Stomach
STOMACH
The stomach is a muscular bag forming the widest and most distensible part of the digestive tube.
Definition
The stomach is also called:
- Gaster (Greek: belly)
- Venter
- From gaster, the adjective gastric is applied to structures related to the organ.
The stomach is a muscular bag forming the widest and most distensible part of the digestive tube.
It is connected:
- Above → to the lower end of the oesophagus
- Below → to the duodenum
It acts as a reservoir of food and helps in digestion of:
- Carbohydrates
- Proteins
- Fats.
Functions of Stomach
-
Acts primarily as a reservoir of food.
- Also acts as a mixer of food.
- Softens and mixes food with gastric juice.
- Produces gastric juice containing enzymes that play an important role in digestion of food.
- Produces hydrochloric acid, which destroys many organisms present in food and drink.
- Produces abundant mucus, which protects the gastric mucosa against the corrosive action of hydrochloric acid.
-
Absorbs:
- Alcohol
- Water
- Salt
- A few drugs
- Produces the intrinsic factor of Castle, which helps in absorption of vitamin B12.
Location
The stomach lies obliquely in the upper and left part of the abdomen.
It occupies
Epigastric region
Umbilical region
Left hypochondriac region
Costal and rib relation
Most of it lies under cover of the left costal margin and ribs.
Shape and Position
The shape of the stomach depends upon:
- Degree of distension of its muscles
- Tone of muscles of the body.
Normal active persons (sthenic)
Its shape is somewhat J-shaped.
Thin, tall persons (hyposthenic)
Its shape is J-shaped.
Broad, strong and very active persons
Its shape is horizontal.
Size and Capacity
Length
About 25 cm.
25 cm Long Structures
Oesophagus
Stomach
Duodenum
Ureter
Capacity
The stomach is a very distensible organ.
| Stage | Capacity |
|---|---|
| At birth | 1 ounce (30 ml) |
| At puberty | 1 litre (1000 ml) |
| In adults | 1–1.5 litres (1000–1500 ml) |
External Features
The stomach has:
1. Two orifices
- Cardiac
- Pyloric
2. Two curvatures
- Lesser
- Greater
3. Two surfaces
- In distended stomach → anterior and posterior
- In empty stomach → superior and inferior.
Anatomical Position
Hold the stomach in such a way that:
- The stomach is flat anteroposteriorly.
- The concave lesser curvature faces to the right.
- The convex greater curvature faces to the left and inferiorly.
- The thick pyloric end is directed downward and to the right.
- The cardiac or upper end lies at a higher level and to the left than the pyloric end.
Two Orifices / Ends
1. Cardiac Orifice
- Joined by the lower end of the oesophagus.
- Lies behind the left 7th costal cartilage, 2.5 cm from its junction with the sternum.
- Located at the level of vertebra T11.
- There is physiological evidence of sphincteric action at this site.
- A sphincter cannot be demonstrated anatomically.
2. Pyloric Orifice
- Opens into the duodenum.
- Its position is indicated on the surface of the stomach by:
a. Pyloric constriction
- A circular groove produced by the underlying pyloric sphincter or pylorus.
- Pylorus = gate guard.
- The pyloric constriction feels like a large firm nodule.
b. Prepyloric vein of Mayo
Lies in front of the constriction.
Position
In an empty stomach and in the supine position:
- Lies 1.2 cm to the right of the median plane.
- At the level of the lower border of vertebra L1 or transpyloric plane.
Two Curvatures
1. Lesser Curvature
- Concave.
- Forms the right border of the stomach.
- Provides attachment to the lesser omentum.
- The most dependent part is marked by:
- Angular notch
- Incisura angularis
2. Greater Curvature
- Convex.
- Forms the left border of the stomach.
- At its upper end, presents the cardiac notch.
- Cardiac notch separates the stomach from the oesophagus.
- Provides attachment to:
- Greater omentum
- Gastrosplenic ligament
- Gastrophrenic ligament.
Two Surfaces
1. Anterior / Anterosuperior Surface
- Faces forwards and upwards.
- Related to greater sac.
2. Posterior / Posteroinferior Surface
- Faces backwards and downwards.
- Related to lesser sac of peritoneal cavity.
