Blood (Intro)

Question 1

State the average circulating volume in a typical adult male.

Answer 1

Average 70kg male - 5L of blood.
- 1L lungs.
- 3L systemic venous circulation.
- 1L heart and arterial circulation.

Question 2

STATE the 5 functions of blood.

Answer 2

Carry compounds (plasma)
Clotting (platelets)
Defence (white blood cells)
Carry gas (red blood cells)
Thermoregulation
Maintenance of ECF pH.

Question 3

Explain the importance of thermoregulation.

Answer 3

Thermoregulation is used to regulate body temperature, this can sometimes achieved by sweating or shivering.
However in relation to blood, thermoregulation could mean the dilation or restriction of the blood vessels to lose or gain heat.

Question 4

Explain the importance of maintaining the pH of the ECF.

Answer 4

The standard pH for the ECF is 7.4 and small fluctuations can lead to chain reactions causing deleterious biochemical reactions to occur.

Question 5

Describe the composition of plasma.

Answer 5

Plasma makes up 4% of our body weight.
95% of plasma itself is water. The remaining 5% is made up of ions (primarily sodium), hormones, enzymes and plasma proteins.

Question 6

Name the 3 categories of plasma protein.

Answer 6

1) Albumin - 60%
2) Globulins, alpha, beta and gamma- 38%
3) Fibrinogen - last 2%

Question 7

Describe the plasma protein, Albumin

Answer 7

Albumin is the most abundant plasma protein.
One function of Albumin is to transport substances that do not dissolve easily in water (e.g. lipids, steroid hormones) around the body.

Question 8

Describe the plasma protein, Globulin

Answer 8

Globulin can either be alpha, beta or gamma.
Alpha and beta globulins are similar to Albumin and carry out similar functions.
Gamma globulins are antibodies and are used to defend the body.

Question 9

Describe the plasma protein, Fibrinogen.

Answer 9

Fibrinogen is the least abundant plasma protein making up, along with other clotting figures, 2% of all plasma proteins.
i.e. Fibrinogen is a clotting figure.

Question 10

Describe the factors responsible for generation of colloid oncotic pressure.

Answer 10

The capillary walls are permeable to most substances, except from blood cells and plasma proteins.
Colloid oncotic pressure is driven by the presence of non-penetrating molecules - plasma proteins. Their presence displaces water from the vessel. Creating a difference in the concentrations inside and outside of the vessel, and therefore creating a concentration gradient.
This thereby increases blood circulation by removal or pull of water into the vessel.
(Interstitial fluid acts as a fluid reservoir).

Question 11

Explain the function of plasma.

Answer 11

“Think of plasma proteins as the London underground and the organic compounds they attach to as passengers”.
Plasma never enters the cell, it carries out its function within circulation -in the blood.

Question 12

Explain how the body counteracts colloid oncotic pressure.

Answer 12

Due to the increase in colloid oncotic pressure, this causes an increase in circulation throughout the capillaries, ultimately putting more pressure on the capillary walls (or membranes) and causing an increase in hydrostatic pressure. This causes more fluid to leave the capillary and enter the interstitial fluid.

Question 13

State the normal lifespan of red blood cells in the circulation.

Answer 13

Erythrocytes (RBCs) live for 120 day within the circulation before they become misshapen, due to the cytoskeleton breaking down. These RBCs are then taken and recycled by the spleen.

Question 14

State the normal lifespan of platelets in the circulation.

Answer 14

Platelets live for 10 days within the circulation, where they primarily adhere to damaged endothelium.

Question 15

Describe the function of the red blood cell.

Answer 15

The red blood cells are essential for the transport of CO2 and O2. These cells are flexible and biconcave. These cells are also non-nucleated meaning they don’t possess a nucleus, meaning they can deform easily.

Question 16

Describe the function of erythropoietin.

