ANATOMY OF SPLEEN

INTRODUCTION

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• The spleen is an organ shaped like a shoe that lies relative to the 9th and 11th ribs and is located in the left hypochondrium and partly in the epigastrium.

DEVELOPMENT

• spleen develops in the cephalic part of dorsal mesogastrium (during the sixth week of intrauterine life) into a number of nodules that fuse and form a lobulated spleen

GROSS ANATOMY

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• The spleen's 2 ends are the anterior and posterior end. The anterior end of the spleen is expanded and is more like a border; it is directed forward and downward to reach the midaxillary line. The posterior end is rounded and is directed upward and backward; it rests on the upper pole of the left kidney.

BORDERS OF SPLEEN

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• The spleen's 3 borders are the superior, inferior, and intermediate. The superior border of the spleen is notched by the anterior end. The inferior border is rounded. The intermediate border directs toward the right.

SURFACES OF SPLEEN

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• The 2 surfaces of the spleen are the diaphragmatic and visceral. The diaphragmatic surface is smooth and convex, and the visceral surface is irregular and concave and has impressions. The gastric impression is for the fundus of stomach, which is largest and most concave impression on spleen. The renal impression is for the left kidney and lies between the inferior and intermediate borders.

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• The colic impression is for the splenic flexure of the colon; its lower part is related to the phrenicocolic ligament. The pancreatic impression for the tail of the pancreas lies between the hilum and colic impression

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HILUM

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• The hilum can be found on the inferomedial part of the gastric impression (see the image above). The hilum transmits the splenic vessels and nerves and provides attachment to the gastrosplenic and splenorenal (lienorenal) ligaments.

PERITONEAL RELATIONS

The spleen is surrounded by peritoneum and is suspended by multiple ligaments, as follows:

• The spleen is surrounded by peritoneum and is suspended by multiple ligaments, as follows:

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• The gastrosplenic ligament extends from the hilum of the spleen to the greater curvature of the stomach; it contains short gastric vessels and associated lymphatics and sympathetic nerves.

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• The phrenicocolic ligament is a horizontal fold of peritoneum that extends from the splenic flexure of the colon to the diaphragm along the midaxillary line; it forms the upper end of the left paracolic gutter.

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• The splenorenal ligament extends from the hilum of the spleen to the anterior surface of the left kidney; it contains the tail of the pancreas and splenic vessels.

VISCERAL RELATIONS

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• The visceral surface of the spleen contacts the following organs:
• Anterior surface of the left kidney
• Splenic flexure of the colon
• The fundus of the stomach
• Tail of the pancreas
• The diaphragmatic surface is related to the diaphragm; the diaphragm separates the spleen from the pleura and the lung.

VASCULAR SUPPLY

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• The splenic artery supplies blood to the spleen. This artery is the largest branch of the celiac trunk and reaches the spleen's hilum by passing through the splenorenal ligament. It divides into multiple branches at the hilum. It divides into straight vessels called penicillin, ellipsoids, and arterial capillaries in the spleen.

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• Its terminal branches aside, the splenic artery also gives off branches to the pancreas, 5-7 short gastric branches, and the left gastro-omental (gastroepiploic) artery.

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VENOUS DRAINAGE

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• The splenic vein provides the principal venous drainage of the spleen. It runs behind the pancreas (after forming at the hilum) before joining the superior mesenteric vein behind the neck of the pancreas to form the portal vein

LYMPHATIC DRAINAGE

• Proper splenic tissue has no lymphatics; however, some arise from the capsule and trabeculae and drain to the pancreaticosplenic lymph nodes.