
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Blood flow
Blood continues through the sinusoids
Hepatocytes absorb solutes from the plasmaSecrete plasma proteins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Blood flow
Blood leaves the sinusoids
Enters the central vein of the lobule
Central veins of each lobule mergeForm the hepatic veins
Empty into the inferior vena cava
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Hepatocytes
Secrete bileReleased into bile canaliculi
Network of narrow channels
Located between adjacent liver cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Histological organization of the liver– Bile canaliculi
Extend outward from the central vein
Carry bile to increasingly larger bile ductsBile eventually leaves through the common hepatic duct
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Histological organization of the liver– Common hepatic duct
Flows into the common bile ductEmpties into the duodenum
Flows into the cystic ductLeads to the gallbladder
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Liver functions– 3 general roles
Metabolic regulation
Hematological regulation
Bile production
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Metabolic regulation– Primary organ that regulates the
composition of circulating blood– Exposed to all blood that leaves
absorptive areas of the digestive tractBefore blood reaches general circulation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Metabolic regulation– Hepatocytes
Extract absorbed nutrients or toxins from the blood
Monitor and adjust circulating levels of organic nutrients
Remove and store excess
Correct deficiencies
Mobilize reserves or synthesize compounds
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Hematological regulation– Largest blood reservoir in the body– Receives 25% of cardiac output– Kupffer cells remove aged or damaged
red blood cellsAlso remove debris and pathogens
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver Hematological regulation– Kupffer cells
Antigen-presenting cells
Can stimulate an immune response
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
Hematological regulation– Hepatocytes
Synthesize plasma proteinsDetermine the osmotic concentration of blood
Transport nutrients
Make up the clotting and complement systems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
The production and role of bile– Synthesized in the liver– Excreted into the lumen of the duodenum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
The production and role of bile– Consists of
Water
Ions
Bilirubin
Cholesterol
Bile salts
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
The production and role of bile– Bile salts
Assortment of lipids
Synthesized from cholesterol
Required for the normal digestion and absorption of fats
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
The production and role of bile– Dietary lipids are not water soluble– Mechanical processing in the stomach
produces large droplets– Pancreatic lipase only interacts with the
surfaceNot lipid soluble
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
The production and role of bile– Lipids
The larger the droplet, the more lipids present
Remain isolated and protected from digestive enzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Liver
The production and role of bile– Bile salts
Break lipid droplets apartProcess called emulsification
Creates tiny droplets
Increases surface area for enzyme attack
Superficial coating of bile salts
Facilitates interaction with enzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Gallbladder
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Gallbladder
Hollow, muscular, pear-shaped organ
Stores and concentrates bile prior to excretion
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The GallbladderCystic duct– Extends from the gallbladder– Joins with the common hepatic duct
Forms the common bile duct
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The GallbladderCommon bile duct– Joins the pancreatic duct– Enters the duodenum at the duodenal papilla
Entrance surrounded by the hepatopancreatic sphincter
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Gallbladder
Bile storage– Bile secreted continuously
Approximately 1 liter per day
– Released into duodenum only when stimulated by CCK
– Hepatopancreatic sphincter remains closed without CCK
CCK forces bile to enter the cystic duct
CCK stored in the gallbladder
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Gallbladder
Bile release– Chyme enters duodenum– CCK released
Secretion increases with the fat content of chyme
– Hepatopancreatic sphincter relaxes– Wall of gallbladder stimulated to contract– Bile released
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Gallbladder
Bile modification– Gallbladder holds 40–70 ml of bile when
full– Composition of bile changes while inside
the gallbladderWater absorbed
Increased concentration of bile salts and other components
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Gallbladder
Gallstones– Precipitation of bile salts
Results when bile salts become too concentrated
– Cause a variety of clinical problems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Horseshoe-shaped
Begins at the end of the ileum
Ends at the anus
Lies below the stomach and liver
Frames the small intestine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Main functions– Reabsorption of water and compaction of
intestinal contents into feces– Absorption of important vitamins freed by
bacterial action– Storage of fecal material prior to
