Blood cells

Question 1

Average diameter of RBC

Answer 1

7.2 um

Question 2

Shape of RBC, and how it is achieved
S_o_a_ocyte
E_h_n_cyte

R_u_e_u_

Answer 2

Three types, dependant on water content:

• Discocyte (biconcave disk)
• Stomatocyte (more swollen
• Echinocyte

Deformability maintained by specialised cytoskeleton:
-e.g. spectrin, ankyrin and band 3 anchoring proteins

Stack end-to-end forming Rouleaux

Question 3

Contents of RBC

Answer 3

No nucleus, no mitochondria
Lots of Hb each with 4 haem groups which can each carry one O2
Enzymes for glucose metabolism
Ions

Question 4

Why is it important that RBCs are deformable, and what physical property does this give to blood?

Answer 4

So they can fit into capillaries

Visco-elasticity so hard to find artificial substitutes:
-viscosity increases with decreased velocity due to their stacking into Rouleaux

Question 5

Normal turnover time of RBC

Answer 5

120 days

Question 6

Where and how are old/defective RBCs cleared?

Answer 6

In the spleen via phagocytosis by macrophages

Destruction gives off iron and waste products:

• iron is transferred by transferrin to the bone marrow
• waste products dealt with by the liver

Question 7

What different types of anaemia are there and what can cause each of them?

Answer 7

Two types:

• microcytic (where there is a low average RBC size) caused by iron deficiency l - accompanied by low haematocrit
• macrocytic (where there is a high average RBC size) caused by vitamin B12 and/or folic acid deficiency

Question 8

Define haematocrit

Answer 8

% of RBC in blood

Question 9

What is EPO?

Answer 9

Erythropoietin - stimulated by hypoxia or increased O2 demand by tissues

Stimulates synthesis of more RBCs

Question 10

Where is endogenous EPO made and what can exogenous EPO be used to treat?

Answer 10

Endogenous EPO synthesised and released by kidneys

Exogenous EPO used to treat anaemia, kidney diseases and chemotherapy side effects, for example

Question 11

Describe the appearance and size of a neutrophil

Answer 11

Multi-lobed nucleus
Granulocyte - lysosomes and toxic granules containing strong oxidisers
10um

Question 12

When and from where does neutrophil number increase?

Answer 12

Acute bacterial infection

Mobilised from reserves and increased production from myeloid progenitors

Question 13

Describe their pathway to sites of acute inflammation

Answer 13

Adhere to vascular endothelium

Transmigrate via diapedesis through capillary walls

Question 14

What do neutrophils leave behind after carrying out phagocytic activity?

Answer 14

Pus - a fluid containing dead neutrophils, liquefied tissue and cellular debris

Question 15

Which white blood cells belong to the granulocyte family?

Answer 15

Neutrophils
Eosinophils
Basophils

Question 16

Describe appearance of eosinophils

Answer 16

Stain pink due to presence of cationic proteins within large ovoid granules
Bigger than neutrophils

Question 17

What is characteristic of eosinophil plasma membranes?

Answer 17

IgE receptors for recognising allergens or certain antigens

Question 18

When does eosinophil number increase?

Answer 18

Chronic allergic conditions and tropical parasitic infection

Question 19

What do basophils secrete on activation?

Answer 19

Histamine

Interleukins/cytokines

Question 20

Is a macrophage a blood cell?

Answer 20

No - but a monocyte is…

Question 21

Define monocyte

Answer 21

A blood cell that can give rise to a macrophage after migrating into a tissue

Question 22

What are the roles of macrophages?

Answer 22

Tissue dependant, but generally they:

• phagocytose, and kill organisms
• remove tissue debris (by secreting enzymes) for repair
• involved in tissue homeostasis and remodelling (e.g. phagocytose apoptotic bodies)

Question 23

Key points of Till & McCullogh 1963 experiment showing the presence of haematopoietic stem cells

Answer 23

Heavily irradiated mice
Injected bone marrow cells, and observed small nodules later dubbed ‘spleen colonies’ in spleen, number of which was proportional to the amount of bone marrow cells injected
Around 10,000 bone marrow cells had to be injected before a nodule formed
Each nodule spawned red cells, white cells and platelets
Hypothesised that each nodule was formed from one stem cell

Question 24

What two main divisions arise from haematopoietic stem cells, and give examples for each?

Answer 24

Common myeloid progenitors - granulocytes, red blood cells, mast cells, monocytes

Common lymphoid progenitors - lymphocytes

Question 25

What are primary lymphoid organs, and which lymphocytes develop where?

Answer 25

PLOs are where lymphocytes mature

T-cells mature in Thymus
B-cells mature in Bone marrow

Question 26

What are secondary lymphoid organs, and give some examples?

Answer 26

Locations where mature lymphocytes encounter antigens, which activate them to proliferate

E.g. lymph nodes, spleen, Peyer’s patches

Question 27

General role of B cell vs T cell

Answer 27

B cells mature into antibody producing plasma cells

T cells undertake a more cell-mediated response:

• regulate the immune response (e.g. T-helper cells secreting cytokines to summon macrophages or T-regulators which stop the immune response)
• kill infected cells directly (e.g. cytotoxic t-cells which kill virus infected cells)

Both can form memory cells

Question 28

Natural killer cell appearance and role

Answer 28

Large, granular lymphocytes

Survey the blood in search of cells without recognisable antigens

Anti-viral and anti-tumour

Question 29

Differences between small and large lymphocytes

Answer 29

Small:

• dormant
• G0
• Long-lived
• numbers expand on stimulation
• recirculating from vasculature to lymphatics in high endothelial venules
• e.g. memory cells

Large:

• activated
• proliferating
• called Lymphoblasts
• large because lots of DNA synthesis
• intermediates of B, T and natural killer cells (effector cells)

Question 30

Examples of things that can harm haematopoietic stem cells

Answer 30

Ionising radiation
Cytotoxic drugs (e.g. chemotherapy)