Haem 1 - Physiology of blood cells and haematological terminology

Question 1

Describe the physiology of the blood cells?

Answer 1

1) All blood cells originate in the bone marrow
2) They derived from multipotent haemopoietic stem cells
3) The multipotent haemopoietic stem cell gives rise to the myeloid stem cell and the lymphoid stem cell, from which red cells, granulocytes, monocytes and platelets are derived

Question 2

Draw the stem cell hierarchy

Answer 2

See diagram

Question 3

What are the essential characteristics of stem cells?

Answer 3

Ability to self renew and produce mature progeny - divides into two cells. Another stem cell and another cell capable of differentiating to mature progeny.

As a result it can preserve the bone marrows ability to constantly reproduce it’s self.

Question 4

Describe the physiology of the red blood cells?

Answer 4

myeloid stem cell –> proerythroblast –> erythroblasts –> erythrocytes

Blasts - indicate that it is a precursor: large nuclei, small amount of cytoplasm. Cytoplasm changes from dark blue to pink.

Life span of 120 days, O2 transport with some CO2 transport, destroyed in the spleen by phagocytic cells

Question 5

What is the process of producing red blood cells?

Answer 5

Erythropoiesis - requires erythropoietin produced from the kidneys in response to hypoxia. Erythropoietin can also be made in the liver.

Process:

1) Hypoxia is detected by the kidneys
2) Increase in erythropoietin synthesis
3) Increase bone marrow activity
4) Increase in RBC production

Question 6

Where is erythropoietin synthesised?

Answer 6

Kidney - juxtatubular interstitial cells (90%)

Liver (10%)

Question 7

Describe the physiology of the white blood cells?

Answer 7

Multipotent haematopoietic stem cells can give rise to myeloblasts which give rise to granulocytes and monocytes. For the differentiation of these cell lineages you need cytokines: G-CSF, M-CSF, GM-CSF and various interleukins

CSF - colony stimulating factor
G - granuloyte
M - macrophage

Question 8

Describe neutrophils

Answer 8

Survives 7-10 hours in circulation before migrating into tissues.
Main function: defence against infection - phagocytoses microorganisms

Question 9

Describe eosinophils

Answer 9

Spends less time in circulation compared to neutrophils
Main function: defence against parasitic infection
Two lobed nucleus

Question 10

Describe basophils

Answer 10

Main function: allergic response

Can’t see nucleus because of the many dark blue spots

Question 11

Describe monocytes

Answer 11

They spend several days in circulation
Main function: Migrate into tissue where they develop into macrophages and other specialised cells with phagocytic function
Large cells with kidney bean shaped nucleus
They store and release iron

Question 12

Describe platelets

Answer 12

Megakaryocyte –> platelets

They survive in the circulation for about 10 days
Main function: haemostasis - they contribute a phospholipid that promotes blood coagulation

Question 13

Describe lymphocytes

Answer 13

The lymphoid stem cells gives rise B, T and NK cells.
They circulate to lymph nodes and other tissues and then back into the blood stream.

Intravascular life span is very variable

Question 14

Define anisocytosis

Answer 14

Red cells show more variation in size than is normal

Question 15

Define poikilocytosis

Answer 15

Red cells show more variation in shape that is normal.
There lots of different shapes:
Spherocytes
Irregularly contracted cells
Sickle cells
Target cells
Elliptocytes
Fragments

Question 16

Define macrocytosis and macrocyte

Answer 16

Red cells are larger than normal
A red cell that is larger than normal
There are 3 different types of macrocytes - round, oval and polychromatic macrocytes

Question 17

Define microcytosis and microcyte

Answer 17

Red cells are smaller than normal

A red cell that is smaller than normal

Question 18

Define microcytic, normocytic and macrocytic

Answer 18

Microcytic - anaemia with small red cells
Normocytic - anaemia with normal size red cells
Macrocytic - anaemia with large red cells

Use lymphocytes as a reference to determine whether the cells are bigger or smaller than normal. Normally a red cell is a bit smaller than a lymphocyte

Question 19

Define hypochromia

Answer 19

The cells have a larger area of central pallor than normal. Normal red blood cells have about one third of the diameter that is pale.

This larger area of central pallor means that there is a lower haemoglobin content and concentration and a flatter cell. Cells are hypochromic.

Hypochromia and microcytosis often go together

Question 20

Define hyperchromia

Answer 20

The cells lack central pallor - thicker than normal or shape is abnormal. Cells showing hyperchromia can be described as hyperchromatic or hyperchromic. There are two important types of hyperchromia:

Spherocytes - approximately spherical in shape with a round regular outline and lack of central pallor. This is caused by the loss of cell membranes without the loss of an equivalent amount of cytoplasm. Hereditary sperocytosis

Irregularly contracted cells - irregular outline but smaller than normal cells, they have lost central pallor. Caused by oxidant damage to the cell membrane and to the haemoglobin.

Question 21

Define polychromasia

Answer 21

Increased blue tinge to the cytoplasm of a red cell - indicates the red cell is young

Question 22

What are reticulocytes?

Answer 22

They are RBC that are slightly younger than the proper mature cells. They can be detected with reticulocyte stain - methylene blue.

Question 23

Describe target cells

Answer 23

Cells with an accumulation of haemoglobin in the centre of the area of central pallor - occur in obstructive jaundice, liver disease, haemoglobinopathies and hyposplenism.

Question 24

Describe elliptocytes

Answer 24

They are elliptical in shape - occur in hereditary elliptocytosis and in iron deficiency. See diagram

Question 25

Describe sickle cells

Answer 25

Sickle or crescent shaped

Result from the polymerization of haemoglobin S when it it present in a high concentration

Question 26

Describe fragments

Answer 26

Fragments or schistocytes are small pieces of RBC indicating it has fragmented.

Question 27

Describe Rouleaux

Answer 27

Stacks of red cells that resemble a pile of coin. It results from alterations in plasma proteins - increased so are pushing the cells together

Question 28

Describe agglutinates

Answer 28

Red cell agglutinates differ from rouleaux in that are irregular clumps, rather than tidy stacks - result from antibodies on the surface of the cell

Question 29

Describe a Howell-jolly body

Answer 29

This is a nuclear remnant in a red cell - commonly caused by lack of splenic function

Question 30

Define the more terminology section

Answer 30

See notes

Question 31

Describe an atypical lymphocyte

Answer 31

An atypical lymphocyte is an abnormal lymphocyte, used to describe the type of lymphocytes seen in infectious mononucleosis (glandular fever) See notes

Question 32

What is Left shift?

Answer 32

This means that there is an increase in non-segmented neutrophils or that there are neutrophil precursors in the blood.

If there are lots of band form neutrophils = left shift. This means you are fighting an infection because the bone marrow is producing lots of lymphocytes. Raised cytokines and inflammation

Question 33

What is toxic granulation?

Answer 33

Heavy granulation of neutrophils resulting from infection, inflammation and tissue necrosis. This is also a normal feature of pregnancy.

Question 34

What is a hypersegmented neutrophil?

Answer 34

This is a neutrophil that has an increase in the average number of neutrophil lobes or segments. Results from a lack of vitamin B12 or folic acid.