Human Biology Sylvia S. Mader Michael Windelspecht Chapter 8 Part 1 Digestive System and Nutrition...
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Transcript of Human Biology Sylvia S. Mader Michael Windelspecht Chapter 8 Part 1 Digestive System and Nutrition...
Human BiologySylvia S. Mader
Michael Windelspecht
Chapter 8 Part 1Digestive
System and Nutrition
Lecture Outline
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into
PowerPoint without notes.
Points to Ponder1. What are the digestive system structures and their
functions?
2. Where does carbohydrate, protein, and fat digestion and absorption occur?
3. What are proteins, lipids, carbohydrates, minerals and vitamins needed for?
4. What is an essential vs. a nonessential nutrient?
5. What are the 3 accessory organs of digestion?
6. What is obesity and why is it a problem?
7. What is LDL and HDL?
8. What are the components of a healthy diet?
9. Name and explain 4 eating disorders.
What are the main steps in the digestive process?
Ingestion: intake of food by the mouth.
Digestion: mechanically or chemically breaking down
food into their subunits
Movement: food must be moved along the GI tract in
order to fulfill all functions.
Absorption: movement of nutrients across the GI tract
wall to be delivered to cell via the blood.
Elimination: removal of indigestible molecules.
8.1 Overview of digestion
What are the 4 major layers that make up the wall of the GI tract?
Mucosa: innermost layer that produces mucus that
protects the lining and also produces digestive enzymes.
Sub mucosa: 2nd layer of loose connective tissue that
contains blood vessels, lymphatic vessels, and nerves.
Muscularis: 3rd layer made of 2 layers of smooth muscle
that move food along the GI tract.
Serosa: outer lining that is part of the peritoneum.
8.1 Overview of digestion
Visualizing the layers of the GI tract
8.1 Overview of digestion
Lumencentral space containingfood being digested
Mucosainner mucous membranelayer modified accordingto the digestive organ
Submucosabroad band of looseconnective tissue thatcontains nerves, blood,and lymphatic vessels
Muscularistwo layers ofsmooth muscle
Serosathin, outermost tissuethat is the visceralperitoneum
nervesupply
lymphvessel
artery
vein
An overview of the digestive system
8.1 Overview of digestion
Livermajor metabolic organ:processes and stores nutrients;produces bile for emulsification of fats
Gallbladderstores bile from liver; sends it tothe small intestine
Pancreasproduces pancreatic juice: contains digestiveenzymes, and sends it to the small intestine;produces insulin and secretes it into theblood after eating
Digestive tract organs
Esophaguspassageway where peristalsis pushesfood to stomach
Stomachsecretes acid and digestive enzymefor protein; churns, mixing food withsecretions, and sends chyme tosmall intestine
Small intestinemixes chyme with digestive enzymesfor final breakdown; absorbs nutrientmolecules into body; secretesdigestive hormones into blood
Large intestineabsorbs water and salt to form feces
Rectumstores and regulates eliminationof feces
Mouthteeth chew food; tongue tastes andpushes food for chewing and swallowing
Pharynxpassageway where food is swallowed
Accessory organs
Salivary glandsecrete saliva: contains digestive enzymefor carbohydrates
Anus
What is the pathway that food follows?
1. Mouth2. Pharynx3. Esophagus 4. Stomach 5. Small intestine 6. Large intestine 7. Rectum 8. Anus
8.1 Overview of digestion
The mouth 3 pairs of salivary glands secrete salivary amylase that
begins carbohydrate digestion.
Tonsils at the back of the mouth and other lymphatic
tissues are important in fighting disease.
Contains teeth that begin the mechanical breakdown of food.
The tongue is covered in taste buds and also assists in the
mechanical breakdown and movement of food.
The tongue forms a bolus(mass of chewed food) and
moves it toward the pharynx.
8.2 First part of the digestive tract
Anatomy of the mouth 8.2 First part of the digestive tract
hard palate
soft palate
uvula
tonsil
incisors (2)
canine (1)
premolars (2)
molars (3)
Teeth 32 in adults used for mechanical breakdown of food
(20 deciduous teeth in babies).
