The gastrointestinal tract has several major functions: 1. Motility through peristalsis and other contractions to move food through the tract. 2. Secretion of enzymes and hormones to aid in digestion. The stomach secretes 2-3 liters of gastric juice per day. 3. Digestion through the breakdown of food molecules by enzymes to allow absorption in the small intestine. 4. Absorption of digested nutrients through the intestinal walls into the bloodstream.

1. PAVITHRA M
FUNCTIONS OF
GASTROINTESTINAL TRACT

2. DIGESTIVE SYSTEM-GI TRACT

3. 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.

4. Functions of GI

5. 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.

6. 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 wavelike
muscular 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 is
thick and constriction of it avoids
the regurgitation of food above.

7.  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

8. Parts Villi and Microvilli
Small Intestine
 Duodenum-20 to 30 cm
 Jejunum- next 2/5th
 Ileum-last part

9. Intestinal Enzymes

10. Segmentation-Contractile Activity Empties in Ileocecal valve
Small Intestine

11. Large Intestine
 Cecum-Blind pouch open at one end.
 Ascending Colon
 Transverse colon
 Descending colon
 Rectum

12. Absorption-Fluid n Electrolyte
Balance
Defeacation-Rectal Pressure
Large Intestine

13. Liver
 It is positioned below the diaphragm in abdominal cavity.
 Made up of Hepatocytes
 Role-Bile secretion.
 Detoxification
 Secretion of glucose
 Secretion of plasma
protein & ketone bodies

14. Gall Bladder
 Bile is stored in the gall bladder
 Sac like organ

15. Pancreas
 Soft glandular organ containing endocrine and exocrine
secretion
 Endocrine secretion- Hormones
 Exocrine – bile juice containing enzymes and bicarbonate.

16. Regulation of Gastric Function (3 Phases)

17. Regulation of Gastric Function (3 Phases)

18. Regulation of Gastric Function (3 Phases)

19. Secretion of pancreatic juice & Bile
 It is stimulated by Ach(adrenocortico trophs) production
in brain

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

21. Carbohydrate Metabolism

22. Lipid metabolism

23. Protein Metabolism

24. INTERACTIONS

25. RECAP

26. GI FUNCTION