defecation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Also referred to as the large bowel
Approximately 5 feet long
Width of 3 inches
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
3 divisions– Cecum
Pouchlike
– ColonLargest portion
– RectumFinal 6 inches
End of the digestive tract
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The cecum– Expanded pouch– Receives material
from the ileumEntrance guarded by the ileocecal valve
– Begins compaction
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The cecum– Appendix
Also referred to as the vermiform appendix
Slender and hollow
Attaches to the posterior medial side of the cecum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The cecum– Appendix
Approximately 3.5 inches long
Shape is variable
Lymphoid nodules dominate the walls
Functions primarily as a lymphatic organ
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The colon– Larger diameter
and thinner wall than the small intestine
– HaustraExternal pouches
Permit distention and elongation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The colon– Taeniae coli
3 longitudinal bands of smooth muscle
Run along the outer surface of the colon
Just beneath the serosa
Muscle tone creates the haustra
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The colon– Divided into 4
segmentsAscending colon
Transverse colon
Descending colon
Sigmoid colon
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Ascending colon– Begins at the ileocecal valve– Ascends along the right side of the
peritoneal cavity– Reaches the inferior margin of the liver– Turns horizontally
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Transverse colon– Continues toward the left side of the
body– Passes below the stomach– Follows the curve of the body wall– Turns inferiorly near the spleen
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Descending colon– Continues along
the left side of the body
– Curves to form the sigmoid
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Sigmoid colon– S-shaped section– Empties into the
rectum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The rectum– Forms the end of the digestive tract– Expanded organ for the temporary
storage of feces– Last portion called the anal canal
Contains longitudinal foldsCalled anal columns
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The rectum– Anal columns
Distal margins joined by transverse folds
Transverse folds mark the boundary between columnar epithelium of the rectum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The rectum– Epidermis becomes keratinized
Occurs close to the anus
Identical to the epidermis on the skin surface
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
The functions of the large intestine– Absorption– Preparation of the fecal material for
elimination
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Absorption in the large intestine– Reabsorption of water
1500 ml of material enter daily
200 ml of feces ejected
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Absorption in the large intestine– Composition of feces
75% water
5% bacteria
Remaining contentsIndigestible materials
Inorganic materials
Remains of epithelial cells
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Absorption in the large intestine– Other absorbed substances
Bile salts and vitamins
Organic waste compoundsExample: bilirubin
Toxins generated by bacterial actions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Bile salts– Most bile salts that remain in the cecum
are reabsorbed– Transported to the liver for secretion in
bile
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Vitamins– Organic molecules– Related to lipids and carbohydrates– Essential for many metabolic reactions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Vitamins– Enzymes require binding of an additional
molecule before binding to substratesReferred to as a cofactor
CoenzymesNonprotein molecules that function as cofactors
Many vitamins are coenzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Vitamins– Bacteria in colon generate 3 vitamins
Vitamin K
Biotin
Vitamin B3
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Vitamins– Vitamin K
Fat-soluble
Needed in the liverAllows the synthesis of 4 clotting factors
Includes prothrombin
Half of daily requirement produced by intestinal bacteria
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Vitamins– Biotin
Water-soluble
Important in glucose metabolism
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Vitamins– Vitamin B3
Pantothenic acid
Water-soluble
Required to manufacture steroid hormones and some neurotransmitters
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Organic wastes– Bacteria convert bilirubin into other
productsSome absorbed in bloodstream
Excreted in the urineProduce the yellow color
Others remain in the colonFurther modified after exposure to oxygen
Produce pigments that give feces its color
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Toxins– Bacterial action breaks down peptides,
generatingAmmonia
Nitrogen-containing compounds
Hydrogen sulfide
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Toxins– Hydrogen sulfide and nitrogen-containing
compoundsResponsible for odor in feces
– Ammonia and other toxinsAbsorbed into hepatic portal system
Removed by the liver for excretion in urine
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Absorption in the large intestine– Indigestible carbohydrates
Not altered by intestinal enzymes
Arrive in the colon intact
Provide nutrient source for resident bacteria
Metabolic activities responsible for intestinal gas
