Blood constituents, haematopoiesis and transfusion

Question 1

% plasma of total blood

Answer 1

55%

Question 2

What is buffer coat and what % of total blood

Answer 2

Leukocyte and platelets

<1% total blood

Question 3

% erythrocytes of total blood

Answer 3

45%

Question 4

Haematocrit of normal blood

Answer 4

0.45

Question 5

How much blood do adults have

Answer 5

5L

Question 6

Haematopoiesis

Answer 6

Formation of blood cells
Multipotential haematopoietic stem cell (pluripotent) –> common myeloid progenitor and common lymphoid progenitor
Common myeloid progenitor –> Mekakaryocyte, erythrocyte (red cells), mast cell, myeloblast
Megakaryocyte –> thrombocytes (platelets)
Myeloblast –> basophil, neutrophil, eosinophil, monocyte (white cells)
Monocyte –> macrophages
Common lymphoid progenitor –> natural killer cell (large granular lymphocytes) and small lyphocyte
Small lymphocyte –> T lymphocyte and B lyphocyte (white cells)
B lymphocyte –> plasma cell (white cell)

Question 7

Blood constituents

Answer 7

Red cells, platelets, white cells

Question 8

Where does haematopoiesis occur?

Answer 8

In bone marrow
-children: all bones
-adults: axial skeleton (e.g. bertebrae, ribs, pelvis)
Embryo: yolk sac then liver and spleen

Question 9

Stem cells are pluripotent

Answer 9

Self replicating

Differentiate into mature cells

Question 10

Mature cells have a finite lifespan in blood

Answer 10

Red cells: 120 days
White cells: 6 hours
Platelets: 7-10 days
-old/ dying cells removed by spleen

Question 11

What stimulates/ controls blood cell production?

Answer 11

Hormones

• red cells: erythropoietin (EPO)
• white cells: granulocyte colony stimulating factor (GCSF)
• platelets: thrombopoietin (TPO)

Question 12

Red cells

Answer 12

Simple cells with no nucleus or mitochondria
Biconcave disc to maximise SA to volume ratio - flexible
Contain haemoglobin - carries oxygen

Question 13

How many red blood cells does blood contain?

Answer 13

4 x 10^12 /L

Question 14

Haemoglobin

Answer 14

Tetramer of 4 polypeptide chains - 2 alpha and 2 beta (each contains molecule of haem)
Reversibly binds oxygen in lungs
Releases oxygen to tissues

Question 15

Anaemia types

Answer 15

Low haemoglobin
Acute e.g. blood loss
Chronic e.g. vitamin deficiencies, sickle cell disease

Question 16

Anaemia symtpoms

Answer 16

Fatigue
Dizziness
Pallor
Headaches

Question 17

Polycythaemia

Answer 17

> in red cells
-> erythropoietin
-hypoxia
< in plasma voume 
-dehydration
-smokers

Question 18

Platelets

Answer 18

Tiny anucleate cells
Made from megakaryotes in bone marrow
Circulate in resting state
Bind to damaged vessel wall - plug hole
Stop bleeding

Question 19

Normal number of platelets in blood

Answer 19

140-400 x 10^9 /L

Question 20

Low platelets

Answer 20

Thrombocytopenia

• platelets <80 increased risk of bleeding
• platelets <20 spontaneous bleeding/ bruising

Question 21

High platelets

Answer 21

Thrombocytosis

> rates of arterial and venous thrombosis

Question 22

Neutrophils

Answer 22

Phagocytose and kill bacteria
> in bacterial infections (neutrophilia)
Release cytokines which cause symptoms e.g. temperature

Question 23

Low neutrophils

Answer 23

Neutropenia

e. g. after chemotherapy
- frequent and severe infections

Question 24

Lymphocytes

Answer 24

Fight viral infections
-e.g. high numbers (lymphocytosis) in EBV infection (glandular fever)
B cells make antibodies
T cells are cytotoxic/ helper cells

Question 25

Lack of lymphs

Answer 25

Results in immunodeficiency | -e.g. HIV virus infects CD4 T cells

Question 26

Plasma proteins

Answer 26

Vast majority albumin -there to maintain oncotic pressure in blood and carries proteins Carrier proteins for nutrients, hormones etc. Immunoglobulins Coagulation proteins

Question 27

Immunoglobulins

Answer 27

Produced by plasma cells in response to exposure to a foreign substance Different classes (IgG, IgA, IgM, IgE) Basis of vaccination

Question 28

Coagulation factors

Answer 28

Series of proteins that circulate in inactive form Function is to make blood clot Convert soluble fibrinogen into insoluble fibrin polymer

Question 29

Overactivity of coagulation factors

Answer 29

Thrombosis (formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system)

Question 30

Failure of coagulation factors

Answer 30

Bleeding

Question 31

Blood transfusion

Answer 31

Red cells, platelets, plasma (fresh frozen plasma), white cells (very rarely), specific proteins e.g. clotting factors Similar to tissue transplantation e.g. donors and recipients need to be matched to avoid rejection

Question 32

Red cell transfusion

Answer 32

Carry proteins on their surface (antigens) which differ between individuals Inherited Over 400 different systems of red cell antigens 2 most important: ABO and Rhesus

Question 33

ABO blood groups

Answer 33

``` 4 groups: A, B, AB, and ABO Inheritance: -O is recessive, so O = O,O -A = AA or AO -B = BB or BO -AB = AB ```

Question 34

ABO blood groups UK population

Answer 34

``` O = 45% A = 40% B = 12% AB = 3% ```

Question 35

Rhesus blood groups

Answer 35

``` Complex system of C, D and E antigens D is most important -D is dominant so DD or Dd = D positive -d is a null product, dd = D negative 85% of population D positive If you are D negative you can make anti D ```

Question 36

Blood groups

Answer 36

Make antibodies if exposed to antigens you don't have -blood tranfusion -pregnancy All transfusions are ABO and RhD compatible Pregnant women given anti D to prevent sensitisation

Question 37

Advantages of blood transfusion

Answer 37

Can be life saving | Precious resource BUT can have serious, life threatening complications

Question 38

Indications for blood transfusion

Answer 38

Hypovolaemia due to blood loss Severe anaemia with symptoms due to inadequate tissue oxygenation (transfusion trigger often = 80 g/L) Anaemia that cannot be corrected by bone marrow function

Question 39

Blood transfusion not indicated for

Answer 39

Iron deficiency or B12/ folate deficiency. Minor blood loss, especially if fit and healthy Asymptomatic anaemia

Question 40

Risks of blood transfusion

Answer 40

``` ABO incompatibility reaction – can be rapidly fatal Delayed transfusion reactions Febrile reactions, urticarial reactions Fluid overload, pulmonary oedema Infections: -bacterial -viral (HIV, hepatitis B and C) -malaria -prions (vCJD) Long term – iron overload: damage to heart, liver ```