FUNCTIONAL ANATOMY OF STOMACH

FUNCTIONAL ANATOMY OF STOMACH

Stomach is a hollow organ situated just below the diaphragm on the left side in the abdominal cavity.

Volume of empty stomach is 50 mL. Under normal conditions, it can expand to accommodate 1 L to 1.5 L of solids and liquids. However, it is capable of expanding still further up to 4 L.

PARTS OF STOMACH

In humans, stomach has four parts:

1. Cardiac region

2. Fundus

3. Body or corpus

4. Pyloric region.

1. Cardiac Region

Cardiac region is the upper part of the stomach where esophagus opens. The opening is guarded by a sphincter called cardiac sphincter, which opens only towards stomach. This portion is also known as cardiac end.

2. Fundus

Fundus is a small domeshaped structure. It is elevated above the level of esophageal opening.

3. Body or Corpus

Body is the largest part of stomach forming about 75% to 80% of the whole stomach. It extends from just below the fundus up to the pyloric region.

4. Pyloric Region

Pyloric region has two parts, antrum and pyloric canal. The body of stomach ends in antrum. Junction between body and antrum is marked by an angular notch called incisura angularis. Antrum is continued as the narrow canal, which is called pyloric canal or pyloric end. Pyloric canal opens into first part of small intestine called duodenum. The opening of pyloric canal is guarded by a sphincter called pyloric sphincter. It opens towards duodenum. Stomach has two curvatures. One on the right side

is lesser curvature and the other on left side is greater

curvature.

STRUCTURE OF STOMACH WALL

Stomach wall is formed by four layers of structures:

1. Outer serous layer: Formed by peritoneum

2. Muscular layer: Made up of three layers of smooth muscle fibers, namely inner oblique, middle circular

and outer longitudinal layers

3. Submucus layer: Formed by areolar tissue, blood vessels, lymph vessels and Meissner nerve plexus.

4. Inner mucus layer: Lined by mucussecreting columnar epithelial cells. The gastric glands are

situated in this layer. Under resting conditions, the mucosa of the stomach is thrown into many

folds. These folds are called rugae. The rugae disappear when the stomach is distended after

meals. Throughout the inner mucus layer, small depressions called gastric pits are present. Glands

of the stomach open into these pits. Inner surface of mucus layer is covered by 2 mm thick mucus.

GLANDS OF STOMACH – GASTRIC GLANDS

Glands of the stomach or gastric glands are tubular structures made up of different types of cells. These

glands open into the stomach cavity via gastric pits.

CLASSIFICATION OF GLANDS OF THE STOMACH

Gastric glands are classified into three types, on the basis of their location in the stomach:

1. Fundic glands or main gastric glands or oxyntic glands: Situated in body and fundus of stomach

2. Pyloric glands: Present in the pyloric part of the stomach

3. Cardiac glands: Located in the cardiac region of the stomach.

STRUCTURE OF GASTRIC GLANDS

1. Fundic Glands

Fundic glands are considered as the typical gastric glands. These glands are long and tubular.

Each gland has three parts, viz. body, neck and isthmus.

Cells of fundic glands

1. Chief cells or pepsinogen cells

2. Parietal cells or oxyntic cells

3. Mucus neck cells

4. Enterochromaffin (EC) cells or Kulchitsky cells

5. Enterochromaffinlike

(ECL) cells.

Parietal cells are different from other cells of the gland because of the presence of canaliculi (singular

= canaliculus). Parietal cells empty their secretions into the lumen of the gland through the canaliculi. But, other cells empty their secretions directly into lumen of the gland.

2. Pyloric Glands

Pyloric glands are short and tortuous in nature. These glands are formed by G cells, mucus cells, EC cells and ECL cells.

3. Cardiac Glands

Cardiac glands are also short and tortuous in structure, with many mucus cells. EC cells, ECL cells and chief cells are also present in the cardiac glands.

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