Haemopoiesis

Question 1

What is haemopoiesis?

Answer 1

The production of blood cells and platelets which occurs in the bone marrow.

Question 2

What is the primary role of erythrocytes (RBC’s)?

Answer 2

O2 and CO2 transport

Question 3

What is the primary role of platelets?

Answer 3

Primary haemostasis

Question 4

What are the 3 main groups of WBC’s?

Answer 4

Granulocytes

Monocytes —-> macrophages

Lymphocytes

Question 5

What are the 3 types of granulocytes and what are their functions?

Answer 5

Neutrophils
- Phagocytosis/acute inflammation

Basophils
- Modulate hypersensitivity reactions

Eosinophils
- Modulate hypersensitivity reactions
- Destroy parasites

Question 6

Functions of macrophages?

Answer 6

Modulate immune reactions

Phagocytic clearance

Regulatory functions

Question 7

What are the types of lymphocytes and what are their functions?

Answer 7

B cells - humoral immunity (antibodies)

T cells - cell-mediated immunity
- regulatory functions

Natural killer (NK) cell -Anti viral/tumour

Question 8

What happens to cells when the body is in a steady state?

Answer 8

Cell loss is balanced by cell production

Question 9

What is lifespan of red cells (x10^12/l)?

Answer 9

~120 days

Question 10

What is lifespan of white cells (x10^9/l)?

Answer 10

~7-8 hours

Question 11

What is lifespan of platelets (x10^9/l)?

Answer 11

~7-10 days

Question 12

What are erythroblasts?

Answer 12

A polychromatic nucleated cell of red bone marrow that synthesises haemoglobin and that is an intermediate in the initial stage of red blood cell formation.

Question 13

What are myeloblasts?

Answer 13

A unipotent (stem cell capable of only forming 1 cell type) precursor of the granulocytes.

Question 14

What is the cell precursor for platelets?

Answer 14

Megakaryocytes

Question 15

What are reticulocytes?

Answer 15

A precursor of the red blood cells that occurs immediately before the mature red blood cell.

Question 16

What are myelocytes?

Answer 16

A nucleated precursor that occurs after myeloblasts and before neutrophils.

Question 17

Ultimately all haemopoietic cells come from haemopoietic stem cells. True/false?

Answer 17

True

They all originate from the haemopoietic progenitor cell

Question 18

Self-renewal is a feature not present in stem cells. True/false?

Answer 18

False

Self-renewal is the process by which stem cells divide to make more stem cells, perpetuating the stem cell pool throughout life.

A property of stem cells, lost in descendants.

Question 19

What is the definition of proliferation?

Answer 19

An increase in cell number.

Question 20

What is differentiation?

Answer 20

Descendants of the stem cells, commit to one or more functions (lineages).

Question 21

What is maturation?

Answer 21

The stem cell descendants acquire functional properties and may stop proliferating.

Question 22

What is apoptosis?

Answer 22

Descendants undergo cell death.

Question 23

Embryonically, where do the haemopoietic stem cells originate?

Answer 23

Mesoderm

Question 24

What is the site of erythroid activity?

Answer 24

The yolk sac and stops by week 10.

Question 25

When does the liver start becoming a site of haemopoiesis?

Answer 25

Liver starts by week 6 of gestation

Question 26

When does the bone marrow become a site of haemopoiesis?

Answer 26

Starts by week 16 of gestation and takes over as the dominant site of haemopoiesis before birth.

Question 27

Where does haemopoiesis occur in adults?

Answer 27

Restricted to the marrow within the axial skeleton, pelvis and proximal long bones.

Question 28

Where can a bone marrow biopsy be carried out in an adult and in a child?

Answer 28

Posterior iliac crest/sternum for an adult. Tibia can be used in young child

Question 29

How is marrow cellularity reduced in older age?

Answer 29

Red (haemopoietically active) versus yellow (fatty inactive) marrow: increase in yellow marrow with age – results in reduction in marrow cellularity in older individuals

Question 30

What is the myeloid: erythroid ratio?

Answer 30

Myeloid: erythroid ratio: relationship of neutrophils and precursors to the proportion of nucleated red cell precursors (ranges from 1.5:1 to 3.3:1) This can change (eg reversal in haemolysis as a compensatory response)

Question 31

What is the bone marrow?

Answer 31

A complex organ surrounded by a shell of bone with a neurovascular supply.

Question 32

Components of the bone marrow?

Answer 32

Cellular compartments: - Haemopoietic cells - Non-haemopoietic cells eg, adipocytes (fat cells), ‘fibroblasts’ osteoclasts, osteoblasts. Connective tissue matrix Vascular elements: - Nutrient artery and periosteal network. - Arterioles drain into the "sinuses" - wide venous vessels, open into larger central sinuses. - In contrast to capillaries, "sinuses" are larger and have a discontinuous basement membrane.

Question 33

Steps for the release of mature cells from the marrow?

Answer 33

Formed blood cells can pass through fenestrations in endothelial cells to enter circulation Release of red cells is associated with sinusoidal dilatation and increased blood flow Neutrophils actively migrate towards the sinusoid Megakaryocytes extend long branching processes called proplatelets into the sinusoidal blood vessels

Question 34

What are routine investigations for haemopoiesis?

Answer 34

Blood count, cell indices (measure the size, shape, and quality of your red blood cells).

Question 35

What is a less common (specialist) investigation for haemopoiesis?

Answer 35

Bone marrow aspiration

Question 36

What are the investigations used for mature (lymphoid and non-lymphoid cells) in haemopoiesis?

Answer 36

For non-lymphoid cells, the blood count/morphological assessment is often sufficient For lymphoid cells, the expression of antigens indicating lineage or stage of development required. This study of antigen expression using specific antibodies is called immunophenotyping Cytochemistry (enzymatic reactions)–rarely used.

Question 37

What are lymphoid and non-lymphoid cells?

Answer 37

Lymphoid cells are crucial for the adaptive immune response, providing a specific and targeted defence against pathogens. Non-lymphoid cells contribute to the immediate, nonspecific defence mechanisms of the innate immune system.

Question 38

What is immunophenotying?

Answer 38

Identify patterns of protein (antigen) expression unique to a cell lineage. Use antibodies (in combination) specific to different antigens.

Question 39

How are cell surface antigens identified?

Answer 39

Using immunophenotyping to look for proteins i.e. CD34. CD34 (Sialomucin) is a member of a family of single-pass transmembrane sialomucin proteins that show expression on early haematopoietic and vascular-associated tissue.