Spleen is the largest single mass of lymphoid tissue in human body. It is reddish in color and oval in shape and has a notched anterior border.
Spleen lies just beneath the left half of the diaphragm close to the ninth, tenth and eleventh ribs. The long axis of the organ lies parallel to the shaft of the tenth rib. It cannot be palpated on clinical examination because its lower pole extends forward only as far as the midaxillary line.
Spleen is completely surrounded by peritoneum, which passes from it at the hilum (as the gastrosplenic ligament) to the greater curvature of stomach. Peritoneal covering also passes to the left kidney as the splenicorenal ligament.
Both these ligaments carry important structures within them. The gastrosplenic ligament carries the short gastric and the left gastroepiploic vessels, whereas the splenicorenal ligament carries splenic vessels and the tail of pancreas.
- Tail of pancreas
- Left colic flexure
- Left kidney
- Left pleura (left costodiaphragmatic recess)
- Left lung
- Ninth, tenth and eleventh ribs
Arterial blood to the spleen is supplied by the large splenic artery. It is the largest branch of the celiac artery. It has a tortuous course as it runs along the upper border of the pancreas.
Near the hilum, the splenic artery divides into about 6 small branches which enter the substance of the organ.
The venous blood from the spleen is drained by the splenic vein. It leaves the hilum and runs behind the tail and the body of the pancreas.
Behind the neck of the pancreas, the splenic vein and the superior mesenteric vein join together to form the portal vein.
The afferent lymph vessels from the organ emerge at the hilum. They pass through a few lymph nodes situated along the course of the splenic artery and ultimately drain into the celiac nodes.
The nerves are derived from the celiac plexus and they reach the organ in company with the splenic artery.