Anatomy & Physiology Chapter 25 Anatomy of the Digestive System.
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Transcript of Anatomy & Physiology Chapter 25 Anatomy of the Digestive System.
Anatomy & PhysiologyChapter 25
Anatomy of the Digestive System
Function Altering the chemical & physical
composition of food so that it can be absorbed & used by body cells (digestion)
Organs of the Digestive System Mouth Oropharynx Esophagus Stomach
Duodenum Jejunum Ileum
Large Intestine Cecum Colon
Ascending colon Transverse colon Descending colon Sigmoid colon
Rectum Anal Canal
Accessory Organs Salivary glands
Parotid Submandibular Sublingual
Tongue Teeth Liver Gallbladder Pancreas Vermiform appendix
Walls of the Gastrointestinal (GI)Tract Tube with 4
layers of tissue Mucosa Submucosa Muscularis Serosa
Mucosa Inner most layer Made of 3 layers of epithelium, connective
tissue & smooth muscle
Submucosa Thicker than mucosal
layer Connective tissue
layer that contains glands, blood vessels, nerve plexus (Meissner plexus)
Muscularis Thick layer of muscle tissue Inner layer of circular smooth muscle Outer layer of longitudinal smooth muscle Myenteric plexus between the muscular
layers
Serosa Outermost layer Made of connective tissue & peritoneum
(visceral layer) Layer of peritoneum that lines the
abdominal cavity= parietal layer Mesentery is the fold of membrane that
connects the parietal & visceral layer of peritoneum
Mouth (Oral cavity) Lips Cheek Tongue Hard & Soft Palates
Lips Surround the orifice of the mouth & form
anterior boundary Covered by skin externally & mucous
membrane internally Philtrum: shallow vertical groove that
marks the midline of upper lip
Cheeks Form lateral boundaries, continuous with
lips, lined by mucous membranes Formed in large part by buccinator muscle
Hard & Soft Palates Hard palate: consists
of 4 bones: 2 maxillae & 2 palatines
Soft palate: partition between mouth & nasopharynx
Uvula: small cone shaped process extending from soft palate
Tongue Intrinsic muscle:
changes in size & shape of tongue; important for mastication (chewing)
Extrinsic muscle: origin outside the tongue; important for deglutition (swallowing) & talking
3 parts: root, body, tip
Papillae Vallate: large, form an
inverted V on posterior part of tongue; 10-14; taste buds on lateral aspect
Fungiform: taste buds on lateral aspect; mostly on sides & tips of tongue
Filiform: no taste buds, over anterior 2/3 of tongue; whitish appearance
Lingual Frenulum Fold of mucous
membrane on the undersurface of the tongue that anchors the tongue to the floor of mouth
Salivary glands Three pairs:
Parotid Submandibular Sublingual
Secrete about 1 L of saliva/day
Parotid Glands Largest Between skin &
masseter muscle in front of & below the ear
Produce a serous (watery) type of saliva
Submandibular glands Mixed gland-contain
both serous & mucus-producing elements
Located below mandibular angle
Sublingual glands Smallest Under the mucous
membrane covering the floor of the mouth
Produce only a mucous type of saliva
Tooth 3 main parts
Crown: exposed portion, covered by enamel
Neck: area surrounded by gingiva
Root: area that fits into jaw
Tooth suspended in place by periodontal membrane
Tooth structure Dentin: makes up
greatest portion of tooth shell, covered by enamel on crown & cementum in neck & root
Dentin contains a pulp cavity consisting of vessels & nerves
Type of teeth Deciduous teeth
(baby): 20; erupt from 6 mos. to 20 mos.
