Blood clotting

Question 1

what is haemostasis?

Answer 1

process that helps your body stop bleeding

Question 2

What are the key cellular components of blood?

Answer 2

Erythrocytes (red blood cells)
Leukocytes (white blood cells)
Platelets
These are suspended in plasma (watery ECF)

Question 3

what is the normal colour of blood plasma?

Answer 3

It has a pale colour. its colour indicates healthy blood

Question 4

There are a range of proteins in blood plasma. How can they be separated?

Answer 4

electrophoresis

Question 5

What proteins are included in the blood plasma?

Answer 5

Albumin
Fibrinogen (clotting protein)
Immunoglobulins

Question 6

What are the properties of Erythrocytes (RBC)?

Answer 6

most abundant cell in blood (haematocrit)
Non-nucleated biconcave discs maximising SA:Vol
Mainly composed of Haemoglobin
Shape maintained by cytoskeleton anchored to plasma membrane

Question 7

what is haematocrit?
*Think of blood samplec

Answer 7

Height of RBC / Total height

Question 8

What are the mechanisms of Haemostasis?

Answer 8

Vasoconstriction (contraction)
Increase tissue pressure
Platelet plug (primary haemostasis) - these are made instantly and temporary
Clot formation (secondary haemostasis)

Question 9

What are the properties of Platelets?

Answer 9

Nucleus free fragments (2-3 microns diameter)
Contain alpha granules (contain VWF, fibrinogen, clotting factor, platelet derived growth factor)
External coat rich in platelet receptors
cytoskeleton contains actin and myosin –> dispersed at rest / dynamic shape change in activation / clot retention

Question 10

why are alpha granules important in platelets?

Answer 10

Alpha granules release von Willebrand factor (VWF), a protein that helps platelets adhere to the injured blood vessel wall.

They release fibrinogen, a protein that binds to receptors on platelets, facilitating their aggregation and the formation of a platelet plug.

platelet derived growth factor- important for wound healing

Question 11

What are the three major functions of erythrocytes?

Answer 11

O₂ carriage from lungs to systemic system
CO₂ carriage from tissues to lungs
Buffering of acids/bases

Question 12

What are the three stages of platelet plug formation?

Answer 12

The three stages are:
Adhesion
Activation
Aggregation

Question 13

Describe the process of platelet adhesion
*Platelet plug formation is a rapid temporary seal to
prevent further blood loss

Answer 13

Damage to endothelium exposes subendothelial collagen – most thrombogenic (blood clotting)

Plasma VWF binds to exposed collagen and platelet receptors

Binding of platelet receptors cascade of IC events

Question 14

Describe the process of Platelet Activation

Answer 14

Secretion platelet derived growth factor (PDGF) –> cell proliferation and wound healing
Thromboxane –> vasoconstriction + inflammation
Cytoskeletal changes *
Expression of fibrinogen receptors *

Question 15

Describe the process of Platelet Aggregation

Answer 15

Platelet fibrinogen receptors bind to plasma fibrinogen *
forms molecular bridges between platelets –> aggregation
plugs breach the endothelium
eventually actin and myosin contract –> more compact platelet plug

Question 16

What is the composition of a blood clot?

Answer 16

Erythrocytes
Leukocytes
Serum
Mesh of fibrin (and platelets)

Question 17

What are the 2 pathways of clotting?

Answer 17

Intrinsic
Extrinsic

Question 18

Describe the intrinsic and extrinsic pathways of clotting

Answer 18

Intrinsic- slower, activated by surface damage
Activated platelet initiates a cascade of protease reactions ending in activated factor 10a

Extrinsic- activated by trauma or inflammation
Injury to endothelium results in activated factor 10a

Question 19

The intrinsic and extrinsic pathway form a common pathway. What is the common pathway?

Answer 19

Factors 10a from both pathways enters common pathway to generate thrombin (enzyme) that forms the final part which is fibrin –> fibrin forms the mesh like clot

Question 20

What are the factors that promote Anti-thrombotic state? (so not making a clot)

Answer 20

Normal endothelial cells

Paracrine factors - e.g. prostacyclin promotes vasodilation, nitric oxide WHICH inhibits platelet adhesion and aggregation

Many anti-coagulant factors (including thrombomodulin - complexes with thrombin)v

Question 21

What would promotion of pro-thrombotic state cause?

Answer 21

-Promotion of pro-thrombotic state VIA
Event of vascular damage
-Leads to hypoxia (lack of oxygen) –> leading to expression of procoagulants

Question 22

Whats the difference between normal and abnormal blood flow, and what leads to abnormal blood flow?

Answer 22

Normal –> parabolic profile - fast flow in the middle and velocity decreases as you get closer to the sides

Abnormal –> turbulent - may blood flow leads to endothelial injury

Question 23

what would cause turbulent flow in blood flow?

Answer 23

Turbulent flow caused by:
Local stenosis (narrowing of blood vessel)
Large radius (e.g. aorta) - not something to worry about tho
High velocity (e.g. high cardiac output) - not something to worry about tho

Question 24

what is thrombus?

Answer 24

A blood clot that forms within blood vessels or chamber of heart