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Movements of the large intestine– Caused by the gastroileal and
gastroenteric reflexesMovement through the cecum to the transverse colon
Very slow
Takes hours to allow for reabsorption of water
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Movements of the large intestine– From the transverse colon through the
rest of the large intestineMass movements
Powerful peristaltic contractions
Occur a few times per day
Stimulated by distention of the stomach and duodenum
Force material into the rectum for defecation
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Rectum remains empty– Powerful peristalsis forces material out of
the sigmoid colon– Rectal wall becomes distended– Defecation reflex triggered
Involves 2 positive feedback loops
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Shorter positive feedback loop
Stretch receptors in rectal wall activated
Receptors stimulate series of increased local peristaltic contractions
Confined to the sigmoid colon and rectum
Contractions move feces toward the anusIncrease the distention of the rectum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Longer positive feedback loop
Stretch receptors in rectal wall activated
Stimulate parasympathetic motor neuronsLocated in the sacral spinal cord
Stimulate increased mass movements in descending and sigmoid colons
Push feces toward the rectumFurther increases distention
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Passage of feces through the anal canal
Requires relaxation of the internal anal sphincter
External anal sphincter automatically closes
Must be opened through voluntary control
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Voluntary control
If not receivedPeristaltic contractions cease
Additional rectal expansion triggers the defecation reflex again
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Other consciously directed activities
Tensing of the abdominal muscles
Exhaling while closing the glottis
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
The Large Intestine
Defecation– Responses of consciously directed
activitiesElevates intra-abdominal pressure
Helps force material out of the rectum
Forces blood into veins in the anal canalCauses them to stretch
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Components broken down differently– Large organic molecules
Broken down before absorption
– Water, electrolytes, and vitaminsAbsorbed before processing
May require special transport mechanisms
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
The processing and absorption of nutrients– Digestive system breaks down physical
structure– Disassembles component molecules into
smaller fragmentsProduces small organic molecules
Can be released into the bloodstream
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
The processing and absorption of nutrients– Small organic molecules
Absorbed by cells
Used to generate ATP; synthesize carbohydrates, proteins, and lipids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
The processing and absorption of nutrients– Foods
Complex chains of simpler moleculesCarbohydrates composed of simple sugars
Proteins composed of amino acids
Lipids are fatty acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
The processing and absorption of nutrients– Hydrolysis
Component molecule bonds broken by digestive enzymes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
The processing and absorption of nutrients– Digestive enzymes have specific targets
Carbohydrases break up sugars
Lipases separate fatty acids from glycerides
Proteases break amino acid bonds
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Carbohydrate digestion and absorption– Begins in the mouth
Salivary amylaseBreaks down complex carbohydrates
Produces a mixture of disaccharides and trisaccharides
Continues to digest starches and glycogen
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Carbohydrate digestion and absorption– Pancreatic amylase
Breaks down remaining complex carbohydrates
Occurs in the duodenum
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Carbohydrate digestion and absorption– Disaccharides and trisaccharides
Fragmented by brush border enzymesFound on the surfaces of intestinal microvilli
Produce simple sugars
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Carbohydrate digestion and absorption– Monosaccharides
Absorbed by intestinal epithelium
Require carrier-mediated transport mechanisms
Facilitated diffusion or cotransport
For example, glucose uptake requires cotransport with sodium ions
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Carbohydrate digestion and absorption– Simple sugars in intestinal cells
Diffuse through the cytoplasm
Cross the basement membrane through facilitated diffusion
Enter interstitial fluid
Delivered to the hepatic portal vein and liver
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Triglycerides
3 fatty acids connected to a glycerol molecule
Unaffected by conditions in the stomach
Form large lipid droplets
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Bile salts in duodenum
Emulsify large lipid drops into tiny droplets
Can be attacked by pancreatic lipase
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Pancreatic lipase
Enzyme that breaks triglycerides apart
Creates a mixture of fatty acids and monoglycerides
Mix with bile salts
Form micellesLipid-bile salt complex
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Micelles
Contact the intestinal epithelium
Triglyceride products diffuse across the cell membrane
Enter the cytoplasm
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Intestinal cells
