Gastrointestinal Tract (Digestive System) Notes PDF/PPT


Gastrointestinal Tract

(Digestive System)



Process to converting food molecule into simpler forms so body can absorb simpler forms of food to generate energy

Gastrointestinal Tract


The gastrointestinal diagram given below represents the different parts of the tract that include the oral cavity, esophagus, stomach, intestines and the anus.


Gastrointestinal Tract Anatomy and Its Functions

  • The gastrointestinal tract in humans begins at the mouth, continuing through the esophagus, stomach, and the small and large intestines.
  • The GI tract is about 9 meters in length.
  • There are many supporting organs, such as the liver, which helps by secreting enzymes that are necessary for the digestion of food.
  • The human GI tract can be divided into two halves, namely:

1.    Upper GI tract

2.    Lower GI tract


Upper Gastrointestinal Tract


·         The upper GI consists of the following organs:



  •  It includes the teeth, tongue, and buccal mucous membranes containing the ends of the salivary glands.
  • Mouth functions by chewing the food and breaks up food particles.
  • Salivary glands produced saliva which maintain moisture and lubricates food.
  • Salivary secret Amylase and its cleaves starch



·         The pharynx is enclosed in the neck and throat.

·         Part of both the digestive system and the respiratory system.

·         Protects the food from entering the trachea and lungs.

·         Help in Swallows foods.




·         A muscular tube-like structure that functions by carrying food to the stomach.



·         Stomach is a J-shaped bag-like organ that stores the food temporarily, breaks it down, mixes and churns it with enzymes.

·         Pepsin Cleaves protein.

·         HCL Activates enzyme, breaks up food, kill germs.

·         Mucous protects stomach wall.

·         Limited absorption.


·         Liver is a large, meaty organ that situated on the right side of the belly.

·        Liver has 2 section called right and left lobes.

·        Liver function as breaks down and build up many biological molecule.

·        Store vitamin and iron.

·        Destroys old blood cells and poisons.

·        Produces bile which help process and digest fat and remove toxins.

·         Gallbladder – Store bile.


·         Pancreas is an orgen located in the abdomen.

·         Pancreas has two main function – Exocrine (digestion), another is Endocrine function.

·         Endocrine function Regulate blood glucose level.

·         Pancreas secrets hormones including insulin and glycogen also secrets enzyme such as Lipase, Amylase, Trypsin and chymotrypsin.

·         Bicarbonates neutralize stomach acid

·         Trypsin and chymotrypsin (Proteases) cleaves Protein.

·         Carboxypeptidase cleaves protein.

·         Amylase cleaves starch and glycogen.

·         Lipase cleaves lipids.

·         Nuclease cleaves nucleic acid.

Lower Gastrointestinal Tract

The lower GI consists of the following organs:


Small Intestine

·         The small intestine is a coiled thin tube, about 6 meters in length.

·         Most digestion takes place here.

·         Mucous protect gut wall

·         Absorbed Nutrients.

·         Protease cleaves proteins.

·         Sucrases cleaves sugars

·         Amylase cleaves starch and glycogen

·         Bile aids in digestion.

·         Lipase cleaves lipids.

·         Nuclease cleaves Nucleic acid.

·         The surfaces of the small intestine function by absorbing the nutrients from the food into the bloodstream, which carries them to the rest of the body.


Large Intestine

·         The large intestine, also known as the Colon,

·         It is a thick tubular organ wrapped around the small intestine.

·         Its primary function is to process the waste products.

·         Absorb any remaining nutrient, ions and water back into the system.


  • Expels waste. 


  • Opening for waste elimination.


Steps in digestion


Breakdown of food in mouth by teeth and saliva enzyme mixed on it.


Transfer of partially digested food through esophagus.


Further digestion in stomach by digestive juice.


Complete digestion and absorption in small intestine.


Assimilation of absorbed food.


Absorption of water and waste generated in large intestine.


Waste stored in Rectum and excreted out via anus.


Disease Related to Gastrointestinal systems


Gastrointestinal Tract Infection

·         Gastrointestinal infection can be caused by viruses, bacteria and parasites that cause inflammation of the gastrointestinal tract, gastroenteritis.

·         These might infect both, the stomach and the small intestine.

·         The microorganisms that can cause these infections include adenovirus, campylobacter, E.coli, Staphylococcus aureus, etc.


·         Constipation refers to infrequent or incomplete bowel movement.

·         This is caused due to inadequate fibers in the diet.

Irritable Bowel Syndrome

·         This is a condition in which the colon muscle contracts more often than in normal people.

·         It causes bloating, abdominal pains and cramps, diarrhoea, etc.

Colon Cancer

·         Colon cancer begins in the large intestine and affects older people.

·         It begins as small, non-cancerous clumps.

·         These clumps gradually convert to cancer.

·         It can be treated with surgery, chemotherapy, and radiation therapy.


·         These are swollen blood vessels that line the opening of the anus.

·          They are caused by excess pressure due to the strenuous movement of the bowel.


Gastrointestinal Tract  (Digestive System) Notes PDF

Gastrointestinal Tract  (Digestive System) Notes PPT

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