Blood Components

Question 1

How much blood is in the average man/woman

Answer 1

Man - 4-6 litres

Woman - 4-5 litres

Question 2

What are the main components of blood

Answer 2

1. Plasma (55%)
2. Formed elements (45%)
   a) erythrocytes (95.8%) = RBC
   b) leukocytes (0.1%) = WBC
   c) thrombocytes (4%) = platelets

Question 3

Describe Plasma

Answer 3

> Straw-coloured liquid (similar to interstitial fluid)
92% water
6-8% plasma proteins (help with clotting/osmotic pressures/ tissue repair etc.)
- albumin - allows blood to carry water better (deficiency leads to swelling as water stays in interstitial fluid)
- fibrinogen - aids clotting
- immunoglobulin
1% other solutes (electrolytes/gases/waste products)

Question 4

Describe erythrocytes

Answer 4

> Red blood cells
made in red bone marrow
bi-concave disc for greater SA
no nuclei/mitochondria/ribosomes etc - more room for O2 carrying (anaerobic glycolysis for energy)
Contain haemoglobin (max 4 O2 molecules - attract each other so 1st is hardest to attach and when full 1st is hardest to detach)

Question 5

Describe leukocytes

Answer 5

> role in inflammation/immune response
have nuclei + other organelles
small no. in blood (mostly in lymph + ct proper)
either
- granulocytes (microscope visible nucleus if stained)
a) neutrophils - 60% - phagocytosis of bacteria
b) eosinophils - 2% - allergic reactions/defence vs parasites/inflammation control
c) basophils - 1% - allergic/inflammatory reactions
- agranulocytes (nucleus not visible)
a) lymphocytes - 30% - immunity - T + B cells
b) monocytes - 6% - phagocytosis of pathogens/large debris + attracts immune cells

Question 6

Describe platelets

Answer 6

> small, colourless disc shaped fragment
> no nucleus
> large numbers in blood
> release important clotting chemicals
> patch damaged vessel walls temporarily
> actively contract tissue after clot formation

Question 7

What are the main functions of blood

Answer 7

> Transportation
- To cells: O2/nutrients/hormones/electrolytes/vitamins
- From cells: CO2/H2O/electrolytes/urea
Regulation
- pH: buffers of CO2/carbonate (7.35-7.45 for enzymes)
- osmotic pressure: proteins control water levels
- thermoregulation: remove excess heat from working muscle
Protection
- From disease - immunity + inflammation
- Haemostasis = clotting to prevent major blood loss

Question 8

What are the three main stages of haemostasis (blood clotting)

Answer 8

> Vascular phase
Platelet phase
Coagulation phase

*Same process throughout body

Question 9

Vascular phase of haemostasis (1st post damage)

Answer 9

1. Immediate vasospasm
   - smooth muscle contracts to reduce lumen
2. Endothelial cells become exposed
   - release chemical factors (ADP/tissue factor) - further smooth muscle contraction
   - Repair begins - cell division begins in endothelial cells/smooth muscle/fibrocytes
3. Sticky endothelial cell membranes - may stop blood loss in very minor injuries

Question 10

Platelet phase of haemostasis

Answer 10

1. Platelet Adhesion
   - ~ 15 seconds post injury
   - adhere to sticky endothelium/basal laminae/exposed collagen fibres
2. Platelet aggregation (forming temporary plug)
   - change in size
   - release chemicals to attract more chemicals and become stickier

Question 11

Coagulation phase of haemostasis

Answer 11

1. clotting involves complex cascade - prevent it happening by accident
2. converts fibrinogen to insoluble fibrin - via enzymes/proenzymes

Question 12

What are the three pathways of the coagulation phase

Answer 12

> Intrinsic 
- damage from within bloodstream
- begins with circulating proenzymes
> Extrinsic 
- damage from outside bloodstream
- begins in vessel wall
> Common pathway 
- where extrinsic and intrinsic converge

Question 13

Describe the clotting process of the common pathway

Answer 13

1. Prothrombin (blood protein) to Thrombin (enzyme) - via prothrombinase/prothrombin activator using calcium ion
2. Fibrinogen (plasma protein) to Fibrin (single protein) - via thrombin
3. Fibrinogen + calcium ion + stabilising factor = fibrin threads
4. fibrin threads + blood cells + plasma = blood clot (covers platelet plug/traps blood cells/seals off area)

Question 14

Describe Anaemia

Answer 14

> too few red blood cells or too little haemoglobin
(normal: men = 120-150, women = 100-130g per litre)
* haematocrit = red blood cell: blood volume ratio (normal = ~45%)
Causes
- blood loss
- folic acid/ vit b deficiency causing:
a) inadequate rbc production
b) excessive rbc destruction
Symptoms
- tiredness/weakness/pale skin/irregular heartbeat/shortness of breath/ chest pain/dizziness/headache/ cold hands/feet

Question 15

Describe polycythaemia

Answer 15

> abnormally high concentration of haemoglobin in blood

• blood = thicker and more likely to clot
• extra stress on heart to pump thicker blood round

(COPD causes polycythaemia as lack of O2 leads to greater haemoglobin production)

Question 16

Leukocytosis

Answer 16

> high white blood cell count
caused by:
- infection
- inflammation
- necrosis (tissue death)
- allergic responses
- leukaemia (abnormal WBC produced at greater rate than normal)

Question 17

Leukopenia

Answer 17

> Low white blood cell count
caused by: 
- bone marrow damage/disorder
- lymphoma
- autoimmune disorders
- dietary deficiencies 
- sepsis
- immune system diseases

Question 18

Blood clotting pathologies

Answer 18

• Platelet deficiency
• defective platelet function (aspirin effects stickiness)
• derangement of clotting factor (haemophilia - type depends on which factor is missing)