Objective 1: Review the Normal Processes of Digestion. Discuss the Subdivisions and Organization of GI Tract

Gastrointestinal (GI) System

System responsible for digesting food, absorbing nutrients, and eliminating waste products.

Motility

Movement of food through the GI tract through muscular contractions that move and mix intestinal contents.

Secretion

Release of saliva, digestive enzymes, mucus, stomach acid, and other fluids that assist with digestion.

Digestion

Mechanical and chemical breakdown of food into smaller molecules that can be absorbed and used by the body.

Mechanical Digestion

Physical breakdown of food into smaller pieces through processes such as chewing and muscular mixing.

Chemical Digestion

Breakdown of complex food molecules into simpler substances through enzymes and digestive secretions.

Absorption

Movement of nutrients across the intestinal wall into the bloodstream or lymphatic system.

Upper GI Tract

Consists of the mouth, esophagus, and stomach; responsible for food intake and initial digestion.

Middle GI Tract

Consists of the duodenum, jejunum, and ileum; responsible for most digestion and nutrient absorption.

Lower GI Tract

Consists of the cecum, colon, and rectum; processes undigested material and prepares waste for elimination.

Mastication

Chewing that mechanically breaks food into smaller pieces and increases surface area for digestion.

Saliva

Moistens and lubricates food and contains enzymes that begin chemical digestion.

Stomach

Temporarily stores food, mechanically mixes it, and combines it with gastric secretions to continue digestion.

Duodenum

First portion of the small intestine; receives partially digested food from the stomach.

Jejunum

Middle portion of the small intestine that participates in digestion and nutrient absorption.

Ileum

Final portion of the small intestine that continues nutrient absorption before material enters the large intestine.

Cecum

First portion of the large intestine that receives material from the ileum.

Colon

Absorbs water and electrolytes, transports intestinal contents, and helps form and store stool.

Rectum

Final storage area for stool before defecation.

Large Intestine

Part of the lower GI tract that absorbs water and electrolytes and prepares undigested material for elimination.

Nutrient Transport

Movement of absorbed nutrients through the blood or lymphatic system to tissues for energy, growth, and repair.

What are the primary functions of the GI system?

Digest food, break nutrients into usable forms, absorb nutrients, and eliminate waste.

What are the four major processes involved in digestion?

Motility, secretion, digestion, and absorption.

What is motility?

Movement of food through the GI tract by muscular contractions that move and mix contents.

What is secretion?

Release of substances such as saliva, enzymes, mucus, and stomach acid to assist digestion.

What is the difference between mechanical and chemical digestion?

Mechanical digestion physically breaks food apart; chemical digestion uses enzymes and secretions to break molecules down.

What happens during absorption?

Nutrients cross the intestinal wall and enter the bloodstream or lymphatic system.

What are the three major subdivisions of the GI tract?

Upper GI tract, middle GI tract, and lower GI tract.

Which organs make up the upper GI tract?

Mouth, esophagus, and stomach.

What are the primary functions of the upper GI tract?

Food intake, initial digestion, food transport, and stomach storage and mixing.

Where does digestion begin?

In the mouth through chewing and the action of saliva.

What is the function of the stomach?

Stores food, mechanically mixes it, and combines it with gastric secretions.

Which organs make up the middle GI tract?

Duodenum, jejunum, and ileum.

What is the primary function of the middle GI tract?

Performs most digestion and nutrient absorption.

What happens in the duodenum?

It receives partially digested food from the stomach and mixes it with digestive secretions.

What are the major functions of the jejunum and ileum?

Continue digestion and absorb nutrients into the blood or lymphatic system.

Which organs make up the lower GI tract?

Cecum, colon, and rectum.

What is the primary function of the lower GI tract?

Processes undigested material, absorbs water and electrolytes, and prepares waste for elimination.

What happens to intestinal contents in the colon?

Water and electrolytes are absorbed, making the remaining contents more solid and forming stool.

What is the function of the rectum?

Stores stool until it is ready to be eliminated.

How do the upper, middle, and lower GI tracts differ?

The upper handles intake and initial digestion, the middle performs most digestion and absorption, and the lower prepares and eliminates waste.

Why is absorption important?

It allows nutrients to enter circulation and reach cells for energy, growth, repair, and normal function.