This document provides an overview of the gastrointestinal system, including its main parts and functions. It discusses the digestive tract, which includes the mouth, esophagus, stomach, small intestine and large intestine. It also mentions the accessory organs that help with digestion, such as the teeth, tongue, salivary glands, pancreas, liver and gallbladder. It provides details on the layers of the GI tract wall and nerve supply. It then focuses on specific parts of the digestive system, including the stomach, pancreas, liver and intestines, outlining their structures, secretions and roles in digestion.

1. Gastrointestinal
System
By.
Aveen M
1st sem Mtech
BMSP&I
RVCE

2. Introduction
• GI System is the route through which the food enters the body.
• Normal young healthy adult consumes 1 kg of solid diet and
1-2 L of liquid diet every day.
• The food consumed cannot be utilized by the body directly.
• The process of conversion of complex food substances into
simple food substances that can be absorbed by the body is
known as Digestion.

3. Parts of Digestive System

4. • Made up of:
- GI Tract and the accessory organs
• GI Tract:
Mouth-Pharynx-Esophagus-Stomach-Small Intestine-Large
Intestine
• Accessory Organs:
Teeth,Tongue,Salivary Glands,Exocrine part of the
Pancreas,Liver,Gall Bladder.

5. Wall Of GI Tract
 Made of 4 layers:
Mucous Layer
Submucous Layer
Muscular layer
Serous or Fibrous layer

6. Nerve Supply to the GI Tract
• Two types of nerve Supply
- Intrinsic Nerve supply
- Extrinsic nerve supply
1). Intrinsic nerve supply:
- Present within the wall of GI Tract
- Fibers are interconnected and form a network called nerve
plexus. Two types :Auerbach’s Plexus and Meissner’s Plexus
2) Extrinsic Nerve Supply. :
- It is from the Autonomic Nerve System
- Both sympathetic and the parasympathetic division of the ANS

7. STOMACH

8. Introduction
• Stomach is a hollow organ situated just below the diaphragm
on the left side of the abdominal cavity.

9. • Specialized for accumulation of food
▫ Capable of considerable expansion (can hold 2-3L)
• Gastric juice converts food into semi solid material called
chyme
• 4 Parts of stomach:
▫ Cardia
▫ Fundus
▫ Body
▫ Pylorus

10. Stomach
• Gastric glands are the glands of the stomach.
• Gastric mucosa has numerous openings called gastric pits
• Gastric glands empty into bottom of pits
• The gastric glands are of three types:
-Fundic gland
-pyloric gland
-cardiac gland.

11. • Different cells of Fundic glands are:
▫ Mucous cells
▫ Chief cells
▫ Parietal cells
▫ Enteroendocrine cells

12. Functions of stomach
1).Mechanical Function:
-Storage Function: Food is stores in stomach for 3-4 hrs
-Formation of chyme: Peristalic movement of stomach mixes the
bolus with the gastric juice and forms a semislid material called
chyme.
2).Digestive Function:
-Gastric juice mainly acts on proteins.
-Proteolytic enzymes –pepsin and renin

13. • Pepsin:
-Major proteolytic enzyme .
-secreted as pepsinogen which is inactive
-Products: Proteoses,Peptones,Polypeptides.
• Gastric Lipase:
- Weak lipatic enzyme
- Hydrolyses fats into fatty acids and glycerols
• Others are:
-urase(acts on urea,produces ammonia)
-Rennin(curdles milk)
- Gelatinase-(converts gelatin to peptides)
-Gastric Amylase(Digestion of carbohydrates)

15. Functions
3).Hemopoietic Function:
4)Protective Function:
- Intrinsic factor of castle
-Thick mucus is responsible for
present in gastric juice helps in
erythropoeisis.
- Necessary for the absorption of
Vitamin B12.
- Deficiency leads to pernecious
anaemia
protection of the gastric wall
from injury,irritation.
-prevents the digestive action of
pepsin on the stomach wall.
-Alkaline in nature due to which
it protects the gastric mucosa
from Hcl of the gastric juice

16. Functions
5).Excretory Function:
6).Secretory Function:
- Substances like Toxins, alkaloids
and metals are excreted through
gastric juice
Hcl present in the gastric juice :
- Activated the pepsinogen to
pepsin
- Bacteriolytic action
- Provides the acid medium for
the actions of hormones.

17. PANCREAS

18. Introduction
• Pancreas is a glandular organ in digestive system
• Pancreas is an organ having Dual functions:
- Endocrine function (Islets of Langerhans)-production of Hormones,
secretion of insulin and glucagon onto the blood.
- Exocrine function(Acinar cells)-secretion of digestive juice called as
pancreatic juice
- Most cells make up pancreatic acini, which produce pancreatic
juice

19. • Secretes pancreatic juice into a pancreatic duct; pancreatic
duct leads to duodenum (small intestine).

