Blood Flashcards
What are the cells in blood known as?
Formed elements
What is the blood composed of?
Cells / formed elements and plasma
What cells / formed elements are found in blood?
erythrocytes, leucocytes, thrombocytes (platelets)
What does plasma consist of?
extracellular fluid, water, electrolytes (e.g. sodium), organic molecules (glucose, fatty acids, glycerides, amino acids…), plasma proteins.
What are the plasma proteins?
albumins (60%), globulins (35%), fibrinogen (4%), regulatory proteins (1%)
What are the most abundant plasma proteins?
Albumins (60%)
Function of albumin
Maintains oncotic pressure - helps retain water in the bloodstream and prevents fluid leaking excessively into tissues. Also responsible for transport of lipids.
Name of swelling caused by excess fluid leaking into tissues
oedema
Function of globulins
Responsible for transport of ions, hormones, lipids and immune function.
Function of fibrinogen
key component of blood clotting
What constitutes regulatory proteins?
Enzymes, hormones
How does blood volume differ between individuals?
Blood volume depends on size with males typically having a greater blood volume (70ml/kg) than females (60ml/kg).
What percentage of the blood volume is made from plasma?
55% (46-63%)
What percentage of blood volume is made of cells/formed elements?
45% (37-54%)
What is the most abundant blood cell?
Over 99% of blood cells are erythrocytes, followed by leucocytes and thrombocytes)
What is the morphology of erythrocytes? (diameter, shape)
6-8um diameter and has a biconcave disk shape
Advantages of biconcave disk shape of erythrocytes
Provides a large SA:vol ratio which allows rapid diffusion of CO2 and O2 across plasma membrane. Can bend in narrow capillaries and expand in hypotonic solutions.
Behaviour of older erythrocytes in hypotonic solutions
older erythrocytes are more fragile and therefore more likely to haemolyse
Appearance of erythrocytes in blood film
Halo effect - outer thicker portion of RBC stains more intensely than thinner, concave centre which appears pale.
Term for red blood cell formation
erythropoiesis
Where are red blood cells formed?
red bone marrow
Average lifespan of erythrocytes
120 days
How are old erythrocytes broken down?
MPS system (mononuclear phagocyte system) which is part of the immune system, removes and breaks down RBCs in the spleen.
Where does the MPS system mostly remove and breakdown old red blood cells?
in the spleen mainly (also in liver and bone marrow)
What happens to the breakdown products of red blood cells?
haemoglobin is broken down into protein (globin) and haem group which are recycled. The protein is broken down into amino acids which enter the pool to make new proteins. Haem is broken down into iron (used in production of new RBCs) and biliverdin (converted into bilirubin).
What is conjugated bilirubin?
The form of bilirubin (bilirubin glucuronide) excreted as bile pigment.
How is conjugated bilirubin / bile pigment formed?
Produced in the liver when bilirubin combines with glucuronic acid to produce bilirubin glucuronide.
What happens to 10% of newly produced erythrocytes?
They are non functional and haemolyse. They are then either engulfed my macrophages in MPS or the haemoglobin is filtered out of the circulation by the kidneys into urine.
What happens to the Fe2+ that is one of the breakdown products of haem (along with biliverdin)?
Fe2+ is transported in the circulation by transferrin back to the red bone marrow for erythropoiesis. (recycled)
What elements are recycled in erythrocyte breakdown?
Amino acids and Fe2+
What happens to bilirubin as it enters the large intestine from the small intestine?
It is broken down into bilirubin-derived products some of which are absorbed into the circulation and filtered out by the kidneys. Most bilirubin-derived products (e.g. urobilins and stercobilins) continue in the large intestine and are eliminated in faeces.
Example of bilirubin-derived products
urobilins and stercobilins
What causes the brown colour of faeces?