Permanent teeth: 32
Pharynx Food now called a
bolus leaves mouth & enters oropharynx
Food does not go thru nasopharynx
Esophagus Collapsible tube,
posterior to trachea Mucosa: stratified
squamous epithelium to resist abrasion
Muscularis: striated in upper third, smooth in lower third
Sphincters of esophagus Upper esophageal
sphincter: helps prevent air from entering during respiration
Lower esophageal sphincter (cardiac sphincter): between stomach & esophagus
Stomach Three divisions:
Fundus: enlarged portion to left & above opening of esophagus
Body & Pylorus
Sphincter of Stomach Pyloric sphincter: controls opening of
pylorus to duodenum
Gastric mucosa Folds (rugae) with
depressions (gastric pits)
Gastric glands are located below the level of the pits
Gastric glands 3 major secretory cells:
Chief cells: secrete enzymes
Parietal cells: secrete HCl & intrinsic factor (binds to Vitamin B12 to protect it)
Endocrine cells: secrete ghrelin (stimulates hypothalamus to increase appetite) & gastrin (regulates gastric function)
Gastric muscle Made of 3 layers instead of 2
Functions of stomach Reservoir Secretes gastric juice to aid in digestion Churns food Secretes intrinsic factor Absorption-small amounts Produces hormones Protects by destroying pathogens
Small intestine Main site of digestion & absorption 3 divisions:
Duodenum Jejunum Ileum
Wall of Small Intestine Has circular folds
(plicae) with many tiny projections (villi)
Each villus contains vessels & lacteal
Epithelial cells on surface of villi have microvilli which form a brush border which increases surface area
Goblet cells Large numbers of
mucus secreting goblet cells on villi & in crypts
Crypts serve as area of rapid mitotic division & at base of crypts secretory cells produce an enzyme that is thought to inhibit bacterial growth
Large Intestine Divisions:
Cecum: blind pouch Colon
Ascending colon: right side, ileum attaches at junction of cecum & ascending colon
Transverse colon: from hepatic flexure to splenic flexure
Descending colon: left side Sigmoid colon: S shaped
Rectum: terminal inch is anal canal
Wall of Large Intestine Intestinal mucus glands which produce
mucus to lubricate feces Longitudinal muscle fibers form strips
called taeniae coli & circular muscles are grouped into rings that produce pouches, haustra
Vermiform appendix Wormlike tubular
organ, communicates with cecum
Peritoneum Large continuous sheet of serous
membrane that lines the walls of abdominal cavity & forms outer serous coat of organs Mesentery: fan shaped projection of
peritoneum encloses the jejunum & ileum Greater omentum: continuation of serosa of
stomach to transverse colon Lesser omentum: from liver to lesser curvature
of stomach
Liver Largest gland in body 2 lobes separated by
falciform ligament: Left lobe (about 1/6) Right lobe
Hepatic lobules anatomical units of
liver Branch of hepatic vein
through center of each lobule
Outer corners of lobules are the branches of hepatic artery, portal vein, hepatic duct
Bile ducts Small bile ducts join to
form right & left hepatic duct which join to form hepatic duct which merges with cystic duct from gallbladder to form common bile duct which opens into duodenum at major duodenal papilla
Functions of liver Detoxify substances Secrete bile Metabolism of foods Store several substances Produces plasma proteins & site of
hematopoiesis during fetal development
Gallbladder Pear shaped on underside of liver Serous, muscular & mucosal layer Functions: stores, concentrates & ejects
bile
Pancreas In curve of duodenum, extending behind stomach Exocrine gland (most)
Acinar cells: secrete enzymes through pancreatic duct that empties into duodenum
Endocrine gland-Islets Alpha cells: produce glucagon Beta cells: produce insulin
Image Citations Slide 6: Brunner’s glands, 2/28/07,
http://w3.ouhsc.edu/histology/Text%20Sections/Lower%20GI.html
Slide 25: Lower esophageal sphincter, 3/13/07, http://hopkins-gi.nts.jhu.edu/pages/latin/templates/index.cfm?pg=disease1&organ=1&disease=13&lang_id=1
Slide 38: The human vermiform appendix, 3/13/07, http://www.talkorigins.org/faqs/vestiges/appendix.html