Stomach

STOMACH

• It is the most dilated part of digestive tube, retains food for about 3-4 hours.
• It secretes mucus, hydrochloric acid, an enzyme pepsin & a hormone gastrin.
• It allows digestion of proteins, absorption of water, glucose, alcohol & few salts.

SITUATION :-

• Stomach occupies epigastric, left hypochondriac & umbilical regions.

SHAPE :-

In the Cadaver - stomach is sickle-shaped.

In the Living - stomach is J-shaped. Presents 3 types.

• Sthenic / Normal type - ‘J’ is slightly oblique
• Hypersthenic type - ‘J’ is more oblique
• Hyposthenic / Asthenic type - ‘J’ is mostly vertical

PRESENTING  PARTS :-

2 Orifices – Cardiac & Pyloric

2 Curvatures – Lesser & Greater

2 Surfaces – Antero-superior & Postero-inferior

3 Subdivisions – Fundus, Body & Pyloric part

Cardiac  Orifice :

Situation –

• 2.5 cm left to the median plane
• Behind left 7^th costal cartilage
• Opposite T11 vertebra

Relations –

• In front- covered with peritoneum, overlapped by left lobe of liver.
• Behind- non-peritoneal bare area, connected to left crus of diaphragm by gastro-phrenic ligament.

Pyloric  Orifice :

• Thicker, movable, identified by the presence of Prepyloric vein of Mayo.

Situation –

• 1.25 cm right to the middle line
• At the lower border of L1 vertebra

Relations –

• In front- covered with peritoneum, quadrate lobe & falciform ligament of liver.
• Behind- neck of pancreas, lesser sac.

Lesser  Curvature :

• Most dependent part of the curvature is known as incisura angularis.
• Gives attachment to the lesser omentum.
• Related to the anastomosis of right & left gastric vessels.

Greater  Curvature :

Begins left to the cardiac notch

arches upwards backwards up to the left 5^th intercostal space

crosses the tip of left 10^th costal cartilage

opposite incisura angularis it bulges downwards as pyloric antrum

ends at the pyloric orifice

Gives attachment to-

• Greater omentum
• Gastro-phrenic ligament at cardiac end
• Gastro-splenic ligament opposite fundus
• Related to the anastomosis of right & left gastro-epiploic vessels.

Antero-Superior  Surface :

Relations –

• It is entirely covered with peritoneum of greater sac.
• Right part is related to-
• Left lobe & quadrate lobe of liver.
• Left upper part is related to-
• Spleen, diaphragm, left pleura, base of left lung, pericardium, heart & left costal margin.
• Left lower part is related to-
• Anterior abdominal wall, transverse colon.

Postero-Inferior  Surface :

• It is covered with peritoneum of lesser sac, except at bare area behind the cardiac end.

Relations – Stomach bed structures-

• Left crus of diaphragm
• Left supra-renal gland
• Anterior surface of left kidney
• Splenic artery
• Anterior surface of pancreas
• Anterior layer of transverse mesocolon
• Spleen

Subdivisions :

Fundus –

• Lies above a horizontal plane passing through the cardiac notch
• Extends beneath left cupola of diaphragm up to left 5^th intercostal space
• Filled with air

Body –

• Separated from pyloric part by a vertical plane passing from incisura angularis to left of pyloric antrum.

Pyloric Part –

• It is 10 cm in length
• Divided into Pyloric antrum (7.5 cm), Pyloric canal (2.5 cm)
• Both are separated by a sulcus intermedius

LIGAMENTS  OF  STOMACH :-

Lesser  Omentum :

It consists of 2 peritoneal layers.

Attachments –

• It connects lesser curvature of stomach & proximal 2.5 cm of duodenum with porta hepatis & fissure for ligamentum venosum of liver (in ‘J’ shape).
• Right side it forms right free margin where both the layers are continuous with each other.
• Left side it reflects on to the left crus of diaphragm as gastro-phrenic ligament.

Parts –

• It has 2 parts- hepato-gastric & hepato-duodenal parts.

Contents –

• Along the lesser curvature- Right gastric vessels, gastric nerves, lymph nodes.
• Within the free margin- Portal vein, bile duct, hepatic artery, plexus of nerves, hepatic lymph nodes.

Greater  Omentum :

• Largest peritoneal fold with 4 layers.
• First layer is continuous with fourth layer & second layer is continuous with third layer.
• Connects stomach to the transverse colon, also called as gastro-colic omentum.
• It presents 3 free borders – lower, right & left borders.

Attachments –

• First & second layers are attached to greater curvature of the stomach.
• Third & fourth layers are attached to transverse colon along the taenia omentalis.

Contents –

• Contains fat, areolar tissue, milky spots by fixed macrophages.
• Between first & second layers- anastomosis of right & left gastro-epiploic vessels in the form of gastric & epiploic arterial arcades.
• Between second & third layers- lesser sac in early life.
• Between third & fourth layers- anastomosis of right & left gastro-epiploic arteries.

Functions –

• It acts as a store-house of fat.
• It acts as abdominal police guard by wrapping an inflamed organ to prevent the spread of infection.

Gastro-splenic  Ligament :

It consists of 2 peritoneal layers.

Attachments –

• It connects fundus of stomach to the upper lip of hilum of spleen.
• Above it is continuous with gastro-phrenic ligament.
• Below it is continuous with greater omentum.
• Behind it is continuous with lieno-renal ligament.

