HEMOSTASIS I Flashcards
Platelet components, functions and structure
what are the major zones of a platelet (ultrastructure)
- Peripheral zone
- Structural zone
- Organelle zone
- Membrane system
mention and explain the parts contained in the peripheral zone of platelet (location within platelet)
- Glycocalyx- it is a cell wall of a platelet
- cytoplasmic membrane- like a cell membrane of platelet
- Open canalicular system- is an internal membrane structure found in platelets.
It comprises a tunneling network of surface-connected channels. - submembranous area- Glycocalyx Coat: A fluffy layer of glycoproteins and glycolipids that covers the platelet’s surface.
what is contained in the structural zone
- microtubules
- microfilaments
- intermediate filaments
what is the role of structural zone in a platelet
1.It is involved in maintenance of shape
2. Involved in shape change on platelet activation
Where is the organelle zone located
internally located
what is contained in membrane systems
dense tubular system
surface connected open canalicular system
what is hemostasis
means maintaining blood within vascular tissue
what is staxia telangectasia
is a disease which causes the blood vessels to be weak and fails to withstand pressure of blood
mention 2 classes of hemostasis
- primary hemostasis
- secondary hemostasis
what are the three stages of primary hemostasis
- platelet adhesion
- platelet activation
- platelet aggregation
differentiate primary and secondary hemostasis
- primary hemostasis happens when there is a small/minor cut while secondary hemostasis heppen when cut or injury is big
- primary hemostasis forms a white clot while secondary hemostasis forms a red clot
what are the functions of platelets
- Passive surveillance
- Formation of primary hemostatic plug
- Provides phospholipid surface for secondary hemostasis
- promotion of healing by stimulation of smooth muscle cells and fibroblasts
Explain platelet adhesion in primary hemostasis
~Binding of platelet receptor “glycoprotein lb” to von willebrand factor wich binds to collagen from basement membrane
~ This step triggers several events leading to platelet activation
what is agonist
molecular substance that promotes coagulation process
Where is von willebrand factor (vWF) produced
It is produced in alpha-granules in platelets and in Weibel palade bodies in endothelial cells
When is platelet activation triggered
it is triggered after paltelet adhesion or exposure to agonist
what is contained in the organelle zone
- alpha granules (50 - 80 per platelet)
- dense granules (3 - 8 per platelet)
- Lysosomal granules
- peroxisomes
- Mitochondria
- Glycogen particles
what are the contents of membrane system
- Dense tubular system (DTS)
- Open canalicular system
what is surface connected open canalicular system
is a system that connects interior of platelet and connects to platelet surface
what is the function of surface connected open canalicular system (SCCS)
- Allows substances to enter platelet and others to exit
- serves as sourse of surface membrane after activation
- plays a role in storage and secretion
explain the function of dense tubular system (DTS)
- site of prostaglandin and thromboxane synthesis
- Primary sourse of ionized calcium
what is the difference between DTS and SCCS
DTS does not connect to platelet surface while SCCS connects to platelet surface
What happens/result when the process of protein activation takes place in primary hemostasis
- the shape of the platelet changes
- the biochemistry of the platelet changes
- new receptor expression changes
- altered orientation of phospholipids
phospholipids are receptors on the cell membrane responsible for transport mechanism, during protein activation the phospholipid rotates and faces the opposite direction
what are the examples of platelet agonists
agonists are molecular substances that promotes coagulation process
- Collagen
- Adenosine diphosphate (ADP)
- Thrombin
- epinephrine
- thromboxane
- aranchidonic acid
epinephrine is also know as adrenaline helps in fight and flight response.
aranchidonic acid is a polyunsaturated omega-6 fatty acid, plays a role in inflammation and immune respose, promotes platelet activation and clot formation. it is a component of ceell membrane phospholipids
what is the other name for cyclooxygenase
prostaglandin-endoperoxide synthatase
what is cyclooxygenase
is an anzyme responsible for biosynthesis of prostanoids from aranchidonic acid
The prostanoids includes thromboxane and prostaglandins
what is the function of cyclooxygenase
helps to regulate blood vessel dilation and prevents excessive clotting
where is thromboxane A2 (TXA2) synthesized from
from arachidonic acid by cyclooxygenase and thromboxane synthetase
what is the function of Thromboxane A2 (TXA2)
- stimulates platelet granule secretion
- enhances vasoconstriction
how does aspirin prevent clotting
by blocking cyclooxygenase
