Lecture 1: Introduction to Haematology

Question 1

What does blood consist of?

Answer 1

Blood consists of plasma, a fluid in which the constituents are suspended. The further constituents of blood are red blood cells (erythrocytes), white blood cells (leucocytes), platelets (thrombocytes). Plasma makes up 55% of blood, the buffy coat (leukocytes and platelets) make up <1% of blood, and erythrocytes make up 45% of total blood.

Question 2

What is the buffy coat?

Answer 2

The thin layer of leukocytes and platelets that will sit in the middle of a precipitation after centrifugation.

Question 3

What is blood plasma?

Answer 3

It is made up mostly (95%) water. the other 5% of plasma includes:
- hormones
- plasma proteins (albumin, fibrinogen, antibodies, coagulation factors)
- inorganic ions
- waste

Question 4

What is colloid osmotic pressure?

Answer 4

The pressure exerted by large molecules in the blood, mostly albumin, that will not diffuse through capillaries. This creates osmotic pressure keeping water in the vascular space.

Question 5

What is oedema, and how is it caused?

Answer 5

Oedema, is the swelling of certain body parts due to fluid build up from too much water leaking into tissues. This fluid build up can be caused by:
1. Increased total extracellular fluid
2. High local venous pressure
3. Lymphatic obstruction
4. Low plasma protein concentration (low serum albumin)
5. Increased capillary permeability

Question 6

What are the formed elements of blood?

Answer 6

Red blood cells (erythrocytes)
White blood cells (leukocytes)
Platelets (thrombocytes)

Question 7

How are haematological diseases identified?

Answer 7

Through FBC (Full Blood Count), an automated system that will count the number of cells, as well as analyse their sizes and properties. Sometimes this will be inaccurate and must be performed manually.

Question 8

Can a FBC be used for a diagnosis?

Answer 8

No, for a diagnosis, someone will need to observe a sample through a microscope.

Question 9

Haematopoiesis is what?

Answer 9

The process in which new blood cells are produced. Starting from multipotent haematopoietic stem cells (hemocytoblasts).

Question 10

What is the lineage of haematopoiesis?

Answer 10

https://en.wikipedia.org/wiki/Haematopoiesis.

Question 11

What is a mast cell?

Answer 11

Residing outside of the bloodstream, in the tissues (skin, lungs, lymph nodes, liver and spleen). They will release granules containing inflammatory molecules such as histamine in response to foreign invaders. Can also incorrectly release granules in an allergic reaction. Distinct from basophils in the fact that they are not present in the blood.

Question 12

Where are the sites of haematopoiesis in utero?

Answer 12

At 1 to 2 months, Yolk sac is the largest site. Liver and spleen are then responsible until around 7 months (with liver producing more), when the bone marrow will begin to take over until birth.

Question 13

Where are the postnatal sites of haematopoiesis?

Answer 13

All haematopoiesis takes place in the bone marrow after birth. With the amount of active marrow decreasing with age. Main sites in order of importance include:
1. Vertebrae and Pelvis
2. Sternum
3. Ribs
4. Femurs
5. Tibias

Question 14

Why do the sites of haematopoiesis decrease in size throughout our lives?

Answer 14

They don’t, the amount of haematopoietically active cells in the bones stays the same, but because they don’t expand in proportion to the rest of the body, the level of active tissue becomes relatively low later in life.

Question 15

Which type of bone marrow is haematopoietically active?

Answer 15

Red bone marrow.

Question 16

Are non-haematopoietic marrow cells relevant to haematology?
What is their function?

Answer 16

They are relevant to haematology in the fact that they can include fatty tissue and certain stromal cells which assist in providing energy to haematopoiesis. The biggest function of yellow bone marrow is creation of bone, cartilage and stromal cells which assist in blood formation.

Question 17

Describe the haematopoietic micro-environment.

Answer 17

Bone marrow contains a mix of haematopoietic stem cells and non-haematopoietic stem cells. This micro-environment is supported by a connective tissue (extra-cellular matrix), which compartmentalises the haematopoietic tissue as well as providing structure support. Both red bone marrow (haematopoietic) and yellow bone marrow (fatty) are highly vascular.

Question 18

What are the two kinds of bone marrow?

Answer 18

There is red bone marrow and yellow bone marrow.

Question 19

What is the organisation of bone marrow?

Answer 19

In bone marrow, different clusters of developing cells are present, this is so that for example developing erythrocytes can assist each other in development. The larger structure of red bone marrow is pockets of marrow compartmentalised by spongy bone. Yellow marrow is more dense in its gross structure, and does not have the same pocket structure that red marrow has. Sinuses, which branch off into sinusoids, allow developed cells to squeeze through and enter circulation.

Question 20

How are samples of bone marrow tested?

Answer 20

Not a smear test, bone marrow requires a biopsy to be analysed.

Question 21

Describe erythrocytes.

Answer 21

Small (7um) diameter, biconcave disks.
Contains haemoglobin, 26.7-32.5 pg/cell

Question 22

What hormones is required for erythropoiesis?

Answer 22

Erythropoietin, this is produced by peritubular endothelial cells in kidney.

Question 23

What are the three main steps of erythropoiesis?

Answer 23

Normoblasts - nucleated red blood cells, “egg” shape, darker colour when stained than erythrocytes, due to large concentration of acidic mRNA, due to needing to produce large amount of haemoglobin. Never seen in peripheral blood without a pathological explanation.

Reticulocytes - Can be seen in peripheral blood

Question 24

What is a reference range?

Answer 24

A range of results that you would expect ~95% of normal individuals to fall into. Known as a Gaussian distribution, demonstrated by a bell curve. A value that falls 2 standard deviations on either side of the average are abnormal.

Question 25

What is haemoglobin?

Answer 25

Haemoglobin is

Question 26

Describe the process of Leukopoiesis.

Question 27

What kinds of leukocytes are there?

Answer 27

Granulocytes:
Neutrophils
Eosinophils

Question 28

Name one of the most common dyes in haematology.

Answer 28

May-Grunwald-Giemsa.

Question 29

What do eosinophils do?

Answer 29

Target macro-parasites, and can release histamine in response to allergens. less than 1% of circulation leukocytes.

Question 30

What do basophils do?

Answer 30

Least numerous of the leukocytes.

Question 31

What are lymphocytes?

Answer 31

Two main types exist:
- T-cell, which matures in the thyroid.
- B-cell, which matures in the bone marrow.
Lymphocytes are morphologically indistinct.

Question 32

What are monocytes?

Answer 32

Cells which are

Question 33

What are macrophages?