Both the spleen and the pancreas are visceral organs in the foregut. Don’t get too excited though, that’s where their similarities end.
Other characteristics such as the shape and function within the body are quite different. So let’s break them down!
Alright, let’s begin with the spleen, which has a few different important functions. Prenatally, it functions as a hematopoietic organ, which means it makes fetal blood cells.
After birth, the spleen is like a hub for lymphocyte proliferation, as well as a recycling center for damaged red blood cells and platelets, and a blood reservoir, from which backup blood can be pumped into circulation after significant hemorrhage. For this reason, we can think of our spleen as our own personal blood bank.
The spleen is oval in shape and is an intraperitoneal organ. The spleen is an oval-shaped organ located in the left upper quadrant of the abdomen, and it is intraperitoneal.
This means that the spleen is entirely enveloped in visceral peritoneum, except at the splenic hilum where the vasculature enters and exits the organ.
The spleen has an anterior, superior and inferior border. The superior border of the spleen is easily recognizable due to its notched appearance.
The outer surface of the spleen can also be divided into two parts; the diaphragmatic surface which is in contact with the concavity of the diaphragm, and the visceral surface that is in contact with the surrounding abdominal viscera.
Now, let’s break down the anatomical relationships of the spleen with its surrounding structures. The left portion of the diaphragm and the 9th to 11th ribs lie posterior to the spleen, with the diaphragm acting like a barrier between the spleen and the ribs.
The stomach lies anterior to the spleen and the two connect at the greater curvature of the stomach via the gastrosplenic ligament.
The spleen is lateral to the left kidney and the two are connected via the splenorenal ligament. The gastrosplenic and the splenorenal ligament contain splenic vessels within them and attach at the splenic hilum.
The tail of the pancreas also often contacts the splenic hilum. Lastly, the spleen lies just superior to the left colic flexure of the large intestine.
Now let’s talk about blood supply, lymphatic drainage and innervation! The spleen gets its blood supply via the splenic artery, which is a branch of the celiac trunk.
After arising from the celiac trunk, the splenic artery takes a tortuous path posterior to the omental bursa, and runs along the superior border of the pancreas, ending at the splenic hilum.
The twisting and turning of the splenic artery gives it a worm-like appearance that is easily distinguishable.
At the level of the hilum, the splenic artery then divides into several branches which enter the spleen to supply its different vascular segments.
Venous blood drains from the spleen via the splenic vein, which travels posterior to the pancreas, receiving the inferior mesenteric vein, and eventually uniting with the superior mesenteric vein to form the hepatic portal vein.
Lymph from the spleen collects in the splenic lymph nodes located at the hilum, which eventually drain to the pancreaticosplenic and the celiac lymph nodes, using lymphatic vessels that run alongside the splenic vessels.
Finally, splenic innervation is provided by nerve fibers of the celiac plexus, which course along the splenic artery.
OK, now let’s take a quick break and try to recall the name and origin of the artery supplying the spleen.
Alright, now let’s shift gears and talk about the pancreas. The pancreas is an elongated, accessory digestive organ that sits directly behind the stomach at the level of the transpyloric plane or the L1 and L2 vertebral bodies.
The pancreas is considered a retroperitoneal organ with the exception of its tail portion which is intraperitoneal.
The pancreas is both an exocrine gland, secreting pancreatic juices into the duodenum to help with digestion; and an endocrine gland, secreting insulin and glucagon directly into the bloodstream, in order to regulate blood sugar metabolism. You could say the pancreas is working two full time jobs!
Anatomically, the pancreas is divided into five parts: the head, the uncinate process, the neck, the body, and the tail, and each of these parts have numerous relationships with surrounding structures.