Unit 2 Lecture 10 Flashcards
What are platelets called?
Thrombocytes
What are platelets?
fragments of megakaryocytes
How long can thrombocyte cell fragments circulate for before death?
5-9 days
What percent of platelets circulate in the body?
66%
Where does the remaining 33% of platelets reside in the body?
In the spleen
Define thrombosis
the formation of a clot
Define thrombus
A clot
Define embolus
A circulating clot
Define hemmorage
a severe uncontrolled bleeding
What term describes how thrombocytes are made?
Thrombocytopoiesis
What type of stem cell produces megakaryocytes?
Myeloid stem cells
How are thrombocytes made from megakaryocytes?
Thrombopoietin (TPO) lets thrombocyte fragments to fall off the megakaryocyte
What internal process is responsible for bleeding to stop?
Hemostasis
What 3 phases make up hemostasis?
- Vascular spasm
- Platelet plug formation
- Coagulation (blood clotting)
What does a vascular spasm do?
Immediately vasoconstricts (makes diameter smaller) in response to injury -> stops blood flow
Where do vascular spasms occur?
In vessels with smooth muscle walls
What is angiotensin II?
a vasoconstricting hormone that effects the renal sympathetic nerves
During plug formation, what do platelets normally NOT do?
do not stick to each other or the endothelial lining of blood vessels
What do platelets stick to in a damaged blood vessel?
Collagen fibers
What do platelets do when they are activated by collagen fibers in damaged blood vessels?
- liberate thromboxane A2, serotonin, and ADP
- release ADP
How does the damaged vessel make a “plug”
ADP makes platelets sticky and thromboxane A2 and serotonin causes cell contraction -> plug
What word means blood clotting
coagulation
Where do most of the clotting factors come from in the body?
Liver
During coagulation, what type of stimulations are present?
intrinstic and extrinsic stimulations