Answer 16

Erythropoietin is a hormone that controls and accelerates red blood formation. A haemorrhage, anaemia, cardiac dysfunction or lung disease could all lead to hypoxia (low O2 delivery to kidney). Hypoxia increases the secretion of erythropoietin to the kidney (85%) and liver (15%)./

Question 17

Describe the process of erythropoiesis.

Answer 17

Erythropoiesis is the process of erythrocyte formation. Erythrocytes = reticulocytes, these are immature blood cells.
All blood cells come from pluripotent hematopoietic stem cells.
These can either become lymphocyte stem cells, or uncommitted stem cells.
The uncommitted stem cells then differentiate into committed progenitor cells. If the composition of the environment is correct for RBC formation, then, still within the bone marrow, these uncommitted progenitor cells will become erythroblasts. At this point the erythroblasts have lost their ribosomes and mitochondria that they need.
After this point the erythroblasts become reticulocytes and enter the bloodstream.
Eventually they will mature further into erythrocytes.

Question 18

Name the 5 main types of white blood cells.

Answer 18

Neutrophils - most abundant.
Basophils - least abundant:
Monocytes - they migrate to connective tissue where they exist as macrophages.
Lymphocytes
Eosinophils.

Question 19

Describe the difference between a monocyte and a macrophage.

Answer 19

Monocytes exist within the circulation for 72 hours, making up 5% of all circulating cells. After the 72 hours are up, they migrate to connective tissue where they become macrophages and live for 3 months. During this time they will phagocytose dead cells and bacteria.

Question 20

Define ‘leukopoiesis’ and describe the factors that control it.

Answer 20

Leukopoiesis is the process of white blood cell formation.
It is controlled by the cocktail of cytokines (proteins/peptides released from one cell type to act on another)
- Colony stimulating factors e.g. granulocyte CSF.
- Interleukins = communication

Question 21

Describe in detail how WBCs are formed.

Answer 21

Cytokines are released from mature WBCs.
This stimulates mitosis and maturation of leukocyte.
In response to infection, leukopoiesis may be stimulated by a bacterial infection (causes an increase in neutrophils), or a viral infection (causes increase in lymphocytes).

Question 22

Describe the unique function of platelets.

Answer 22

Platelets are membrane bound cell fragments of megakaryocytes. Their formation is governed by thrombopoietin.
Platelets primary function is to adhere to damaged vessel walls. The platelets stick to the walls, plugging the hole until they are sealed by clotting factors. Platelets don’t adhere to healthy intact endothelium.
**Platelets act as scaffolding for clotting factors to build upon or around.

Question 23

Define “haematocrit”.

Answer 23

Haematocrit refers to the % of red blood cells as a fraction to the whole blood (sample).

Question 24

State the normal value for haematocrit.

Answer 24

Normal range 40-50%.

Question 25

Describe how haematocrit may differ in changing environments.

Answer 25

Haematocrit will increase under the influence of erythropoietin as it accelerates production of RBCs.
Also increases by acclimatation process
- less O2 in the air at altitude so erythropoietin release is enhanced to improve O2 carrying
capacity of blood.
Haematocrit will decrease in anaemia and following haemorrhage.

Question 26

Describe what is meant by blood viscosity.

Answer 26

Viscosity refers to how thick/sticky a substance is compared to water. So a blood viscosity would be the number of times the blood is more viscous than water.

Question 27

Describe how viscosity may change in certain circumstances.

Answer 27

Viscosity is not an absolute value.
It depends on;
Haematocrit = when there is a 50% increase in haematocrit, there is a 100% increase in viscosity.
Temperature = A decrease in temperature results in an increase in viscosity.
Flow rate = A decrease in flow rate, leads to an increase in viscosity.

Question 28

Describe the effect that temperature has to our health in relation to viscosity.

Answer 28

Dangerous effect.
In the circumstance of hypothermia, the decrease in temperature causes an increase in viscosity, which makes it hard for heart to pump blood.