Blood Cells And Haemopoesis

Question 0

In haemopoiesis what two cell lines derive from stem cells?

Answer 0

Myeloid blasts - precursors of erythrocytes, megakaryocytes, granulocytes and monocytes
Lymphoblasts - precursors of lymphocytes

Question 1

Where are blood cells made in the developing foetus?

Answer 1

Initially by the mesoderm of the yolk sac, then by the liver and spleen, then eventually by the bone marrow.

Question 2

What is the fate of lymphocytes on leaving the bone marrow?

Answer 2

Some pass through the thymus and go to form T lymphocytes- involved in cell mediated immunity
Others are B cells - produce antibodies for humoral immunity.
Further division may occur in lymph nodes and lymphoid aggregates.

Question 3

What regulates the release of blood cells from the bone marrow?

Answer 3

Early blood cells are held in the bone marrow by adhesion molecules (collagen and fibronectin)
As the blood cells mature the expression of adhesion molecule receptors on the cell surfaces leading to release into the blood.

Question 4

What regulates the production of erythrocytes?

Answer 4

The peritubular endothelial cells of the kidney release erythropoietin in response to hypoxia. This increases rate of production and release of erythrocytes.

Question 5

How long does the average erythrocyte remain in the circulation?

Answer 5

120 days

Question 6

Where are erythrocytes broken down?

Answer 6

Liver and spleen.

Question 7

What happens to haem when red blood cells are broken down?

Answer 7

Iron is recycled, protoporphyrin ring is metabolised to bilirubin.

Question 8

What are the three polymorphonuclear granulocytes?

Answer 8

Neutrophils
Eosinophils
Basophils

Question 9

What are the agranulocytes?

Answer 9

Monocytes

Lymphocytes

Question 10

What is the appearance of a neutrophil?

Answer 10

Multilobed nucleus

Small granules in the cytoplasm

Question 11

What is the function of a neutrophil?

Answer 11

Migrate to site of infection by chemotaxis, destroy foreign material by phagocytosis.

Question 12

What chemotactic substances cause neutrophils to migrate?

Answer 12

Substances released by bacteria or other white blood cells already present.

Question 13

How long does an average neutrophil survive?

Answer 13

10 hours

Question 14

What is the role of G-CSF. What does it stand for?

Answer 14

Granulocyte colony stimulating factor.

Increases neutrophil production and increases chemotaxis and phagocytosis.

Question 15

What are the granules in a neutrophil?

Answer 15

Lysosomes containing digestive enzymes

Question 16

What is a accumulation of neutrophils?

Answer 16

Pus

Question 17

What is the appearance of eosinophils?

Answer 17

Bilobed nucleus, orange granules.

Question 18

What is the function of eosinophils?

Answer 18

Weakly phagocytic, ingest antigen - antibody complexes.

Question 19

In what group of patents is the blood level of eosinophils high?

Answer 19

Those with allergic conditions such as hay fever and asthma.

Question 20

How can eosinophils damage larger particles?

Answer 20

Release cytotoxic enzymes onto their surfaces.

Question 21

What is the appearance of basophils?

Answer 21

Granules stain blue

Question 22

Are basophils common?

Answer 22

No, least common of all blood cells.

Question 23

What is the function of basophils?

Answer 23

Mediate inflammation by secreting antihistamine - vasodilation, and increased permeability of capillaries leads to oedema
serotonin
heparin - anticoagulant.

Question 24

What is the appearance of monocytes?

Answer 24

Large cell with folded nucleus and grey/blue cytoplasm. | Occasional vacuoles.

Question 25

What is the function of monocytes?

Answer 25

Migrate into the tissue after 20-40 hours and act as macrophages. Kupffer cells in liver Glial cells in brain

Question 26

Do monocytes exhibit chemotaxis, and if so what do they move towards?

Answer 26

Yes - infection, neoplasm, inflammation.

Question 27

What is the name of a monocyte that has migrated into surrounding tissue?

Answer 27

Histiocyte

Question 28

What is the appearance of lymphocytes?

Answer 28

Small cells, round nucleus and rim of pale blue cytoplasm.

Question 29

What proportion of lymphocytes are T lymphocytes?

Answer 29

75%

Question 30

What property must lymphocytes have in order to be released into the blood stream?

Answer 30

Must recognise HLA (self histocompatability molecules -human leukocyte antigens) antigens but not react against them.

Question 31

What lymphocytes express CD4? What do they do?

Answer 31

T helper cells. Recognise antigens bound to HLA class 2 molecules and: Stimulate cytotoxic T cells which recognise and kill virally infected host cells Permit B cells to transform into plasma cells and produce antibodies (immunoglobulin)

Question 32

What lymphocytes express CD8?

Answer 32

Cytotoxic T cells

Question 33

What happens to a b lymphocyte stimulated by antigens?

Answer 33

Transform into immunoblasts then plasma cells which secrete immunoglobulins.

Question 34

What are platelets produced from?

Answer 34

The cytoplasm of megakaryocytes

Question 35

What does the cytoplasm of a platelet contain?

Answer 35

Alpha granules - fibrinogen, von willebrands factor Delta granules - calcium ions and ADP, Serotonin - vasoconstriction Factor 3 - activates prothrombin.

Question 36

What is the appearance of platelets.

Answer 36

Small, purple staining

Question 37

What is the role of activated platelets in blood clotting?

Answer 37

Adhesion to damaged cell wall and aggregation with other platelets Presents phospholipid surface - binding site for clotting factors.

Question 38

How do you classify blood?

Answer 38

Loose connective tissue

Question 39

What is the total blood volume, and what proportion is made up of plasma?

Answer 39

6 litres, 55%

Question 40

What proportion of body weight is blood?

Answer 40

7%

Question 41

What is the name of a newly formed red blood cell?

Answer 41

Reticulocyte.

Question 42

How do lymphocytes return to the circulation?

Answer 42

Lymphatic system.

Question 43

What proteins are found in plasma?

Answer 43

Include albumins, globulins, and fibrinogen.