Platelet Plug Formation

Platelets stick to exposed ends of injured blood vessels. They adhere to any rough surface, particularly to the collagen in connective tissue underlying the endothelial lining of blood vessels.

When platelets contact collagen, their shapes change drastically, and numerous spiny processes begin to protrude from their membranes. At the same time, platelets stick to each other, forming a platelet plug in the vascular break. A plug may control blood loss from a small break, but a larger one may require a blood clot to halt bleeding. Figure 14.17 shows the steps in platelet plug formation.

Endothelial lining Collagen fiber

Endothelial lining Collagen fiber

(1) Break in vessel wall

(2) Blood escaping through break

(1) Break in vessel wall

(2) Blood escaping through break

(3) Platelets adhere to each other, to end of broken vessel, and to exposed collagen

(4) Platelet plug helps control blood loss

Figure 14.17

Steps in platelet plug formation.

U What is hemostasis?

^9 How does a blood vessel spasm help control bleeding? ^9 Describe the formation of a platelet plug.

Essentials of Human Physiology

Essentials of Human Physiology

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.

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