Ticket 6

Question 1

what are blood platelets called and what are some features

Answer 1

thrombocytes

small, nonnucleated , membrane bound fragments
originate from MEGAKARYOCYTES

Question 2

What is the function of platelets

Answer 2

promote blood clotting to help repair minor tears and leaks in blood vessels

prevent blood loss from microvasculature (arterioles, capillaries, venules)

Question 3

What do you call the development of thrombocytes

name what stimulates megakaryopoiesis

How long do they last

Answer 3

Thrombopoiesis

thrombopoietin

10 days

Question 4

briefly go through platelet role in haemorrhage

Answer 4

Primary aggregation- collagen binding protein in platelet membrane binds a break in the microvascular endothelium

Secondary aggregation- platelet produces adhesive glycoprotein and ADP which increases size of the plug

Blood coagulation- fibrogen, von Willebrand factor, platelet factor 4 gives rise to fibrin polymer that traps RBCs and more platelets to form blood clot/thrombus

Clot retraction- clot bulges into blood vessel lumen, then contracts a bit due to platelet actin and myosin interaction

Clot removal- protected by the clot, the endothelium forms new tissue. Clot removed by proteolytic enzyme plasmin

Question 5

Briefly go through thrombopoiesis

Answer 5

• thrombopoietin stimulates megakaryopoiesis
• thrombopoietin binds to receptor on megakaryocyte progenitor cells
• upon binding, intracellular signalling leads to megakaryocyte growth, maturation, granule formation, diviiding cytoplasm into regions to fragment to become platelets
• proplatelet processes further fragment into platelets