TEAS Digestive System

mastication

the voluntary act of chewing in the mouth

deglutition

swallowing using the skeletal muscles of the mouth and pharynx

buccal phase

the voluntary phase of deglutition

pharyngeal and esophageal phase

the involuntary phases of deglutition

muscularis externa

the layer of the digestive tract that consists of two layers of muscle tissue (three in the stomach) that contract radially and then relax to squeeze food in one direction

peristalsis

a series of involuntary, wave-like muscle contractions and relaxations that move food, fluid, and waste through the digestive tract

segmentation

non-adjacent portions of the digestive tract contract and relax to move the chyme back and forth

mass peristalsis

the movements that occur two to four times a day to push large amounts of chyme toward the rectum

saliva

lubricating fluid that is secreted by hundreds of minor salivary glands that are scattered throughout the oral cavity and three pairs of major glands

salivary amylase

begins the chemical breakdown of polysaccharides into simpler sugars

lingual lipase

begins the breakdown of fats

lysozyme

an enzyme that works with immunoglobulin A to break down the cell walls of many bacteria

bicarbonate ions

contents of saliva that help maintain a pH that is optimal for salivary enzymes

mucin

a protein that helps to form a gel-like coating that lubricates the bolus of food

esophagus

a 25 cm tube that extends from the pharynx to the stomach that functions as a passageway for food

mucosa, submucosa, muscularis externa, adventitia

the 4 layers of the esophagus and the alimentary canal

stomach

a muscular organ located in the left superior region of the abdomen

gastroesophageal sphincter

found at the junction between the esophagus and the stomach, helps prevent the reflux of acidic contents

cardiac region

the region of the stomach where food is emptied into the stomach

fundus

the most superior portion of the stomach

body

the most central region of the stomach. curves toward the right to form a “J” shape with a lesser and greater curvature

pylorus

the funnel shaped region at the end of the stomach

pyloric sphincter

the valve that regulates the release of small amounts of chyme into the small intestine

rugae

the gastric folds of the mucosa that allow the stomach to stretch and expand

chyme

food mixed with gastric juices, created in the stomach

gastric glands

located in the mucosa of the stomach which open into gastric pits

endocrine cells

release hormones such as gastrin into the blood and do not contribute to gastric juices

parietal cells

secrete intrinsic factor and hydrochloric acid

intrinsic factor

required for the absorption of vitamin B12

chief cells

secrete pepsinogen

pepsin

the active form of pepsinogen, a digestive enzyme that breaks down proteins into smaller peptide chains

gastric lipase

secreted by chief cells, for the digestion of fats

mucous cells

secrete bicarbonate-containing mucus to protect the stomach from the acidity and digestive enzymes

liver

an accessory organ that performs functions such as the production of bile, nutrient metabolism, and detoxification

alimentary canal

the primary pathway of the digestive system, also known as the GI (gastrointestinal) tract

bile

a yellow-green solution of bile salts, pigments, cholesterol, and electrolytes. also enhances the absorption of fat-soluble vitamins A, D, E, and K

bile salts

mechanically digest by emulsifying fats into smaller globules called micelles that can be acted on by lipases in the small intestine

gallbladder

stores and concentrates bile

CCK (cholecystokinin)

a hormone which signals the gallbladder to contract when food enters the small intestine

hepatic portal vein

the vein that allows blood from the digestive tract to enter the liver

glycogenesis

if blood sugar is too high, the liver polymerizes glucose to form glycogen

glycogenolysis

if blood sugar is too low, liver cells break down stored glycogen and release glucose monomers in a process called ______

gluconeogenesis

when the liver can produce glucose from non-carbohydrate sources such as proteins and animal fats

pancreas

A triangular-shaped organ with both endocrine and exocrine functions. located below the stomach and extends from the duodenum to the spleen

secretin

secreted by the pancreas, stimulates the duct cells to release a bicarbonate-rich solution that raises pH

pancreatic amylase

digests starch

pancreatic lipase

digests fats

small intestine

a long tube that extends from the pyloric sphincter to the ileocecal valve

doudenum

the shortest segment (25 cm) of the small intestine, but with the widest diameter. receives chyme from the stomach and neutralizing digestive juices from the pancreas. most of the chemical digestion of food occurs here

jejunum

the main site of absorption in the small intestine, about 2.5 meters in length. has prominent plicae circulares, long villi, and dense microvilli

ileum

the longest segment of the small intestine (3.5 meters). the narrowest in diameter. absorbs vitamin B12, bile salts, and any nutrients that were not absorbed in the jejunum. terminates at the ileocecal valve

Peyer’s patches

small aggregates of lymphatic cells that are common in the ileum of the small intestine

ileocecal valve

controls the movement of chyme into the large intestine

brush border enzymes

pancreatic enzymes and enzymes of the small intestine that continue the digestion of food so that nutrients are small enough to be absorbed. embedded in microvilli

microvilli

tiny folds of the apical cell membrane that increase surface area

brunner’s glands

glands of the duodenum that secrete bicarbonate-containing fluid that neutralizes the acidic chyme to provide the optimal pH for enzyme activity

dextrinase and glucoamylase

the two brush border enzymes that act on oligosaccharides

large intestine

the portion of the alimentary canal that begins at the ileocecal valve and terminates at the anus

cecum

the first portion of the large intestine. receives chyme from the small intestine. also the site of the appendix

colon

the middle portion of the large intestine that can be subdivided into 4 parts

sigmoid colon

lies in the pelvic cavity and becomes the rectum, which opens to the anus

haustra

small, pouch-like sacculations that are formed by the contraction of smooth muscle within the muscularis layer of the large intestine

rectum

the final 12-15 cm of the digestive tract

anal canal

the last portion of the rectum, ending with an involuntary internal sphincter and a voluntary external sphincter

rectal ampulla

a dilated region superior to the anal canal that functions as a storage area for feces before elimination