Stomach
Definition
Stomach is a dilated portion of the alimentary tract situated in the upper part of the abdomen
Structure
- Continuous with oesophagus
- through Cardiac orifice - guarded by a physiological sphincter called
cardiac sphincter.
- Continuous with duodenum
- through Pyloric orifice - pyloric sphincter
- The curved right border is called the lesser curvature
- The curved left border is called the greater curvature
Walls of the stomach
- adventitial layer: - peritoneum
the adventitial layer extends beyond the greater curvature as the greater omentum
- muscle layer:- outer longitudinal fibres, middle layer of circular fibres, an inner
layer of oblique fibres
- submucosal layer - consists of areolar tissue containing the blood vessels and lymphatics
- mucosal layer :- columnar epithelial cells - longitudinal folds of mucosa called rugae - disappear when the stomach is full. - gastric glands - gastric juice.
Parts of the stomach
- the part above the cardiac orifice fundus
- the main part body
- the lower part antrum
- pylorus
Posterior relations of the stomach
diaphragm,
spleen,
left suprarenal gland
left kidney,
anterior surface of the pancreas,
left colic flexure, and the upper layer of the
transverse mesocolon.
These structures form a shallow bed, the stomach bed
Blood supply
- coeliac artery - its branches - right and left gastric arteries and splenic artery
- splenic artery gives off left gastroepiploic artery which anastomoses
with the right gastroepiploic artery
- venous drainage into the portal vein
Nerve supply
- sympathetic supply from coeliac plexus
- parasympathetic supply from the vagus nerves
Functions
- Temporary storage allowing time for the digestive enzymes, pepsins to act
- Chemical digestion - pepsin converts proteins to polypeptides
- Mechanical digestion - the stomach contents are triturated and made into
smaller particles chyme
- Limited absorption of water, alcohol and some lipid soluble drugs.
- Non-specific defence against microbes - by hydrochloric acid , vomiting
- Helps iron absorption to be done in the small intestines.
- Production of intrinsic factor needed for absoption of vitamin B12
- Controlled release of the stored contents into the duodenum.