20. Functions of pancreas
1). Digestive Functions of pancreatic juice:
a. Digestion of Proteins :
- Proteolytic enzymes: trypsin, chymotrypsin, carboxypeptidase ,
nucleases , elastase , collagenase
proteins
peptides;
• stored and released as inactive form in zymogen granules
• trypsinogen is activated to trypsin by enterokinase
• trypsin then activates chymotrypsin and carboxypeptidase

21. b. Digestion of Carbohydrates:
• (Starch and Glycogen)
maltose and dextrin
With the help of pancreatic amylase .
c. Digestion of Fats/Triglycerides :
• Fats/Triglycerides
2 fatty acids + monoglyceride
With the help of pancreatic lipase,colipase,cholestrol ester
hydrolase, phospholipase A and B,Bile salt-lipase.
d. Digestion of Nucleic Acids:
• Nucleic acids
nucleotides.
With the help of nucleases

22. 3).Endocrine Function:
Consists of Islets of langerhans.(alpha cells,Beta cells and delta
cells).
2). Neutralizing action of pancreatic Juice:
- Bicarbonate ions are also released to neutralize acidic chyme
entering from the stomach.
- This protects the intestine from destructive action of the acidic
chyme.

23. LIVER

24. Introduction
•
•
•
•
Largest internal organ.
Location: below diaphragm / right side
Contains hepatocytes
also contains Kupffer’s cells (macrophages)
remove and destroy:
-microbes;
-foreign matter.
-worn platelets and erythrocytes

26. Functions Of Liver

Metabolism of monosaccharides, lipoproteins, amino
acids.

Storage (glycogen, Vitamin A, B12, D, iron),
 Filtering of blood (worn blood cells and debris),
 Destruction of toxic chemicals (alcohol and drugs),
 Production/secretion of bile.

Heat Production

Hemopoetic Function

Inactivation of Hormones and drugs(catabolism)

Hemolytic Function (kupffer’s cells)

Synthesis of glucose, few proteins

27. Functions of Liver
Synthetic
functions
Immunity
Metabolic
functions
Examples
Clotting factors
Detoxification
Functions
Hormone
Inactivation
Storage
Functions
Kupffer cells
Drugs , Alcohol
Steroid
Hormones
Urea, cholesterol
Steroid binding proteins
Acute phase proteins
Protein
metabolism
Fat
Metabolism
Carbohydrate
Metabolism
Urea Synthesis
Glycogenesis
Plasma proteins
β oxidation
Enzymes
Bile
secretion
Glycogen
Vit A

28. INTESTINE

29. Small Intestine

30. • 3 Parts:
-Duodenum-nearest stomach
-Jejunum- mid-region
-Ileum- near large intestine
• Mucous membrane of SI is covered by minute projections
called as villi
• Primary site for digestion and absorption of nutrients
• Bile duct and pancreatic duct empty into duodenum

31. Functions of Small Intestine
 Digestive Functions:
• Secretions from SI is called succus entericus.
• Enzymes of succes entericus acts on partially digested food
and converts into final digestive products.

32. Functions
Digestive Function:With the help of proteolytic and
Amyloytic ,lipolytic enzyme.
Protective Function: Mucus secreted by succus entericus
protects the wall of intestine and paneth cells(secretes
defensins)
Activator Function: Enterokinase activated trysinogen to
trypsin.
Hemopoetic Function(intrinsic factor of castle)
Hydrolytic Function(helps in enzymatic reactions)
Secretory function(secretes enterokinase,succus entericus)
Mechanical Function
Absorptive Function
Hormonal Function (secretes GI hormones like secretin)

33. Large Intestine

34. • Parts of Large Intestine:
o
cecum - nearest ileum of small intestine; (appendix is a
blind pouch in this region);
o
colon –
majority of length;(ascending,transverse,Descending,sigmoid)
o
rectum - distal region of colon;
o
anal canal - narrowing of rectum & opening to outside;
•
•
•
•
Reabsorbs water and electrolytes
Eliminates waste
NO Villi
Mucosa contains numerous tubular glands called crypts
▫ Responsible for mucus secretion

35. Functions of Large Intestine
Secretion - only mucin and other inorganic substances(cl)
Absorption of water , electrolytes.
Formation of Feces –unwanted substances form feces
Bacterial flora of LI - synthesises vit B12,folic acid,vit K.
Excretory Function-Excretes heavy metals like
bismuth,mercury,lead through faeces.

36. Function TestsEndoscopies

37. Endoscope
• Endoscopy is a nonsurgical procedure used to examine a
person's digestive tract.
• Using an endoscope, a flexible tube with a light and camera
attached to it, your doctor can view pictures of your digestive
tract on a color TV monitor.

39. • An endoscopy is often used to confirm a diagnosis when other
devices, such as an MRI , X-ray, or CT scan are considered
inappropriate.
•
•
•
•
•
- The following conditions and illnesses are most commonly
investigated or diagnosed with an endoscopy:
Breathing disorders
Chronic diarrhea
Incontinence
Internal bleeding
Irritable bowel syndrome

40. Thank you