DIGESTIVE SYSTEM Major structures involved
STRUCTURES MAIN ORGANS
Mouth Pharynx Esophagus Stomach Small Intestine
DUODENUM JEJUNUM ILEUM
Large Intestine/Colon ASCENDING COLON TRANSVERSE COLON DESCENDING COLON SIGMOID COLON RECTUM ANAL CANAL
ACCESSORY ORGANS TEETH & TONGUE SALIVARY GLANDS
PAROTID SUBMANDIBULAR SUBLINGUAL
LIVER GALLBLADDER PANCREAS APPENDIX
Mouth/Oral Cavity Chemical digestion of carbohydrates:
Salivary glands secrete salivary amylase Mechanical digestion of food into a bolus: Teeth
and tongue
Deglutition
Pharynx (and upper esophageal sphincter)
Passes food to esophagus Upper Esophageal Sphincter
During swallowing Upper esophageal sphincter
opens Allows food, liquids to pass
Reduces backflow of food, liquids from the esophagus into the pharynx.
Esophagus and Lower esophageal sphincter
Esophagus: Muscular walls (longitudinal and circular) causes peristalsis
Cardiac/Lower Esophageal Sphincter- prevents backflow of acidic food contents
Stomach and Pyloric Sphincter
Mechanical digestion of food into chyme: 3 layers of muscle (longitudinal, circular, oblique)
Chemical digestion of proteins Pepsin
When empty, lining lies in folds called rugae
Peristalsis drives movement of materials
Peristalsis in stomach
Small Intestine: Duodenum, Jejunum, Ileum
Mech/Chem Digestion Absorption of Nutrients Circular folds:
Plicae (plica, s) Folds covered with:
Villi (villus, s) Fingerlike projections Covered w/ microvilli
Nutrient absorption takes place in capillaries of villi
oPlicae/Villi SA, which nutrient absorption
Absorption of nutrients in the SI: Villi & Microvilli
Duodenum Bile from liver/gallbladder emulsifies fat (breaks it
into smaller droplets)—mech dig. Lipase from pancreas released here
Other pancreatic enzymes:
Proteases (protein)Amylase (carbohydrates)
Small Intestine, cont’d
Secrete intestinal enzymes: Peptidases (peptides amino acids) Sucrase, lactase, maltase (disaccharides
monosacharides)
Ileocecal valve
Regulates flow of materials between ileum (SI) and cecum (LI)
Plicae of the small intestine & large intestine, appendix
Large Intestine (all these words!!!) Cecum (and appendix) Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anal Canal
Large Intestine Water Absorption/Stool Formation
Transit time Too fast diarrhea (too much water in stool) Too slow constipation (too little water in stool)
Vitamins B & K Production Result from bacteria feeding on undigested material
Peritoneum Visceral Peritoneum: surrounds digestive tract Parietal Peritoneum: lines abdominal cavity Extensions:
Greater Omentum: hangs down from lower edge of stomach/transverse colon over intestines (“lace apron”)
Mesentery: connects intestines/ anchors intestines to posterior abdominal wall
Rectum
Stores feces prior to elimination Anal sphincter regulates movement through
anal canal Under voluntary control
Learned during “potty training”
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