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Blood, Heart and Lungs > Haematopoiesis > Flashcards

Haematopoiesis Flashcards

1
Q

What does blood plasma contain?

A
  • Water
  • Small organic compounds (eg glucose) and electrolytes (sg. Sodium)
  • Proteins: Albumin, Globulins (α, β, γ), Fibrinogen – involved in clotting
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2
Q

What type of cells give rise to all blood cells and where are they found?

A

Haemopoietic stem cells (HSCs) in the bone marrow give rise to all haemopoietic cell lineages

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3
Q

What are the general stages of haematopoiesis?

A

1) Proliferation – mitosis, making more cells
2) Differentiation – which lineage will the cell go down?
3) Maturation – after a cell has committed to being a certain type, it will develop

These processes overlap.

The process is dependent on glycoprotein growth factors produced mainly by bone stromal cells – exceptions being erythropoietin (kidneys) and thrombopoietin (liver).

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4
Q

List the different types of potency from most potent to least potent

A

Totipotent cells can differentiate into any cell type, including embryonic and extraembryonic

Pluripotent cells can differentiate into any cell type of the embryo

Multipotent cells can differentiate into several different, but related cell types

Oligopotent cells can differentiate into a small number of very closely related cell types

Unipotent cells can produce more cells of identical cell type

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5
Q

What cell types can arise from the common myeloid progenitor?

A
  • Megakaryocyte
  • Erythrocyte
  • Mast cell
  • Myeloblast
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6
Q

What cell type can arise from a megakaryocyte?

A

thrombocytes

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7
Q

What cell type can arise from myeloblasts?

A
  • Basophil (granulocyte)
  • Neutrophil (granulocyte)
  • Eosinophil (granulocyte)
  • Monocyte -> Macrophage
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8
Q

What cell type can arise from the common lymphoid progenitor?

A
  • Natural killer cell

- Small lymphocyte

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9
Q

What cell types can arise from the small lymphocyte?

A
  • T lymphocyte

- B lymphocyte -> plasma cell

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10
Q

Describe the characteristics of the 3 types of granulocytes

A

Neutrophils are phagocytic, with lytic enzymes within granules, including peroxidase and lysozyme - very effective in killing ingested bacteria

Eosinophils are most important in defence against larger parasites

Basophils are non-phagocytic and release active substances from their granules

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11
Q

Describe the differences between monocytes and macrophages

A

Monocytes circulate in the blood

Macrophages are formed by differentiation of monocytes are 5-10x bigger and found in the tissues

Macrophages ingest small pathogens and other material by phagocytosis

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12
Q

Describe the stages in thrombopoiesis

A

Thrombopoiesis = production of platelets

Megakaryoblast → Promegakaryocyte
→ Megakaryocyte → Thrombocytes (Platelets)

Megakaryocytes in the bone marrow are situated adjacent to blood sinusoids.
Segments of megakaryocyte cytoplasm protrude into the blood sinusoids.
The blood flow splits off cytoplasmic fragments, which become platelets.
Platelets circulate in the blood for 7 -10 days.
40% are located in the spleen.

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13
Q

What is leukocytosis?

A

High white cell count

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14
Q

What is leukopenia?

A

Low white cell count

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15
Q

What is lymphocytosis?

A

High lymphocyte count

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16
Q

What is lymphocytopenia?

A

Low lymphocyte count

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17
Q

What is neutrophilia?

A

High neutrophil count

18
Q

What is neutropenia?

A

Low neutrophil count

19
Q

What is thrombocytosis?

A

High platelet count

20
Q

What is thrombocytopenia?

A

Low platelet count

21
Q

Describe erythropoiesis

A

Proerythroblast → Erythroblast → Reticulocyte → Erythrocyte

22
Q

What are the 4 characteristics of erythrocyte maturation?

A

1) Decrease in cell size
2) Haemoglobin production
3) Loss of organelles (inc. nucleus)
4) Acquisition of biconcave disc shape

It is controlled by erythropoietin (EPO) and requires Iron, Folic acid and Vitamin B12

23
Q

What is the purpose of the biconcave shape in erythrocytes?

A

1) Maximises surface area
2) Minimises distance from surface
3) Increases flexibility

Structural proteins to maintain shape

Simplified internal structure (lack organelles)

Simplified metabolism

24
Q

What vitamins etc. are required for erythropoiesis and why?

