Lecture 2 - Primary haemostasis Flashcards
What is the difference between plasma and serum?
Plasma: Is the liquid part of blood with clotting factors. Obtained by centrifuging blood treated with anticoagulants.
Serum: Is the liquid left after blood clots, lacking clotting factors. Obtained by letting blood clot, then centrifuging.
In which part of the blood sample are platelets present?
In the small white part also called the buffy coat.
Does blood have many platelets?
Yes, there are many platelets in blood, around 150.000 per microliter. But that is not without a good reason. Platelets have a typical life span of 10 days which is why there are so many platelets needed because it’s essential for blood clotting.
Where are platelets produced?
In the bone marrow
From what cells are platelets formed?
Megakaryocytes
Do megakaryocytes have a nucleus?
Yes they do, multiple nuclei. Megakaryocytes undergo DNA replication up to 7 times (also called endomitosis) without actually undergoing nuclear or cytoplasmic division. This results in a polyploid cell with multiple copies of its DNA in it lobed nucleus.
From what part of the megakaryocytes are the platelets actually formed?
The outer edges of the megakaryocytes in bone marrow stretch through vessel walls into blood channels, where these extensions break off into small, disk-shaped platelets.
Fill in: Platelets are bigger/smaller than red blood cells, are colorless/have color, and have no nucleus/a nucleus.
Platelets are smaller than red blood cells are colorless and have no nucleus.
What are megakaryocytes?
Megakaryocytes are large bone marrow cells that produce platelets, which are crucial for blood clotting.
Name the cytokine that regulates growth and maturation in megakaryocytes
Thrombopoietin (TPO) is a glycoprotein that regulates the growth and maturation of megakaryocytes, the parent cells of platelets.
What regulates the formation of platelet cells?
While platelets are made in the bone marrow, it’s the hormone thrombopoietin (TPO) that regulates the process, they stimulate the megakaryocytes to make more platelet cells.
Where is thrombopoietin (TPO) primarily formed?
Primarily in the liver but also kidneys
Explain the feedback system TPO has when there is high platelet count.
When you have enough or too many platelets they ‘soak up’ the TPO, thereby reducing TPO levels in the blood. This slows down the production of new platelets because the bone marrow doesn’t get as much TPO stimulation.
Explain the feedback system TPO has when there is low platelet count (thrombocytopenia).
When platelet levels are low, more TPO remains available in the blood (since fewer platelets are around to use it up). This increased TPO then stimulates megakaryocytes to produce more platelets to correct the low count
