GIT Physiology Overview

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Questions and Answers

What is the name of the canal or tract called gastrointestinal tract?

GIT

What is the length of the gastrointestinal tract (GIT)?

5 meters

What is the term for the protective layer of the digestive tract wall?

Serosa

Which of the following is not a function of the salivary glands?

Digestion of fats Signup and view all the answers

What is the primary function of gastric HCl?

Activates pepsinogen into pepsins Signup and view all the answers

The pancreas secretes which two hormones?

Insulin and Glucagon Signup and view all the answers

What are the two main types of motility patterns in the small intestine?

Segmentation and Peristalsis Signup and view all the answers

What is the name of the mixing process occurring in the large intestine that causes the contents to be continuously mixed?

Haustration Signup and view all the answers

The total volume of GIT secretions is about ______ L/day

6-8 Signup and view all the answers

Which of the following are functions of bile salts?

All of the Above Signup and view all the answers

The gall bladder concentrates bile.

True Signup and view all the answers

Motility in the mouth are and .

Chewing or Mastication, Swallowing Signup and view all the answers

Functions of saliva are , , and __.

Lubrication, Antibacterial Action, Buffering Signup and view all the answers

Gastric HCl activates into .

Pepsinogen, Pepsins Signup and view all the answers

Bile salts combine fat soluble vitamins to form ______.

Micelles Signup and view all the answers

Pancreatic secretion contains ______, which is important for neutralizing stomach acid.

HCO3 Signup and view all the answers

Signup and view all the answers

Study Notes

GIT Physiology

The gastrointestinal tract (GIT) is a 5-meter long hollow muscular tube
Accessory glands, including salivary glands, liver and gall bladder, and pancreas, are also part of the digestive system
The GIT consists of oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus

Learning Objectives

List the parts of the GIT and their functions
Identify the structure of the digestive tract wall
Describe movements in the GIT
Describe mastication and swallowing
List the source and functions of GIT secretions

Structure of the Digestive Tract Wall

Mucosa: Inner layer with exocrine and endocrine cells
Submucosa: Connective tissue layer with blood and lymph vessels, and submucosal plexus
Muscularis Externa: Smooth muscle layer with an inner circular layer and an outer longitudinal layer, with myenteric plexus between layers
Serosa: Outer protective layer

Regulation of GIT Functions

Neural (Nervous): Enteric nervous system (local nerve plexuses) and autonomic nerves (sympathetic and parasympathetic) control secretions and motility
Hormonal: Polypeptides secreted from mucosal endocrine cells (APUD) throughout the GIT act as local hormones, regulating functions

Main Functions of Digestive Tract

Motility: Propels food from mouth to rectum
Secretion: Releases digestive juices (e.g., saliva)
Digestion: Breaks down food into absorbable molecules
Absorption: Transports nutrients, electrolytes, and water from the GIT to the bloodstream

GIT Motility

GIT smooth muscle cells have pacemaker cells (pace setters)
The basic electrical rhythm (BER) are slow wave depolarizations and repolarizations that smooth ms cells produce spontaneously.
Nerves and hormones influence the BER to reach the necessary firing level to facilitate action potential.
Smooth muscle cells form functional syncytium, where ions pass and circulate freely between adjacent cells via gap junctions

Motility of the GIT (Mouth)

Mastication: Chewing food into smaller pieces to aid swallowing
Swallowing: Transport of food from mouth to stomach. Occurs in 3 phases (buccal, pharyngeal and esophageal)

Motility of the Esophagus

The esophagus is a 25 cm muscular tube.
Upper esophageal sphincter prevents air entering GIT
Lower esophageal sphincter prevents gastric contents re-entering the esophagus
Peristalsis sweeps food down the esophagus

Motility of the Stomach

Proximal area (fundus and body) has thin walls and weak contractions for food storage (receptive relaxation)
Distal area (pylorus) has thick walls and strong peristaltic contractions to move food into the duodenum

Motility of the Small Intestine

Two main patterns: segmentation mixes contents with enzymes and other secretions, maximizes exposure for absorption and digestion
Peristalsis propels the contents into the large intestine

Motility of the Large Intestine

Hahustration: mixing contents
Mass movement: propels contents through one segment into the next downstream segment
Defecation: involves involuntary and voluntary reflexes to evacuate colonic contents through the anal canal

Secretions of GIT

The total secretion volume is approximately 6-8 liters per day arising from specialized cells lining the GI tract
Pancreas, liver, and gallbladder secrete digestive juices
GI secretions involve lubricating (water and mucus), protecting (mucus), sterilizing (HCl), neutralizing (HCO3-), and digesting (enzymes)

Secretions of GIT: Saliva

Three pairs of salivary glands: parotid, sublingual, and submandibular
Parotid glands secrete serous saliva
Sublingual and submandibular glands secrete a mix of serous and mucous saliva.
Salivary glands contribute to antibacterial action, buffering acidic materials, cleaning food remnants.

Gastric Secretions

Gastric HCL activates pepsinogens into pepsin, enhances pH for pepsin activity. It helps in protein digestion, kills bacteria, and facilitates iron and calcium absorption.
Intrinsic factor aids vitamin B12 absorption

Pancreatic Secretions

Pancreas has both endocrine and exocrine functions
Exocrine secretions (pancreatic juice) include an aqueous component containing HCO3- (neutralizing stomach acid) and an enzymatic component (trypsin, chemotrypsin, lipase, and amylase) for carbohydrate, fat, and protein digestion.

Functions of the Liver

Metabolic Regulation: Stores absorbed nutrients (vitamins) and releases them as needed.
Hematological Regulation: Produces plasma proteins and removes old red blood cells.
Production of Bile: Liver makes bile to aid fat digestion and absorption

Gall Bladder Secretion

Bile aids fat digestion. Emulsifies fats, exposes more surface area for enzymatic action, forming micelles which are water soluble and aids fat absorption
Bile has alkali content, important in neutralizing HCl in the duodenum.
Contains mucin for lubrication

Functions of the Gall Bladder

Stores and concentrates bile.
Aids in fat digestion and absorption in the intestine
Aids absorption of fat-soluble vitamins in the small intestine

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Description

This quiz covers the key components and functions of the gastrointestinal tract (GIT), including its structure, movement, and secretions. It aims to enhance understanding of the GIT's anatomy, from the oral cavity to the anus, and the physiological processes involved in digestion.