Contents –

• Short gastric & left gastro-epiploic vessels.

Gastro-phrenic  Ligament :

Attachments –

• It connects the bare area behind the cardiac end of stomach to the left crus of diaphragm.

Contents –

• Left gastric artery, occasionally left supra-renal gland.

Left / Superior  Gastro-pancreatic  Fold :

• Sickle shaped peritoneal fold.
• Derived from gastro-phrenic ligament.
• Contains left gastric artery.

ARTERIAL  SUPPLY :-

Left gastric artery –

• Branch of coeliac trunk
• Runs along the lesser curvature
• Principal artery, supplies upper 2/3^rd of stomach

Right gastric artery –

• Branch of common hepatic artery
• Anastomose with left gastric artery along the lesser curvature

Short gastric artery –

• 3 – 4 in number
• Branches of splenic artery
• Supplies fundus of stomach

Left gastro-epiploic artery –

• Branch of splenic artery
• Runs along the greater curvature

Right gastro-epiploic artery –

• Branch of gastro-duodenal artery
• Anastomose with left gastro-epiploic artery along the greater curvature

Posterior gastric artery –

• Branch of splenic artery
• Supplies posterior wall of fundus

VENOUS  DRAINAGE :-

Veins correspond to the arteries.

• Right & left gastric veins drain into the trunk of Portal vein
• Short gastric & left gastro-epiploic veins drain into Splenic vein
• Right gastro-epiploic vein drains into the trunk of Superior mesenteric vein

LYMPHATIC  DRAINAGE :-

• Lymphatics form 3 sets of inter-communicating plexuses- submucous, intra-muscular & subserous.
• They drain into groups of regional lymph nodes.

From left part of stomach –

• Drain into Pancreatico-splenic & Para-cardiac lymph nodes.

From right upper 2/3^rd of stomach –

• Drain into Left gastric lymph nodes.

From right lower 1/3^rd of stomach –

• Drain into Right gastro-epiploic lymph nodes.

From pyloric part of stomach –

• Drain into Hepatic, Pyloric & Left gastric lymph nodes.

Efferents from above lymph nodes drain into Coeliac group of Pre-aortic lymph nodes.

NERVE  SUPPLY :-

Sympathetic  Supply :

Motor fibres –

• They are vasomotor in function, stimulate the pyloric sphincter & stimulate gastric musculature.

Pre-ganglionic fibres arise from T6 – T9 segments of spinal cord

pass through greater splanchnic nerves

reach coeliac plexus

Post-ganglionic motor fibres arise from coeliac plexus

reach the stomach

Sensory fibres –

• They covey painful sensations from stomach
• Their cell bodies are located in dorsal root ganglia of T6 – T9 spinal nerves.

Parasympathetic  Supply :

• Derived from vagus nerves in the form of anterior & posterior vagal trunks.

Anterior vagal trunk –

• Formed by left vagus nerve.
• Divides into hepatic & gastric branches.
• Hepatic branch supplies pre-pyloric part & pyloric sphincter of the stomach.
• Gastric branch (nerve of Latarjet) supplies antero-superior surface & pyloric antrum of the stomach.

Posterior vagal trunk –

• Formed by right vagus nerve.
• Divides into gastric & coeliac branches.
• Gastric branch (nerve of Latarjet) supplies postero-inferior surface

Motor fibres –

• They are secreto-motor in function, stimulate gastric musculature & inhibit pyloric sphincter.

Sensory fibres –

• They convey hunger & nausea sensations
• Their cell bodies are located in ganglion nodosum of vagus nerve.

APPLIED  ANATOMY :-

Traube’s  Space :

Boundaries-

• Above - left lung
• Below - left costal margin
• Right side - liver
• Left side – spleen

Clinical importance-

• It is obliterated in cases of hepatomegaly, splenomegaly & pleural effusion.

Gastric  Triangle :

Boundaries-

• Right side - lower border of liver
• Left side - left costal margin
• Below - transverse colon

Clinical importance-

• In complete oesophageal obstruction a tube is introduced in to the stomach by gastrostomy at gastric triangle for feeding the patient.

Hypertrophic  Pyloric  Stenosis :

• It is a congenital defect with neuro-muscular inco-ordination of pyloric sphincter.
• Surgical division of hypertrophied muscle is done by Ramstedt operation.

Peptic  Ulcers :

Frequent site of peptic ulcer formation in the stomach is lesser curvature, due to..

• Absence of submucous plexus of vessels, presence of long slender mucosal vessels which may get occluded frequently and produce ischaemia of mucous membrane.
• Presence of arterio-venous anastomoses in the submucous coat, cause dilatation of anastomotic channels in persistent hyperchlorhydria, shunting the blood bypassing the capillaries, produce ischaemia of mucous membrane.

Surgically it is treated by truncal or selective or highly selective vagotomy..

• Truncal vagotomy involves section of main trunks of both vagi followed by pyloroplasty or gastro-jejunostomy.
• Selective vagotomy involves section of the nerves of Latarjet of both vagi.
• Highly selective vagotomy involves denervation of only those branches of nerves of Latarjet which supply acid-bearing area.

Carcinoma  of  Stomach :

• It usually spread towards the oesophagus but does not extend into the duodenum, as the lymphatics of stomach are continuous with the oesophageal lymphatics.