DIGESTIVE SYSTEM PART -2

DEMONSTRATION

STOMACH

The stomach is the widest and most distensible part of the alimentary canal between the esophagus and the duodenum.

FUNCTION

The main functions of stomach are:

•1. Forms a reservoir of food.

•2. Mixes food with gastric secretions to form a semifluid substance called chyme.

•3. Hydrochloric acid secreted by the gastric glands destroys bacteria present in the food and drink.

Shape & Size

The stomach is mostly “J” shaped.

•Size and Capacity Length: 10 inches.

Capacity.

The capacity of the stomach is variable as the stomach is highly distensible.

•1. At birth the capacity is only 30 ml (1 ounce).

•2. At puberty the capacity is 1000 ml (1 L). •3. In adults the capacity is 1500 to 2000 ml.

EXTERNAL FEATURES

•1. Two ends: Cardiac and pyloric.

•2. Two curvatures: Greater and lesser.

•3. Two surfaces: Anterior (anterosuperior) and posterior (posteroinferior).

PARTS

The stomach has four parts:

  1. Cardiac part (or cardia).
  2. Fundus.
  3. Body.
  4. Pyloric part.

Visceral Relations

1. Relations of the anterior (anterosuperior) surface:

  1. The right side of this surface is related to the gastric impression of the left lobe of  liver and near the pylorus to the quadrate lobe of liver.
  2. The left half of this surface is related to the diaphragm and rib cage.
  3. The lower part of this surface is related to the anterior abdominal wall.

2. Relations of the posterior (posterio -inferior) surface:

This surface is related to a number of structures on the posterior abdominal wall which collectively form the stomach bed.

•These structures are.

  1. Diaphragm.
  2. Left kidney.
  3. Left suprarenal gland.
  4. Pancreas.
  5. Transverse mesocolon.
  6. Left colic flexure (splenic flexure of colon).
  7. Splenic artery.
  8. Spleen.

ARTERIAL SUPPLY

The stomach has rich arterial supply derived from the coeliac trunk and its branches.

•1. Left gastric artery, a direct branch from the coeliac trunk.

•2. Right gastric artery, a branch of the common hepatic artery.

•3. Left gastroepiploic artery, a branch of the splenic artery.

•4. Right gastroepiploic artery, a branch of the gastroduodenal artery.

•5. Short gastric arteries (five to seven in number), branches of the splenic artery.

VENOUS DRAINAGE

The veins of the stomach correspond to the arteries and drain directly or indirectly into the portal vein.

•1. Left gastric vein.

•2. Right gastric vein.

•3. Left gastroepiploic vein.

•4. Right gastroepiploic vein.

•5. Short gastric veins.

NERVE SUPPLY

The stomach has both sympathetic and parasympathetic innervation.

Sympathetic Innervation The sympathetic fibers are derived from T6 to T10 spinal segments via greater splanchnic nerves, and coeliac and hepatic plexuses.

Parasympathetic Innervation The parasympathetic fibers are derived directly from the vagus nerves.

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