The spleen is an organ located in the upper left abdomen, which is approximately the size of a clenched fist. In the adult body, the spleen's main role is to act as a filter to remove old red blood cells from the bloodstream, but it also contributes to both cell-mediated and humoral immune responses.
This article will discuss the anatomy of the spleen, including its anatomical position, structure, vasculature, and clinical relevance.
The spleen is situated in the upper left quadrant of the abdomen, tucked away and hidden from view. It is covered by the diaphragm, ribcage, and peritoneum - all of which obstruct its palpability during physical examination. This also means that, unless it is enlarged, it cannot be felt. It is an intraperitoneal organ, which means that it is surrounded by the peritoneum, with the exception of the splenic hilum.
The spleen is connected to the stomach and kidney by parts of the greater omentum - the double fold of peritoneum that originates from the stomach. In particular, it is connected by the gastrosplenic ligament (which lies anterior to the splenic hilum) to the greater curvature of the stomach, and the splenorenal ligament (which lies posterior to the splenic hilum) to the left kidney. This latter ligament also contains the splenic vessels and tail of the pancreas. In between these two ligaments is the lesser sac.
The spleen is egg-shaped. It is protected by a soft capsule that does not inhibit its ability to expand when needed. Its outer surface can be broken down into two parts: the diaphragmatic surface, which is the area in contact with the diaphragm and ribs; and the visceral surface, which is the surface in contact with the other abdominal organs. The spleen contains anterior, superior, posteromedial and inferior borders, with smooth posteromedial and inferior borders, and notched anterior and superior borders. If the spleen becomes enlarged (a condition known as splenomegaly), the superior border moves inferiorly and the notches can be felt.
The spleen is located in close proximity to several other internal structures in the abdomen. Its anterior border borders the stomach, its posterior abuts the diaphragm, the left lung, and ribs 9 to 11. Its inferior border is adjacent to the left colic flexure (splenic flexure). And its medial border is positioned beside the left kidney and the tail of the pancreas.
The spleen is highly vascular, and its arterial supply is mainly provided by the splenic artery, which runs laterally along the superior aspect of the pancreas within the splenorenal ligament. The splenic artery branches out into five vessels once it reaches the spleen, each of which supplies a different portion of the organ. These vessels do not anastomose (connect) with each other, thus forming vascular segments that can be surgically removed whilst preserving the other areas (known as a subtotal splenectomy).
Venous drainage of the spleen is provided by the splenic vein, which then joins forces with the superior mesenteric vein to become the hepatic portal vein.
The nerve supply to the spleen is provided by the coeliac plexus.
The lymphatics of the spleen run along the same vessels as the arterial branches, and then drain into the pancreaticosplenic lymph nodes and the coeliac nodes.
The spleen is the abdominal organ with the highest risk of injury. A splenic rupture occurs when there is a tear or break in its fibroelastic membrane, disrupting the parenchyma below. This tear can be caused by either blunt or penetrating trauma, and is often associated with left rib fractures.
As the spleen is highly vascular, its rupture can result in massive bleeding into the peritoneal cavity. To address this potential fatal issue, a surgical procedure known as a splenectomy may be employed to remove the affected organ. Splenectomy is only carried out when the injury to the spleen and subsequent haemorrhage are life-threatening.
The spleen is an intraperitoneal organ located in the left hypochondriac region of the abdominal cavity. It is connected to the stomach and kidney by parts of the greater omentum, a double fold of peritoneum that originates from the stomach. It is protected by the rib cage and is surrounded by the greater omentum and the gastrosplenic and splenorenal ligaments. At rest, the spleen measures approximately 12–15 cm in length and weighs around 150–200 g. It has a diaphragmatic and a visceral surface and two poles. The external surface of the spleen can be divided into two parts – the diaphragmatic surface, which is in contact with the diaphragm and ribcage, and the visceral surface, which is in contact with other abdominal viscera. In enlargement of the spleen (known as splenomegaly), the superior border moves inferomedially, and its notches can be palpated. Its anterior and superior borders contain notches, while its posteromedial and inferior borders are smooth. The spleen lies in close proximity to other structures in the abdomen, such as the stomach and diaphragm anteriorly, the left lung and ribs 9-11 posteriorly, and the left colic flexure (splenic flexure) inferiorly. Medially, it is in contact with the left kidney and the tail of the pancreas.
The spleen is a highly vascular organ, receiving most of its arterial supply from the splenic artery. This vessel arises from the coeliac trunk, running laterally along the superior aspect of the pancreas, within the splenorenal ligament. As the artery reaches the spleen, it branches into five vessels – each supplying a different part of the organ. These arterial branches do not anastomose with each other – giving rise to vascular segments of the spleen which can be removed individually (a procedure known as a subtotal splenectomy). Venous drainage of the spleen occurs through the splenic vein, which combines with the superior mesenteric vein to form the hepatic portal vein. The nerve supply to the spleen is from the coeliac plexus, and the lymphatic vessels from the spleen drain into the pancreaticosplenic lymph nodes, and ultimately the coeliac nodes.
The spleen plays an important role in the body as a part of the lymphatic system, acting as a blood filter, and in the cell-mediated and humoral immune responses. It produces lymphocytes, involved in the fight against bacteria and viruses, and it also plays a role in red blood cell formation and the destruction of old cells.
Rupture of the spleen is a serious medical condition and may be life threatening due to the profuse bleeding that results when the fibroelastic capsule of the spleen is disrupted. There are indications for splenectomy, such as when injury or haemorrhage is life threatening. In these cases, a sub-total (partial) or total splenectomy may be performed. The liver and bone marrow take over some of the functions of the spleen, but individuals with no spleen are more susceptible to bacterial infections and require lifelong antibiotics. Splenectomy may also be indicated for haematological conditions such as haemolytic anaemia, idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura, hypersplenism and proliferative disorders such as myelofibrosis of lymphoma.
The spleen is a vital organ, playing important roles in the body such as filtering the blood, producing lymphocytes, and aiding in the destruction of old cells. Although it is protected by the rib cage, it is still susceptible to injury and rupture, which can be life-threatening and require surgical intervention. Individuals who have had the spleen removed need to take antibiotics for life to reduce their risk of infection, as they are more vulnerable to bacteria without a functioning spleen.
