Blood

Question 1

What is the average circulating volume of blood in a typical adult male?

Answer 1

5 Litres
o 1 in Lungs
o 3 in systemic venous circulation
o 1 in heart and arterial circulation

Question 2

List the functions of blood

Answer 2

o	Carriage of physiologically active compounds e.g. hormones, nutrients
o	Clotting e.g. Prothrombin + Fibrinogen
o	Defence e.g. Leukocytes
o	Carriage of gas e.g. Oxygen/CO2
o	Thermoregulation
o	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 composition can be indicative of problems elsewhere. Plasma proteins can be divided into 3 sub catagories.
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

Oncotic pressure, or colloid osmotic pressure, is a form of osmotic pressure exerted by proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that usually tends to pull water into the circulatory system.

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 structure and function of a red blood cell

Answer 5

Red cells are the most abundant (between 4 and 6x1012/L).
They have a 120 day life span and are needed to carry oxygen around the body using haemoglobin. They are highly flexible, bi concave and non-nucleated.
No mitochondria so rely on glycolysis

Question 6

Describe the function of erythropoietin, where it is synthesised 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;
o	Hypoxia
o	Haemorrhage
o	Anaemia
o	Lung disease

Question 7

Name the 5 main types of leukocytes

Answer 7

Neutrophils - phagocytic
Eosinophils - parasites and allergy
Basophils - heparin and histamine
Monocytes - macrophages
Lymphocytes - adaptive T and B

Question 8

Describe neutrophils

Answer 8

• 68% of WBC population (2.5-2.7x10-9/L)
• Half-life of around 6 hours
• Phagocytic and mainly deal with bacterial infection
• Can trap bacteria in NETS

Question 9

Describe eosinophils

Answer 9

• Around 1.5% of population (0.1-0.44x10-9/L)
• Attack pathogens too large for other leukocytes (eg. Parasites)
• Number rapidly increases in allergic reactions

Question 10

Describe basophils

Answer 10

• Around 0.5% of population (0.1x10-9/L)

* Release histamine and heparin to promote inflammation

Question 11

Describe monocytes

Answer 11

• 5% (0.2-0.8x10-9/L)
• Largest leukocyte
• 72 hour life span in circulation
• Migrate to tissues and become macrophages (phagocytic)

Question 12

Describe lymphocytes

Answer 12

• 25% (1.3-3.5x10-9/L)
• Key components of immune system
• T and B cell variants

Question 13

What factors influence WBC formation?

Answer 13

Leukopoiesis is more complex that erythropoiesis and is controlled by a cocktail of cytokines.
o Growth Stimulating Factors
o Interleukins

They are released by endothelial cells, fibroblasts and mature white cells, and stimulate mitosis and maturation of leukocytes. The cocktail is dynamic and changes its composition to suit which specific cell type is needed at any given moment.

Question 14

What are the functions of platelets?

Answer 14

Platelets are unique membrane bound fragments of megakaryocytes. Their formation is governed by thrombopoietin.
Platelets adhere to damaged capillary walls and exposed connective tissue to mediate blood clotting. They do not adhere to healthy epithelium.

Question 15

Define haematocrit

Answer 15

The percentage of blood made up of red blood cells. In males, it is usually between 40-54% and for females, between 37-47%, but these can be changed by certain factors. For example, living at altitude can increase haematocrit due to the need for more haemoglobin to bind the lower conc. of oxygen.

Question 16

Define what is meant by blood viscosity, and factors that can affect blood viscosity

Answer 16

The thickness of blood in comparison to water. Plasma is 1.8x thicker, whole blood is 3-4x thicker. This can change with haematocrit, temperature and flow rate.

Question 17

Outline the mechanisms of platelet formation

Answer 17

Platelets are produced in the bone marrow, the same as the red cells and most of the white blood cells. Platelets are produced from very large bone marrow cells called megakaryocytes.

Question 18

Define the healthy blood volume of a newborn baby

Answer 18

350ml

Question 19

What is hypoproteinemia and what can cause it?

Answer 19

Abnormally low levels of circulating plasma protein. Causes include:
o Prolonged starvation
o Liver disease
o Intestinal diseases
o Nephrosis (kidney disease)
Common characteristic - oedema due to loss of oncotic pressure, often seen in ankles and wrists. This is due to the movement of water from low protein containing plasma into tissues

Question 20

What causes the colour change in blood?

Answer 20

Colour change seen depending on state of cell and state of haemoglobin 
o	Oxyhaemoglobin (arterial) - bright red
o	Deoxyhaemoglobin (venous) - dull red/purple, almost blue