Haem 1 - Physiology of Blood cells and haematological terminology

Question 1

Explain the origin of blood cells

Answer 1

ALL blood cells (all types) originate in bone marrow

• They are derived from multipotent haemopoietic stem cells which give rise to lymphoid stem cells and myeloid stem cells

Question 2

What can arise from myeloid stem cell precursor

Answer 2

1. Granulocyte-monocyte
2. Erythroid
3. Megakaryocyte

Question 3

What can arise from lymphoid stem cell

Answer 3

T cell/ B cell/ NK cell

Question 4

What is an essential characteristic of a stem cell

Answer 4

It can self renew and produce mature progeny - 2 cells formed, 1 stem cell and 1 differentiable cell

Question 5

Explain how RBCs arise

Answer 5

Myeloid stem cell precursor gives rise to pro erythroblast (has nuclei) –> which then gives rise to (early/intermediate/late) erythroblast —-> erythrocytes (anuclei)

Question 6

Erythropoiesis (producing RBC) requires erythropoietin. Where is erythropoietin synthesised in response to what

Answer 6

Erythropoietin synthesised in kidney in response to hypoxia (/anaemia)

In the juxtatubular interstitial cell of the kidney (90%)

(Also 10% erythropoietin in the liver - hepatocyte and interstitial cells)

Question 7

Ultimately, how are RBCs destroyed

Answer 7

Phagocytic cells of spleen

Question 8

How are white cells formed

Answer 8

Multipotent haemopoietic stem cell - gives rise to myeloblast –> in turn gives rise to granulocytes and monocytes

It requires cytokines (G-CSF, M-CSF, GM-CSF) and various interleukins

Question 9

How long do neutrophil granulocytes survive in circulation before migrating to tissues?

Answer 9

7-10 hours

Question 10

What is the main function of an eosinophil

eosinophils also arise from myeloblasts

Answer 10

Defence against parasitic infection

Eosinophils spend less time in circulation than neutrophil

Question 11

Myeloblasts can also give rise to basophils. What are their main function

Answer 11

Allergic responses

Question 12

Myeloblasts can also give rise to monocyte precursors and then monocytes. How long do monocytes spend in circulation?

Answer 12

Several days

Question 13

What do monocytes do

Answer 13

They migrate into tissues - where they develop into macrophages and other specialised cells - have a phagocytic and scavenging function

Macrophages also store and release iron

Question 14

How do platelets arise and how long do they spend in the circulation

Answer 14

Haemopoietic stem cells - give rise to megakaryocytes –> platelets

10 days in circulation

Question 15

What 2 roles do platelets have

Answer 15

1. Primary haemostasis

2. They contribute phospholipid - promoting blood coagulation

Question 16

What do lymphoid stem cells give rise to, and what do these differentiated cells do

Answer 16

Lymphoid stem cell –> T/B/NK cells

Lymphocytes recirculate to lymph nodes and other tissues - then go back to blood stream

Lymphocytes have variable intravascular lifespan

Question 17

What is anisocytosis?

Answer 17

red cells show more variation in size than normal

Question 18

What is poikilocytosis?

Answer 18

Poikilocytosis - red cells show more variation in shape than normal

“Pointy = shape”

Question 19

What is microcytosis and what is macrocytosis

Answer 19

Microcytosis - cells smaller than normal

Macrocytosis = cells larger than normal

Question 20

What are the specific types of macrocytes (Red Cells larger than normal)

Answer 20

1. Round macrocytes
2. Oval macrocytes
3. Polychromatic macrocytes - 2 colours, blue tinge on the outside - indicates a young cell, newly released from bone marrow

Question 21

Define microcytic, normocytic, macrocytic

Answer 21

Microcytic - red cells smaller than normal or anaemia with small red cells

Normocytic - red cells normal size or anaemia with normal sized red cells

Macrocytic - red cells larger than normal or anaemia with large red cells

Question 22

Normal red cells have a third of the diameter that is pale - why?

Answer 22

The centre has less Hb so it is paler (due to disk shape)

Question 23

What is hypochromia?

What is it often associated with?

Answer 23

Hypochromia = cell have larger area of central pallor than normal - as as result of lower Hb conc/content and flatter cell

Hypochromia often associated with microcytosis

Question 24

What is hyperchromia

Answer 24

Hyperchromia = cells lack central pallor - may occur because cells are thicker than normal or abnormal shape

Question 25

Name 2 important hyper chromatic cell types

Hyperchromia has many causes - because many abnormally shaped cells lack central thinner area

Answer 25

1. Spherocytes - spherical in shape (and lack central pallor) - as a result of loss of cell membrane but not cytoplasm, the cell must adopt round shape to include cytoplasm

(Can be inherited - “hereditary spherocytosis”)

2. Irregularly contracted cells

Question 26

Irregularly contracted cells are a form of hyperchromatic cell - what are they the result of

Answer 26

Usually caused by oxidant damage to cell membrane and Hb

Question 27

What does polychromasia indicate ?

Answer 27

Polychromasia = increased blue tinge to cytoplasm of red cell

Indicates a young cell

Question 28

How can we detect young cells?

Answer 28

Do a reticulocyte stain - expose red cells to new methylene blue - precipitates as a reticulum (network)

only 1-2% reticulocytes

(Also polychromasia indicates a young cell - but reticulocyte identification more reliable)

Question 29

What are the various shapes that poikilocytes may come in?

Answer 29

1. Spherocytes
2. Irregularly contracted cells
3. Sickle cells
4. Target cells
5. Elliptocytes
6. Fragments

Question 30

Describe target cells (poikilocyte type)

Answer 30

Target cells = cells with accumulation of Hb in centre (where there should be pallor)

Target cells occur in obstructive jaundice, liver disease, haemoglobinopahies and hyposplenism

Question 31

Elliptocytes are elliptical in shape. When do they occur

Answer 31

1. In hereditary elliptocytosis

2. Iron deficiency

Question 32

Sickle cell - what are the causes

Answer 32

Sickle cell results from polymerisation of Hb S (when present in high enough conc)

Usually we have Hb A

Question 33

What are fragments/”schistocytes”

Answer 33

Small pieces of red cells - indicate red cell has fragmented

Question 34

Describe rouleaux formation

Answer 34

Rouleaux = stack of red cells - as a result of alteration in plasma proteins

Question 35

Describe agglutinates

Answer 35

Red cell agglutinates = irregular clumps (whereas rouleaux = tidy stacks)

• They result from antibody on surface of cells

Question 36

Describe Howell-Jolly body

Answer 36

Howell-Jolly body = nuclear remnant in RBC - indicates lack of splenic function

Question 37

What are the terms associated with white cells / neutrophils / lymphocytes / eosinophils

Answer 37

1. Leucocytosis = too many white cells
2. Leucopenia = too few white ells
3. Neutrophilia/penia = too many/too few neutrophils
4. Lymphocytosis = too many lymphocytes
5. Eosinophilia = too many eosinophils

Question 38

Thrombo =?
Erythro =?
Reticulo = ?
Lympho = ?

Answer 38

Thrombo = platelet

Erythro = RBC

Reticulocytosis = Reticulocytes (young RBCs)

Lymphopenia = lack of lymphocytosis

Question 39

Describe the term “atypical lymphocyte”

Answer 39

Atypical lymphocyte = abnormal lymphocyte

Often used to describe abnormal cells in glandular fever (/”infectious mononucleosis”)

Question 40

What is left shift

Answer 40

Increase in non-segmented neutrophils (or neutrophil precursors present in blood) - e.g. band forms, myelocytes or even promyelocytes

It is a sign of infection or inflammation

Question 41

What is toxic granulation

Answer 41

Heavy granulation of neutrophils - may arise from infection, inflammation and tissue necrosis

(it is also a normal feature in pregnancy)

Question 42

What is a hypersegmented neutrophil

Answer 42

Neutrophil hyper segmentation = increase in average number of neutrophil lobes/segments

Usually results from lack of Vit B12 or folic acid