A

Folic acid (B9), Cobalamin (B12) and Intrinsic factor are required for DNA synthesis

Vitamin B6 and Iron are needed to make the globin chains and haem for haemoglobin synthesis

25
Q

What can cause megaloblastic/pernicious anaemia?

A

Folic acid (folate; vitamin B9) is required for DNA synthesis and therefore cellular proliferation

Cobalamin (vitamin B12) is involved in the recycling of folic acid

Lack of either can lead to megaloblastic anaemia, although plentiful folic acid can ameliorate the effects of vitamin B12 deficiency

Intrinsic Factor (IF) is a glycoprotein produced by the parietal cells of the stomach.
It binds to vitamin B12 and is essential for it’s absorption in the ileum.
Lack of Intrinsic Factor, most often due to an autoimmune response to parietal cells, leads to pernicious anaemia (megaloblastic anaemia)
26
Q

Where in the body are folic acid and cobalamin absorbed and how long are they stored for?

A 
Folic acid (B9) is absorbed in the duodenum and jejunum.
Normal stores of folic acid last about 3-7 months.
Folic acid deficiency can arise from inadequate intake, malabsorption, increased demand, drugs (e.g. alcohol).

Cobalamin (B12) is absorbed in the terminal ileum.
Normal stores of cobalamin last about 3-4 years.
Cobalamin deficiency is usually due to malabsorption (rarely inadequate intake).

27
Q

Name some inherited disorders of the globin chains

A

α or β thalassemia, sickle cell anaemia

28
Q

How are haem groups synthesised?

A

Synthesis of haem groups occurs by a metabolic pathway, with steps in the mitochondria and cytoplasm.
Vitamin B6 is an essential co-enzyme in this pathway

29
Q

What are inherited disorders in heme synthesis called?

A

Porphyrias

30
Q

Where is iron stored?

A

Most of the absorbed iron is transported to the bone marrow where it is used to make haem.
The remainder is stored in the liver and spleen or used by other tissue cells in enzymatic processes.
Iron absorption is regulated by the hormone hepcidin, which is released by the liver when iron levels are too high.
Hepcidin inhibits iron absorption by decreasing ferroportin activity on the basolateral membrane of intestinal epithelial cells.

31
Q

Define anaemia

A

A deficiency of red cells or haemoglobin in the blood

32
Q

Define macrocytic anaemia

A

Involves large erythrocytes, but in low number and/or with low Hb content per cell

33
Q

Define microcytic anaemia

A

Involves small erythrocytes and usually low Hb content per cell

34
Q

Define normocytic anaemia

A

Involves erythrocytes of normal size, but usually present in inadequate number

35
Q

Describe iron deficiency anaemia and its causes

A

Deficiency of iron leads to decreased amounts of haemoglobin; low levels of haemoglobin in turn decreases the production of RBCs

Caused by blood loss, diet low in iron, poor absorption of iron

36
Q

Describe pernicious anaemia and B vitamin deficiency

A

RBCs do not develop as they normally would because of a lack of B vitamins (B9, B12), which leads to decreased production of RBCs

Causes: Lack of intrinsic factor, diet low in B vitamins, decreased absorption of B vitamins

37
Q

Describe aplastic anaemia and its causes

A

Bone marrow is unable to produce enough blood cells; a life threatening condition

Causes: Cancer therapy, exposure to toxic substances, autoimmune disorders, viral infections

38
Q

Describe haemolytic anaemia and its causes

A

RBCs are destroyed faster than the bone marrow can replace them

Inherited causes include sickle cell and thalassemia

39
Q

Describe anaemia of chronic diseases and its causes

A

Various illnesses over a long time can reduce the production of RBCs

Causes: Rheumatoid arthritis, kidney disease, diabetes, tuberculosis or HIV

40
Q

What is erythropoietin (EPO)?

A

Erythropoietin (EPO) is released by fibroblasts in the kidneys in response to cellular hypoxia and stimulates erythropoiesis in the bone marrow. It binds to a specific receptor on proerythroblasts / basophilic erythroblasts and promotes cell survival.

41
Q

What is thrombopoietin?

A

Thrombopoietin is produced in the liver and elsewhere and primarily stimulates the differentiation of megakaryocytes and thrombocytes (platelets). There is a negative feedback loop in which thrombocytes reduce thrombopoietin levels.

Blood, Heart and Lungs (33 decks)

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