MEDICAL BIOLOGY, ANATOMY, HUMAN PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedonyuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 7. THE NUTRITIONAL PROCESS AND ITS PATHOLOGY

ANATOMY AND PHYSIOLOGY OF THE DIGESTIVE ORGANS

STOMACH

1. STRUCTURE OF THE STOMACH

The Stomach (ventriculus, gaster) is an expanded section of the digestive tract. It is located in the upper storey of the Abdominal cavity—specifically in the epigastric and left hypochondriac regions (Fig. 7.14). The size of the stomach depends on individual characteristics and its degree of filling. The dimensions of a newborn's stomach are up to 5 cm in length, whereas in an adult, they reach 25 cm. It features anterior and posterior walls. The concave margin directed upward and to the right is called the lesser curvature, while the convex margin directed downward and to the left is known as the greater curvature (Fig. 7.15). The part of the stomach adjoining the esophageal entrance is termed the cardiac part. To the left of this region lies a dome-shaped protrusion—the Cytology/practical/108.html">Fundus of the stomach (or fornix). The middle portion forms the body of the organ, and the region transitioning into the duodenum is the pyloric part.

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Fig. 7.14. PROJECTION OF THE stomach onto the anterior abdominal wall

Fig. 7.15. Stomach; anterior view

X-ray Examination reveals the following gastric shapes: a hook shape (where the stomach lies almost vertically, and its pyloric part is directed upward, to the right, and backward), a horn shape (where the stomach lies almost horizontally), and a stocking shape (where the stomach lies vertically).

The stomach wall consists of the following layers: the mucous membrane (mucosa), submucosa, muscular layer, and serous coat. The mucosa features numerous folds running in various directions (Fig. 7.16). Along the lesser and greater curvatures, these folds are longitudinal. Between the folds lie elevations known as gastric areas, which contain gastric pits. The excretory ducts of the gastric glands open into these pits, with their terminal secretory sections located within the gastric mucosa.

Fig. 7.16. Internal surface of the posterior stomach wall

There are Three types of gastric glands: proper gastric glands, cardiac glands, and pyloric glands.

The proper gastric glands are located in the region of the body and fundus of the stomach. These glands are composed of five Cell types that secrete the following products:

- pepsinogen, a proenzyme that is converted in the gastric cavity into the active form of the enzyme—Pepsin, which has The ability to hydrolyze (break down) Proteins;

- chymosin, which breaks down milk proteins and is produced primarily during childhood;

- H⁺ ions, which create an acidic environment in the stomach;

- mucus;

- BIOLOGICALLY ACTIVE SUBSTANCES that regulate (enhance or inhibit) the Synthesis and Secretion of gastric juice, gastric motility, and Blood supply, as well as regulate The activity of adjacent Organs. These substances are secreted by endocrine Cells belonging to the diffuse neuroendocrine System of the gastrointestinal tract, or the APUD system.

The cardiac and pyloric glands are located in the corresponding Regions of the stomach. Their cells produce mucus and dipeptidase Enzymes. The cardiac and pyloric glands also contain a significant number of endocrine cells belonging to the APUD system.

The muscular coat has three layers: longitudinal, circular, and oblique. In the pyloric region, the circular Muscle layer thickens to form the pyloric sphincter, while the mucosa at this site forms the pyloric valve. During contraction of the sphincter, it completely separates the gastric cavity from the duodenal cavity.

The outermost layer of the stomach is the serous coat (Peritoneum), which covers the organ on all sides, meaning it lies intraperitoneally.