Introduction to blood

Question 1

What is the average circulating volume in the typical adult male?

Answer 1

5 liters

• 1 in lungs
• 3 in systconstriction when cold

emic venous circulation
- 1 in heart and arterial circulation

Question 2

List the functions of blood

Answer 2

Carriage of physiologically active compounds
- Hormones, Enzymes, Nutrients

Clotting
- Prothrombin + Fibrinogen

Defence
- Leukocytes

Carriage of gas
- Oxygen/CO2

Thermoregulation
- Vasodilation when hot, vasoconstriction when cold

Maintenance of ECF pH

Question 3

Describe the composition of plasma

Answer 3

Plasma is 95% water and is used to circulate biologically active molecules and compounds.
Small changes in protein can be indicative of problems elsewhere
Plasma proteins can be divided into 3 sub categories.

Albumin:

• transports lipid and steroid hormones
• Helps create colloid oncotic pressure

Globulins:

• Alpha/Beta transport lipids and fat-soluble vitamins
• Gamma globulins are antibodies

Fibrinogen and other clotting factors

Question 4

Define the term oncotic pressure and describe the factors responsible for its generation.

Answer 4

Plasma proteins do not readily cross the capillary wall. These proteins displace water and create an osmotic potential. This creates a pressure that can pull water from the interstitial space into the lumen. When the water moves, chemicals, and nutrients move too, however, this only changes the volume, not the concentration.

Question 5

Describe the function of the red blood cell.

Answer 5

Red cells are the most abundant (between 4 and 6 times 10 to the power of 12 per liter). They have a 120 days life span and are needed to carry oxygen around the body using hemoglobin. They are highly flexible, biconcave, and non-nucleated.

Question 6

Describe the function of erythropoietin, where it is synthesized, and the factors which may increase secretion.

Answer 6

Erythropoiesis is controlled and accelerated by the protein Erythropoietin. It is mainly secreted by the peritubular capillary cells found in the kidneys, and also the hepatocytes of the liver (85%/15% respectively).
It speeds up the differentiation of pluripotent stem cells into erythroblasts. Secretion is increased when the oxygen supply to the kidneys is reduced. This can be caused by a number of factors, for example;
-Hypoxia
-Haemorrhage
- Anaemia
-Lung disease