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Flashcards in Session 11 Deck (27):

What is the lifespan of red blood cells?

- 120 days


What is the lifespan of platelets?

- 10 days


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

- Neutrophils: 2-4 days
- Lymphocytes: 1 day-years


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

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


What controls haemopoiesis?

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


What is haemopoiesis?

- Formation of blood cellular components


What are blood cellular components derived from?

- Multipotent haemopoietic stem cell (haemoblast)


What are the stages of haemopoiesis?

- Proliferation
- Differentiation


Describe proliferation in haemopoiesis

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


Describe differentiation in haemopoiesis

- 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


What are the functions of red blood cells?

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


How does the structure of RBCs suit its functions?

- 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


What metabolic pathways take place in RBCs?

- Glucose -> Lactate (generation of ATP)
- Glucose-6-phosphate metabolised (generation of NADPH)


What controls erythropoiesis?

- 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


Where are white blood cells formed?

- Bone marrow by multipotent haemopoietic stem cells
- May mature elsewhere eg T-cells in thymus


What do WBCs do?

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


What types of white blood cells are there?

- Neutrophils
- Basophils
- Eosinophils
- Monocytes
- Lymphocytes


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

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


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

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


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

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


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

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


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

- 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


What is the structure and function of erythrocytes?

- 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


What is the structure and function of reticular cells?

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


What is the structure and function of platelets?

- 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


What happens during RBC catabolism?

- 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


Where are most platelets stored?

- Spleen