blood disorders:

Question 1

functions of the blood:

Answer 1

Transport role:

• O2 and nutrients to cells and tissues
• waste products from cells (e.g. CO2, urea, creatinine)
• hormones

Homeostasis:

• temperature
• acid-base balance
• water
• electrolyte balance

Defence:

• clotting
• immune responses

Question 2

composition of blood:

Answer 2

plasma - 54%

buffy coat = leukocytes (wbc) and platelets - 1%

hematocrit = erythrocytes (rbc) - 45%

Question 3

plasma:

Answer 3

water = solvent/transport medium

electrolytes = ions regulate membrane excitability/osmotic concentration

nutrients = glucose, amino acids, lipids, vitamins

dissolved gases

waste products = creatinine, urea

hormones

plasma proteins

Question 4

plasma proteins: albumins

Answer 4

60% of plasma proteins

synthesized in liver

transports thyroid hormones, biliruben and fatty acids

produces 75% of oncotic pressure

low levels associated with liver failure and nephrotic syndrome

Question 5

plasma proteins: globulins

Answer 5

α and β globulins synthesized by the liver

Transport role – e.g. bind iron (transferrin)

Inactive precursor hormones
e.g. angiotensinogen

Involved in blood clotting

γ globulins are immunoglobulins, synthesised by lymphocytes

Question 6

plasma proteins: fibrinogen

Answer 6

factor 1

synthesized by liver

Converted to fibrin during blood clotting

Elevated levels in cardiovascular disease

Smoking and lack of exercise associated with increased fibrinogen levels

Question 7

at arterial end of capillary…

Answer 7

high hydrostatic pressure forces fluid out of capillary to surrounding tissue

Question 8

at the venous end of capillary…

Answer 8

fluid is drawn back in by osmotic pressure

Question 9

regulators of erythropoiesis:

Answer 9

interleukins, stem cell factor, colony stimulating factors, erythropoietin (EPO)

nutrients - vitamin B12, iron, folate

Question 10

erythropoietin (EPO) =

Answer 10

cytokine hormone secreted by kidney in response to hypoxia

stimulates RBC production in bone marrow

Question 11

breakdown of red blood cells:

Answer 11

90% broken down by macrophages in the spleen, liver, and lymph nodes

10% lyse spontaneously in the blood – fragments engulfed by macrophages

Haem is broken down to bilirubin

Iron is transported back to bone marrow bound to transferrin

Question 12

disorders of erythropoiesis:

Answer 12

anaemia

polycythaemia

Question 13

anaemia =

Answer 13

A decrease in the level of haemoglobin in the blood = fewer rbc

may be asymptomatic

symptoms:
fatigue, headache, faintness, angina, breathlessness

diagnostic signs:
pallor, tachycardia, systolic flow murmur, cardiac failure

Question 14

small rbc anaemia =

Answer 14

low mean corpuscular volume

caused by…
iron deficiency
thalassaemia
sickle cell disease

Question 15

normal rbc anaemia =

Answer 15

normal mean corpuscular volume

caused by...
acute blood loss
renal failure
marrow failure
haemolytic anaemias

Question 16

large rbc anaemia =

Answer 16

high mean corpuscular volume

caused by..
megaloblastic marrow = vitamin B12 deficiency
or..
normoblastic marrow = 
alcohol poisoning
haemorrhage
liver disease

Question 17

ferritin:

Answer 17

an iron storage protein

prevents toxic effects of intracellular iron

releases iron in a controlled way

Question 18

hepcidin:

Answer 18

reduces iron absorption when iron stores are full by degrading ferroportin

Question 19

iron deficiency anaemia:

Answer 19

rbcs are smaller and paler

caused by…

poor intake - nutritionally poor diet

loss of blood from GI tract due to hookworm infestation

Question 20

thalassaemia:

Answer 20

Genetic disorders – fewer red blood cells due to imbalance in α or β Hb chain

severe anaemia, expansion of marrow + spleen + liver

treatment = regular transfusions + folic acid; marrow transplant may be an option, future prospects for gene therapy

Question 21

sickle cell disease:

Answer 21

Autosomal, recessive genetic disorder

single base mutation on B chain

homozygous = sickle cell anamia

heterozygous = asymptomatic, protected against malaria

Question 22

sickle cell anaemia:

Answer 22

Deoxygenated Hb molecules polymerise

‘sickling’ but becomes irreversible over time

sickled rbcs reduced flexibility

Question 23

vitamin B12 (cobalamin) deficiency:

Answer 23

B12 has a key role in DNA syntheis

bone marrow contains megaloblasts:

• large erythroblasts with immature nuclei
• reduced erythrocyte production

symptoms:
- anaemia

Question 24

B12 absorption:

Answer 24

B12 intake bound to protein complexes into stomach

its liberated by gastric enzymes and binds to R protein

its liberated by pancreatic enzymes and then intrinsic factor

its absorbed by cells of ileum

its transported to bone marrow

Question 25

pernicious anaemia:

Answer 25

causes;

• autoimmune disease attacking gastric mucosa
• antibodies produced to intrinsic factor, preventing B12 absorption = deficiency

Question 26

polycythaemia:

Answer 26

an increase in haemoglobin

increased red blood cell count (blood cancer) = thick blood

= clots, stroke, heart attack, splenomagaly

cause = JAK2 mutation means EPO receptor is always active

treated by chemotherapy, phlebotomy, radioactive phosphorus

Question 27

secondary polycythaemia:

Answer 27

high altitude
lung disease
cardiovascular disease
smoking