The stomach is a muscular, elastic, pear-shaped bag, lying crosswise in the abdominal cavity beneath the diaphragm. Its main purpose is digestion of food through production of gastric juices which break down, mix and churn the food into a thin liquid.
The stomach is situated between the oesophagus and the small intestine in the
upper abdomen. The stomach is not the only part of your digestive system that
absorbs food but rather is a part of the digestive system and important for
churning food into a consistency that is easier to digest for the rest of your
intestines.
Stomach structure
The stomach can be divided into four distinct parts.
These are the cardia, fundus, corpus, and pylorus.
The
cardia is the first portion of
the stomach and is where food content passes from the oesophagus into the
stomach. The acids and enzymes referred to as the gastric juices are
manufactured in the cardia.
The
fundus stores undigested food and
also the gases released from the chemical digestion of food.
The body of the stomach or the corpus is the largest
of the four parts that make up the stomach. And this is where the bulk of the
partial digestion occurs.
The
pylorus is connected to the
duodenum or the beginning of the small intestine. The contents of the stomach
move into the small intestine via the pyloric canal.
THE STOMACH WALL
The walls of the stomach consist of four layers,
similar to other parts of the gastrointestinal tract. These layers, starting
from the innermost layer, are named mucosa, sub-mucosa, muscularis externa, and
the serosa.
The mucosa consists mainly of the gastric glands that
secrete the digestive juices. It is covered by a layer of columnar epithelial
tissue. The sub-mucosa consists of dense connective tissue and has blood
vessels, lymphatic vessels, and nerves running through it. The sub-mucosa
supports the mucosa and allows it to move in a flexible manner during peristalsis.
Peristalsis is the contraction and relaxation of the stomach
muscles to physically breakdown food and propel it forward. These contractions
are created by the muscular wall of the stomach which consists of inner circular
and outer longitudinal smooth muscle. The outermost layer of the stomach wall,
the serosa consists of an epithelial layer and connective tissue which connects
to the surrounding organs. The mucosa and the sub-mucosa are present as folds
termed rugae. When the stomach is distended with food, the rugae are flattened
out and appear smooth.
THE STOMACH cells
There are four main types of cells for stomach secretions spread all
over the inner surface of the stomach
that help with digestion:
·
Mucous cells
secrete the alkaline mucous for shielding the epithelium from hydrochloric
acid. These are found in the fundic, cardiac, and pyloric region.
·
Parietal
cells, located in the fundic, cardiac, and
pyloric region, secrete hydrochloric acid; the acid activates release of pepsin
for protein digestion. The acid also kills micro-organisms swallowed with the
food.
·
Chief cells secrete pepsin (An enzyme that splits proteins into
peptones). These cells are located in the fundic region.
·
G cells are found in the fundic, pyloric, and gastric region.
These secrete gastrin which stimulates the secretion of hydrochloric acid.
FUNCTIONS OF THE Human STOMACH
Temporary storage organ: It acts as a
temporary storage organ. Because of this, the frequency of eating is reduced.
Secretory function: It secretes HCl and pepsin
apart from other things including mucus. The G cells of pyloric region secrete
gastrin hormone which is one of the GI tract hormones.
Digestive function is because of pepsin enzyme. It is a proteolytic enzyme.
Protective function is because of high acidic medium due to presence of HCl, many of the
micro-organisms die. Thereby it protects the GI tract from getting invaded by
the microorganisms.
Hemopoietic function is because of the intrinsic factor which is secreted by gastric glands.
Intrinsic factor is essential for absorption of vitamin B12 in the ileum
region.
Absorptive function is also one of the functions
of stomach. Some amount of water and alcohol is absorbed in the stomach region.
Motor Functions of Stomach: The movement of
stomach serves important objectives namely:
It enables the stomach to act as a temporary reservoir
of food.
The movements of stomach convert solid food into a
fluid paste called chyme and delivers this in small quantities to duodenum for
proper digestion in small intestine.
Anatomical basis of gastric motility: The
movement of stomach depends on the arrangement of smooth muscle in the wall. The
arrangement is as follows:
·
Outer longitudinal muscle layer.
·
Inner circular muscle layer.
·
Oblique muscle which is inner to the circular muscle
layer and restricted to upper part of stomach.
·
The muscularis mucosa present in the submucosa.
All the muscles are supplied by vagus and sympathetic fibres.
HEALTHY HABITS FOR A HEALTHY STOMACH
Certain lifestyle habits can help you maintain stomach health and also
counter abdominal obesity. If you notice that certain food types do not agree
with you, try to keep away from them. Limit unnecessary food. If you experience
bouts of acidity, consider adding to your diet food items that are alkaline in
nature. Take walks, it aids digestion, will help you shed calories, and prevent
a condition like GERD from occurring. In fact, a sedentary lifestyle with
little or no exercise contributes to stomach-related problems.
SOME STOMACH CONDITIONS AND DISEASES
The umbrella term for stomach disease is gastropathy. Some common
stomach disorders include:
·
Dyspepsia: This is a condition characterised by a feeling of
fullness; indigestion; and pain in the upper abdomen or lower chest. Other
symptoms include nausea and vomiting. Dyspepsia can be a precursor to GERD and
may also indicate angina.
·
GERD: Gastroesophageal Reflux
Disease is a condition in which the stomach
acids rise up the oesophageal passage. Heartburn is a common symptom of the
condition.
·
Peptic Ulcers – These can occur when the protective mucous lining
of the stomach walls is damaged by the stomach acids. The bacterium,
Helicobacter pylori is thought to be an important factor in the development of
gastric and duodenal ulcers.
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