Blood & CV systems

Question 1

Functions of blood

Answer 1

Transports oxygen, carbon dioxide, water, hormones, nutrients, waste products, heat
Protects - blood clotting, immunity, inflammation
Regulates body fluid, pH, hormones, temperature

Question 2

Properties of blood

Answer 2

Viscosity (resistance to flow)

Osmololality (concentration)

Question 3

How many litres of blood does an average adult have?

Answer 3

4-6L
Plasma (55%) - clear extracellular fluid
Cells (45%)
Centrifugation separates cells from plasma

Question 4

What are the components of plasma?

Answer 4

Nutrients: glucose, gases, electrolytes, Na+ (90% of plasma electrolytes) hormones,
plasma proteins
Organic waste products:
Urea, creatinine, uric acid
toxic breakdown products removed by the kidneys

Question 5

Name the 3 plasma proteins found in the blood

Answer 5

Albumin - 
- most abundant plasma protein
produced by liver
- influences blood pressure, flow and fluid balance
Fibrinogen and clotting factors-
- produced by liver
- responsible for coagulation of the blood
Globulins -
- produced by plasma cells
- immunity

Question 6

Erythrocytes (RBC)

Answer 6

Gas transport: O2 and CO2 
Disc-shaped cell with thick rim =
increased surface area/volume ratio
No nucleus or organelles 
Cannot multiply (120 days life span)
Contain:
- haemoglobin 
- carbonic anhydrase enzyme
produces carbonic acid from CO2 and water

Question 7

Haemoglobin structure

Answer 7

4 protein chains (globins)
Each chain contains haem which allows oxygen to bind
Each Hb molecule can carry 4 oxygen molecules
Foetal Hb has a higher affinity to oxygen than adult Hb

Question 8

How do you measure erythrocyte concentration in clinical practice?

Answer 8

Haematocrit - packed cell volume (PCV)
Mean cell volume (MCV)
Erythrocyte count
Mean cell Hb (MCH)

Question 9

Define erythropoiesis

Answer 9

Process of the development of red blood cells from stem cells
Immature cells released into bloodstream as reticulocytes, and mature into erythrocytes

Question 10

What 2 things are required for blood cell synthesis?

Answer 10

Vitamin B12 and folic acid (have to be bound to intrinsic factor to allow absorption to take place

Question 11

Which hormone regulates red blood cell production?

Answer 11

Erythropoietin, produced in the kidneys

Question 12

What is haemolysis?

Answer 12

The breakdown of erythrocytes

Question 13

Leukocytes (WBC)

Answer 13

Important function in defence and immunity
Contain nuclei
Granulocytes:
> neutrophils - increase in bacterial infections, phagocytosis
> eosinophils - increase in parasitic infections eg. worms
> basophils - closely associated with allergic reactions (contain histamine), chicken pox
Agranulocytes:
> lymphocytes - increase in chronic infections and immune response, destroy foreign/virally cells, found in lymph nodes and spleen
> monocytes - become tissue macrophages, produce interlukin-1

Question 14

Platelets

Answer 14

Secrete:
- clotting factors
- factors for endothelial repair
- vasoconstrictors in broken vessels
Form temporary platelet plugs
Dissolve old blood clots 
Attract WBCs to sites of inflammation to phagocytose bacteria

Question 15

Define haemopoiesis

Answer 15

Production of blood cells

Question 16

What tissues produce blood cells?

Answer 16

1.yolk sac (in embryo)
2. liver, spleen (until birth)
3. red bone marrow
produces RBCs, WBCs and platelets
4. lymphoid tissues
WBC production, maturation

Question 17

Erythrocyte production

Answer 17

Erythropoiesis in red bone marrow produces  2.5 mil RBCs/second
Development takes 3-5 days
- reduction in cell size
- synthesis of Hb
- loss of nucleus

Question 18

Recycling of erythrocytes

Answer 18

RBCs live for 120 days
- fragile membrane  
- cell bursts in narrow channels in the spleen
Macrophages in spleen & liver
- digest cell components
- convert haem to bilirubin
- becomes bile product in faeces

Question 19

Erythrocyte homeostasis

Answer 19

NEGATIVE FEEDBACK 
- drop in RBC count = hypoxemia to kidneys
- EPO production increases
- stimulation of bone marrow
- RBC count increases in 3-4 days
Causes of hypoxia:
Lung disease
smoking
high altitude
increase in exercise
bleeding

Question 20

What is anaemia?

