Session 11

Question 0

What is the lifespan of platelets?

Answer 0

• 10 days

Question 1

What is the lifespan of red blood cells?

Answer 1

• 120 days

Question 2

What is the lifespan of white blood cells (neutrophils and lymphocytes)?

Answer 2

• Neutrophils: 2-4 days

- Lymphocytes: 1 day-years

Question 3

Where are red blood cells, platelets and most white blood cells produced?

Answer 3

• Bone marrow
• Extensive throughout the skeleton in infants
• More limited distribution in adults, mainly in: pelvis, sternum, skull, ribs, vertebrae

Question 4

What controls haemopoiesis?

Answer 4

• Cytokines (hormones)
  ~ erythropoietin (production of RBCs)
  ~ thrombopoeitin (production of platelets)

Question 5

What is haemopoiesis?

Answer 5

• Formation of blood cellular components

Question 6

What are blood cellular components derived from?

Answer 6

• Multipotent haemopoietic stem cell (haemoblast)

Question 7

What are the stages of haemopoiesis?

Answer 7

• Proliferation

- Differentiation

Question 8

Describe proliferation in haemopoiesis

Answer 8

• Stem cell divides in two

- One replaces original stem cell (self-renewal) and the other is used in differentiation

Question 9

Describe differentiation in haemopoiesis

Answer 9

• Stem cell will first differentiate to form a myeloid blast or a lymphoid blast
• Type of cell that is differentiated into depends of the influence of a particular cytokine

Question 10

What are the functions of red blood cells?

Answer 10

• Deliver oxygen to tissues and remove carbon dioxide
• Carry haemoglobin and maintain it in its reduced state
• Maintain osmotic equilibrium
• Generate ATP

Question 11

How does the structure of RBCs suit its functions?

Answer 11

• Biconcave flexible disc 8um diameter: can pass through microcirculation that has a minimum diameter of 3.5um
• 4 globin chains: each has a haem molecule that can bind to 1 molecule of O2 each
• Exist in 2 conformations: variation in oxygen affinity

Question 12

What metabolic pathways take place in RBCs?

Answer 12

• Glucose -> Lactate (generation of ATP)

- Glucose-6-phosphate metabolised (generation of NADPH)

Question 13

What controls erythropoiesis?

Answer 13

• Reduced pO2 detected in kidneys
• Increased production of erythropoietin
• Stimulates maturation and release of red cells from marrow
• Haemoglobin rises
• pO2 rises; erythropoietin falls; RBC production falls

Question 14

Where are white blood cells formed?

Answer 14

• Bone marrow by multipotent haemopoietic stem cells

- May mature elsewhere eg T-cells in thymus

Question 15

What do WBCs do?

Answer 15

• Circulate in the blood and lymphatic system until signalled by damaged tissue (by injury/infection)

Question 16

What types of white blood cells are there?

Answer 16

• Neutrophils
• Basophils
• Eosinophils
• Monocytes
• Lymphocytes

Question 17

What is the function of neutrophils and what is their nucleus like?

Answer 17

• Phagocytosis
• Migrate out of circulation to site of infection
• Increased production by G-CSF (granulocyte colony stimulating factor)
• Multi-lobed nucleus and granular cytoplasm

Question 18

What is the function of eosinophils and what is their nucleus like?

Answer 18

• Capable of phagocytosis
• Release cytotoxic particle to damage larger particles
• Bi-lobed nucleus

Question 19

What is the function of basophils and what is their nucleus like?

Answer 19

• Mediate acute inflammatory reactions using heparin and histamine
• Bi- or Tri-lobed nucleus

Question 20

What is the function of monocytes and what is their nucleus like?

Answer 20

• Migrate to become macrophages in many organs of the body
• Capable of phagocytosis and interact with T cells
• Kidney shaped nucleus

Question 21

What is the function of lymphocytes and what is their nucleus like?

Answer 21

• B cell: humoral immunity; stimulated by antigens to transform into plasma cells which secrete immunoglobulins (antibodies); antigen presenting cells
• T cell: express CD4 on surface (helper cells); can be killer cells; permit the transformation of B cells into plasma cells
• Deep staining nucleus

Question 22

What is the structure and function of erythrocytes?

Answer 22

- Structure:
    ~ Biconcave disc
    ~ 4 globin chains (2xa, 2xB)
    ~ each molecule carries a haem
- Function:
    ~ Carries O2 from lungs to tissues 
    ~ Carries CO2 from tissues to lungs

Question 23

What is the structure and function of reticular cells?

Answer 23

• Structure:
  ~ Synthesise reticular fibres and surround them with cytoplasm
• Function:
  ~ Direct T and B lymphocytes to specific regions with the lymphatic tissues

Question 24

What is the structure and function of platelets?

Answer 24

• Structure:
  ~ Small, round, blue particles
  ~ Produced by megakaryocytes in the bone marrow
  ~ Complex surface membrane
  ~ Cytoplasm contains a and dense granules
  ~ a contains glycoproteins, fibrinogen and Von Willebrand’s factor
  ~ Dense contains ADP and Ca2+
• Function:
  ~ Clotting cascade activation-interact with clotting factors eg factor VII, IX, X
  ~ Adhere to damaged cell walls and aggregate together

Question 25

What happens during RBC catabolism?

Answer 25

• RBCs -> Haemoglobin -> Haem -> Bilirubin -> Bilirubin in liver -> Bilirubin through gall bladder and duct (if there is a blockage here can cause jaundice) into the small intestine and large intestine -> (stercobilin out of the body) urobilinogen to the kidney -> urobilinogen is excreted

Question 26

Where are most platelets stored?

Answer 26

• Spleen