Physiology of Blood Cells and Haematological Terminology

Question 1

Outline the stem cell heirarchy

Answer 1

pluritpotent lympphoid-myeloid stem cell ->lymphoid stem cell/ multipotent myeloid stem cell or precursor

lymphoid sc-> t cell/ b cell/ nk cell

myeloid sc-> granulocyte-monocyte/erythroid/magakarocyte

Question 2

outline normal erythroid maturation

Answer 2

multipotent myeloid sc-> proerythroblast -> early,intermediate and late erythroblats-> erythrocyte

Question 3

What stmulates erythropoiesis? Where does it occur?

Answer 3

hypoxia/anaemia

90% of erythropoietin from juxtatubular interstitial cells of the kidneys.

10% of erythropoietin from hepatocytes and interstitial cells of the liver

Question 4

How long do erythrocytes survive?

Answer 4

about 120 days in the blood stream and transport CO2 and O2 -> then destroyed by phagocytes in spleen

Question 5

outline the normal granulocyte maturation?

Answer 5

multipotent myeloid sc-> myeloblast -> promyelocyte-> myelocyte-> band form -> neutrophil

Question 6

What is the physiological function of neutrophils?

Answer 6

Neutrophil granulocyte survives 7-10 hours in circulation before migrating to tissues.

Defence against infection - phagocytoses and then kills microorganisms

Question 7

What is the physiological function of eosinophils?

Answer 7

Spends less time in circulation than neutrophil.

Defence against parasitic infection

also involved in allergic reactions

Question 8

What is the physiological function of basophils?

Answer 8

allergic responses

Question 9

What is the physiological function of monocytes?

Answer 9

Spend several days in the circulation.

Phagocytose bacteria, fungi and dead tissue.

Migrate to tissues to become macrophages.

Macrophages store and release iron

Question 10

What is the physiological function of platelets?

Answer 10

Multipotent haematopoietic stem cell -> megakaryocyte -> platelet.

Survive 10 days in circulation.

Have a role in primary haemostasis in contributing phospholipid to promote blood coagulation

Question 11

What is the physiological function of lymphocytes?

Answer 11

Lymphoid stem cell gives rise to T, B and NK cells.

Lymphocytes recirculate to lymph nodes and other tissues and then back into the blood stream.

Lifespan intravascular is very variable

Question 12

What do anisocytosis and poikilocytosis mean?

Answer 12

Anisocytosis – red cells show more variation in size than is normal

Poikilocytosis – more variation in shape than is normal

Question 13

What do microcytosis and macrocytosis mean?

Answer 13

Microcytosis – red cells smaller than normal.

Macrocytosis – larger than normal.

types of macrocytes :
Round macrocytes.
Oval macrocytes.
Polychromatic macrocytes (darker blue due to ribosomes -> newly synthesized)

Question 14

What arethe categories of anaemia?

Answer 14

Microcytic – red cells that are smaller than normal or an anaemia with small red cells.

Normocytic – red cells of normal size or an anaemia with normal sized red cells.

Macrocytic – red cells that are larger than normal or an anaemia with large red cells

Question 15

What is hypochromia?

Answer 15

RBCs that have a large central pallor – less haemoglobin in the cell and thus a flatter cell and less colour

Normal RBCs have one-third a diameter that is pale.

*Often Hypochromia and Microcytosis go hand-in-hand - both caused by reduced haemoglobin

Question 16

What is hyperchromia?

Answer 16

The cells LACK central pallor – the cells are thicker than normal or have an abnormal shape.

There are 2 important types of cell in Hyperchromia;

1. Spherocytes
   - These are approximately spherical in shape and so lack central pallor.

• They result from the loss of cell membrane without the equivalent loss of cytoplasm so the cell is forced to round up - One such disease of these – Hereditary spherocytosis.

2. Irregularly contracted cells – top picture.
   - Irregular in outline but smaller than normal cells and have lost central pallor.

• A result of oxidant damage to the cell membrane and haemoglobin

Question 17

What is polychromassia?

Answer 17

Describes an increased blue tinge to the cytoplasm of a red cell.

This indicates the cell is young and is often much larger.

Another way to detect young cells like these is in a “reticulocyte stain” which exposes living red cells to NMB (New Methylene Blue) which precipitates the network seen inside the cell.

Should only have 1-2% of these cells in the population circulating.

Identifying these is more reliable than looking for Polychromasia on a slide so you should do this to diagnose Polychromasia

Question 18

What are the different types of poikocytes?

Answer 18

spherocytes

irregularly contracted cells

Target Cells

Elliptocytes

Sickle cells

Fragments/Shistocytes

Question 19

What causes sickle cell?

Answer 19

result from polymerisation of haemoglobin S chains when present at a high enough concentration

Question 20

What causes shistocytes?

Answer 20

small pieces of red cells indicating a cell has fragmented

Can be due to abnormal stress on the red cell or from if the cell is intrinsically abnormal

Question 21

What are target cells?

Answer 21

cells with an accumulation of haemoglobin in the centre of the area of central pallo

Occur in obstructive jaundice, liver disease, Haemoglobinopathies and hyposplenism.

Question 22

What are ellipocytes?

Answer 22

elliptcal in shape

Occur in hereditary elliptocytosis and in iron deficiency.

Question 23

What is rouleaux formation?

Answer 23

STACKS of red cells.

Result from alterations in plasma proteins.

*like a stack of coins

Question 24

What are agglutinates?

Answer 24

irregular clumps of red blood cells.

Result of antibodies on the surface of the cells

*like an untidy pile of coins

Question 25

What is a Howell-Jolly body?

Answer 25

a nuclear remnant in a red cell.

Commonest cause is a lack of splenic function

Question 26

What is leucocytosis and leucopenia

Answer 26

Leucocytosis - too many white cells.

Leucopenia – too few white cells.

Question 27

What is neutrophilia and neutropenia?

What are the words for too many lymphocytes and too many eosinophils?

Answer 27

Neutrophilia – too many neutrophils.

Neutropenia – too few neutrophils

lymphoctyosis and eosinophilia

Question 28

What is left shift?

Answer 28

describes the increase in non-segmented neutrophils or that there are neutrophil precursors in the blood.

So there would be more non-segmented neutrophils in the plasma (otherwise known as “band form”)

Question 29

What is toxic granulation?

Answer 29

heavy granulation of neutrophils.

A result of infection, inflammation and tissue necrosis (but also normal in pregnancy)

Question 30

What is hypersegmentation of neutrophils?

Answer 30

means there is an increase in the average number of neutrophil lobes or segments.

It is usually a result of lack of vitamin B12 or folic acid

Question 31

Why is there more space between blood cells in anaemic patients?

Answer 31

blood is less viscous so when you place it on a slide it spreads more thinly

Question 32

How does sickle cell lead to Howell jolly bodies?

Answer 32

occlusion of blood vessels in spleen -> infarction of spleen -> subsequent loss of splenic function