Atherosclerosis predisposes a person to thrombosis, the formation of a blood clot within a vessel. The clot, called a thrombus, interrupts blood flow to the tissues supplied by that vessel, resulting in necrosis (tissue death). Blockage of a vessel by a thrombus or other mass carried in the bloodstream is an embolism, and the mass itself is called an embolus. Usually the mass is a blood clot that breaks loose from the wall of a vessel, but it may also be air (as from injection or trauma), fat (as from marrow released after a bone break), bacteria, or other solid materials. Often a venous thrombus will travel through the heart and then lodge in an artery of the lungs, resulting in a life-threatening pulmonary embolism. An embolus from a carotid artery often blocks a cerebral vessel, causing a cerebrovascular accident (CVA), commonly called stroke (see Chapter 17).
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.