The document summarizes the key components and functions of the gastrointestinal (GI) tract. It describes the GI tract as the system of organs from the mouth to the anus that digests food, extracts nutrients, and expels waste. It outlines the main sections - upper GI tract including the mouth, esophagus and stomach, and lower GI tract including the small and large intestines. It then details the major digestive organs, their locations in the GI tract, and their functions in digesting different nutrients and expelling waste.

1. GASTRO-
INTESTINAL
SYSTEM

2. INTRODUCTION
• THE GASTROINTESTINAL TRACT (GI TRACT, GIT, DIGESTIVE TRACT, DIGESTION
TRACT, ALIMENTARY CANAL) IS THE TRACT FROM THE MOUTH TO THE ANUS
WHICH INCLUDES ALL THE ORGANS OF THE DIGESTIVE SYSTEM IN HUMANS AND
OTHER ANIMALS.
• FOOD TAKEN IN THROUGH THE MOUTH IS DIGESTED TO EXTRACT NUTRIENTS
AND ABSORB ENERGY, AND THE WASTE EXPELLED AS FECES.

3. FUNCTIONS
• INGESTION
• SECRETION
• MIXING AND PROPULSION
• DIGESTION
• ABSORPTION
• DEFECATION

4. STRUCTURE
• UPPER GASTRO INTESTINAL TRACT
• MOUTH
• PHARYNX
• OESOPHAGUS
• STOMACH
• DUODENUM AND
• THE SALIVARY GLANDS, LIVER, PANCREAS AND GALL BLADDER HAVE IMPORTANT FUNCTIONS IN THE
DIGESTIVE SYSTEM.
• LOWER GASTRO INTESTINAL TRACT
• SMALL INTESTINE
• LARGE INTESTINE

5. FUNCTIONS

6. SUMMARY OF ORGANS OF THE DIGESTIVE
SYSTEM AND THEIR FUNCTIONS
ORGANS FUNCTIONS
Tongue Helps food for mastication, shapes food into a bolus, manuevers food
for deglutition, detects sensations for taste, and initiates digestion of
triglycerides.
Salivary glands Saliva produced by these glands softens, moistens, and dissolves foods;
cleanses mouth and teeth; initiates the digestion of starch
Teeth Cut, tear and pulverize food to reduce solids to smaller particles for
swallowing.
Pancreas Pancreatic juice buffers acidic gastric juice in chyme, stops the action of
pepsin from the stomach, creates the proper pH for digestion of
Carbohydrate, proteins, triglycerides and nuclei acids
Liver Produce bile, which is required for the emulsification and absorption of
lipids in the small intestine
Gall bladder Stores and concentrates bile and releases it into the small intestine

7. ORGANS FUNCTIONS
Mouth The cheeks and lips keep food between the teeth during
mastication, and buccal gland lining the mouth produce saliva
Pharynx Receives a bolus from the oral cavity and passes it into the
esophagus
Esophagus Receives the bolus from pharynx and moves it into the stomach;
this requires relaxation of the upper esophagus sphincter and
secretion of mucus
Stomach Mixing waves combine saliva, food and gastric juice which
activates pepsin, initiates protein digestion, kills microbes in food,
helps absorb vitamin B12 , contracts the lower esophageal sphincter,
increases stomach motility, relaxes the pyloric sphincter, and
moves chyme into small intestine
Small intestine Segmentation mixes chyme with digestive juices, peristalsis
propels chyme towards the ileocecal sphincter; digestive secretions
from the small intestine, pancreas and liver complete the digestion
of carbohydrates, proteins, lipids and nuclei acids, circular folds,
villi, and microvilli help absorb about 90 percent of digested
nutrients
Large intestine Haustral churning, peristalsis and mass peristalsis drive the
colonic contents into the rectum, bacteria produce some B

8. DEFECATION
• DEFECATION IS AN EPISODIC EVENT FOR THE ELIMINATION OF THE FECES
• IT IS CONTROLLED BY THE NEUROLOGICAL REFLEX AND SPHINCTER WHICH
ORDINARILY OCCURS ONLY IN APPROPRIATE CIRCUMSTANCES AND TIMES

9. SMALL INTESTINE

10. LARGE INTESTINE

11. DEFECATION REFLEX

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