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12 Cards in this Set

  • Front
  • Back

Define digestion

Digestion is the chemical and mechanical breakdown of food into absorbable units

What is the difference between digestion and metabolism?

Digestion takes place in the GI tract lumen, which is external to the body; metabolism takes place in the body's internal environment

What is the difference between absorption and secretion?

Absorption moves material from the GI lumen into the ECF; secretion moves substances from the cells or the ECF into the lumen

Is the lumen of the digestive tract on the apical or basolateral side of the intestinal epithelium? On the serosal or mucosal side?

The lumen of the digestive tract is on the apical or mucosal side of the intestinal epithelium

Name the four layers of the GI tract wall, starting at the lumen and moving out.

The four layers are mucosa, submucosa, muscularis externa, and serosa.

Name the structures a piece of food passes through as it travels from mouth to anus.

Mouth -> pharynx > esophagus -> stomach (fundus, body, antrum) -> small intestine (duodenum, jejunum, ileum) -> large intestine (colon, rectum) -> anus

Why is the digestive system associated with the largest collection of lymphoid tissue in the body?

Because the GI tract has a large, vulnerable surface area facing the external environment, it needs the immune cells of lymphoid tissue to combat potential invaders.

Why are some sphincters of the digestive system tonically contracted?

Some sphincters are tonically contracted to close off the GI tract from the outside world and to keep material from passing freely from one section of the tract to another.

Do bile salts digest triglycerides into monoglycerides and free fatty acids?

Bile salts do not digest triglycerides. They simply emulsify them into small particles so that lipase can digest them.

Bile acids are reabsorbed in the distal intestine by an apical sodium-dependent bile acid transporter (ASBT) and a basolateral organic anion transporter (OAT). Draw one enterocyte. Label the lumen, ECF, and basolateral and apical sides. Diagram bile acid reabsorption as described.

The ASBT faces the lumen and brings Na+ and bile acid into the enterocyte together. The OAT transports bile acid by itself out of the enterocyte and into the ECF.

List the actions of CCK on the digestive system, and explain how these functions coordinate to promote fat digestion and absorption.

CCK slows gastric motility and acid secretion, promotes release of pancreatic enzymes and bile, and promotes intestinal motility. Bile from the gallbladder and pancreatic lipase and colipase are necessary for efficient fat digestion. Fat digestion takes longer than digestion of other foodstuffs, and slowing gastric motility gives the intestine more time to digest fats. Decreasing gastric acid secretion also delays movement of chyme from stomach to intestine. Promoting intestinal motility ensures that bile salts can emulsify fats and that micelles will get adequate exposure to the brush border, where they are absorbed.

In secretory diarrhea, epithelial cells in the intestinal villi may be damages or may slough off. In these cases, would it be better to use an oral rehydration solution containing glucose or one containing sucrose? Explain your reasoning.

Damage to epithelial cells means that brush border sucrase may be less effective or absent. In these cases, sucrose digestion would be impaired, so it would be better to use a solution containing glucose because this sugar need not be digested before being absorbed.