Use the fatty acids and monoglycerides
Manufacture new triglyceridesCoated with proteins
Creates a soluble complex
Referred to as a chylomicron
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Chylomicrons (1 of 2)
Secreted by exocytosis into interstitial fluids
Pass through large gaps between adjacent endothelial cells
Enter intestinal lacteals
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Lipid digestion and absorption– Chylomicrons (2 of 2)
Proceed along lymphatic vessels
Travel through the thoracic duct
Enter the bloodstream at the left subclavian vein
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Protein digestion and absorption– Complex structure– Digestion complex and time-consuming
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Protein digestion and absorption– Structure of food disrupted
Proteolytic enzymes attack individual protein molecules
Involves mechanical processing through mastication
Chemical processing with hydrochloric acid
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Protein digestion and absorption– Acidic contents of the stomach
Provides the proper environment for pepsinProteolytic enzyme
Secreted by chief cells of the stomach
Reduce large proteins into polypeptide segments
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Protein digestion and absorption– Pancreatic proteolytic enzymes
Begin when chyme enters the duodenum
Trypsin, chymotrypsin, and carboxypeptidase
Break peptide bonds in different amino acids
Complete disassembly of polypeptide fragments
Create short peptide chains and amino acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Protein digestion and absorption– Peptidases
Enzymes on the surface of the intestinal microvilli
Complete the breakdown of peptide chains into amino acids
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Protein digestion and absorption– Amino acids absorbed into intestinal
epithelial cellsRequires facilitated diffusion and cotransport
– Carrier proteins release absorbed amino acids into interstitial fluid
– Most diffuse into intestinal capillaries
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Water and electrolyte absorption– Water conservation
Roughly 9000 ml of water enter the digestive tract daily
150 ml lost through fecal wastes
Occurs passively, following osmotic gradients
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Water and electrolyte absorption– Dissolved nutrients and ions
Continually absorbed by intestinal epithelial cells
Gradually lower solute concentration of intestinal contents
Forces water to move into surrounding tissues
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
Water and electrolyte absorption– Calcium absorption
Occurs under hormonal control
Requires the presence of parathyroid hormone and calcitrol
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
The absorption of vitamins– Essential organic compounds– Required in very small quantities– 2 major groups
Fat-soluble vitamins
Water-soluble vitamins
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
4 fat-soluble vitamins– A, D, E, and K– Enter the duodenum in fat droplets
Mixed with dietary lipids
– Remain associated with lipids with micelle formation
– Absorbed from micelles with the products of lipid digestion
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Digestion and Absorption
9 water-soluble vitamins– B vitamins common in milk and meats
B12 not easily absorbed by digestive epithelium
Must bind with intrinsic factor first
– Vitamin C found in citrus
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
Digestion and absorption remain essentially normal
Changes in the digestive system parallel changes in other systems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
The division rate of epithelial stem cells declines– Digestive epithelium becomes more
susceptible to damageAbrasion, acids, or enzymes
Peptic ulcers more likely
– Stratified epithelium becomes thinner and more fragile
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
Smooth muscle tone decreases– General motility decreases– Peristaltic contractions are weaker
Slows intestinal movement and promotes constipation
– Sagging and inflammation of the haustra– Weakened muscular sphincters lead to
reflux
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
The effects of cumulative damage become apparent– Gradual loss of teeth
Dental caries or cavities
Gingivitis or inflammation of the gums
– Chronic exposure to toxins and chemicals
Leads to liver diseases
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
Cancer rates increase– Most common in organs with stem cell
division to maintain epithelium
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Aging and the Digestive System
Changes in other systems have direct or indirect effects on the digestive system– Reduction in bone mass and calcium
content in the skeletonLeads to erosion of the tooth sockets
– Decline in smell and taste sensitivityLeads to dietary changes
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Integration with Other Systems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Integration with Other Systems
Bledsoe et al., Anatomy & Physiology for Emergency Care, 2nd Ed.© 2008 by Pearson Education, Inc. Upper Saddle River, NJ
Summary
Identify the organs of the digestive system and describe their functionsDescribe the histology of the digestive system componentsDescribe the process of digestion and how the parts of the digestive tract interactDescribe the functions of the accessory organs of digestionUnderstand how materials are digested and absorbed