Anatomy of Spleen and its Function
The spleen is the largest lymphoid organs in the body.
Functions of the spleen
It consists if the following functions of the spleen-
1- To filter blood by removing worn-out RBCs and microbial agents from the circulation.
2- To manufacture RBCs in metal life and lymphocytes after birth.
3- To provide immunity to the body by producing immunoglobulins M by plasma cells.
4- To store RBCs and release them in circulation when required.
Location of the spleen
The spleen in located at the left hypochondrium between the fundus of the stomach and the diaphragm, behind the midaxillary line opposite the 9th,10th and 11th ribs. Its long axis lies parallel to the long axis of the 10th rib. It moves a bit in living during respiration.
Size, Shape and Colour
The spleen is a wedge-shaped soft organs with purple colour. The size of the spleen roughly corresponds to the fist of the subject.
Measurements of the spleen are:
Thickness - 1 inch
Breadth - 3 inches
Length - 5 inches
Weight - 7 oz
External features
The spleen presents the following external features -
1- Two ends
2- Two borders
3- Two surfaces
Ends
It is divided into two ends -
Anterior end - it is a broad and is more like a Border. It is directed downward, forward and to left. It is related to the left colic flexure in front and phrenjicocolic ligaments below.
Posterior end - it is a blunt and rounded. It is directed upward, backward and medially towards the vertebral column.
It is divided into three borders-
Superior border - it is a thin and convex. It separate the visceral surface from the diaphragmatic surface.
Inferior border - it separates the visceral surface from the diaphragmatic surface.
Intermediate border - it is rounded and separates the gastric impression from the renal impression on the visceral surface.
Surfaces
It is divided into two surface -
Diaphragmatic surface - it is smooth, convex and directed upward backward and to the left.
Visceral surface - the visceral surface is concave and irregular. It presents four impression; gastric, renal, colic and pancreatic.
Peritoneal relation
The spleen is completely enclosed in the peritoneum except at its hilum, from where two peritoneal folds extends - one to the stomach and one to the left kidney, called gastrosplenic ligament and lienoranal ligament .
Visceral relation
The visceral surface of the spleen is related to the following viscera-
1- Fundus of the stomach
2- Anterior surface of the left kidney
3- Left colic flexure
4- Tail of pancreas
Arterial supply
The spleen is supplied by the splenic artery, the largest branch of the coeliac trunk. It traverses through the lienoranal ligament to reach near the hilum of the spleen, where it divides into five or more branches, which enter the spleen through its hilum to supply it.
Venous drainage
It consists of the following veins-
Short gastric veins
Left gestropiploic vein
Pancreatic vein
Inferior mesenteric vein
Nerve Supply to Spleen
The spleen is supplied by the sympathetic fibres derived from the coeliac plexus. They supply blood vessels and smooth muscle fibres present in the trabeculae and capsule.
Development
The spleen develops between the two layers of the upper parts of the dorsal mesogastrium from a number of condensation of mesenchymal cells. These separate masses of mesenchymal cells fuse together to form the lobulated spleen. The notches on the superior border of the adult spleen indicate the lobulated development of the organ.
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