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What does PCV stand for?
Packed cell volume
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What is the PCV/haematrocrit of a blood sample?
It is the percentage of the packed cells (RBCs) of the total length of cells and plasma
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How much of a blood sample is normally made up of
a) cellular components
b) fluid components
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What is the colour of plasma dependent on?
- The species of animal
- The diet of the animal
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What does murky plasma indicate?
Murky plasma indicates that it has a high lipid content e.g. the animal is eating a high fat diet. However, some clinical conditions can cause cloudy plasma so it must be investigated.
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What are the sites of blood cell production in
a) foetus
b) young animal
c) old animal
- a) bone marrow (all bones), liver and spleen
- b) bone marrow (all bones)
- c) bone marrow (long bones - red marrow)
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Describe the linages that form from a pluripotent stem cell in blood cell production.
A pluripotent stem cell can either divide to form a lymphoid stem cell (which forms lymphocytes) or a myeloid stem cell (which forms erythrocytes, neutrophils, monocytes, eosinophils, basophils, or platelets)
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Explain cooperative binding in haemoglobin
Once Hb binds one O2 molecule it is much easier to bind the second O2 molecule, once it has bound two it is even easier to bind the third O2 molecule and so on
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Why is it easy to bind O2 in the lungs?
The CO2 concentration, acidity and temperature are all very low which causes Hb to have a high affinity for O2 in the lungs
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How many molecules of O2 can a haemoglobin molecule carry?
Four (as there are four haem groups present within a Hb molecule)
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Why does CO make an efficient poison?
As Hb has a greater affinity for CO than O2. Hb will bind to CO in preference to O2 - if CO is bound to Hb it cannot bind to O2 and transport O2 around the body.
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What facilitates the maternal-foetal O2 transfer?
The foetal form of Hb has a higher affinity for O2 than adult Hb so it is able to pull O2 off the maternal Hb.
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Where is there a store of approximately 1/3 of RBCs in the body?
The spleen
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Contraction of the spleen to release the RBC store into the circulation is regulated by which type of nervous system?
The autonomic, sympathetic nervous system
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What qualities of RBCs vary between species?
- Total number of RBCs
- Diameter and shape of RBCs
- Lifespan of RBCs
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How are erythrocytes removed from the circulation?
- Intravascular haemolysis
- Extravascular haemolysis
- Mononuclear phagocytic or macrophage systems (MPS)
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How are RBCs removed by intravascular haemolysis?
This is the breakdown of RBCs within the blood vessels. Aged cells lyse (as they are less flexible and cannot navigate through narrow capillaries), Hb binds to the plasma protein haptoglobulin and is taken to the bone marrow to be recycled, the lysed RBC is engulfed by cells of the MPS system.
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How are RBCs removed by extravascular haemolysis?
This is the breakdown of RBCs outside the blood vessels. Old RBCs are recognised as they pass through certain organ systems (most commonly the spleen which has very narrow capillaries that aged RBCs struggle to move through) and are engulfed by cells of the MPS and removed from the blood vessels to be broken down.
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What components are required for erythropoiesis and why?
- Amino acids, lipids and carbohydrates
- Iron - for Hb production
- Folic acid - for DNA and RNA synthesis
- Vitamin B12 (cobalt) - maturation of erythrocytes and formation of DNA
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What hormone is erythropoiesis regulated by?
Erythropoietin (EPO)
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What organ stimulates EPO production and how does it do it?
The kidneys stimulate EPO production by a negative feedback system. Decreased O2 delivery to the kidneys stimulates increased EPO production which stimulates RBC production in the bone marrow. Increased O2 delivery to the kidneys halts EPO production until O2 levels within the body are back to the normal level.
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What does the MCV stand for?
Mean corpuscular volume
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What does the MCH stand for?
Mean corpuscular Hb content
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What does the MCHC stand for?
Mean corpuscular Hb concentration
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What is anaemia?
The general term for insufficient levels of Hb in the blood.
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What are the three main types of anaemia?
- Haemorrhagic
- Hypoproliferate
- Haemolytic
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Which of these anaemias are regenerative / non-regenerative?
- Haemorrhagic - regenerative
- Hypoproliferate - non-regenerative
- Haemolytic - regenerative
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What is the cause of haemolytic anaemia?
Blood loss
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What are some of the causes of acute haemorrhagic anaemia?
- External/internal bleeding due to trauma/surgery
- Coagulation disorders eg warfarin, sweet clover
- Parasites eg hookworm, coccidia
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What are some of the causes of chronic haemorrhagic anaemia?
- GI lesions
- Coaggulation disorders eg vit K deficiency, haemophilia
- Parasites eg ticks, lice, hookworms
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What is the cause of hypoproliferate anaemia?
Decreased erythropoiesis
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What can lead to decreased erythropoiesis and therefore hypoproliferate anaemia?
- Dietary deficiencies e.g. iron (hypochromic anaemia) and Vit b12/folic acid (megaloblastic anaemia)
- Destruction of bone marrow e.g. irradiation/x-rays, certain chemicals, myeloproliferative disorders
- Bracken poisoning
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What is the cause of haemolytic anaemia?
Destruction of erythrocytes
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What can cause destruction of erythrocytes and therefore haemolytic anaemia?
- Blood parasites e.g. trypanosomiasis
- Bacterial infections eg leptospirosis
- Chemicals and drugs e.g. copper and lead poisoning
- Poisonous plants and venoms
- Immune mediated causes e.g. autoimmune haemolysis, blood transfusions
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What part of RBCs causes blood transfusion reactions?
Antigens on the surface of blood cells cause blood transfusion reactions. They also give rise to different blood groups in animals.
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Will an animal, e.g. a dog, have a transfusion reaction after their first blood transfusion? Why?
No. Although animal have antigen on the surface of their red blood cells they do not have naturally occurring isoantibodies. This means you can take blood from one animal and give it to another and it will not have the antibodies to react against the donated blood. However, the animal will then recognise the donor cells as being foreign and it will generate immune mediate antibodies against the donor cells. These antibodies will stay in the animal's circulation for (potentially) the rest of its life meaning if you used the same donor again for a second transfusion the animal would show an immune response - have a transfusion reaction.
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What animal does express naturally occuring isoantibodies?
Cats
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Why do greyhounds make good blood donors?
As their blood is not very antigenic
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