Each tooth is made of a crown and a root.
A hard covering called enamel and dentin covers the
crown with an inner pulp area with nerves and blood
vessels.
Dental caries (cavities) occur when bacteria metabolize
sugars and produce acids, so limiting sugar intake and
brushing teeth reduces these.
8.2 First part of the digestive tract
Anatomy of a tooth8.2 First part of the digestive tract
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
root
crown
enamel
dentinpulpgum
jawbone
root canal
periodontalmembrane
cementum
The pharynx and esophagus
• Pharynx: is a cavity between the mouth
and esophagus that serves as a
passageway for food (and air).
• Esophagus: is a long, muscular tube that
carries food to the stomach.
8.2 First part of the digestive tract
How do we swallow food?• Voluntary phase:
– The beginning of food being swallowed from the mouth
into the pharynx.
• Involuntary phase:
– Once the food is in the pharynx swallowing becomes a
reflex action perform automatically.– The epiglottis covers the voice box to make sure food
is routed into the esophagus.– Food moves down the esophagus through peristalsis
(rhythmic contraction).
8.2 First part of the digestive tract
How do we swallow food?
8.2 First part of the digestive tract
Soft palate closesoff nasopharynx.
Larynx rises andepiglottis coversglottis.
Lower gastroesophagealspincter relaxes andfood enters stomach.
hard palate food bolusnasopharynx
softpalate
a. Swallowing
trachea(airway)open
Esophagusis closed.
epiglottis
esophagusopens
b. Peristalsis
esophagus
peristalticwave
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
glottis
bolus
stomach
Health focus: Heartburn Occurs when acids from the stomach pass into the
esophagus (acid reflux).
Burning sensation in the esophagus.
Chronic heartburn is called gastro esophageal reflux disease (GERD).
Tips for decreasing heartburn:
Avoid high fat meals.
Don’t overeat.
Eat several small meals rather than the standard 3 larger meals
each day.
Exercise lightly.
8.2 First part of the digestive tract
The stomach
• The stomach is an enlarged part of alimentary
canal and receives food from esophagus.
• The stomach like J shape with a thick wall.
• Mucous membrane lining stomach contains
folds called rugae.
• Folds disappear as stomach fills with food.
o Its structure is divided into 4 main region:
o Funds: bulge o Body : largest region o Antrum:o Pylorus : pyloric
sphincterso It has two sphincters:Cardiac sphincter.Pyloric sphincter.
Function of stomach
store food, start digestion of proteins
controls movement of chyme into the small intestine.
Mixing of the food in the stomach produces Chyme.
Mixing movement mainly occurs in the Antrum.
Controlled emptying of gastric content into
duodenum.
HCl SecretionHCl Secretion gives the stomach a pH of 2 which
activates pepsin and helps kill bacteria found in food.
Anatomy of the stomach8.3 The stomach and small intestine
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Mucosa layerhas rugae.
Muscularis layerhas three layersof muscle.
lower gastroesophagealsphincter
cells that secretegastric juice
d. How the stomach empties
esophagus
lower gastroesophagealsphincter
pyloricsphincter
a. Stomach
gastric pit
gastric gland
b. Gastric glands
pyloricsphincter
SEM 3,260xgastric pitc. Gastric pits in mucosa
c: © Dr. Fred Hossler/Visuals Unlimited
The small intestine Averages 6m (18 ft) in length
Enzymes secreted by the pancreas into the small intestine
digest carbohydrates, proteins, and fats.
Bile is secreted by the gallbladder into the small intestine to
emulsify fats.
Digested food is absorbed through large surface area
created by numerous villi (finger-like projections) and
microvilli.
Amino acids and sugars enter the capillaries while fatty acids and glycerol enter the lacteals (small lymph vessels).
8.3 The stomach and small intestine
Anatomy of the small intestine
8.3 The stomach and small intestine
Small intestine
Section of intestinal wall
lumen
lymphnodule
villus
lacteal
Villi arteriole
lymphaticvessel
venule
gobletcell
bloodcapillaries
microvillivillus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(villi): © Manfred Kage/Peter Arnold/Photolibrary; (microvilli):Reprinted from Medical Cell Biology, Charles Flickinger, copyright 1979, with permission from Elsevier.
