Haematopoiesis

Question 1

What are the cellular components of blood?

Answer 1

Erythrocytes
Leukocytes
Plasma
Platelets
Water

Question 2

What does blood plasma contain?

Answer 2

Water
Small organic compounds and electrolytes
Proteins (Albumins, Globulins + Fibrinogen)

Question 3

What is blood made up of?

Answer 3

Cells + Plasma

Question 4

What is haematopoiesis?

Answer 4

Production of all types of mature blood cells (RBCs, WBCs and platelets)

Question 5

Where are haemopoietic stem cells found?

Answer 5

Bone marrow

Question 6

What are the functions of the biconcave disc shape of erythrocytes?

Answer 6

Maximise surface area
Minimise distance from surface
Increases flexibility

Question 7

What is folic acid used for?

Answer 7

DNA synthesis and cell proliferation

Question 8

What is Cobalamin (B12) used for?

Answer 8

Recycling of folic acid

Question 9

What causes megaloblastic anaemia?

Answer 9

Folic acid or B12 deficiency

Question 10

Where is folic acid absorbed?

Answer 10

Duodenum

Jejunum

Question 11

How does folic acid deficiency arise?

Answer 11

Inadequate intake
Malabsorption
Increased demand

Question 12

Where is vitamin B12 absorbed?

Answer 12

Terminal ileum (requires Intrinsic Factor)

Question 13

What is the usual cause of vitamin B12 deficiency?

Answer 13

Malabsorption (rarely due to inadequate intake)

Question 14

What is pernicious anaemia?

Answer 14

Lack of Vit B12 or Folic Acid causes RBCs to not develop as normal leading to increased size of RBCs (macrocytic anaemia)
Caused by lack of intrinsic factor, low B vitamins in diet, decreased absorption of B vitamins

Question 15

What is a totipotent stem cell?

Answer 15

The most potent form of stem cell that is able to differentiate into any cell type (inc. embryonic and extraembryonic)

Question 16

What is a pluripotent stem cell?

Answer 16

A cell that can differentiate into any cell type of the embryo

Question 17

What is a multipotent stem cell?

Answer 17

A cell that can differentiate into several different, but related, cell types

Question 18

What is an oligopotent stem cell?

Answer 18

A cell that can differentiate into a small number of very closely related cell types

Question 19

What is a unipotent stem cell?

Answer 19

A cell that can produce more cells of an identical cell type

Question 20

What are the 2 lineages of haematopoiesis differentiation?

Answer 20

Myeloid (which produces thrombocytes, erythrocytes, granulocytes, mast cells and macrophages)
Lymphoid (which produces natural killer cells, T/B lymphocytes and plasma cells)

Question 21

What are the stages of erythropoiesis?

Answer 21

1. Differentiation (down myeloid lineage)

2. Maturation (from immature cells to mature cells - Proerythroblasts to Erythroblasts to Reticulocytes to Erythrocytes)

Question 22

What is involved in the maturation process in erythropoiesis?

Answer 22

1. Decrease in cell size
2. Hb production
3. Loss of organelles (even nucleus!)
4. Acquisition of biconcave shape (inv. cytoskeleton)

Question 23

What controls the maturation process of erythrocytes?

Answer 23

EPO (Erythropoietin) - released by fibroblasts in response to cellular hypoxia and stimulates erythropoiesis in the bone marrow.
Requires iron, folic acid and B12

Question 24

What are the nutritional requirements for erythropoiesis to occur?

Answer 24

DNA synthesis requires Folic Acid, Vit B12 (+IF)

Hb synthesis requires Vit B6 and Iron (for haem)

Question 25

What happens to absorbed iron in the body?

Answer 25

Majority transported to bone marrow to make haem | Rest stored in liver or spleen or used in enzymatic processes in other tissue cells

Question 26

What is Hepcidin?

Answer 26

Hormone released by the liver in response to high iron levels. Works by decreasing Ferroportin action (on basolateral membrane of intestinal epithelial cells thus reducing ability to absorb iron)

Question 27

What are the different types of anaemia?

Answer 27

``` Iron deficiency Pernicious anaemia/ B12 deficiency Aplastic Haemolytic Anaemia of chronic diseases ```

Question 28

What is iron deficiency anaemia?

Answer 28

Iron deficiency leading to low Hb which in turn decreases the production of RBCs Caused by blood loss, low iron in diet or poor iron absorption

Question 29

What is aplastic anaemia?

Answer 29

A life threatening condition in which the bone marrow is unable to produce enough blood cells Caused by cancer therapies, exposure to toxic substances, autoimmune disorders and some viral infections

Question 30

What is haemolytic anaemia?

Answer 30

RBCs are destroyed faster than the bone marrow can replace them. Caused by inherited disorders such as sick cell anaemia or thalassemia

Question 31

What is anaemia of chronic diseases?

Answer 31

Certain chronic illnesses (e.g. Rheumatoid, kidney disease, diabetes, TB or HIV) can reduce the production of RBCs

Question 32

How can different types of anaemia be classified in terms of size of cell?

Answer 32

``` Macrocytic = large erythrocytes that are low in number (or have low Hb count per cell) Microcytic = small erythrocytes Normocytic = normal size erythrocytes but usually low in number ```

Question 33

How is anaemia classified in terms of amount of Hb per RBC?

Answer 33

``` Hypochromic = pale in colour due to lack of Hb (and therefore less oxygen) Normochromic = normal colour, normal Hb ```

Question 34

What is leukocytosis?

Answer 34

A white cell count disorder characterised by high level of white cells

Question 35

What is leukopenia?

Answer 35

Low white cell count

Question 36

What controls differentiation of platelets?

Answer 36

Thrombopoietin - produced in the liver and stimulates differentiation of megakaryocytes and thrombocytes (platelets) Negative feedback loop so thrombocytes reduce thrombopoietin levels