PAVITHRA M

FUNCTIONS OF GASTROINTESTINAL TRACT

DIGESTIVE SYSTEM-GI TRACT

The Major functions - GI Tract

1.Motility: This refers to the movement of food through digestive

tract through the processes of

a. Ingestion: Taking food into the mouth.

b. Mastication: Chewing the food and mixing it with saliva.

c. Deglutition: Swallowing food.

d. Peristalsis and segmentation: Rhythmic, wavelike

contractions (peristalsis), and mixing contractions in different

segments (segmentation), move food through the

gastrointestinal tract.

2. Secretion: This includes both exocrine and endocrine secretions.

a. Exocrine secretions: Water, hydrochloric acid, bicarbonate,

and many digestive enzymes are secreted into the lumen of the

gastrointestinal tract.The stomach alone, for example, secretes

2 to 3 liters of gastric juice a day.

b. Endocrine secretions: The stomach and small intestine

secrete a number of hormones that help to regulate the

digestive system

3. Digestion:

This refers to the breakdown of food molecules into their

smaller subunits, which can be absorbed.

4. Absorption:

This refers to the passage of digested end products into the

blood or lymph.

5. Storage and elimination:

This refers to the temporary storage and subsequent

elimination of indigestible food molecules.

6. Immune barrier:

The simple columnar epithelium that lines the intestine,

with its tight junctions betweencells, provides a physical

barrier to the penetration of pathological organisms and

their toxins. Also, cells of the immune system reside in the

connective tissue located just under the epithelium to

promote immune responses.

Functions of GI

Layers of GI Tract

Mucosa: It is absorptive and major secretory layer. Goblet cells in mucosa secrete Mucus.

Sub mucosa: Thick,vascular layer. it Contains glands and nerve plexuses.Muscalaris(circular muscle): Segmental contractions ,peristaltic movement. Provides major nerve supply to the entire GI tract.Serosa: Outer complete layer and protective wall of the GI tract.

Oesophagus

The oesophagus is the portion of the GI tract that connects the pharynx to the stomach.

Movement of food from mouth to stomach occurs through the peristaltic movement of oesophagus. Peristalsis is the wavelikemuscular contractions occurs because of the circular smooth muscle contracts behind and relaxes in front to push the bolus along the GI tract. Lower oesophageal sphincher isthick and constriction of it avoidsthe regurgitation of food above.

Structure of stomach J-shaped most distensible part of

GI tract. Notice that pyloric region is the

widest and ends with pyloric sphincter.

Functions The functions of the stomach are

to store food, to initiate the digestion of proteins, to kill bacteria with the strong acidity of gastric juice, and to move the food into the small intestine as a paste material called chyme.

Stomach

Parts Villi and Microvilli

Small Intestine

Duodenum-20 to 30 cmJejunum- next 2/5th Ileum-last part

Intestinal Enzymes

Segmentation-Contractile Activity Empties in Ileocecal valve

Small Intestine

Large Intestine

Cecum-Blind pouch open at one end.Ascending ColonTransverse colonDescending colonRectum

Absorption-Fluid n Electrolyte Balance Defeacation-Rectal Pressure

Large Intestine

Liver

It is positioned below the diaphragm in abdominal cavity.Made up of HepatocytesRole-Bile secretion.DetoxificationSecretion of glucoseSecretion of plasma protein & ketone bodies

Gall Bladder

Bile is stored in the gall bladderSac like organ

Pancreas

Soft glandular organ containing endocrine and exocrine secretion

Endocrine secretion- HormonesExocrine – bile juice containing enzymes and

bicarbonate.

Regulation of Gastric Function (3 Phases)

Regulation of Gastric Function (3 Phases)

Regulation of Gastric Function (3 Phases)

Secretion of pancreatic juice & Bile

It is stimulated by Ach(adrenocortico trophs) production in brain

Trophic effect of the GI tract

Trophic effect of the GI tract is the production of gastrin once digestion starts – gastric mucosa is secreted.

Carbohydrate Metabolism

Lipid metabolism

Protein Metabolism

INTERACTIONS

RECAP

GI FUNCTION