Blood and haemotopoesis

Question 1

Functions of blood

Answer 1

Transport- oxygen from lungs to tissues, carbon dioxde from tissues to lungs, nutrients, waste products, metabolites, hormones
Help protect from microorganisms
Regulation of body temperature
Repair of tissue damage

Question 2

Blood composition

Answer 2

Red blood cells (erythrocytes) 45% of total blood
White blood cells (leucocytes) less than 1% of total blood
Platelets (thrombocytes) less than 1% of total blood
Plasma 55% of total blood

Question 3

Plasma composition

Answer 3

Water
Organic solutes e.g. amino acids, glucose
Ions
Proteins
Enzymes
Hormones
Vitamins
Gases in solution

Question 4

Plasma proteins (7.3g/dL)

Answer 4

General functions: buffers, transport
Albumin (60%)- colloid oncotic pressure, ~25mmHg
Globulins (35%)- immunity
Fibrinogen (5%)- clotting

Question 5

Erythrocytes- morphology and composition

Answer 5

Bi-concave disk- flexible and maximum surface/volume ratio
Uniform size
65% Water
35% Haemoglobin
No nucleus or cell organelles

Question 6

Erythrocytes

Answer 6

Red blood cell membrane is more permeable to water than to solutes
In hypertonic solution, becomes crenated
In hypotonic solution, cells swell and burst
Limits of tonicity determine fragility of cell

Question 7

Erythropoiesis

Answer 7

Process of making RBCs
Haemocytoblast- stem cell directs ribosomes to make globin for Hb
Happens in red marrow
Takes 3-5 days

Question 8

Erythrocyte elimination

Answer 8

Engulfed by reticulo-endothelial cells in the spleen, connective tissue, lungs, liver and lymphoid tissue
Porphorin from haem makes bilirubin (yellow colour)
Protein returned to amino acid pool
Iron retained

Question 9

Blood transfusions and blood groups

Answer 9

Fatal haemolytic reactions may occur- antigen/antibody reactions
400 RBC antignes
Antibodies in serum- ABO are naturally occurring, rhesus are immune antibodies
At least 18 blood group systems

Question 10

Incompatible transfusions cause:

Answer 10

Haemolysis of donor and recipient cells
Fall in blood pressure due to adenosine nucleotide release
Renal failure due to toxic substances released from haemolysing cells
Leakage of Hb through glomerular membranes

Question 11

Rhesus factors

Answer 11

Subjects are Rh+ or Rh-
Rh antibodies do not occur naturally
Rh antibodies induced only after infusions of Rh+ blood or pregnancy
Antigen determined by dominant trait

Question 12

Rh +ve transfusion in patient with Rh antibodies causes

Answer 12

Agglutination and haemolysis of red cells (erythoblastic)

Question 13

Rhesus and pregnancy

Answer 13

Problems caused by Rh antibodies are only associated with Rh -ve mothers
Rh -ve mother carrying Rh -ve foetus is not a problem as no anti-Rh antibodies are generated
First Rh +ve baby carried by Rh -ve mother causes mother to generate anti-Rh antibodies
Second Rh +ve baby carried by Rh -ve mother is at risk of becoming erythroblastic due to attack from anti-Rh antibodies circulating in maternal bloodstream

Question 14

Prevention of erythroblastic foetus

Answer 14

Delivered by caesarian
Immediate transfusion of Rh -ve blood to eliminate the Rh +ve antibodies and damaged cells
Give mum IV anti-globulin near time of delivery to mop up Rh antibodies

Question 15

Platelet function

Answer 15

Play a vital role in cessation of bleeding

Have no nucleus and therefore cannot generate new proteins