Parts of Stomach
The stomach is divided into 4 parts:
1. Fundus
2. Body
3. Pyloric antrum
4. Pyloric canal
Lines Dividing the Stomach
- A horizontal line at the level of the cardiac notch extends to the greater curvature.
- A slightly oblique line extends from the incisura angularis to a notch on the left side of the pyloric antrum on the greater curvature.
- Sulcus intermedius is an occasional sulcus between the pyloric antrum and pyloric canal.
1. Fundus
- Upper convex part of the stomach.
- Lies above the horizontal line passing through the cardiac notch to the greater curvature.
2. Body
- Lies between the fundus and pyloric antrum.
- Separated from the pyloric antrum by a slightly oblique line extending to the left from the incisura angularis to the greater curvature.
3. Pyloric Antrum
- Separated from the pylorus by the sulcus intermedius.
- About 7.5 cm long.
4. Pylorus / Pyloric Canal
- About 1–2 cm long.
- Narrow, tubular part.
- Continues with the duodenum at its right end.
Traube’s Area
Traube’s area is the area overlying the fundus of the stomach.
It is tympanic on percussion.
Boundaries
Superiorly
Lower border of left lung
Inferiorly
Left costal margin
On the left
Spleen
On the right
Lower border of the left lobe of liver
Clinical Note
Traube’s space shows a dull note on percussion in case of:
- Pleural effusion
- Splenomegaly.
Relations of Stomach
Peritoneal Relations
- The stomach is lined by peritoneum on both surfaces, except:
- Where the vessels run along its curvatures
- Bare area of the stomach.
Bare Area of Stomach
- Small area devoid of peritoneum.
- Comes in direct contact with the left crus of diaphragm.
- Located near the cardiac end on the posterior surface.
Folds of Peritoneum Extending from Stomach
1. Lesser omentum
Extends from lesser curvature to the liver.
2. Greater omentum
Extends downward from greater curvature.
3. Gastrosplenic ligament
Extends from upper part of greater curvature to the spleen.
4. Gastrophrenic ligament
Extends from fundus of stomach to the diaphragm.
- Gastrophrenic ligament
- Gastrosplenic ligament
- Greater omentum from above downwards.
Relations of Anterior Surface
The anterior surface of the stomach is related to:
- Liver
- Diaphragm
- Anterior abdominal wall
The diaphragm separates the stomach from:
- Left pleura
- Pericardium
- 6th to 9th ribs
- Costal cartilages.
Areas of Anterior Surface
The anterior surface gives:
- Area related to liver
- Area related to diaphragm
- Area related to abdominal wall.
Relations of Posterior Surface / Stomach Bed
The posterior surface of the stomach is related to structures forming the stomach bed.
All these structures are separated from the stomach by the cavity of the lesser sac.
Structures of Stomach Bed
1. Diaphragm
2. Spleen
3. Left kidney
4. Left suprarenal gland
5. Pancreas
6. Transverse mesocolon
7. Left colic flexure
8. Splenic artery
- All structures of the stomach bed are separated from the stomach by the cavity of the lesser sac, except the spleen, which is separated from the stomach by the cavity of the greater sac.
- Gastric nerves and vessels ramify deep to the peritoneum.
Blood Supply
Arterial Supply
The stomach is supplied by the following arteries:
1. Left gastric artery
Branch of coeliac trunk.
2. Right gastric artery
Branch of common hepatic artery.
3. Left gastroepiploic artery
Branch of splenic artery.
4. Right gastroepiploic artery
Branch of gastroduodenal artery.
5. Short gastric arteries
5–7 in number; branches of splenic artery.
6. Posterior gastric artery
Branch of splenic artery.
Venous Drainage
The venous blood from the stomach is drained by:
- Left gastric vein
- Right gastric vein
- Left gastroepiploic vein
- Right gastroepiploic vein
- Short gastric veins
- Posterior gastric vein.
Lymphatic Drainage
Lymphatics from the stomach follow the course of the arteries supplying the stomach.
