EMBRYOLOGY, BLOOD SUPPLY AND RELATED SURGICAL ANATOMY

OF STOMACH (Ventriculus, Gaster)

Dr. MVR SarmaDept. of Anatomy

GSL Medical CollegeRajahmundry

Stomach – organ of 2nd phase of digestion

The stomach is a muscular, hollow, dilated part of the digestion system, which functions as an important organ of the digestive tract.

It is involved in the second phase of digestion, following mastication (chewing).

The stomach is located between the esophagus and the small intestine.

Stomach – Embryonic foldings

The trilaminar embryonic plate undergoes four foldings to produce the ultimate three dimensional embryo.

Stomach – Formation of primitive gut

During the cephalocaudal and lateral folding of embryo, a portion of the endoderm lined yolk sac is incorporated into the embryo to form the primitive gut.

ForegutMidgut

Hindgut

Subdivisions ofprimitive gut

Foregut Midgut Hindgut

Embryonic extension of GIT

2 – 3 weeks (IUL)

The gastrointestinal tract (GIT) extending from the

Buccopharyngeal membrane to the Cloacal membrane

arises initially from the endoderm of the trilaminar embryo.

It later has contributions from all the germ cell layers.

Stomodeum

Cloacal membrane

Septumtransversum

Foregut

Midgut

Hindgut

Divisions of foregut : Derivatives of foregut

Larygo-tracheal groove

Pre laryngeal (Cephalic part)

Post laryngeal (Caudal part)

Foregut

OesophagusStomach

Duodenal segmentOff shoots – liver

(biliary apparatus) & Pancreas

Development of stomach

The stomach appears as a dilation of the foregut caudal to the esophagus during the fourth week of development.

Stomach

Oesophagus

Intestines

Buccopharyeal membrane

Cloacal membrane

Ventral(Anterior)

Dorsal(Posterior)

RL

Position adjustment of stomach

Descent-Due to rapid elongation of the esophagus,

the cardiac end of the stomach descends from C2 at 4 weeks to T11 at 12 weeks As stomach enlarges, it slowly rotates through 90 degrees,

Axes of stomach

The stomach evolves by two rotations along a 1. Longitudinal and

02. Anteroposterior axis.

Longitudinal axis

Anteroposterioraxis

1st Rotation – on longitudinal axis

The longitudinal rotation of the stomach involves a 90° clockwise rotation resulting in the right side of the stomach becoming posteriorly oriented and the left side of the stomach facing anteriorly.

Change of position of vagii

This explains why the left vagus nerve innervates the anterior wall of the stomach and the right vagus nerve innervates the posterior wall of the stomach in the adult.

2nd Rotation – positioning of fundus & duodenum

The stomach subsequently rocks on its longitudinal axis, causing the pylorus to shift to right and the cardiac orifice to shift to the left.

Positioning of stomach

• Initially the two ends of the stomach lie in the midline.

• During rotation:– the cranial end moves to

the left and slightly downward.

– the caudal end moves to the right and upward.

• After rotation, stomach assumes its final

position with its long axis running from above left to below right.

Formation of curvatures – during Rotation

During this rotation one side of the stomach grows faster than the other forming the greater and lesser curvatures of the stomach

Oesophagus

Intestines

Stomach

Less

er c

urva

ture

Gre

ater

cur

vatu

re

Mesenteries – Development of omentumDevelopment of omentum

• Ventral border of stomach – connected with anterior body wall by ventral mesogastrium

• Dorsal border of stomach - connected with posterior abdominal wall by dorsal mesogastrium.

Dorsal mesogastrium

Ventralmesogastrium

Mesenteries – Development of omentum

Hepatic bud divides ventral mesogastrium into

1) Lesser omentum 2) Falciform & coronary ligament.Developing spleen divides the

dorsal mesogastrium into 1) Gastro-splenic ligament 2) Lieno-renal ligament .

Lienorenal Ligament

GastrosplenicLigament

Lesseromentum

FalciformLigament

Omental bursa – Lesser sac

Begins as small isolated clefts in the dorsal mesogastrium, that soon join to form a single cavity

Rotation of stomach pulls the dorsal mesogastrium to the left thus enlarging the cavity

The bursa expands transversely and cranially and lies between the stomach and the posterior abdominal wall

Omental bursa – Lesser sac

The superior part of the bursa is cut off as the diaphragm develops. Inferiorly it persists as the superior recess of the omental bursa

The inferior part grows Within the 4-layered greater omentum forming the inferior recess of the omental bursa.

The inferior recess later on closes down because of fusion of the layers of the greater omentum.

Stomach - Arterial supply

Factors demanding rich vascularity:

1. Highly distensible & mobile area in GI Tract (Frequent changes in volume)2. Five types of cells – High metabolic activity3. 2nd phase of digestion – Brisk peristalsis4. Three layers of sheets of muscles.5. Propulsive pressures against pyloric sphincter and physiological oesophageal sphincter.

Coeliac trunk : Direct anterior branch from aorta is main source of arterial supply.

Stomach - Blood supply

Arterial arcade

Subserosal plexus

Intramuscular plexus

Sub mucosal plexus

Mucosal plexus

Mucosal capillaries

Along the lesser and the greater curvature of stomach

Patch of mucosa is prone to vascular

obstruction

They do not anastomose with each other

Stomach – Venous drainage

Parts of stomach

Anterior relation of Stomach

Stomach bed

Structures & factors maintaining Intra abdominal position of stomach

1.Oesophagus2.Duodenum3.Lesser omentum4.Phrenico colic lig.5.Gastro splenic lig.6.Blood vessels – Coeliac trunk7.Veins, Lymphatics & Nerves8.Structures forming stomach bed9.Liver, spleen and diaphragm 10.anterior and lateral abd. Wall11.Intra abdominal pressure.

Omenta & ligaments of stomach

Anomalies of Stomach

01. Malrotation of stomach

02. Changes in shapes of stomach

03. Variation of origin of blood vessels

04. Congenital hypertrophic pyloric stenosis

Some of the recorded variations Gastroduodenal artery

Some of the recorded variationsCoeliac trunk

Malrotation of Stomach - Volvulus

Gastric volvulus or volvulus of stomach a twisting of all or part of the stomach by more than 180 degrees with obstruction of the flow of material through the stomach, variable loss of blood supply and possible tissue death.

The twisting can occur around the long axis of the stomach

- organoaxial or

around the axis perpendicular to this

- mesentericoaxial.

About one third of volvulus cases are associated with hiatus hernia.

Malrotation of Stomach - Volvulus

Gastric volvulus is a rare but potentially life-threatening clinical entity due to possible gastric necrosis.

A wandering spleen may also be associated with gastric volvulus.

Clinical features - Volvulus

Borchardts triad: 1. Severe epigastric pain

02. Vomiting followed by violent retching with inability to vomit

03. Inability to pass NGT

Volvulus - Organoaxial

The stomach rotates around an axis that connects the Gastro-esophageal junction and the pylorus.

Antrum rotates in opposite direction to the fundus of stomach

Comprises 59% of cases of gastric volvulus.

Obstruction is common in organoaxial volvulus

Short axis

Antrum

Volvulus - Mesentericoaxial

The axis bisects the lesser and greater curvatures.

The antrum rotates anteriorly and superiorly so that the posterior surface of the stomach lies anteriorly

Comprises 29% of cases of gastric volvulus.

Ischaemia is common in mesentericoaxial volvulus.

Greatercurvature

Long axisLessercurvature

Volvulus – Combined rotation

A

A

AB

B

B

Department of AnatomyGSL Medical College

Rajahmundry