Faal Gastro

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GastrointestinalPhysiology

Irfan Idris

Physiology departmentMedical faculty of UNHAS


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LEARNING CONCEPT

STRUCTURE

GI TRACT

ORAL CAVITY

PHARYNX

ESOPHAGUSSTOMACH

SMALL INTESTINE

LARGE INTESTINE

RECTUM

ANAL CANAL

ACCESSORY

ORGANS

TONGUE

TEETH

SALIVARY GLANDS

PANCREAS

LIVER

GALL BLADDER

FUNCTION

INGESTION

DIGESTION

ABSORPTION

SECRETION

MOVEMENT


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The alimentary tract provides the body with acontinual supply of water, electrolytes, and

nutrients:

(1) movement of food through the alimentary tract;

(2) secretion of digestive juices and digestion of the

food;

(3) absorption of water, various electrolytes, and

digestive products;

(4) circulation of blood through the gastrointestinal

organs to carry away the absorbed substances;and

(5) control of all these functions by local, nervous,and

hormonal systems


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Functional Types of Movements in

the Gastrointestinal Tract

Propulsive movement : Peristalsis : a contractile ring appears around the gut and

then moves forward;

this is analogous to putting ones fingers around a thindistended tube, then constricting the fingers and slidingthem forward along the tube

Mixing movement In some areas, the peristaltic contractions themselves cause

most of the mixing. This is especially true when forward progression of the

intestinal contents is blocked by a sphincter, so that aperistaltic wave can then only churn the intestinal contents,rather than propelling them forward


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law of the gut

(usus)


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Stimulus for intestinal

peristalsis Distention of the gut

Chemical or physical irritation of theepithelial gut

Parasympathetic nervous signals


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General Principles of Alimentary

Tract Secretion Single-cell mucous glands called simply

mucous cells (goblet cells)

Pits that represent invaginations of theepithelium into the sub mucosa. In the smallintestine, these pits, called crypts ofLieberkhn

Deep tubular glands Complex glandsthe salivary glands,

pancreas, and liver


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Secretion of Water andElectrolyte

1. Nerve stimulation on basal portion of the cellmembrane, causing active transport of Cl- ions tothe inside the cell

2. The resulting increase in electronegativity insidethe cell the causes positive ions also move to theinterior of the cell

3. The excess of both these ions inside the cellcreates an osmotic force that pulls water to theinterior, thereby increasing the hydrostatic

pressure inside the cell and causing the cell toswell

4. The pressure in the cell then results in ruptures ofsecretory border of the cell causes flushing ofwater, electrolyte, and organic materials out of

the glandular cell into the lumen of the gland


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Basic Regulatory Mechanism ofGlandular Cells Effect of Local Contact

The mechanical present of food causes the glandsto secrete moderate to large quantities ofdigestive juice

Effect of enteric nervous system Tactile stimulation

Chemical irritation

Distention of the gut wall

Autonomic stimulation Parasympathetic increase the rate of secretion Sympathetic can have dual effect; increase or

decrease the secretion depend on the rate ofstimulation

Hormonal


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DIGESTION PROCESS


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Absorption of water and ion


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Absorption of Nutrients

Absorption of Carbohydrates Glucose is transported by a Sodium Co-Transport Mechanism Fructose is transported by facilitated diffusion

Absorption of Proteins sodium co-transport mechanism

Absorption of Fats monoglycerides and free fatty bile micelles

Diffusion

Absorption in the Large Intestine: Formation of Feces active absorption of sodium electrical potential gradient created by absorption of the sodium

causes chloride absorption as well


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