Digestive System Flashcards
Digestion
The degradation of large molecules into smaller molecules that can be absorbed into the bloodstream and used directly by cells
Oral cavity
The mouth where mechanical and chemical digestion begins
Mechanical disgestion
Breakdown of large food particles into smaller particles through physical actions or churning motion of the stomach
Chemical digestion
The enzymatic breakdown of macromolecules into smaller molecules
Saliva
Lubricates food to facilitate swallowing
Provides solvent for food
Contains amylase (ptyalin) which hydrolyzes starch to maltose
Bolus
Food that has been moistened and chew enough to be swallowed
Esophagus
The muscular tube leading from the mouth to the stomach
Peristalsis
Involuntary muscular contractions that move food down the esophagus
Lower esophageal (cardiac) sphincter
Muscular structure that contracts to close off the esophagus from the stomach
Gastroesophageal reflux
The positive pressure of the abdominal cavity favours continual reflux of gastric materials into the negatively pressured esophagus
Reflux after spontaneous transient lower esophageal sphincter relaxations
Decreased lower esophageal sphincter pressure
Stomach
A large, muscular organ located in the upper abdomen
Stores and partially digests food
Gastric mucosa
A mucous membrane lining the stomach walls
Contain gastric glands
Muscous cells secrete mucus to protect the stomach lining from HCl
Chief cells
Within the gastric glands
Synthesize pepsinogen, with HCl converts to pepsin and breaks down proteins
Parietal cells
In gastric glands
Synthesize and release HCl
Kills bacteria
Release intrinsic factor for absorption of vitamin B12
Chyme
Acidic, semifluid mixture of partially digested food produced by the mechanical and chemical digestion in the stomach
Duodenum
First segment of the small intestine
Small intestine
Duodenum, jejunum, ileum Highly adapted to absorption Extremely long (>6 meters) and highly coiled
Villi
Finger-like projections extended out of the intestinal wall
Contain capillaries and lacteals
Lipases
Digests fat
Aminopeptidases
Digestion polypeptides
Disaccharidases
Digest maltose, lactose, sucrose
Gastrin
Produced in the G cells of the duodenum
Stimulate histamine and pepsinogen secretion
Increase gastric blood flow
Stimulate parietal cells to produce HCl
Intrinsic factor
Secreted by parietal cells
Facilitate absorption of vitamin B12 across the intestinal lining
Cholecystokinin (CCK)
Produced and stored in the I cells of the duodenal and jejunal mucosa
Stimulate pancreatic enzyme and somatostatin secretion
Stimulate gallbladder contraction
Hunger suppressant
Secretin
Synthesized and stored in S cells of the upper intestine
Stimulates secretion of bicarbonate-containing substances from the pancreas
Inhibits gastric emptying and gastric acid production
Liver
Produces bile Storages glycogen Converts ammonia to urea Protein synthesis Detoxification Cholesterol metabolism
Bile
Produced in the liver
Stored in the gallbladder
Emulsifies fats from large globules into small droplets increasing surface area for pancreatic lipase
Pancreas
Produces amylase, trypsin and lipase
Releases chymotrypsin and enterokinase. Enterokinase cleaves trypsinogen to trypsin. Trypsin cleaves and actives other zymogens
Secretes bicarbonate-rich juice to neutralize acidic chyme
Zymogens
Enzyme precursors
Large intestine
1.5 m long
Absorbs salts and water not already absorbed by the small intestine
Rectum
Transient storage of feces before elimination through the anus
