physiology of blood cellsand haematological terminology

Question 1

where do blood cells originate?

Answer 1

bone marrow

Question 2

what are RBCs derived from?

Answer 2

They are ultimately derived from multipotent haemopoietic stem cells

Question 3

what do the multipotent stem cells give rise to?

Answer 3

The multipotent stem cells gives rise to lymphoid stem cells and myeloid stem cells, from which red cells, granulocytes, monocytes and platelets are derived

Question 4

what is the stem cell hierarchy?

Answer 4

There are two branches of differentiation.
The multipotent lymphoid myeloid stem cell differentiates into myeloid stem cell (precursor) or lymphoid stem cells.

myeloid stem cell (precursor) differentiates into granulocyte-monocyte, erythroid, megakaryocyte

lymphoid stem cells differentiates into T cell, B cell or NK cell

Question 5

what are essential stem cell characteristics?

and how is that achieved?

Answer 5

Ability to self-renew and produce mature progeny

Ability to divide into two cells with different characteristics, one another stem cell and the other a cell capable of differentiating to mature progeny

Question 6

how does a myeloid stem cell turn unto an erythrocyte?

Answer 6

The myeloid stem cell/precursor can give rise to a proerythroblast
This in turn gives rise to erythroblasts and then erythrocytes or red cells

Question 7

what is the process of producing RBCs called?

Answer 7

The process of producing red cells is called erythropoiesis

Question 8

what does the process of forming RBCs required?

Answer 8

Normal erythropoiesis requires the presence of erythropoietin

Question 9

where is erythropoietin synthesised?

Answer 9

Erythropoietin is synthesized mainly by the kidney, in response to hypoxia, by juxtatubular interstitial cells.

Question 10

what is the process that occurs to increase red cell production?

Answer 10

Hypoxia is detected by the kidneys 
This leads to an increase in erythropoietin synthesis 
This increases bone marrow activity 
This leads to an 
increase in red cell product
ion

Question 11

how long do erythrocytes last?

Answer 11

The erythrocyte survives about 120 days in the blood stream

Question 12

what are the functions of erythrocytes?

Answer 12

Its main function is oxygen transport

It also transports some carbon dioxide

Question 13

how are erythrocytes destroyed?

Answer 13

Ultimately it is destroyed by phagocytic cells of the spleen

Question 14

how does a multipotent haemopoietic stem cell give rise to granulocytes and monocytes?

Answer 14

The multipotent haemopoietic stem cell can also give rise to a myeloblast and a monoblast, which in turn give rise to granulocytes and monocytes
Cytokines such as G-CSF, M-CSF, GM-CSF and various interleukins are needed

Question 15

how long can the neutrophil survive?

Answer 15

The neutrophil granulocyte survives 7–10 hours in the circulation before migrating to tissues

Question 16

what is the main function of the neutrophil?

Answer 16

Its main function is defence against infection; it phagocytoses and then kills micro-organisms.

• adhesion and margination
• rolling
• diapedesis
• migration
• phagocytosis

Question 17

what is the function of the eosinophils?

Answer 17

A myeloblast can also give rise to eosinophil granulocytes
The eosinophil spends less time in the circulation than does the neutrophil
Its main function is defence against parasitic infection

Question 18

what do basophils do?

Answer 18

A myeloblast can also give rise to basophil granulocytes

Basophils have a role in allergic responses

Question 19

what do monocytes do?

Answer 19

The myeloid stem cell can also give rise to monocyte precursors and thence monocytes
Monocytes spend several days in the circulation
Monocytes migrate to tissues where they develop into macrophages and other specialized cells that have a phagocytic and scavenging function
Macrophages also store and release iron

Question 20

how long do the platelets survive?

what do the platelets do?

Answer 20

The haemopoietic stem cell can also give rise to megakaryocytes and hence platelets
Platelets survive about 10 days in the circulation
Platelets have a role in primary haemostasis
Platelets contribute phospholipid, which promotes blood coagulation

Question 21

what do the lymphocytes work?

Answer 21

The lymphoid stem cell gives rise to T cells, B cells and natural killer (NK) cells
Lymphocytes recirculate to lymph nodes and other tissues and then back to the blood stream
Intravascular life span is very variable

Question 22

define:
- anisocytosis
- poikilocytosis

Answer 22

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

Question 23

define:
- microcytosis
- macrocytosis

Answer 23

Microcytosis – red cells are smaller than normal

Macrocytosis – red cells are larger than normal

Question 24

macrocytes can be pf specific types

-what are they?

Answer 24

Macrocytes can be of specific types
Round macrocytes
Oval macrocytes
Polychromatic macrocytes

Question 25

define: - microcytic - normocytic - macrocytic

Answer 25

Microcytic – describes red cells that are smaller than normal or an anaemia with small red cells Normocytic – describes red cells that are of normal size or an anaemia with normal sized red cells Macrocytic – describes red cells that are larger than normal or an anaemia with large red cells

Question 26

define hypochromia and what does it result from?

