Chapter 14- The Digestive System

Pepsinogensin

inactive protein-digesting enzymes

Pepsin

active protein-digesting enzymes; HCl converts pepsinogen to it

Gastrin

(stomach) stimulates the release of gastric juice and stomach emptying; secreted caused by food in stomach (digested proteins) and ACh

Intestinal Gastrin

(duodenum) stimulates gastric secretion and emptying; secreted by food in stomach

Histamine

(stomach); activates parietal cells to secrete hydrochloric acid; secreted by food in stomach

Somatostatin

(stomach/duodenum); inhibits secretion of gastric juice and pancreatic juice and the emptying of stomach and gallbladder; secreted caused by food in stomach and sympathetic nerve fibers

Secretin

(duodenum) increased output of pancreatic juice rich in bicarbonate ions ad bile output by liver; inhibits gastric mobility and gastric gland secretion; secretion by acidic chyme and partially digested foods in duodenum

Cholecystokinin (CCK)

(duodenum) increases output of enzyme-rich pancreatic juice, stimulates gallbladder to expel stored bile, relaxes sphincter of duodenal papilla ot allow bile and pancreatic juice to enter the duodenum; caused by fatty chyme and partially digested proteins in duodenum

Gastric Inhibitory Peptide (GIP)

(duodenum) inhibits secretion of gastric juice nad stimulates insulin release; secreted by food in duodenum

Amylase

in saliva; bicarbonate-rich juice that begins the process of starch digestion

Lysozyme and IgA antibodies

inhibit bacteria

Pancreatic Amylase

breaks down starch in small intestine

Brush border enzymes

in small intestine; dextrinase, glucoaylase, lactase, maltase, sucrase (break down carbohydrates); aminopeptidase, carboxypeptidase, dipeptidase (protein digestion)

Pancreatic Enzymes

trypsin, chymotrypsin, carboxypeptidase; break down large polypeptides into small polypeptides in small intestine

Lingual and gastric lipases

break down unemulsified fats in mouth and stomach

Pancreactic Lipase

breaks down unemulsified fats in small intestine

Renin

second protein-digestine enzyme produced by the stomach to digest milk protein

Digestion occurs in

mouth, stomach, small intestine

What is the main place for digestion and absorption?

Small intestine

Gallbladder

stores and concentrates bile

small intestine

major (chemical) digestive organ; absorbs (nearly all) nutrients

large intestine

dry out the indigestible food residue by absorbing water and to eliminate these residues from the body (feces)

Liver

produce bile

Stomach

stores and breaks down food; churns, mixes, and pummels it; chemical & mechanical digestion

Peristalsis

involuntary; alternating waves of contraction adn relaxation of the longitudinal muscles in the organ wall to squeeze food along the tract

Mastication

chewing; mechanical breakdown of food (first step)

Bile

contains bile salts that physically break down large fat globules into small ones to allow fat-digesting enzymes to work on

Pancreas

produces enzymes that break down all categories of digestible foods; produces hormones: insulin and glucagon

Glycogen

combined glucose molecules and stored in liver

Glucagon

hormone produced by the pancreas to raise blood sugar by stimulating the liver to released glycogen (stored glucose) and produce more glucose (gluconeogenesis)

Glucose

primary source of energy for body

Insulin

hormone produced by the pancreas that allows glucose to be stored in the liver as glycogen

Blood Glucose Levels are high

insulin is released to store excess glucose as glycogen and help glucose enter cells

Blood Glucose Levels are low

glucagon signals the liver to release stored glycogen back into the bloodstream

1

Esophagus

2

Cardioesophageal Sphincter

3

Stomach

4

Pyloric Sphincter/valve

5

Duodenum

6

Transverse Colon

7

Ascending Colon

8

Jejunum

9

Descending Colon

10

Sigmoid colon

11

Ileum

12

Rectum

13

Appendix

Irritable Bowel disease

chronic complex intestinal condition that caused inflammation in the digestive tract; possible causes are genetics, environment, or immune; abdominal pain, diarrhea, fever, anemia, bowel obstruction

Diverticulitis

mucosa protrudes through the colon walls; diverticula becomes inflamed; pouches form on the wall of the colon

Gastroenteritis

intestinal infection (aka stomach flu); diarrhea, cramps, vomiting, fever

Crohn's disease

chronic inflammatory bowel disease that causes inflammation in your gastrointestinal tract; probably genetics; diarrhea, cramping, weight loss, fatigue

Ulcerative colitis

chronic inflammation in the large intestine (colon and rectum) so colon damage; abdominal pain, bloody stools, fatigue, frequent bathroom trips

Peptic ulcer

sores that develop in the lining of the stomach or duodenum; from imbalance in gastric juices, bacterial infection, smoking, alcohol abuse; symptoms- heartburn, chest pain, vomiting, weight loss

Dysentery

inflammation of the intestines accompanied by bloody diarrhea; abdominal pain, fever, malaise; from shigella bacteria or amoeba

1

Lesser curvature

2

Duodenum

3

Pyloric Sphincter/Valve

4

Pyloric Region of stomach

5

Rugae (of mucosa)

6

Greater Curvature

7

Body

8

Fundus

9

Cardioesophageal Sphincter

10

Esophagus

Valve opens from esophagus to stomach

Cardioesophageal sphincter

Valve opens from stomach to small intestine

pyloric sphincter/valve

Intestinal villi

increase the surface area of the small intestine; completes the digestion of proteins and carbohydrates in its plasma membrane and absorbs nutrients through the mucosal cells

6 Steps of GI Tract

ingestion, propulsion, mechanical breakdown, digestion, absorption, defecation

Ingestion

food is placed in the mouth

Propulsion

food is propelled from one organ ot the next; ex: swallowing, peristalsis

Mechanical Breakdown

physically fragments food into smaller particles, increasing surface area, prepares food for further degradation by enzymes; ex: segmentation, chewing, churning of food in stomach

Segmentation

moves food back and forth across internal wall of small intestine to propel food through small intestine; mechanical digestion

Digestion

large food molecules are chemically broken down ot their building blocks by enzymes

Absorption

transport of digestive end products from lumen of GI tract to blood or lymph by entering mucosal cells; mainly in small intestine

Defecation

elimination of indigestibel residues and gut bacteria from the GI tract via the anus in the form of feces

Bolus

food that has been chewed and mixed with saliva; formed in mouth

Chyme

food grinded by stomach (liquid); formed in stomach

Gastric Glands

secrete gastric juice components

Chief Cells

make pepsinogen

Parietal cells

produce hydrochloric acid

Mucous neck cells

produce thin acidic mucus

Enteroendocrine cells

make local hormones

Intrinsic factor

required for absorption of vitamin B12

Mucosa

innermost layer of moist mucous membrane lining the lumen of the GI tract

Submucosa

deep to mucosa; made of connective tissue containing blood vessles, nerves, mucosa-associated lymphoid tissue (MALT), lumphatic vessels

Muscularis externa

smooth muscle layer iwth inner circular layer and outer longitudinal layer

Serosa

outermost layer (aka visceral peritoneum); continuous with parietal peritonem lingin the cavity

Mesentery

double layer of peritoneum

Deglutition

aka swallowing; complex coordinated effort involving the tongue, soft palate, pharynx, and esophagus

Buccal phase

voluntary; occurs in the mouth when the tongue forces the food bolus toward the pharynx

Pharyngeal-Esophageal phase

involuntary; transports food through teh pharynx and esophague controlled by the vagus nerves