HEMOSTASIS I

Question 1

what are the major zones of a platelet (ultrastructure)

Answer 1

1. Peripheral zone
2. Structural zone
3. Organelle zone
4. Membrane system

Question 2

mention and explain the parts contained in the peripheral zone of platelet (location within platelet)

Answer 2

1. Glycocalyx- it is a cell wall of a platelet
2. cytoplasmic membrane- like a cell membrane of platelet
3. Open canalicular system- is an internal membrane structure found in platelets.
   It comprises a tunneling network of surface-connected channels.
4. submembranous area- Glycocalyx Coat: A fluffy layer of glycoproteins and glycolipids that covers the platelet’s surface.

Question 3

what is contained in the structural zone

Answer 3

1. microtubules
2. microfilaments
3. intermediate filaments

Question 4

what is the role of structural zone in a platelet

Answer 4

1.It is involved in maintenance of shape
2. Involved in shape change on platelet activation

Question 5

Where is the organelle zone located

Answer 5

internally located

Question 6

what is contained in membrane systems

Answer 6

dense tubular system
surface connected open canalicular system

Question 7

what is hemostasis

Answer 7

means maintaining blood within vascular tissue

Question 8

what is staxia telangectasia

Answer 8

is a disease which causes the blood vessels to be weak and fails to withstand pressure of blood

Question 9

mention 2 classes of hemostasis

Answer 9

1. primary hemostasis
2. secondary hemostasis

Question 10

what are the three stages of primary hemostasis

Answer 10

1. platelet adhesion
2. platelet activation
3. platelet aggregation

Question 11

differentiate primary and secondary hemostasis

Answer 11

1. primary hemostasis happens when there is a small/minor cut while secondary hemostasis heppen when cut or injury is big
2. primary hemostasis forms a white clot while secondary hemostasis forms a red clot

Question 12

what are the functions of platelets

Answer 12

1. Passive surveillance
2. Formation of primary hemostatic plug
3. Provides phospholipid surface for secondary hemostasis
4. promotion of healing by stimulation of smooth muscle cells and fibroblasts

Question 13

Explain platelet adhesion in primary hemostasis

Answer 13

~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

Question 14

what is agonist

Answer 14

molecular substance that promotes coagulation process

Question 15

Where is von willebrand factor (vWF) produced

Answer 15

It is produced in alpha-granules in platelets and in Weibel palade bodies in endothelial cells

Question 16

When is platelet activation triggered

Answer 16

it is triggered after paltelet adhesion or exposure to agonist

Question 17

what is contained in the organelle zone

Answer 17

1. alpha granules (50 - 80 per platelet)
2. dense granules (3 - 8 per platelet)
3. Lysosomal granules
4. peroxisomes
5. Mitochondria
6. Glycogen particles

Question 18

what are the contents of membrane system

Answer 18

1. Dense tubular system (DTS)
2. Open canalicular system

Question 19

what is surface connected open canalicular system

Answer 19

is a system that connects interior of platelet and connects to platelet surface

Question 20

what is the function of surface connected open canalicular system (SCCS)

Answer 20

1. Allows substances to enter platelet and others to exit
2. serves as sourse of surface membrane after activation
3. plays a role in storage and secretion

Question 21

explain the function of dense tubular system (DTS)

Answer 21

1. site of prostaglandin and thromboxane synthesis
2. Primary sourse of ionized calcium

Question 22

what is the difference between DTS and SCCS

Answer 22

DTS does not connect to platelet surface while SCCS connects to platelet surface

Question 23

What happens/result when the process of protein activation takes place in primary hemostasis

Answer 23

1. the shape of the platelet changes
2. the biochemistry of the platelet changes
3. new receptor expression changes
4. 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

Question 24

what are the examples of platelet agonists

agonists are molecular substances that promotes coagulation process

Answer 24

1. Collagen
2. Adenosine diphosphate (ADP)
3. Thrombin
4. epinephrine
5. thromboxane
6. 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

Question 25

what is the other name for cyclooxygenase

Answer 25

prostaglandin-endoperoxide synthatase

Question 25

what is cyclooxygenase

Answer 25

is an anzyme responsible for biosynthesis of prostanoids from aranchidonic acid

The prostanoids includes thromboxane and prostaglandins

Question 26

what is the function of cyclooxygenase

Answer 26

helps to regulate blood vessel dilation and prevents excessive clotting

Question 27

where is thromboxane A2 (TXA2) synthesized from

Answer 27

from arachidonic acid by cyclooxygenase and thromboxane synthetase

Question 28

what is the function of Thromboxane A2 (TXA2)

Answer 28

1. stimulates platelet granule secretion
2. enhances vasoconstriction

Question 29

how does aspirin prevent clotting

Answer 29

by blocking cyclooxygenase