A thrombus is defined as which of the following?

• A. A nerve cell
• B. A hormone
• C. A type of white blood cell
• D. A blood clot

Answer: (D)

Thrombus refers to a blood clot that forms inside a blood vessel or the heart, blocking or narrowing blood flow. It’s made up of platelets and a fibrin mesh that trap red and white blood cells. This is different from a nerve cell (neuron), which is a cell of the nervous system; a hormone, which is a chemical messenger used to signal processes in the body; or a white blood cell (leukocyte), which is part of the immune system. The defining idea is that a thrombus is a clot that develops within the vascular system and can lead to blockage of blood flow, with potential clinical consequences if it grows or travels as an embolus.