A personalized and smart learning plan
Take a test on your terms and definitions
Scientifically backed study method
See how quickly you can match all your cards
Study terms and definitions
Functions of the digestive system:
Tags & Description
View all (104)
New cards (104)
Ingestion of food
Propulsion of food through GI tract (includes peristalsis)
Alternate waves of contraction and relaxation
Physical mixing of food with digestive enzymes
Catalyzed by enzymes
Uptake of small molecules though intestinal lining
Elimination of feces or stool
Portions of the digestive system: Gastrointestinal (GI) Tract
oral cavity → pharynx (oro & laryngo- pharynx) → esophagus → stomach → small intestine → large intestine
Portions of the digestive system: Accessory organs
Salivary glands, liver, gallbladder & pancreas
What are the serous membranes of the abdomen?
Parts of the peritoneum:
Visceral and parietal peritoneum
Adheres to the surface of abdominal organs
Adheres to the wll of the abdominal cavity
Some portions of the peritoneum have different names:
Associated with stomach
Associated with large intestine
Associated with small intestine
These structures are located against posterior wall behind the parietal peritoneum. This keeps them fixed in place.
What are the retroperitoneal structures?
Aorta & IVC, kidneys, pancreas, duodenum, and some portions of large intestine
Layers of the GI Tract wall
*4 layers that are present from the esophagus to the rectum.
Adventitia or serosa
Innermost layer; lines the hollow lumen
What does the mucosa contain?
Epithelium, lamina propria, & muscularis mucosae
Simple columnar epithelium in stomach and intestines
Connective tissue; also capillaries for nourishment & absorption; & lymphatic tissue to defend against pathogens
Thin layer of smooth muscle around lamina propria
What are the function of the mucosa?
Secretion of mucus, digestive enzymes, and hormones ; absorption of the end products of digestion ; protection against pathogens in food
Connective tissue layer containing blood and lymphatic vessels, nerve fibers, and lymphatic tissue
Two layers of smooth muscle being:
a. inner circular muscularis (INC) \n b. outer longitudinal muscularis (OUL)
What are the functions of the muscularis externa?
Responsible for muscular contractions (including peristalis) which:
a. move food along GI tract
b. mix food with GI tract secretions
c. physically break down food
Thickens at some points to form sphincters
Outer layer of GI tract above diaphragm specifically around esophagus
What is adventitia composed of?
Fibrous connective tissue
Outer layer of GI tract below diaphragm, specifically around stomach and intestines
What is serosa composed of?
A serous covering that binds/anchors GI tract. Same as visceral peritoneum
What is the oral cavity responsible for?
Chewing & mixing food with saliva ; initiating chemical digestion of carbohydrates by an enzyme called salivary amylase
Passageway carrying chewed food (bolus) from oral cavity to esophagus; performs no additional chemical digestion
Tube that carries food from pharynx to stomach; performs no chemical digestion
Point where esophagus penetrates diaphragm
Cardiac (gastroesophageal) sphincter
Thickening of the muscularis just above stomach
Functions of the stomach:
Mixes food with gastric secretions
Initiates protein digestion
Limited absorption (ex. absorbs alcohol + aspirin)
Gross anatomy of the stomach
Cardiac region (cardia), fundus, body, pyloric region. pyloric sphincter (rugae, lesser curvature, greater curvature)
Surrounds the entrance of esophagus
Dome shaped; bulges superiorly & laterally to the cardia region
Large middle portion of the stomach
Funnel-shaped portion of the stomach leading into duodenum
Between stomach and duodenum; a valve that controls movement of food
Large folds of mucosa ( and submucosa) present in stomach wall when empty
Concave, medial surface of the stomach
Convex, lateral surface of the stomach
What does the stomach wall contain?
An extra oblique muscle layer in the muscularis (+ INC & OUL) ; gastric pits, which contain glands that make gastric juice
Cells of the gastric glands:
Mucous neck cells, parietal cells, chief cells, enteroendocrine (G) cells
Mucous neck cells
Secrete thin, acidic mucus
Secrete HCI and intrinsic factor
HCI (hydrochloric acid)
Aids in absorbtion of vitamin B12
Secrete pepsinogen, an inactive enzyme that's converted to pepsin by HCI in the lumen
A protein-digesting enzyme
Enteroendocrine (G) cells
Secrete a hormone called gastrin into the blood that stimulates secretion of gastric juice
Summary of the stomach:
Food enters stomach as a bolus and leaves as chyme, a semi-fluid mixture that passes through the pyloric sphincter
What is the hostile environment of the stomach?
Extremely acidic; contains protein-digesting enzymes; few pathogens can survive
Mucosal barrier of the stomach:
Protects stomach from it's own harsh internal environment
The mucosal barrier of the stomach is formed by:
Mucus coat and tight junctions between epithelial cells
Thick, bicarbonate-rich mucus is built up on the stomach wall
Tight junctions between epithelial cells
Prevent gastric juice from leaking into underlying tissues
What are the function of the small intestine?
Primary digestive organ
Primary sight of absorption
What does the small intestine being the primary digestive organ mean?
Completes digestion of carbohydrates and proteins ; performs digestion of lipids (fats)
Portions of the small intestine:
Duodenum, jejunum, ileum
Receives chyme from stomach ; most chemical digestion occurs here ; also receives secretions from pancreas, liver & gallbladder ; contain Brunner's (duodenal) glands in submucosa
Brunner's (duodenal) glands in submucosa
Secrete alkaline mucus to neutralize acidic incoming chyme
2nd portion of small intestine
Distal segment; carries chyme to large intestine
What are the structural modifications of the small intestine?
Circular folds, villi, and microvilli
Large folds of mucosa and submucosa
Fingerlike projections of mucosa
"brush border" : tiny projections of the intestinal mucosal cell's plasma membrane
What is the function of the 3 modifications?
They all increase surface area for absorbtion
Histology of the small intestine
Have tight junctions between absorptive columnar cells; many goblet cells = secrete mucus ; enteroendocrine cells - secrete 2 hormones
What 2 hormones do enteroendocrine cells secrete in the small intestine?
Secretin and cholecystokinin
Other features of the small intestine:
Intestinal crypts, peyer's patches, capillaries, lacteals
Pockets between the villi that secrete intestinal juice (watery mixture w/ mucus)
Aggregations of lymphoid tissue → prevent bacteria of intestine from entering blood
In villi; transport absorbed sugars and amino acids
Lymphatic capillaries in villi that transport absorbed fats
What are the functions of the large intestine?
Absorption of some water and electrolytes
Defecation (elimination of feces)
Vitamin K and folic acid production - by bacteria within the large intestine
Undigested food residues, mucus, sloughed-off epithelial cells, bacteria, and some water
What are the 5 regions of the large intestine?