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”