Concept about Stomach-The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.
Concept about Stomach
The stomach is a J-shaped hollow muscular bag connected to the oesophagus at its upper end and to the duodenum at the lower end just above the first part of the small intestine and below the diaphragm. One of the functions of the stomach is to serve as a mixing chamber of food and holding as a temporary reservoir.
Volume:-
The volume of stomach is 1200-1500 ml, but its capacity is greater than 3000 ml.
Curvature:-
The stomach has two curvatures:-
The lesser curvature: The concavity of the right inner curve is called lesser curvature.
The greater curvature: The convexity of the left outer curve is the greater curvature.
Parts of stomach:-
The stomach has four main regions:
1. The cardia: surrounds the superior opening of the stomach. The stomach then curves upward.
2. The fundus: The portion superior and to the left of the cardia is the fundus
3. The body: Inferior to the fundus is the large central portion of the stomach, called the body.
4. The pylorus: The narrow, most inferior region is the pylorus Between the pylorus and duodenum is the pyloric sphincter.
Layers of stomach
There are four layers of stomach wall, from the inside to out, are:
- The mucosa,
- Submucosa,
- Muscularis, and
- Serosa
Blood supply to stomach:
The stomach is supplied by a rich system of arteries derived from the celiac trunk, the first major visceral branch of the abdominal aorta. The lesser curvature of the stomach is supplied by the left and right gastric artery, which are branches of the celiac trunk and the common hepatic artery respectively
Gastric juice
About 2 liters of gastric juice are secreted daily by special secreted glands in the mucosa. It consists of:
- Water
- Mineral salts
- Mucus secreted by globlet cells in the glands and on stomach surface.
- Hydrochloric Acid (HCI)
- Intrinsic factor
- Pepsinogen is an inactive precursor of pepsin secreted by the chief cells of gastric glands.
Anatomical relations of stomach/ organs associated to the stomach:
Anteriorly:- Left lobe of the liver and abdominal wall
Posteriorly:- Abdominal aorta, pancreas, spleen, left kidney and adrenal gland
Superiorly:- Diaphragm, oesophagus and left lobe of liver
Inferiorly:-Transverse colon and small intestine.
To the left:- Diaphragm and spleen.
To the right:- Liver and duodenum.
(Ref:- W. Anne, G. Allison, Ross and wilson-Anatomy and Physiology in Health and Illness, 9 edition, P-295,296, 297)
Gastric glands contain several types of cells that secrete different products:
- Mucous neck cells, which secrete mucus (these supplement the surface mucous cells. which line the luminal surface of the stomach and the gastric pits).
- Parietal cells, which secrete hydrochloric acid (HCI),
- Chief (or zymogenic) cells, which secrete pepsinogen, an inactive form of the protein- digesting enzyme pepsin;
- Enterochromaffin-like (ECL) cells, found in the stomach and intestine, which secrete histamine and 5-hydroxytryptamine (also called serotonin) as paracrine regulators of the Gl tract,
- G cells, which secrete the hormone gastrin into the blood; and
- D cells, which secrete the hormone somatostatin.
Functions of stomach
- Mechanical or motor functions:-
- Storage of food.
- Mixing of food.
- Slow emptying of food into duodenum occurs to provide proper time for digestion and absorption by small intestine.
- Digestive functions:- Only small amount of foods are digested in stomach as:
- Carbohydrate digestion depends on the action of salivary amylase.
- Protein digestion, about 10% of ingested protein is broken down completely in the stomach. Pepsins convert proteins to polypeptides.
- Fat digestion in stomach is minimal due to the restriction of gastric lipase activity to triglycerides containing short chain (< 10 carbon) fatty acids
- Absorptive function:- Stomach contributes little in absorption function as little water, alcohol and some drugs.
- Reflex functions:- Various reflexes initiated from from the stomach are:
- Gastri-salivary reflex
- Gastro-ileal reflex
- Gastro-colic reflex and
- Presence of food in the stomach reflexly stimulates for secreting of pancreatic juice and expulsion of bile.
- Antiseptic action:- HCI present in the gastric juice kills the bacteria and other harmful substances
- Production and secretion of intrinsic factor needed for absorption of Vitamin-Bu
- Secretion of local hormone gastrin
(Ref:- K. Indu, Text book of Anatomy and Physiology for Nurses, 1″ edition P-275)
Read more: