Blood and Blood Groups Flashcards
What is blood made of?
Plasma (approx 55%, including plasma proteins, electrolytes, enzymes, nutrients)
Erythrocytes (approx 45%, red blood cells)
Leukocytes (<1%, white blood cells)
Thrombocytes (<1%, platelets)
Describe the structure/function of erythrocytes
Biconcave discs, no nucleus- 7 micrometers.
Function = transport gas, haemoglobin (found in the cytosol of the cell, carries O2) and carries CO2.
Specialised- biconcavity increases surface area, thin cell membranes = fast exits and entry, flexible = can squeeze through narrow capillaries, no intracelluar organelles = more haemoglobin, flattened = can pile like dimmer plates, reducing turbulence.
Membrane made up of certain glycolipids which are antigens- responsible for differences in blood types.
Life span: live for 120 days due to wear and tear.
Describe how red blood cells are made (erythropoiesis)
- Starts in the bone marrow as a pluripotent stem cell
- Differentiates into pro erythroblast
- Synthesis of haemoglobin and nucleus expelled = reticulocyte
- Reticulocyte matures over 1-2 days after leaving bone marrow = erythrocyte
- Erythropoiesis stimulated by low O2 levels
- Juxtaglomerular cells of kidney detect low O2, secrete erythropoietin into blood which increases speed of maturation in bone marrow to produce more RBCs
Identify the important factors of erythropoiesis
The number of blood cells are fairly constant because the production rate is equal to the rate it’s destroyed due to negative feedback mechanism
Hormone that helps stimulate = erythropoietin
Stimulus for high erythropoietin is hypoxia (deficient oxygen levels to certain body cells)
Erythropoietin stimulates increase production of proerythroblasts and more reticulocytes in blood and speeds up in reticulocyte maturation
When erythropoietin is low, red cell formation does not happen even in hypoxia situations
Describe the structure/function of leukocytes
Plasma membranes have proteins called major histocompatibility (MHC) antigens used for immunological purposes
Combat infection by phagocytosis (neutrophils, macrophages and eosinophils) or by immune responses (predominantly lymphocytes)
Have a nucleus
2 different classifications:
1. Granular (eosinophils, basophils and neutrophils)- filled with granules in their cytoplasm
2. Agranular (lymphocytes and monocytes which develop into macrophages in tissues)- no granules
Nb: monocytes and granular leucocytes develop from myeloid stem cells, lymphocytes from lymphoid stem cell
Life span: can live for months/years, most just for a few hours/days
Can leave blood stream to deal with invading pathogens, granulocytes never return, lymphocytes freely circulate in and out of blood vessels
Describe the structure/function of thrombocytes
Formed from fragments of megakaryocytic under influence of thrombopoietin in red bone marrow, then enter circulation
Disc shaped
No nucleus, many vesicles
Cytoplasm packed with granules which has substances that promote blood clotting- causes haemostasis
Involved in haemostasis by forming platelet plug, Vado spasm and blood clotting
Lifespan: 5-9 days
Describe the 4 main blood types
- Type A- A antigens and anti-B anti bodies
- Type B- B antigens and anti-B antibodies
- Type AB- both A and B antigens and no antibodies (universal recipient)
- Type O- no antigens and both A- antibodies and B- antibodies (universal donor)
How are blood groups categorised?
Presence or absence of the antigens on the cell surface
Surface of erythrocytes have a genetically predetermined coating of glycoproteins and glycolipids. These act as antigens (have immunogenicity and reactivity to antibodies). Aka agglutinogens or isoantigens
What are the two major blood groups?
ABO and rhesus.
NB: one blood group may contain different blood types
Explain the concept of compatibility/incompatible between donor and recipient
If it’s in the same group (same cell surface antigens), the immune system won’t recognise them as foreign and will not reject them
If it’s from an individual of a different blood type (different antigens), the immune system will generate antibodies to foreign antigens and destroy the cells
How are blood types inherited?
Due to multiple allele inheritance
Blood types A and B are dominant to blood type O
Blood types A and B are co-dominant
What is ABO blood group based on?
Based on two antigens, A and B determine the type:
People with surface antigen A on erythrocyte are blood type A
Surface antigen B -> blood type B
Surface antigen A and B -> blood type AB
People with no surface antigens are blood type O
Describe the rhesus blood group
3 inherited alleles responsible for coding the rhesus antigen: C, D and E
The D antigen is specifically responsible for the rhesus status of an individual
If the D antigen is present on the surface of the RBC, the individual is Rh+
Rh+ is dominant to Rh- in the inheritance pattern for this group
Outline the important of the rhesus factor in grouping blood
Rhesus antigen = a protein present on the RBC of a person with the Rh+ blood (around 85% of a population) so do not make anti-Rhesus antibodies
Other 15% = no rhesus antibodies- makes anti-rhesus antibodies but only do so in certain situations like pregnancy or incompatible blood transfusion
Unlike the ABO system, antibodies to the Rh factors are not produced until the individual is exposed to Rh factors
Describe rhesus incompatibility in pregnancy
Occurs when mother is Rh- and fetus is Rh+
RhD antigens from fetus mix with maternal blood
Mother makes anti D antibodies
IgG antibodies due to their molecular size can then cross the placenta
These anti D antibodies will them attack and haemolyse the fetal erythrocytes carrying the D surface antigen
This can cause iso-immunisation, fetal anaemia and hydrops fetalis (severe liver swelling and fluid build up in the fetus or newborn- possibly fatal)
May lead to jaundice in the first 48 hours of life
