Composition of blood

Question 1

Composition of blood

Answer 1

• Blood travels within blood vessels to transport materials to cells & away from them
• Blood is a liquid containing plasma & suspended cellular elements
– Erythrocytes (red blood cells) – Leukocytes (white blood cells) – Platelets (thrombocytes)
• It makes up ~8% of our body weight – 5L in women
– 5.5L in men

Question 2

Composition of blood 2

Answer 2

• Constant flow of blood keeps cellular elements evenly dispersed
• If we collect a sample & let it sit, heavier cells drop to the boiom
• Haematocrit is packed cell volume of blood
• The rest is plasma

Question 3

Composition of blood: plasma

Answer 3

• Plasma is 90% water
• It is a medium for materials being carried in blood:
– Proteins
– Electrolytes (Na+, Cl-, HCO3-, K+, Ca2+, & other ions) – Nutrients (glucose, amino acids, lipids, vitamins) – Waste products (crea4nine, bilirubin, urea) – Dissolved gas (O2 & CO2)
– Hormones

Question 4

Composition of blood: plasma 2

Answer 4

• Plasma proteins (albumin, globulin, & fibrinogen) are not ‘just
being transported’
• They normally stay in plasma & have important functions:
– Establish a colloid osmotic gradient which prevents excessive bulk flow > maintains plasma volume
– Help to buffer changes in pH
– Albumin: non-specifically bind poorly soluble substances
– Globulins: α and β specifically bind poorly soluble substances & blood clorng. γ are antibodies or immunoglobulins (defense)
– Fibrinogen: blood clorng
• Synthesised by the liver, except antibodies which are made by type of white blood cell

Question 5

Composition of blood:

erythrocytes/RBCs

Answer 5

• Main function: O2 transport • Special features:
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- Flat, disc-shaped, indented in middle on both sides with flat centre: biconcave disc provides a larger surface area for O2 diffusion from plasma & into the cell
- Flexible membrane: deform & squeeze in single file through narrower capillaries
- Contain haemoglobin: O2 is poorly soluble in plasma so it is transported bound to haemoglobin, also helps to transport CO2. Reddish colour when oxygenated & bluish when deoxygenated
- Lacks nucleus & organelles: maximises haemoglobin content - Some enzymes for metabolism

Question 6

Composition of blood:

leukocytes/WBCs

Answer 6

• Main function: mobile elements of immune defense system
• Rapidly travel to sites of invasion or tissue damage
• Can exit blood through capillary pores by a wriggling behaviour

Question 7

platelets/thrombocytes

Answer 7

• Main function: Haemostasis to prevent blood loss via i) vascular spasm, ii) formation of platelet plug, and iii) blood coagulation

Question 8

Summary

Answer 8

• MAP is what the body monitors & regulates: the driving pressure head for blood flow to 4ssues
• MAP is determined by CO & TPR, thus all factors that influence these too
• Short- & long-term responses to regulate MAP
– Baroreceptor reflex
– LeQ atrial volume receptors & hypothalamic osmoreceptors
• The cardiovascular system under stress
– Physiological, e.g. exercise
– Pathological, e.g. hypertension & hypotension
• Composition of blood

Question 9

long term blood pressure

Answer 9

Left atrial vol. receptors & hypothalamic osmoreceptors regulate long-term responses in MAP

Question 10

long term blood pressure

high ecf osmolarity

Answer 10

high ecf osmolarity > stimulates hypothalamic receptors (controls thirst and vasopressin secretion) > stimulates hypothalamic neurons > increase thirst > increase h20 intake > decreases osmolarity and inc. ECF volume

Question 11

long term blood pressure

low ecf vol.

Answer 11

low ecf vol > stimulates Left atrial vol. receptors (important for large changes in ECF vol/arterial pressure) > hypothalamic neurons > incr. vasopressin (tells kidney to keep water >1. arteriolar vasconctriction wich relieves low bp or 2.increase H2O permeability of distal collecting tubules > h2O reabsoprtion > decrs. urine output > inc. ECF volume and dec. ECF osmolarity