Blood and Blood Groups Flashcards
What are constituents of blood
Plasma approx 55% ( including plasma proteins, electrolytes, enzymes, nutrients)
Erythrocytes approx 45%
Leucocytes- below 1%
Thrombocytes- below 1%
Describe erythrocytes (RBCs)
Biconcave discs, flexible membrane so can squeeze through capillaries
Carry haemoglobin
Carry some CO2
Membrane made up of certain glycolipids which are antigens ( responsible for differences in blood type)
Lack a nucleus and organelles ( so can’t reproduce or synthesise new components)
Live for 120 days due to wear and tear
What is erythropoiesis
How red blood cells are made
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 kidneys detect low O2, secretes erythropoietin into blood which increases maturation speed process in bone marrow to produce more RBCs leucocytes
Explain leucocytes ( WBCs)
Has a nucleus
Plasma membranes have proteins called major histocompatibility ( MHC) antigens used for immunological purposes
Can live for months/ years, most just for a few hours/days
Combat infection by phagocytosis or by immune responses
Can leave blood stream
What are the different classifications of leucocytes
Granular - ( eosinophils, basophils, neutrophils) filled with granules
Agranular-( lymphocytes and monocytes ) monocytes develop into macrophages in tissues
Monocytes and granular leucocytes develop from myeloid stem cells, lymphocytes from lymphoid stem cell
Explain thrombocytes
Formed from fragments of megakaryocytes under influence of thrombopoietin in ed bone marrow then enter circulation
Disc shaped
No nucleus, many vesicles
Life span 5-9 days
Involved in haemotasis by forming platelet plug, vasopasm and blood clotting
Why are there different blood groups
Surface of erythrocytes have genetically predetermined coating of glycoproteins and glycolipids
These act as antigens
How are blood groups categorised
By the presence or absence of the antigens on the cell surface
At least 24 blood groups and over 100 surface antigens
Two major blood groups are ABO and Rhesus
One blood group may contain different blood types
Describe the ABO blood types
Determined based on antigens A and B :
Surface antigen A on erythrocyte = blood type A
Surface antigen B on erythrocyte = blood type B
Surface antigen A&B on erythrocyte = blood type AB
No surface antigens = blood type O
What are other aspects of blood types
Blood plasma also contains antibodies
Antibodies aka agglutinins or isoantibodies
Specific antibodies will react with specific antigens
What is the antibody reactivity
Anti A antibody will react with antigen A
Anti B antibody will react with.antigen B
The plasma doesn’t contain antibodies that will react with antigens of its own erythrocytes
The plasma may contain antibodies which will react with antigens that the body’s own RBCs lack
What are the inheritance pattern of blood types
Inheritance of blood type is due to multiple allele inheritance
Blood type A and B are dominant to blood type O
Blood types A and B are co-dominant
What are 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
What is ABO incompatibility in pregnancy
Happens when a mother’s blood type is O, and her baby’s blood type is A or B, the mother’s immune system may react and make antibodies against her baby’s RBCs
What is rhesus incompatibility in pregnancy
Occurs when mother is Rh - and fetus is Rh +
RhD antigens from foetus 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 then attack and haemolytic the foetal erythrocytes carrying the D surface antigen
This can cause iso- immunisation, fetal anaemia and hydrops fetails
May lead to jaundice in 1st 48 hours of life
