**1.2. Peritoneal relations**

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

The gastrosplenic ligament: This 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

The splenorenal ligament: This 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

The phrenicocolic ligament: This ligament is a horizontal fold of peritoneum extending from the splenic flexure of the colon to the diaphragm in the midaxillary line; it forms the upper end of the left paracolic gutter.

#### **1.3. Visceral relations**

The visceral surface of the spleen is related to the following organs:


The diaphragmatic surface is related to the diaphragm, which separates the spleen from the pleura and the lung.

#### **1.4. Blood supply**

The blood supply of the spleen is by the splenic artery (in the past called the lienal artery), which is the largest branch of the celiac trunk. The artery passes through the splenorenal ligament to reach the hilum of the spleen. At the hilum, it divides into multiple branches. Within the spleen, it divides into straight vessels called penicillin, ellipsoids, and arterial capillaries.

The splenic circulation is adapted for the mechanism of separation and storage of the red blood cells. On the basis of the blood supply, the spleen has superior and inferior vascular segments. The 2 segments are separated by an avascular plane.

Apart from its terminal branches, the splenic artery gives off branches to the pancreas, 5-7 short gastric branches, and the left gastro-omental (gastroepiploic) artery (see the image below).

**Figure 3.**

#### **1.5. Venous drainage**

The principal venous drainage of the spleen is through the splenic vein. It is formed at the hilum and runs behind the pancreas then joins the superior mesenteric vein behind the neck of the pancreas to form the portal vein. Its tributaries are the short gastric, left gastroomental, pancreatic, and inferior mesenteric veins.

#### **1.6. Lymphatic drainage**

Splenic tissue proper has no lymphatics. However, a few arise from the capsule and trabeculae and drain to the pancreaticosplenic lymph nodes.

#### **1.7. Nerve supply**

Sympathetic fibers are derived from the celiac plexus.[2, 3, 4]

#### **1.8. Surface marking**

The spleen is marked on the left side of the back with the long axis of the 10th rib. The upper border is marked along the upper border of the 9th rib; the lower border, along the 11th rib. The medial end lies 5 cm from the midline, and the lateral extension is to the midaxillary line.[5]

Microscopically, the spleen is made up of 4 components: (1) supporting tissue, (2) white pulp, (3) red pulp, and (4) vascular system.

Supporting tissue is fibroelastic and forms the capsule, coarse trabeculae, and a fine reticulum.

The white pulp consists of lymphatic nodules arranged around an eccentric arteriole called the Malpighian corpuscle.

The red pulp is formed by a collection of cells in the interstices of the reticulum, in between the sinusoids. The cell population includes all types of lymphocytes, blood cells, and fixed and free macrophages. The lymphocytes are freely transformed into plasma cells, which can produce large amounts of antibodies and immunoglobulins. The vascular system traverses the spleen and permeates it.[3]
