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Renin Angiotensin Mechanism.

Digestive System: Alimentary Canal Introduction.

 

Digestive System Introduction:

  • Digestion is the process of breaking large and complex food molecules into smaller and simple molecules easy for absorption, with help of digestive enzymes and acid.

  • Like other systems of the body, the Digestive system also works in coordination with other systems.

  • The branch of science that deals with the structure, function, diagnosis and treatment of stomach and intestine diseases is called Gastroenterology.

  • It consists of,

    1. Gastrointestinal Tract (Alimentary Canal):

      • Mouth,

      • Pharynx,

      • Oesophagus,

      • Stomach,

      • Small Intestine.

      • Large Intestine.

    2. Accessory Organs:

      • Teeth,

      • Tongue,

      • Salivary Glands,

      • Liver,

      • Gallbladder and Pancreas.

Activities of Digestive System:

  • Digestive system performs following major activities,

  1. Ingestion: Eating

  1. Movement of Food: Through peristalsis from mouth to anus.

  2. Digestion: Chemical and Mechanical

  3. Absorption: Entry of digested material in blood circulation.

  4. Defecation: Elimination of undigested waste.

Alimentary Canal:

  1. Alimentary canal is made up of ‘Four Types' of layers throughout its length.

  2. These layers are,

    1. Mucosa.

    2. Submucosa.

    3. Muscularis.

    4. Serosa. 

  3. These layers are in continuation with mesentery ( Double fold of peritoneal layer)

  1. Mucosa: 

  1. It is also called  “Mucous Membrane” as mucous production is one of its main functions.

  2. It is made up of three sub layers,

    • Epithelium

    • Lamina propria.

    • Muscularis mucosa.

  3. Mouth, Phyrenx, Oesophagus and anal canal contains Squamus stratified epithelium.

  4. Stomach and intestines contain Columnar epithelium off which some are modifies to “Goblet Cells” which secrete mucus.

  5. Lamina propria contains some connective tissue and is associated with lymphocytes and forms MALT ( Mucosa associated Lymphoid Tissue) which protects from food borne infections.

  6. Muscularis mucosa is a thin layer of smooth muscles responsible for folding of the stomach and intestinal tissues.

  1. Submucosa:

  1. It is a broad layer of connective tissues consisting of blood vessels and nerves.

  2. It also contains glands that secrete digestive enzymes.

  1. Muscularis:

    1. Third layer is also called “Muscularis externa”.

    2. It is a muscular layer that imparts mechanical digestion.

    3. In the upper and lower part it is made up of skeletal muscles providing voluntary control on digestion and evacuation.

    4. In the intestines it is double layer while in the stomach it is three layered.

  2. Sclerosa: 

    1. Present only on organs inside the abdominal cavity.

    2. Made of a layer of visceral peritoneum and a loose connective tissue.

    3. Main function is to keep organs in position.

    4. Instead of Serosa the mouth, pharynx and oesophagus contains a dense sheet of collagen fibers called adventitia.

Commonly Asked Questions.

  1. Define digestion and Name different parts of the Digestive System.

  2. With a well labelled diagram describe various layers of alimentary canal.
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