Chapter 18, Lesson 5: Platelets and the Control of Bleeding

Flashcards from Chapter 18, Lesson 5 of McGraw Hill Anatomy and Physiology, Ninth Edition, by Kenneth S. Saladin.

Hemostasis

The cessation of bleeding with platelets

Platelets

Small fragments of megakaryocytes in bone marrow with no nucleus and granules with secretions; moves in ameboid manner with foot (pseudopod)

Open canicular system

The internal system of channels that open onto the platelet surface

Platelet functions

• Secrete vasoconstrictors to reduce blood loss

• Create platelet plugs to seal small breaks

• Secrete procoagulants (clotting factors)

• Attract neutrophils to inflamed sites

• Dissolve clots when necessary with enzyme

Thromobopoiesis

The production of platelets

Thrombopoietin

A chemical that triggers stem cells to become megakaryoblasts, which replicate DNA to become megakaryocytes

Megakaryocytes

Cells 100 micrometers in diameter in the bone marrow; fragments split off to become platelets

Platelet life span

5 to 6 days

Vascular spasm

The first step in hemostasis that constricts blood vessels quickly before platelet plugs and clotting

Platelet plug formation

The second step in hemostasis where platelet pseudopods (feet) stick together to form a platelet plug

Coagulation (clotting)

The last defense against bleeding which uses clotting factors to aid in clotting

Clot retraction

The stoppage of clots where clots compact

Bleeding time

Aids in measuring coagulation efficiency

Hemophilia

A family of hereditary disease characterized by deficiencies of one clotting factor or another; blood cannot clot most effectively and is often sex-linked recessive

Thrombosis

Abnormal formations of a clot in an unbroken vessel; can be very harmful in vital organs to cause tissue death

Clot management

Done through prevention (vitamin K antagonists to prevent factor production) or dissolution of clots