How are nutrients digested and transported out of the small intestine?
8.3 The stomach and small intestine
+carbohydrate
pancreatic amylase
cell ofintestinalvillus
maltase
glucose
pH = basic
blood capillary
a. Carbohydrate digestion
b. Protein digestion
blood capillary
pH = basic
protein
peptides
trypsin
peptidase
amino acids
bile salts fat globules
emulsificationdroplets
lipase
monoglyceridesand freefatty acids
chylomicron
c. Fat digestion
lymphaticcapillary
pH = basic
What are the major digestive enzymes?
8.3 The stomach and small intestine
The three accessory organs
8.4 Three accessory organs and regulation of secretions
• Pancreas
• Liver
• Gallbladder
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
gallbladder
common bile duct
duodenum
a.
bile
common hepatic duct
pancreatic ductpancreas
pancreaticjuice
centralvein
bile canals
branch ofhepaticartery
branch ofhepatic
portal veinbile ductb.
The pancreas• Fished-shaped spongy organ behind the stomach• Functions of the pancreas:
1. Secretes enzymes into the small intestine• Trypsin: digests proteins.• Lipase: digests fats.• Pancreatic amylase: digests carbohydrates.
2. Secretes bicarbonate into the small intestine to neutralize stomach acids
3. Secretes insulin into the blood to keep blood sugar levels under control
8.4 The accessory organs and regulation of secretions
The liver and gallbladder
• Large metabolic organ that lies under the diaphragm and is
made of 100,000 lobules.Function:1. Filters blood from the GI tract thus acting to remove poisons
and detoxify the blood.2. Removes iron, vitamins A, D, E, K and B12 from the blood and
stores them.3. Stores glucose as glycogen and breaks it down to help retain
blood glucose levels.4. Makes plasma proteins and helps regulate cholesterol levels by
making bile salts.5. Makes bile that is then stored in the gallbladder to be secreted
into the small intestine to emulsify fats.6. Breaks down hemoglobin.
8.4 The accessory organs and regulation of secretions
Liver disorders• Hepatitis:
– Inflammation of the liver– Caused by Hepatitis A, B, and C– This can lead to liver damage, cancer and/or death
• Cirrhosis:
– The liver becomes fatty and eventually this tissue is replaced by fibrous scar tissue.
– Seen in alcoholics and obese people.– This can lead to liver failure in which the liver
cannot regenerate as fast as it is being damaged.
8.4 The accessory organs and regulation of secretions
How do hormones control digestive gland secretions?
8.4 The accessory organs and regulation of secretions
gallbladder liver
stomach
pancreas
blood vessel
duodenum
gastrinCCK
secretin
The large intestine• Includes the cecum, colon, rectum
and anal canal• Larger in diameter but shorter than
the small intestine• The cecum has a projection known
as the appendix that may play a role in fighting infections
• Functions to:
1. Absorb water to prevent
dehydration.
2. Absorbs vitamins (B complex and
K) produced by intestinal flora.
3. Forms and rids the body of feces through the anus.
8.5 The large intestine and defecation
vermiformappendix
orifice ofappendix
transverse colon
ascendingcolon descending
colon
smallintestine
cecum
anal canal
internal anal sphincter external anal sphincter
anus
sigmoid colonrectum
Disorders of the colon and rectum
1. Diarrhea: increased peristalsis and water is not reabsorbed due
to either an infection or nervous stimulation.
2. Constipation: condition when feces are dry and hard that may
be controlled with water and fiber.
3. Hemorrhoids: enlarged and inflamed blood vessels of the anus
due to chronic constipation, pregnancy, aging, and anal
intercourse.
8.5 The large intestine and defecation
To understand weight and nutrition we first
have to understand nutrients
• Nutrients are a component of food that is needed
to perform a physiological body function.
• Nutrients include: CarbohydratesProteinsLipidsMineralsVitamins
8.6 Nutrition and weight control
Any question?
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