Lymph Nodes
1. Left paracardial nodes
2. Lesser curvature nodes
3. Right paracardial nodes
4. Left gastric nodes
5. Short gastric nodes
6. Left gastroepiploic nodes
7. Splenic hilar nodes
8. Splenic nodes
9. Right gastroepiploic nodes
10. Infrapyloric nodes
11. Suprapyloric nodes
12. Common hepatic nodes.
Four Lymphatic Territories of Stomach
Lymphatics from the stomach follow 4 territories.
The stomach is divided into:
- Right 2/3rd
- Left 1/3rd
This division is made by its long axis.
Each area is further divided into upper and lower areas.
- Upper 2/3rd part of right 2/3rd of stomach.
- Largest area.
- Lies along the lesser curvature.
- Drains into left gastric nodes.
- Lower 2/3rd part of left 1/3rd of stomach.
- Lies along:
- Pyloric antrum
- Pyloric canal
- Greater curvature of stomach
- Drains into:
- Right gastroepiploic nodes
- Pyloric nodes
- It is the most common site for gastric carcinoma.
- Upper 1/3rd of left 1/3rd area of stomach.
- Drains into pancreaticosplenic nodes.
- Lower 1/3rd of right 2/3rd of stomach.
- Includes:
- Pyloric antrum
- Pyloric canal along lesser curvature of stomach
- Drains into:
- Right gastric nodes
- Hepatic nodes.
Final Lymphatic Pathway
- Lymph from all areas of the stomach ultimately reaches the coeliac nodes.
- From here, it passes through the intestinal lymph trunk to reach the cisterna chyli.
Nerve Supply
The stomach is supplied by:
Sympathetic nerves
Parasympathetic nerves
Sympathetic Innervation
- Sympathetic nerves are derived from T6–T10 of the spinal cord.
- They pass via:
- Greater splanchnic nerves
- Coeliac plexus
- Hepatic plexus
- They travel along the arteries supplying the stomach.
Functions
- Vasomotor
- Motor to pyloric sphincter, but inhibitory to the rest of the gastric musculature.
- Chief pathway for pain sensations from the stomach.
Parasympathetic Innervation
- Parasympathetic nerves are derived from the vagi.
- They pass through:
- Oesophageal plexus
- Gastric nerves
Anterior Gastric Nerve
- Made up of one or two trunks.
- Contains mainly the left vagal fibres.
- Also called anterior nerve of Latarjet.
- Divides into:
a. Gastric branches
A number of branches for the anterior surface of:
- Fundus
- Body of stomach
b. Pyloric branches
Two branches:
- One for pyloric antrum
- Another for pylorus
Posterior Gastric Nerve
- Made up of one to two trunks.
- Contains mainly the right vagal fibres.
- Also called posterior nerve of Latarjet.
- Divides into:
a. Gastric branches
Smaller branches for the posterior surface of:
- Fundus
- Body
- Pyloric antrum
b. Coeliac branches
Larger branches for the coeliac plexus.
Functions of Parasympathetic Fibres
- Vasodilation
- Motor to gastric musculature; inhibitory to pyloric sphincter
- Carry sensation of:
- Hunger
- Nausea.
Interior of Stomach
The interior of the stomach shows thick, soft and velvety mucosa.
1. Gastric Rugae / Gastric Folds
- Mucosal folds present in an empty stomach.
- Longitudinal along the lesser curvature.
- Irregular elsewhere.
- Rugae disappear (flatten) on distention of stomach.
2. Gastric Pits
- Surface of mucosa shows small depressions.
- These are openings of gastric glands.
3. Gastric Canals / Magenstrasse
- Longitudinal mucosal folds or rugae along the lesser curvature.
- They extend from the cardiac orifice to the pyloric antrum.
- They give passage to the fluid content of food without encountering other parts of the stomach.
Z-Line
Z-line is a line of demarcation at the gastroesophageal junction.
It separates:
- Pale-coloured oesophageal mucosa → lined by stratified squamous epithelium
- Pink-coloured gastric mucosa → lined by tall columnar epithelium
Z-line is a circumferential zigzag line.
- The lesser curvature gets maximum exposure to swallowed foods and drinks.
- This makes it more vulnerable to peptic ulcers.
Muscle Layers of Stomach
The muscle coat consists of 3 layers:
Inner layer
→ oblique fibres
Middle layer
→ circular fibres
Outer layer
→ longitudinal fibres