Hemostasis and Blood Clotting Mechanisms

What are the four mechanisms by which hemostasis is achieved?

Vascular constriction, formation of a platelet plug, formation of a blood clot, eventual growth of fibrous tissue into the blood clot

What are the characteristics of platelets?

They are minute discs formed in the bone marrow, don't have a nucleus, have a lifespan of 8 to 12 days, and are removed by the tissue macrophage system in the spleen

What is the normal concentration of platelets in the blood?

Between 150,000 and 300,000 per microliter

How do platelets change their characteristics when they come in contact with a damaged vascular surface?

They swell, pseudopods form on their surfaces, and they become sticky, adhering to collagen in the vessel wall and to each other Signup and view all the answers

What is the role of vascular constriction in achieving hemostasis?

It results from local myogenic spasm, factors released from damaged tissue & platelets, and nerve reflex Signup and view all the answers

What is the eventual outcome of the growth of fibrous tissue into the blood clot in hemostasis?

To close the hole in the vessel permanently Signup and view all the answers

What is the purpose of the platelet plug in the blood vessel?

To seal a small cut in the blood vessel. Signup and view all the answers

What is the role of tissue plasminogen activator (t-PA) in the process of fibrinolysis?

It converts plasminogen to plasmin, which then removes the remaining unnecessary blood clot. Signup and view all the answers

What is the purpose of the Hess test in investigating bleeding disorders?

To test capillary resistance. Signup and view all the answers

How is bleeding time measured using Ivy's method?

By counting the number of spots formed on the filter paper and dividing it by two. Signup and view all the answers

What does the Clotting Time (CT) measure?

The time taken for the blood to clot outside the vascular system. Signup and view all the answers

Name one condition that can cause excessive bleeding in humans.

Vitamin K deficiency Signup and view all the answers

What is the term for an abnormal clot that develops in a blood vessel?

Thrombus Signup and view all the answers

What is the purpose of an emboli in the bloodstream?

To freely circulate (travel) through the bloodstream. Signup and view all the answers

What initiates the clotting process in the blood?

Factors from damaged tissue, platelets, and blood proteins. Signup and view all the answers

What is the role of fibrinolysis in the repair of the blood vessel?

To clean up extra clot and old clot by breaking down the clot. Signup and view all the answers

What is the normal range for bleeding time using Duke's method?

2 - 6 minutes Signup and view all the answers

What does the Hess test count as abnormal?

Counts of more than 8 petichial hemorrhages (blue dots) on the circle. Signup and view all the answers