Difference Between Spleen and Kidney

The spleen and the kidney are two important organs found in the abdominal cavity of the human body. Their physiology is different because of their different functions in the body system.


The spleen is a wedge-shaped lymphoid organ and is considered as the largest lymphoid mass located in the upper abdominal cavity, inferior to the diaphragm. Generally, it is 1 inch thick, 3 inches broad, and 5 inches long and weigh about 7 ounces. The spleen is made up of lymphatic cells. Usually the final shape of the spleen is due to its nearby contacts. As such, it has three concave places where it touches the left kidney, stomach, and large intestine, and a convex where it contacts the diaphragm. The ‘hillus’ is the place, where the blood vessels enter and leave the spleen. The spleen has a similar structure of lymph nodes. It is surrounded by a capsule of connective tissue that extends inwardly to form the numerous regions called lobules, which consist of cells and tiny blood vessels. The splenic artery brings the blood into the spleen while the splenic vein removes the blood from the spleen. In the cortex of the spleen, the lymphocytes cells are largely found while, in the medulla region, the cells are present in less numbers.

There are three main functions of spleen; (a) it is the place where both B-lymphocytes and T-lymphocytes multiply and mature, (b) it contains macrophages, which are responsible for the destruction of red blood cells, leukocytes, and bacteria, and (c) formation of blood cellular components [hemopoiesis] during the fetal life.



Kidneys are paired organs in the urinary system, located on either side of the vertebral column, near the posterior abdominal wall, behind the peritoneum. Each kidney is bean-shaped and weighs about 150 g. Each kidney has a hollow called hilum on its medial side, through which renal vein, renal artery, nerves, lymphatics, and renal pelvis enters into kidney. Kidney has two distinctive regions; an outer cortex and an inner medulla. The medulla has cone shaped regions called pyramids. Kidney is mainly composed of numerous structures called ‘nephrons’, which are considered as the basic structural and functional units of kidney. Usually, each kidney consists of about 1.2 to 1.5 million nephrons.

Kidneys have three basic functions; (a) filtration, by which the fluid in the blood is filtered to produce urine for excretion, (b) reabsorption, the process of which the important solutes such as glucose, amino acids, and other valuable inorganic ions are absorbed back into the extracellular fluid from the filtrate, (c) secretion, the process of which the substances are expelled into the filtrate and tubule system in order to remove toxic substances.

What is the differences between Spleen and Kidney?

• Kidneys are paired organs, unlike the spleen.

• Kidneys belong to the urinary system, whereas spleen belongs to the immune system.

• Spleen is a wedge-shaped organ while kidneys are bean- shaped organ.

• Spleen is mainly composed of lymphatic cells, whereas kidneys are made up of nephrons, which are multicellular in structure.

• The main functions of the spleen are the production of lymphocytes, destruction of erythrocytes, and hemopoiesis, whereas those of kidneys are filtration, reabsorption, and secretion.


Read more: 

1. Difference Between Left and Right Kidney 

2. Difference Between Liver and Kidney 

3. Difference Between Circulatory System and Lymphatic System