1st sem Mtech
• 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.
• Made up of:
- GI Tract and the accessory organs
• GI Tract:
• Accessory Organs:
Teeth,Tongue,Salivary Glands,Exocrine part of the
Wall Of GI Tract
Made of 4 layers:
Serous or Fibrous layer
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
• Stomach is a hollow organ situated just below the diaphragm
on the left side of the abdominal cavity.
• Specialized for accumulation of food
▫ Capable of considerable expansion (can hold 2-3L)
• Gastric juice converts food into semi solid material called
• 4 Parts of 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:
• Different cells of Fundic glands are:
▫ Mucous cells
▫ Chief cells
▫ Parietal cells
▫ Enteroendocrine cells
Functions of stomach
-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
-Gastric juice mainly acts on proteins.
-Proteolytic enzymes –pepsin and renin
-Major proteolytic enzyme .
-secreted as pepsinogen which is inactive
• Gastric Lipase:
- Weak lipatic enzyme
- Hydrolyses fats into fatty acids and glycerols
• Others are:
-urase(acts on urea,produces ammonia)
- Gelatinase-(converts gelatin to peptides)
-Gastric Amylase(Digestion of carbohydrates)
- Intrinsic factor of castle
-Thick mucus is responsible for
present in gastric juice helps in
- Necessary for the absorption of
- Deficiency leads to pernecious
protection of the gastric wall
-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
- Substances like Toxins, alkaloids
and metals are excreted through
Hcl present in the gastric juice :
- Activated the pepsinogen to
- Bacteriolytic action
- Provides the acid medium for
the actions of hormones.
• 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
- Most cells make up pancreatic acini, which produce pancreatic
• Secretes pancreatic juice into a pancreatic duct; pancreatic
duct leads to duodenum (small intestine).
Functions of pancreas
1). Digestive Functions of pancreatic juice:
a. Digestion of Proteins :
- Proteolytic enzymes: trypsin, chymotrypsin, carboxypeptidase ,
nucleases , elastase , collagenase
• stored and released as inactive form in zymogen granules
• trypsinogen is activated to trypsin by enterokinase
• trypsin then activates chymotrypsin and carboxypeptidase
b. Digestion of Carbohydrates:
• (Starch and Glycogen)
maltose and dextrin
With the help of pancreatic amylase .
c. Digestion of 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
With the help of nucleases
Consists of Islets of langerhans.(alpha cells,Beta cells and delta
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
Largest internal organ.
Location: below diaphragm / right side
also contains Kupffer’s cells (macrophages)
remove and destroy:
-worn platelets and erythrocytes
Functions Of Liver
Metabolism of monosaccharides, lipoproteins, amino
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.
Inactivation of Hormones and drugs(catabolism)
Hemolytic Function (kupffer’s cells)
Synthesis of glucose, few proteins
• 3 Parts:
-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
Functions of Small Intestine
• Secretions from SI is called succus entericus.
• Enzymes of succes entericus acts on partially digested food
and converts into final digestive products.
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
Activator Function: Enterokinase activated trysinogen to
Hemopoetic Function(intrinsic factor of castle)
Hydrolytic Function(helps in enzymatic reactions)
Secretory function(secretes enterokinase,succus entericus)
Hormonal Function (secretes GI hormones like secretin)
• Parts of Large Intestine:
cecum - nearest ileum of small intestine; (appendix is a
blind pouch in this region);
majority of length;(ascending,transverse,Descending,sigmoid)
rectum - distal region of colon;
anal canal - narrowing of rectum & opening to outside;
Reabsorbs water and electrolytes
Mucosa contains numerous tubular glands called crypts
▫ Responsible for mucus secretion
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.
• 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.
• An endoscopy is often used to confirm a diagnosis when other
devices, such as an MRI , X-ray, or CT scan are considered
- The following conditions and illnesses are most commonly
investigated or diagnosed with an endoscopy:
Irritable bowel syndrome