Spleen Anatomy and Physiology
Spleen Anatomy and Physiology
Structure and Location :
The spleen sits in the upper left of the abdomen, protected by the rib cage. It is the largest organ of the lymphatic system — the circulation of the immune system. It recycles old red blood cells and stores platelets (components of the blood that help stop bleeding) and white blood cells.
The spleen although it varies in size between individuals, a spleen is typically around 3–5.5 inches long and weighs 5.3–7.1 ounces (oz). The spleen is a soft organ with a thin outer covering of tough connective tissue, called a capsule.
There is a handy rule to remember the rough dimensions of the spleen, called the 1x3x5x7x9x11 rule:
It measures approximately 1 inch by 3 inches by 5 inches, weighs around 7 oz, and is positioned between the 9th and 11th ribs.
The spleen contains two main regions of tissue called white pulp and red pulp.
Red pulp: Contains venous sinuses (cavities filled with blood), and splenic cords (connective tissues containing red blood cells and white blood cells).
White pulp: Mostly consists of immune cells (T cells and B cells).
The Physiology of Spleen:
The spleen’s primary job is to filter the blood. As blood flows into the spleen, it performs a quality control service, detecting any red blood cells that are old or damaged. Blood flows through a maze of passages in the spleen. Healthy cells flow straight through, but those considered to be unhealthy are broken down by large white blood cells called macrophages.
Once the red blood cells are broken down, the spleen stores useful leftover products, such as iron, which it eventually returns to the bone marrow, which makes hemoglobin (the iron-containing part of blood).
The spleen also stores blood — the blood vessels of the spleen can expand significantly. In humans, around 1 cup of blood is kept in the spleen, ready to be released if there is a significant loss of blood, after an accident, for instance. Interestingly, when a racehorse is at rest, up to half of its red blood cells are kept in the spleen.
The spleen also plays a role in the immune response by detecting pathogens (bacteria, for instance), and producing white blood cells in response
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