Answer 20

Inability of the blood to carry enough oxygen to meet body needs

• low levels of haemoglobin
• faulty haemoglobin
• loss of blood
• inadequate nutrition

Question 21

Terms used to describe RBC characteristics

Answer 21

Normochromic - cell colour normal
Normocytic - cells normal size
Microcytic - cells smaller than normal
Macrocytic - cells bigger than normal
Hypochromic - cells paler than normal
Haemolytic - rate of cell destruction raised
Megaloblastic - cells large and immature

Question 22

Types of anaemia

Answer 22

Diet induced:
eg. iron deficiency
eg. Vitamin B12/folic acid deficiency - pernicious (autoimmune) and dietary deficiency
Macrocytic/microcytic
Haemolytic - RBCs are destroyed or removed prematurely
Aplastic - bone marrow failure

Question 23

Haemostasis

Answer 23

Primary haemostasis = temporary platelet plug

Secondary haemostasis = coagulation, stable clot

Question 24

Vascular spasm

Answer 24

Prompt constriction of broken vessel
Triggered by:
> pain receptors (few mins)
> injury to smooth muscle (longer-lasting constriction)
> platelets release chemicals = serotonin
- provides time for other 2 mechanisms to work

Question 25

Platelet plug formation

Answer 25

Injury = primary haemostasis 
- vasoconstriction (immediately)
- platelet adhesion (seconds)
- platelet aggregation (minutes) = 
> broken vessel, rough surface (collagen exposed)
> platelets stick to it and other platelets
> release a variety of substances (ADP)
POSITIVE FEEDBACK

Question 26

Coagulation

Answer 26

Clotting factors in plasma:
- inactive form produced in liver
- one factor activates the next
= reaction cascade
                   THROMBIN
fibrinogen ------------------->> Insoluble fibrin
                 polymerisation

Question 27

Coagulation pathways

Answer 27

EXTRINSIC pathway = very fast
- factors released by tissues start it
INTRINSIC pathway
- factors found only in blood cause it
\+ occur together, converge in a common pathway, calcium required for both

Question 28

Coagulation factors

Answer 28

Factor 1 = fibrinogen
Factor 11 = prothrombin
Factor 111 = thromboplastin
Factor IV = Calcium
Factor VIII = anti-haemophiliac factor A

Question 29

How does a blood clot stop?

Answer 29

Platelets release chemicals to inhibit clotting
Other substances eg. heparin also inhibit process
Clot dissolves = fibrinolysis
Plasmin = fibrin -dissolving enzyme/clot buster

Question 30

What are clots not formed all the time?

Answer 30

• platelets don’t stick to smooth vessel wall
• clotting factors diluted by rapid blood flow (slow blood flow = DVT)
• natural anticoagulants present in the blood
  > anti-thrombin produced by the liver
  > heparin secreted by basophils and mast cells

Question 31

Blood groups

Answer 31

Antibodies in plasma cause agglutination in mismatched blood transfusions
- don’t have antibodies that would react with your antigens

Question 32

ABO system

Answer 32

Group   Antigen   Antiobody     
A           A              Anti-B
B           B              Anti-A
AB        A&B         None 
o           None       Anti-A and Anti-B

Question 33

RH group

Answer 33

D antigens on RBCs
Anti-D body not normally present
- forms only after exposure to Rh+ blood
- pregnancy, transfusion
O- packed cells can be given to any individual

Question 34

What could happen in a mismatched transfusion reaction?

Answer 34

Agglutination = blockage of vessels
Haemolysis = free Hb can block kidney tubules and cause death

Question 35

Haemolytic disease of newborn

Answer 35

Causes severe anaemia and toxic brain syndrome (excess bilirubin)
Prevention:
- blood typing of pregnant women
- Anti-D immunoglobulin given during pregnancy, after delivery, within 3 days of birth