SMALL INTESTINE

 

Small intestine 

1.INTRODUCTION:-  It is continous with the stomach at the pyloric sphincter      and  leads into the large intestine at the ileocaecal valve.

2.SITUATION:-  It lies in the abdominal cavity surrounded by the large intestine 

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3.SHAPE:- Tube like structure

4.MEASURMENT:-

LENGTH: Over 5meters  long

DUODENUM:25 c.m

JEJNUM :2 meters long

ILEUM: 3 meters long

    5.ORGANS ASSOCIATED WITH DUODENUM

ANTERIOR : Gall bladder, Quadrate lobe of liver.

POSTERIOR: Bile duct,Gastroduodenal artery,portal vein, IVC, Head of Pancrease.

SUPERIOR: Neck of Pancrease,Greater omentum, Head of Pancreas.

TO THE RIGHT : Right kidney,Ascending colon.

TO THE LEFT: Left Kidney,Descending colon.

INFERIOR: Right Ureter,Left Ureter,INFERIOR VENECAVA.

6. SECTIONS:

The Small intestine comprises 3 main sections continous with each other.

v  Duodenum is 25 cm long and Curves  around the head of the pancrease.

v  Jejnum is the middle section of the Small intestine and is about 2 meters long.

v  The ileum or terminal section is about 3 meters long and ends at  the ileocaecal valve, which controls the flow of material from the ileum to the caecum ,the first part of the large intestine , prevents Regurgitation.

7. STRUCTURE OF THE SMALL INTESTINE:

The walls of the Small intestine are composed of the four layers of tissue.

Ø  PERITONEUM

Ø  MUCOSA.

           PERITONEUM:

                                    A Double layer of Peritoneum called the mesentry attaches the jejnum and ileum to the posterior abdominal wall.

           MUCOSA:

The Surface area of the small intestine mucosa is greatly increased by permanent circular folds, Villi and Microvilli.

Ø  The villi are tiny finger-like projections of the mucosal layer into the intestinal lumen, about 0.5 to 1mm long.

Ø  Their walls Consist of columnar epithelial cells (or) enterocytis . with tiny microvilli on their free border.

Ø  Goblet cells that Secrete mucus are interpersed between the enterocytes.

Ø  These epithelial cells enclose a network of blood and lymph capillaries.

Ø  The lymph capillaries are called LACTEALS because absorbed fat gives the lymph a milky appearance.

Ø  The intestinal glands are simple tubular glands situated below the surface between the villi.

        7.BLOOD SUPPLY

        ARTERIAL SUPPLY: Superior mescentric artery.

        VENOUS DRIANAGE: Superior mescentric vein that joins to the portal vein.

        8.NERVE SUPPLY:

                                    SYMPATHETIC NERVE SUPPLY.

                                    PARA SYMPATHETIC NERVE SUPPLY.

        9. INTESTINAL JUICE:

v  About 1500 ml of juice are secreted daily by the glands of the small intestine .

v  It consists of

v  Water

v  Mucus

v  Mineral salts

v  The PH of Intestinal juice is usually between 7.8 & 8.0

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