Bilirubin-derived products e.g. urobilins and stercobilins
Stages of erythropoiesis
day 1 - proerythroblast
day 2 - basophilic erythroblast (dark staining)
day 3 - polychromatophilic erythroblast (pink)
day 4 - normoblast
Nucleus ejected (no longer an erythroblast)
days 5-7 - reticulocyte
enters circulation as a mature erythrocyte
Summary of erythropoeisis
cell size is reduced and nucleus is ejected
Which substances are required for the reduction in cell size and nucleus regression during erythropoiesis?
Folic acid and vitamin B12
What substance is required to increase haemoglobin content of the reticulocyte (after nucleus is ejected)?
iron
Which hormone regulates erythropoiesis?
Erythropoietin (based in kidneys)
Term to describe low blood oxygen
hypoxia
How does the body counteract low blood oxygen (hypoxia)?
Usually due to decreased RBC numbers. This means less oxygen is delivered to cells. The kidney detects low blood oxygen and releases erythropoietin which travels to the red bone marrow and stimulates increased erythropoiesis. More erythrocytes in the blood increases the blood oxygen.
How can the amount of oxygen Hb can carry at different partial pressures be plotted?
Hb-O2 dissociation curve
Function of haemoglobin
transports O2 and CO2
Which enzyme regulates the transport of CO2 by haemoglobin?
Carbonic anhydrase (catalyses conversion of CO2 and H2O -> H2CO3)
Which products are formed during CO2 transport by haemoglobin?
Bicarbonate ions (H2CO3 dissociates) and carbamino compounds
What type of protein is haemoglobin?
Globular (spherical)
Molecular weight of haemoglobin
68000 Daltons
How many haem groups are there in one molecule of haemoglobin?
4 haem groups - one in each chain
How many protein chains are in haemoglobin?
2 alpha chains diagonal to each other and 2 beta chains diagonal to each other.
What is a haem group composed of?
A porphyrin ring (C and N atoms) with an iron atom in the centre that reversibly binds to O2.
How many haemoglobin molecules are in one erythrocyte?
200-300 million
How does foetal haemoglobin differ to adult haemoglobin?
Foetal haemoglobin is Hb-F which has a higher affinity for O2.
Axes labels of Hb-O2 dissociation curve
X axis is partial pressure of O2 (pO2) and Y axis is oxygen saturation (%)
Where in the body would haemoglobin be almost fully saturated?
In the lungs as there is a high partial pressure of O2
Where in the body does haemoglobin O2 saturation drop?
At respiring tissues where there is a low partial pressure of O2. Oxygen is therefore released from Hb here.
Why is the Hb-O2 dissociation curve sigmoid shaped?
At high pO2, Hb is almost saturated and does not lose O2 readily therefore the curve is plateaued. As pO2 decreases, once the first O2 molecule is released, Hb dissociates from O2 more readily. However, at low pO2 the final O2 dissociates more slowly. This sigmoid dissociation prevents all the oxygen being released at the same time. The graph can also be read the other way round - Hb is slow to bind to O2 at low pO2 but once the first O2 binds, Hb associates with O2 more readily until it is saturated.
What are the different types of leucocytes (WBCs)?
Granulocytes - neutrophil, basophil, eosinophil
Agranulocytes - monocyte, lymphocyte
What is the difference between granulocytes and agranulocytes?
Granulocytes are leucocytes with granules in their cytoplasm whereas agranulocytes do not contain visible granules.
Function of neutrophils
First responders to acute inflammation. They have a non-specific phagocytic response.
Function of basophils
They are circulating mast cells that produce histamine (improves blood flow to damaged tissues) and heparin (prevents blood clots) - inflammatory response.
Function of eosinophils
involved in allergic reactions and defence against parasites (larger invaders)
Function of monocytes
Antigen presenting cells. Become macrophages in tissues which are involved in breakdown of erythrocytes.