Answer 26

Hypochromia means that the cells have a larger area of central pallor than normal This results from a lower haemoglobin content and concentration and a flatter cell Red cells that show hypochromia are described as hypochromic Hypochromia and microcytosis often go together

Question 27

normally which part of the RBC should look pale?

Answer 27

Normal red cells have about a third of the diameter that is pale This is a result of the disk shape of the red cell; the centre has less haemoglobin and is therefore paler

Question 28

define hyperchromia

Answer 28

Hyperchromia means that cells lack central pallor This can occur because they are thicker than normal or because their shape is abnormal Cells showing hyperchromia can be described as hyperchromatic or hyperchromic

Question 29

what are the causes of hyperchromia?

Answer 29

Hyperchromia has many causes since many abnormally shaped cells lack the central thinner area

Question 30

what are the two types of hyperchromia?

Answer 30

However there are only two important types, spherocytes and irregularly contracted cells

Question 31

define spherocytes and how are they formed?

Answer 31

Spherocytes are cells that are approximately spherical in shape They therefore have a round, regular outline and lack central pallor They result from the loss of cell membrane without the loss of an equivalent amount of cytoplasm so the cell is forced to round up Spherocytes in hereditary spherocytosis – but not all the cells are spherical

Question 32

define irregularly contracted cells and how are they formed?

Answer 32

Irregularly contracted cells are irregular in outline but are smaller than normal cells and have lost their central pallor They usually result from oxidant damage to the cell membrane and to the haemoglobin

Question 33

what is polychromasia?

Answer 33

Polychromasia describes an increased blue tinge to the cytoplasm of a red cell It indicates that the red cell is young. As a RBC ages, it turns from dark blue to pink

Question 34

what is another way to detect young cells?

Answer 34

Another way to detect young cells is to do a reticulocyte stain. Reticulocytes are RBCs that are slightly younger than the proper mature cells. They can be stained with methylene blue. This exposes living red cells to new methylene blue, which precipitates as a network or ‘reticulum’

Question 35

Polychromasia vs reticulocyte staining- which one is better for detecting young cells?

Answer 35

Detecting polychromasia or increased numbers of reticulocytes gives you similar information However, identification of reticulocytes is more reliable so they can be counted

Question 36

what are the different types in poikilocytosis?

Answer 36

``` Spherocytes Irregularly contracted cells Sickle cells Target cells Elliptocytes Fragments ```

Question 37

what are target cells and when do they occur?

Answer 37

Target cells are cells with an accumulation of haemoglobin in the centre of the area of central pallor They occur in obstructive jaundice, liver disease, haemoglobinopathies and hyposplenism

Question 38

define elliptocytes and when do they occur?

Answer 38

Elliptocytes are elliptical in shape | They occur in hereditary elliptocytosis and in iron deficiency

Question 39

define sickle cells and when do they occur?

Answer 39

Sickle cells are sickle or crescent shaped | They result from the polymerisation of haemoglobin S when it is present in a high concentration

Question 40

what are fragments and what do they indicate?

Answer 40

Fragments or schistocytes are small pieces of red cells | They indicate that a red cell has fragmented

Question 41

define rouleaux and when do they occur?

Answer 41

Rouleaux are stacks of red cells The resemble a pile of coins They result from alterations in plasma proteins

Question 42

define agglutinates and when do they occur?

Answer 42

Red cell agglutinates differ from rouleaux in that they are irregular clumps, rather than tidy stacks They usually result from antibody on the surface of the cells

Question 43

define howell-jolly body and when does it occur?

Answer 43

A Howell‒Jolly body is a nuclear remnant in a red cell | The commonest cause is lack of splenic function

Question 44

terminology: ``` Leucocytosis — Leucopenia — Neutrophilia — Neutropenia — Lymphocytosis — Eosinophilia — ```

Answer 44

``` Leucocytosis — too many white cells Leucopenia — too few white cells Neutrophilia — too many neutrophils Neutropenia — too few neutrophils Lymphocytosis — too many lymphocytes Eosinophilia — too many eosinophils ```

Question 45

terminology: ``` Thrombocytosis — Thrombocytopenia — Erythrocytosis — Reticulocytosis — Lymphopenia — ```

Answer 45

Thrombocytosis -too many platelets Thrombocytopenia too few platelets Erythrocytosis lots of red blood cells Reticulocytosis -lots of reticulocytes Lymphopenia -decrease in the number of lymphocytes

Question 46

define atypical lymphocyte

Answer 46

An atypical lymphocyte is an abnormal lymphocyte Often the term is used to describe the abnormal cells present in infectious mononucleosis (‘glandular fever’) ‘Atypical mononuclear cell’ is an alternative term

Question 47

define left shift

Answer 47

Left shift means that there is an increase in non-segmented neutrophils or that there are neutrophil precursors in the blood An increase in non-segmented neutrophils

Question 48

what is toxic granulation

Answer 48

Toxic granulation is heavy granulation of neutrophils | It results from infection, inflammation and tissue necrosis (but is also a normal feature of pregnancy)

Question 49

define hypersegmented neutrophil

Answer 49

Neutrophil hypersegmentation means that there is an increase in the average number of neutrophil lobes or segments It usually results from a lack of vitamin B12 or folic acid