PHYSIOLOGY: Haematopoiesis and haemostasis Flashcards
What makes up blood plasma?
90% water
proteins eg. albumin, immunoglobulins, clotting factors
nutrients
salts
What makes up the buffy coat of blood?
white cells and platelets
How much of the blood do red blood cells make up?
45%
What do plasma proteins do?
balance osmotic pressure between the blood and surrounding tissues
transport lipids and ions
What do alpha globulins do?
transport proteins that bind to lipids, fat soluble vitamins and metal ions
What does albumin do?
maintains osmotic pressure
What is haemopoiesis?
the formation of blood cells
What cell is the starting point of haemopoeisis?
haemopoietic stem cell
What property does a haemopoietic stem cell have that other blood cells don’t?
can self renew
What does a haemopoietic stem cell produce?
progenitor cell
What two lineages are produced from haemopoietic progenitor cells?
myeloid and lymphoid
What cells have a lymphoid lineage?
B cells
T cells
NK cells
dendrites
What does a naive B cell become in the tissues?
plasma cell
What is the function of
a) B cell?
b) T cell?
c) NK cell?
a) humoral response
b) cell mediated response
c) anti-viral and anti-tumour
What cells have a myeloid lineage?
erythrocytes platelets granulocytes monocytes dendrites
What does a monocyte become in the tissues?
macrophage
Give an example of 3 granulocytes and their function
neutrophil - phagocytosis and acute inflammation
basophil - modulate hypersensitivity
eosinophil - destroy parasites and modulate hypersensitivity
What is proliferation?
an increase in cell numbers
What is differentiation?
descendent commit to one or more lineages
What is maturation?
descendants acquire functional properties and may stop proliferating
What is apoptosis?
descendants undergo cell death
What is the site of haematopoiesis in an embryo?
yolk sac stops week 10
liver begins week 6 (+ spleen)
bone marrow week 16
Which type of bone marrow is haemopoietically active?
red
In adults, where does haematopoiesis mainly occur?
axial skeleton
bone marrow of skull, ribs, sternum, pelvis, proximal ends of femur.
What lineage do dendritic cells have?
myeloid and lymphoid
Are immature progenitors or mature cells more common in the bone marrow?
mature cells
Give the progression of haematopoiesis that forms an erythrocyte
haemocytoblast
proerythroblast
early erythroblast
late erythroblast
reticulocyte
mature erthyrocyte
What change occurs between an erythoblast and a reticulocyte?
organelles are lost to give biconcave shape
What change occurs between reticulocyte to erythrocyte?
cell moves to blood
loses its nucleus + ribosomes
Where does platelet production occur?
on the periphery of a megakaryocyte, it buds off
How is CO2 carried in the blood?
mostly as bicarbonate (60%)
• 10% is dissolved
• 30% bound to Hb as carbamino-Hb
What is extra medullary haematopoiesis?
occurs out with bone marrow eg. liver, thymus, spleen
What is haemostasis?
the arrest of bleeding and maintenance of vascular patency
What is primary haemostasis?
the formation of a platelet plug
How does endothelial damage attract platelets?
exposes collagen and releases VWF so that platelet adhesion occurs, the platelets then release chemicals to cause platelet aggregation
What can cause failure of the platelet plug to form?
vascular causes, reduced no (thrombocytopenia), reduced function or due to VWF
What are the signs of failure of the platelet plug to form?
- Spontaneous bruising and purpura
- Mucosal bleeding eg epistaxis, GI, conjunctival, menorrhagia
- Intracranial haemorrhage
- Retinal haemorrhage
How can primary haemostasis be investigated?
platelet count
What is secondary haemostasis?
the formation of a fibrin clot
How is secondary haemostasis triggered?
damage to vessel wall releases clotting factors that convert prothrombin to thrombin, then thrombin converts fibrinogen to fibrin
fibrin strands adhere to the platelet plug to form an insoluble clot
What usually causes
a) single clotting factor deficiency?
b) multiple clotting factor deficiency?
a) hereditary eg. haemophilia
b) acquired eg. DIC
How does fibrinolysis occur?
tPa converts plasminogen to plasmin which breaks fibrin down into fibrin degradation products
How can secondary haemostasis be investigated?
Prothrombin time
Activated partial thromboplastin time
Name some naturally occuring anticoagulants
- Serine protease inhibitors
* Protein c and protein s