Function of lymphocytes
Can be T cells (cell-mediated immunity) or B cells (humoral immunity - production of antibodies)
Order of abundance of leucocytes
Neutrophils (50-70%)
Lymphocytes (25-30%)
Monocytes (2-8%)
Eosinophils (2-4%)
Basophils (1%)
(Never Let Monkeys Eat Bananas)
Features of neutrophil
Granular cytoplasm, multilobed nucleus with condensed chromatin, basophilic, 12-14um diameter, few organelles, lifespan of a few days
Features of eosinophil
12-17um diameter, bilobed nucleus, eosinophilic (v pink) cytoplasm.
Features of basophil
14-16um, bilobed nucleus, very basophilic, formed in bone marrow.
Which is the largest leucocyte?
Monocyte
Features of monocyte
up to 20 um diameter, circulate for 3-4 days before entering tissues (chemotaxis), highly phagocytic, can mature into various macrophages, large kidney shaped nucleus, frosted-glass cytoplasm appearance due to granules and vacuoles.
Features of lymphocytes
Large nucleus that takes up majority of cytoplasm, can be small lymphocytes (6-9um diameter), 3% are large lymphocytes (9-20um diameter).
What cells are platelets derived from?
Megakaryocytes (large bone marrow cells)
What are platelets?
Cell fragments about 2um in diameter
Function of platelets
Involved in haemostasis - release vasoconstrictors, form platelet plug, coagulate blood.
What is haemostasis?
Process of stopping bleeding
How do platelets contribute to haemostasis?
Release vasoconstrictors (TxA2) which reduce blood flow to the damaged area, platelets aggregate at the site of vessel injury to form a platelet plug, platelets are a source of phospholipids for coagulation.
Example of vasoconstrictor released by platelets
thromboxane (TxA2)
Normal platelet count
150-400 x 10^9 per litre
How are blood groups determined?
By the presence / absence of AB antigen or the Rhesus (Rh) antigen on the erythrocyte membrane.
What are antigens?
Substances that cause an immune response
What blood type are you if the rhesus antigen is present on your erythrocyte membrane?
Rh +
What is haematocrit / PCV?
The percentage of blood volume occupied by RBCs.
Why do adult males have a greater red blood cell count / haematocrit / [Hb] ?
Men have a greater muscle mass, females, menstruate, men have more testosterone (increase RBCs)
Dominance of A, B, O alleles
A and B are codominant, O is recessive.
Which blood group does not have any antigens on the erythrocyte membrane?
O
Which blood group does not produce any natural antibodies?
AB
Possible genotype for blood group A
AA, AO
Possible genotypes for blood group B
BB, OB
Possible genotypes for blood group AB
AB
Genotype for blood group O
OO
Which antibodies are produced by blood group A?
Anti-B
Which antibodies are produced by blood group B?
Anti-A
Which antibodies are produced by blood group O?
Anti-A and anti-B
What Rh-blood group is most common?
Rh+ (83% of population)
Which Rh blood group will have the Rh (D) antigen present on its surface?
Rh+ (Rh- does not have antigen)
Genotype for Rh+
DD, DO (only one parent needs to be Rh+ because it is dominant)
Genotype for Rh-
OO
What happens if a Rh- person receives Rh+ blood?
They develop anti-Rh antibodies. This doesn’t affect recipient (don’t have Rh antigen and Rh+ cells eventually die)
What happens is a Rh- female conceives a Rh+ foetus?
Some Rh+ foetal RBCs can enter maternal circulation at birth which triggers production of anti-Rh antibodies. If the subsequent pregnancy is also of a Rh+ foetus, the anti-Rh antibodies can haemolyse RBCs of foetus causing a haemolytic disease of the baby.
What is the ideal scenario in blood transfusions?
Donor blood should be cross-matched so that the blood groups match the patient’s.
Why is group O(-) the universal donor?
O has no antigens therefore cannot trigger an immune response. Rh- doesn’t have antigens either; however, Rh+ blood wouldn’t affect the recipient (only potential pregnancies with Rh+ baby).
Why is blood group AB the universal recipient?
They already have both antigens so do not produce antibodies (no reaction)
