Blood

Question 1

2 main components of blood

Answer 1

Plasma (55%)
Formed Elements (45%)

Question 2

6 components of plasma

Answer 2

proteins
amino acids
wastes
nutrients
gases
electrolytes

Question 3

Formed Elements

Answer 3

Includes erythrocytes (red blood cells), leukocytes (white blood cells) and platelets.

Question 4

Function of Erythrocytes (Red Blood Cells)

Answer 4

• Deliver Oxygen to Cells
• Remove Carbon Dioxide from Cells

Question 5

Function of Leukocytes (White Blood Cells)

Answer 5

• Defends the body from diseases (foreign pathogens, toxins, bacteria).
• Divided into granulocytes and agranulocytes.

Question 6

Granulocytes

Answer 6

• Cytoplasm CONTAINS very fine granules .
• Consist of neutrophils, basophils and eosinophils.

Question 7

Agranulocytes

Answer 7

• Cytoplasm DOES not contain granules .
• Consist of lymphocytes and monocytes.

Question 8

Neutrophils

Answer 8

Recognise, engulf snd destroy pathogens via phagocytosis
Release preformed granules ( hydrolytic enzymes, antimicrobial
proteins).

Question 9

Eosinophils

Answer 9

• target extracellular pathogens that are too large to be engulfed by phagocytosis eg. parasites
• Facilitate allergic Reactions

Question 10

Basophils

Answer 10

Contains granules of histamine which are released to initiate an allergic response

Question 11

Lymphocytes

Answer 11

Specialised WBC that defends against specific pathogens

Question 12

7 Function of Platelets

Answer 12

• Secrete vasoconstrictors that constrict blood vessels when damaged
• Form temporary platelet plugs to stop bleeding
• Includes clotting factors to promote blood clotting
• Dissolve blood clots when no longer needed
• Digest and destroy bacteria
• Secrete chemicals that attract neutrophils and monocytes to sites of inflammation
• Secrete growth factors to maintain the lining of blood vessels

Question 13

What happens if there are too few red blood cells

Answer 13

• Reduced oxygen carrying capacity
• Increased risk of hypoxia (oxygen deprivation)

Question 14

What happens if there are too many red blood cells

Answer 14

• Increases blood viscosity
• Increases resistance to flow through blood vessels
• Increases risk of blood clotting

Question 15

Steps for Feedback Loop of RBC

Answer 15

1. Stimulus: Decrease O2 carrying ability.. Due to ..
   - Decreased RBC Count
   - Decreased amount of haemoglobin
   - Decreased availability of O2
2. Receptors: Receptors in the Kidney respond to low oxygen levels.
   - Kidney’s increase EPO secretion into the bloodstream.
   - EPO circles in higher numbers.
3. Control Center: Stimulates proerythroblasts activating bone marrow to produce reticulocytes (immature RBC).
4. Effectors: Reticulocytes enter circulating blood resulting in a larger number of red blood cells in circulation.
5. Response: Increased oxygen delivery to tissues
6. Return to homeostatic levels.

Question 16

3 Steps in Haemostasis

Answer 16

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

Question 17

Vascular Spasm

Answer 17

• Blood vessels respond to injury by contracting (vasoconstriction)
• Acts to decrease blood flow to the area of injury (restricts blood loss) enabling for other steps of
  haemostasis to occur

Question 18

Platelet Plug Formation

Answer 18

• Occur via a positive feedback cycle.
• Platelets come into contact with exposed collagen.
• Platelets adhere to exposed collagen. Platelets develop
  pseudopods
• Cytokines are released (Thromboxane, ADP, 5HT)
• Cytokines activates and attract more platelets to the site
  of injury
• More platelets aggregate into the region resulting in
  formation of plug
• Act through positive feedback loop to activate more
  platelets

Question 19

Coagulation

Answer 19

Phase 1:
- Both pathways are triggered by tissue damaging events and vitamin K is necessary for normal clotting factor production
- Both pathways lead to production of factor X
- Intrinsic (slower) = activated by injury that occurs within the blood vesse. This begins the activation of factor XII (12)
- Extrinsic (Faster) = Activated by exposed blood to tissue (RELEASES, factor 7). Production of factor X that similarly produces prothrombin activator

Phase 2: Common Pathway to Thrombin
- The production of factor X and Prothrombinactivator cleaves Prothrombin to Thrombin. 3.

Phase 3: Common Pathway to Fibrin Mesh
- Thrombin catalyses the transformation of Fibrinogen to Fibrin.
- Fibrin molecules band together to form long hair-like insoluble strands
- Glue platelets together to form a structural web
- In presence of calcium, factor XIII (crosslinking enzyme), tightly binds fibrin to stabilise the fibrin
mesh.

Question 20

Fibrinolysis

Answer 20

• Process that removes unneeded clots when healing has occurred
• Crucial process as clots continually form and need to be degraded to prevent clogging of blood vessels

Question 21

Antithrombotic Drugs

Answer 21

• reduce the formation of blood clots
• For Example: Warfarin, and Aspirin

Question 22

Warfarin Action

Answer 22

Warfarin blocks Vitamin K epoxide reductase, and prevents the activation of the vitamin K related factors such as prothrombin which is involved in clotting cascade.

Question 23

Aspirin Action

Answer 23

• Aspirin blocks cyclooxygenase enzymes, preventing the release of thromboxane.
• Decreases the amount of platelet activation and aggregation.

Question 24

Monocytes

Answer 24

Monocytes in blood differentiate into macrophages

Question 25

HAEMOSTASIS

Answer 25

A mechanism that leads to the cessation of bleeding from a blood vessel. Fast, localised and controlled.

Question 26

STEPS OF HAEMOSTASIS:

Answer 26

(1) INJURY TO THE BLOOD VESSEL - causes disruption to the endothelium, exposing the connective tissue under the endothelium. - Causes collagen fibres to be exposed to blood and platelets. (2) PLATELET PLUG FORMATION - Platelets resultantly become activated (because of exposure to collagen fibres). - Platelets RELEASE ADP, which activates other platelets. - Causes platelets to swell and stick together to form a plug – positive feedback cycle. - Reduces the blood loss at the site of injury. (3) COAGULATION (process of a liquid changing to a solid/semi-solidstate.) - Fibrin forms a mesh that traps RBC and platelets, allowing the formation of a clot. - Activation of Fibrogen to fibrin. Fibrin covalently linked mesh that contracts and retards RBC movement. - COAGULATION CASCADE – release of clotting factors. Blood goes from liquid to a gel.