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Flashcards in Haematopoiesis Deck (42)
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1

What are the components of blood?

Plasma:

  • Water
  • Proteins:
    • Globulins (y, a, B)
    • Albumins 
    • Fibrinogen
  • Small organic compounds and electrolytes
    • e.g. glucose, Na+, Ca2+

Red blood cells

White blood cells 

 

 

 

2

What are the roles of albumin?

Maintain oncotic pressure

Acts as a carrier protein for insoluble molecules

 

3

Which cells are granulocytes?

Basophils

Neutrophils

Eosinophils

4

Which cells can differentiate into macrophages?

Monocytes

5

What are the lifespans of:

  • Neutrophils
  • Lymphocytes
  • Monocytes
  • Erythrocytes
  • Eosinophils
  • Basophils
  • Platelets

What % of leukocytes do they make up?

  • Neutrophils: 
    • 1-2 days
    • 60% of leukocyte count
  • Lymphocytes:
    • ​3 days - 20 years
    • 20-30% of leukocyte count
  • Erythrocytes:
    • 4 months
    • 99% of all blood cells
  • Eosinophils:
    • ​1-2 days
    • 1-3% of leukocyte count
  • Basophils:
    • Hours - days
    • 0-1% of leukocyte count
  • Platelets:
    • 10 days
  • Monocytes:
    • ​3 days
    • 4-10% of leukocyte count 

6

What is haematopoiesis?

Which type of cell is responsible for haematopoiesis?

What processes are involved?

The production of all types of mature blood cells

  • Red blood cells = erythropoiesis
  • White blood cells = myelopoiesis and lymphopoiesis
  • Platelets = thrombopoiesis

Haematopoietic stem cells are responsible for all haematopoetic lineages through:

  • Proliferation 
  • Differentiation
  • Maturation

 

 

7

What is the process of haematopoiesis dependent on?

Glycoprotein growth factors produced by bone stromal cells 

Except:

  • Erythropoetin: produced in the kidneys 
  • Thrombopoietin: produced by liver 

8

What is differentiation?

New stem cells differentiate into specialised type of cell 

9

What is proliferation?

Mitosis of stem cells to produce greater number of cells

10

What is maturation?

Maturation of specialised cell to become mature version of that cell. 

11

Define:

Totipotent

Pluripotent

Multipotent

Oligopotent

Unipotent

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

  • Initial cells (first cell divisions) of the embryo

Pluripotent= cells that can differentiate into any cell type of the embryo

  • Produce the embryo

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

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

Unipotent= cells that can produce more cells of an identical cell type 

12

Describe the process of haematopoiesis

13

Which cells originate from the common myeloid progenitor cell?

What type of potency does the common myeloid progenitor have?

  • Megakaryotes → Thrombocytes
  • Erythrocytes
  • Mast cells
  • Myeloblasts →
    • Basophils
    • Eosinophils
    • Neutrophils
    • Monocytes → macrophages

Common myeloid progenitor = multipotent

14

Which cells originate from the common lymphoid progenitor cell?

Which type of potency does the common lymphoid progenitor have?

  • Natural killer cells (large, granular lymphocytes)
  • Small lymphocytes →
    • T-lymphocytes
    • B-lymphocytes → plasma cells 

Common lymphoid progenitor = oligopotent

15

Where do monocytes differentiate into macrophages?

In the tissues

16

Describe the maturation process of erythrocytes

What is involved in this process?

  1. Proerythroblast 
    1. Basophilic erythroblast
  2. Erythroblast
    1. Orthochromatic erythroblast
  3. Reticulocyte
  4. Erythrocyte

Involves:

  • Decrease in cell size
  • Haemoglobin production
  • Loss of organelles (including nucleus)
  • Acquisition of biconcave disc shape 

17

Which substance controls the maturation of erythrocytes?

What substances does erythropoiesis require?

Erythropoetin (EPO)

Erythropoiesis requires:

DNA synthesis:

  • Folic acid (B9)
  • Vit B12 (cobalamin)
  • Intrinsic factor

Haemoglobin synthesis:

  • Globins a2 and B2 (protein chains)
  • Haem (requires Fe2+ and B6)

18

What is the role of the biconcave disc of erythrocytes?

Increases surface area

Increases flexibility

Minimises distance from surface (enables gas exchange)

 

19

What is the role of folic acid (B9) and B12 in erythropoiesis?

What can a lack of either of these substances lead to?

Folic acid is required for DNA synthesis and therefore cellular proliferation 

B12 required for the recycling of folic acid 

Lack of either of these can lead to megaloblastic anaemia

  • Folic acid can ameliorate the effects of B12 deficiency

20

What is megaloblastic anaemia?

Large erythrocytes made in unsatisfactory amounts 

21

Where is folic acid absorbed?

How long do normal stores last?

How can a folic acid deficiency arise?

Absorbed in the duodenum and jejunum

Normal stores last 3-7 months

Deficiencies can arise from:

  • Inadequate dietary intake
  • Malabsorption
  • Increased demand
  • Drugs (e.g alcohol)

22

Where is B12 (cobalamin) absorbed?

How long do normal stores last?

How can deficiencies arise?

What is required for absorption?

Absorbed in the terminal ileum

Normal stores last 3-4 years

Deficiencies usually arise from malabsorption (rarely inadequate intake) 

Intrinsic factor is required for absorption as it binds to B12 and carries it to the terminal ileum where it is absorbed. 

23

What is intrinsic factor? Where it is produced?

Where do deficiencies stem from?

What can deficiencies lead to?

Why is intrinsic factor needed?

Glyprotein produced by parietal cells of the stomach

Deficiencies mainly caused by autoimmune destruction of parietal cells

Deficiencies can lead to pernicious anaemia (form of megaloblastic anaemia- large erythrocytes few in number)

Intrinsic factor is needed for B12 absorption which is required for recycling of B9 which is needed for DNA synthesis. 

24

Name some inherited disorders of globin chains

a or B chain thalassaemia

Sickle cell anaemia

25

What is sickle cell anaemia?

How is it caused?

Point mutation of base pair: HbA to HbS (A-T becomes T-A)

Leads to erythrocyte deoxygenation which leads to sickle cell shape 

26

How is iron absorbed?

How is it lost from the body?

Dietary iron:

  • Some lost in faeces
  • Some absorbed into epithelial cells and stored in ferritin pools
    • Some absorbed into the blood bound to transferrin
    • Some sloughed off due to high turnover of epithalial cells- lost in faeces

Excess iron in blood taken up via the basolateral membrane of GI epithelial cells via ferroportin and bound to ferritin for storage 

27

Where is most absorbed iron transported to?

Mostly transported to bone marrow to make haem. 

Remainder stored by the liver and spleen to or used by other tissue cells in enzymatic processes 

28

What is iron deficiency anaemia?

What is it caused by?

Iron deficiency leads to decreased levels of haemoglobin 

Low levels of haemoglobin decreases the production of RBCs

Causes:

  • Blood loss
  • Low dietary intake of iron
  • Poor iron absorption

29

What is pernicious anaemia?

What is it caused by?

Form of megaloblastic anaemia: erythrocytes produced are large but few in number due to deficiency in B12 and/or B9) which leads to decrease number of erythrocytes. 

Causes:

  • Lack of intrinsic factor
  • Diet low in B vitamins
  • Decreased absorption of B vitamins

 

 

 

30

What is aplastic anaemia?

What causes it?

Bone marrow is unable to produce enough RBCs :

  • Life threatening 

Causes:

  • Cancer treatments
  • Exposure to toxic substances
  • Autoimmune disorders
  • Viral infections