Lecture 20: Composition and general function of blood

Question 1

What are the general functions of blood

Answer 1

1. Transport of:
   - O2, nutrients,CO2 and other waste products
   - hormones; coordinates the activities of organs
   - phagocytic cells, antibodies & coagulation factors
2. Immune response: via phagocytes, antibodies & fighting infections
3. Coagulation; preventing of bleeding via platelets

Question 2

What is blood composed of?

Answer 2

1. Plasma = fluid portion
2. Cells = formed elements
   e. g RBCs or erythrocytes
   e. g WBC’s or leukocytes
   - WBCs are granulocytes from myeloid cells or lymphocytes

Question 3

What is plasma?

What is it comprised of?

Answer 3

Plasma = fluid portion
Plasma comprises of:
- water 90%
- solutes 10%

Question 4

What 3 main groups is plasma divided up into?

Answer 4

1. Albumins: maintain osmotic pressure; buffers blood; binds and transports insoluble substances e.g hormones & coagulation factors
2. Globulins: many different antibodies are globulins
3. Fibrinogen; is the precursor of fibrin during blood coagulation

Question 5

All blood cell are derived form what common progenitor cells?

What do the progenitor cells differentiate into?

Answer 5

All blood cells are derived from:

• Myeloid stem cells
• Lymphoid stem cells

They differentiate into RBC’s WBC and platelets

Question 6

White blood cells are granulocytes or lymphocytes

• what are the various granulocyte types?
• what are they derived from?

Answer 6

• Neutrophils 65% = cellular defence & phagocytosis

- Basophils

Question 7

White blood cells are are granulocytes or lymphocytes

• where are lymphocytes?
• what are they derived from?

Answer 7

Lymphocytes 25% = humoral defence - secrete antibodies

= derived from lymphoid stem cells

Question 8

What is the structure of RBCs?

What does it allow them to do?

Answer 8

Structure: Biconcave disc shape - large surface area

• shape allows for efficient diffusion of gases
• Flexibility of movement through narrow capillaries
• Contain large amounts of haemoglobin

Question 9

What is RBC production stimulated by?

What does it require?

Answer 9

Production is stimulate by erythropoietin EPO and RBC production is controlled by a homeostatic control loop. It is augmented by testosterone
RBC production requires
- folic acid
- Vitamin B12
- Thymine for mitosis of stem cells
- Iron for haemoglobin stimulus
RBC production = RBC destruction
Reduction if RBC's causes a decreased in O2 delivery

Question 10

What happens when RBC’s are broken apart?

What happens to the components that make up RBCs?

Answer 10

RBC break apart in the capillaries; these fragmented RBC’s are removed by macrophages

• Hb is broken down into ammoniac’s, iron & bilirubin
• Iron is transported to bone marrow
• amino acids are used for energy.
• Bilirubin is transported to the liver and excreted in bile

Question 11

What is anaemia?

What does it cause?

Answer 11

Is a reduction in the concentration of Hb - reduces O2 capacity and results in insufficient O2 supply to tissue
- causes bleeding; acute loss of blood and O2 carrying capacity many result in shock; chronic bleeding

Question 12

What causes anaemia?

Answer 12

Decreased production of RBC’s
= resulting from reduced proliferation of defective maturation
Increased destruction of RBC’s
= resulting from cellar defects or from an extracellular defect