Blood: regneration, clotting

Question 1

Overall Makeup of Blood

Answer 1

Specialized cells in plasma
55% plama
45% specialised cells

Question 2

Structure and function of plasma

Answer 2

Structure: 90% water, 8% proteins, 1% inorganic salts, 0.5% lipids, 0.1% glucose and other minor components
Function: regulates distribution of fluid between plasma and extracellular space, transport

Question 3

Structure and function of erythrocytes

Answer 3

Structure: no nucleus, biconcave shape, haemoglobin
Function: transport oxygen from lungs and remove CO2, passively circulate in system

Question 4

Function of Leucocytes

Answer 4

Defense and immune system

Question 5

Structure and function of thrombocytes

Answer 5

Structure: cell fragments produced by fragmentation of megakaryocyte cytoplasm (largest type of progenitor cells in bone marrow), contain 2 types of granules, abundant surface receptors
Function: bind to and coat damaged vessel walls, plug small ddefects in blood vessel walls, activate clotting cascade, source of growth factors, essential for haemostasis

Question 6

Define haematopoiesis

Answer 6

the production of mature blood cells from precursors

Question 7

Where does haematopoiesis occur?

Answer 7

Foetus: yolk sac, liver and spleen, bone marrow
Inflants: bone marrow found in all bones
Adults: vertebrae, ribs, sternum, skull, sacrum, pelvis, proximal ends of femur

Question 8

Process of haematopoiesis:

Answer 8

Asymmetric division of haematopoietic stem cells (1 identical to parent, 1 progenitor cell)
Non-identical daughter cell –> myeloid progenitor or common lymphoid progenitor
Progenitor divides and differentiates

Question 9

How is haematopoiesis regulated?

Answer 9

Controlled by regulatory molecules/ growth factors:
- glycoproteins in blood
- an act on more than one cell lineage
- promote proliferation, differentiation and maturation

Question 10

Examples of major haematopoietic growth factors:

Answer 10

Stem cell factor
Granulocyte-monocyte colony stimulating factor (GM-CSF)
IL3
Il 11 - megakaryocyte
Il 5 - eosinophil
Granulocyte CSF
Monocyte CSF
Thrombopoietin (TBO) - megakaryoctye and RBC
Erythropoietin (EPO) - RBC

Question 11

Stages of erythropoiesis

Answer 11

Hemocytoblast –> common myeloid progenitor cell –> proerythroblast –> erythroblast/ normoblast (different stages) –> reticulocytes –> Erythrocytes
Take 120 days

Question 12

Production of granulocytes:

Answer 12

haematopoietic stem cell –> common myeloid progenitor cell –> myeloblast –> promyelocytes
–> develop different type of granulocytes

Question 13

Production of platelets

Answer 13

Common myeloid progenitor cell –> megakaryoblast –> fragments into platelets

Question 14

3 stages of haemostasis

Answer 14

1. Vascular Spasm/ vasoconstriction
2. Platelet Plug Formation
3. Coagulation

Question 15

Describe the extrinsic pathway in coagulation

Answer 15

Triggered by external trauma causing blood to escape circulation.
1. Damage to blood vessel results in Factor VII exiting circulation into surrounding tissue and is activated
2. Tissue factor (AKA thromboplastin or factor III) released by damaged cells outside ciruclation
These can both activate common pathway

Question 16

Describe the intrinsic pathway in coagulation

Answer 16

Activated by blood trauma with blood coming in contact with collagen fibres of damaged endothelial cells or damaged platelets releasing phospholipids.
1. Collagen (or other) activates Factor XII,
2. XIIa activates XI
3. XIa activates IX in the presence of Ca2+
4. Factor VIII is also activated simulatneously
5. Activated VIII and IX can both activate common pathway

Question 17

Describe the Common Pathway in Coagulation

Answer 17

1. Tissue factor, VIIa (both form extrinsic) and VIIIa and IXa (from intrinsic) can activate factor X in the presence of Ca2+ ions
2. Factor Xa converts prothrombin to thrombin
3. Thrombin converts fribrinogen to fibrin
4. Thrombin also activates factor XIII which causes fibrin to form a stable fibrin clot
   POSITIVE FEEDBACK:
   - Factor V increases prothrombinase synthesis
   - thrombin increases platelet activation

Question 18

What tests can be used for each pathway?

Answer 18

PT test for extrinsic pathway
APTT test for intrinsic pathway

Question 19

Describes stages in vasoconstriction

Answer 19

1. Nerves in endothelial cells and muscle cells trigger reflexive contraction of blood vessels to limit blood flow and decrease blood loss
2. Endothelial cells secrete endothelin causing smooth muscle to contract
3. Damaged endothelial cells expose collagen below and release von Willebrand’s factor which binds to exposed collagens

Question 20

Describe the formation of the platelet plug

Answer 20

Aims to form a temoporary seal against blood loss
1. Platelets in blood bind to von Willebrand’s factor by receptor on surface
2. Binding of platelets to von-W factor activates platelets: change shape so bind to other platelets, release vW factor, seretonin (attracts platelets) and Ca2+, release ADP and thromboxane, induce vasoconstriction
3. Increased activation of more platelets in positve feedback loop - limited to site of injury by platelet inhibitors
4. Aggregation: ADP and thromboxane cause platelets to bind to collagen and activates platelts so they can receptor enabling them to bind to fibrinogen linking platelets together.

Question 21

Describe the production of fibrinolysis

Answer 21

1. Platelets pull on fibrin threads causing them to contract
2. Torn edges of damaged vessel drawn together
3. Fibroblast begins to form new connective tissue and new endothelial begin to repair lining of ruptured vessel
4. Clot dissolved in fibrinolysis: inactive plasminogen enzyem accumulates in clot as it forms
5. Thrombin, XIIa and tissue plasminogen activor convert inactive plasminogen to plasmin
6. Plasmin digest fibrin threads, dissolving clot. Also inactivates fibrinogen, factor V and XII, and prothrombin