Cardiovascular Flashcards
What percentage of the blood is in the cellular phase? What percentage of this are erythrocytes?
45% and 99%
What percentage of the blood is in the fluid phase?
55%
How many litres of blood do we have?
5 litres
What is haemocrit?
The percentage of red blood cells in the blood by volume (45% or 0.45)
What is haematopoesis?
Process by which red blood cells are created. Continues throughout life
Where does haematopoesis occur in adults?
Bone marrow
Where does haematopoesis occur in the foetus?
Liver and spleen and other organs
How long do platelets live for?
7-10 days
How long do erythrocytes live for?
120 days
How long do white blood cells live for?
6 hours
Where are the precursor cells of red blood cells located in adults and children?
Bone marrow of axial skeleton (skull, neck, thorax and spine) for adults, bone marrow of all bones for children
Describe the locations in which red blood cells are progressively produced in utero
Yolk sac, liver, spleen, bone marrow
Are precursor cells found in the blood?
No
What is it called when precursor cells are found in the blood
Leukaemia
What stimulates precursor stem cells to proliferate and differentiate?
Hormonal growth factors
Which hormonal growth factor stimulates
a) red blood cells
b) white blood cells
c) platelets
a) EPO (erythropoietin)
b) G-CSF (granulocyte colony stimulating factor)
c) TPO
Which direction will the oxygen dissociation curve shift when
a) pH decreases
b) temperature decreases
a) right
b) left
What is a young red blood cell called?
Reticulocyte
What does a red blood cell contain?
Plasma membrane
Enzymes of glycolysis
Haemoglobin
Cytoplasm
What does haemoglobin do?
Carry oxygen from lungs to tissues, where it transfers oxygen to myoglobin in muscles
Describe the structure and function of haemoglobin
2 alpha chains
2 beta chains
4 haem groups
Quaternary structure
Describe blood typing
Some individuals have the gene that codes for the A antigen on the surface of their erythrocytes (Type A)
Some individuals have the gene for the B antigen (Type B)
Some have the gene for both and these antigens are codominant (Type AB)
Some have the gene for neither (Type O)
Type A = anti-B antibodies in the blood
Type B = anti-A antibodies in the blood
Type AB = neither of these
Type O = anti A and anti B antibodies on the surface of the erythrocytes
Which blood group is the
a) universal donor?
b) universal recipient?
a) O
b) AB
Is the O antigen dominant or recessive?
Recessive
What type of antibodies are being described when it comes to red blood cells?
Anti-erythrocytes antibodies
natural antibodies
Why do problems occur when an incompatible blood transfusion is given?
Antibodies (be specific about which ones) in the recipients blood attack the antigens (again, be specific) on the donor’s erythrocytes
What do Rhesus positive and negative mean?
D antigen is present/ absent
What is anaemia?
Reduction in haemoglobin in the blood
What is the range of normal haemoglobin values?
12.5-15.5 g/dL
What is polycthaemia?
Abnormally high haemoglobin levels
What causes polycthaemia?
Smoking, lung diseases, inefficient lungs - less oxygen is exchanged so more haemoglobin is required
What are the symptoms of anaemia?
Tiredness, lethargy, malaise, reduced exercise tolerance, shortness of breath on exertion, angina
What are the signs of anaemia?
Pallor, pale mucus membranes and palmar creases (pink hands), glossitis (sore tongue), angular stomatitis (cracking at the corners of the mouth), kylonychia (spoon shaped nails)
Different types/ classifications of anaemia?
Iron deficiency, B12/ folate deficiency, anaemia of chronic disorder, haemolysis, bone marrow failure/ infiltration
Describe why an iron deficiency causes anaemia
Iron is required for haemoglobin production
A lack of iron results in the reduced production of red blood cells
What is MCV, and what are the normal values?
Mean corpuscular volume
Measure of the size of erythrocytes, and 89 +-7 fl (82-96fl)
What happens to MCV in an iron deficient anaemic patient?
Decreases to below 80fl
What causes iron deficiency anaemia?
Bleeding
- Occult gastrointestinal (most common type of bleeding)
- Menorrhagia (heavy periods)
Dietary
- Not enough iron in the diet
- Most common cause of iron deficiency anaemia
What is macrocytic anaemia, and what causes it?
MCV of erythrocytes is above 100fl (large erythrocytes)
It is a symptoms of B12 and folate deficiency
- can occur without anaemia (raised MCV and normal haemoglobin levels) and this is caused by liver disease, alcohol and hypothyroidism
- vitamin B12 and folate are needed for DNA synthesis
- when deficient in them, fewer erythrocytes can be made in the bone marrow
- therefore, fewer, larger erythrocytes are released
- deficiency affects all dividing cells but bone marrow is active so is affected first
What causes B12 deficiency?
Stomach damage
- intrinsic factor is required for the absorption of B12 in the terminal ileum
- produced by gastric parietal cells in the stomach
- damaged stomach means fewer gastric parietal cells
- less absorption of B12
- anaemia occurs
What is pernicious anaemia?
Autoimmune disease
Antibodies made against gastric parietal cells which produce intrinsic factor
Less intrinsic factor is produced
Less B12 can be absorbed
Liver has 4 year store of B12 so slow onset
Causes of folate deficiency?
Found in fruit and vegetables
- malabsorption due to coeliac disease
- not eating enough fruit and veg
- increased need due to haemolysis
What is haemolysis?
Normal or increased cell production but decreased life span of erythrocytes
What are the congenital causes of haemolysis?
Spherocytosis
- spherical blood cells
- get stuck in blood vessels easily
- dominant but variable penetrance
Pyruvate kinase deficiency
- converts phosphoenolpyruvate to pyruvate
- less ATP production
- build up of phosphoenolpyruvate
G6PD deficiency
Sickle Cell Anaemia
- sickle shaped erythrocytes become stuck in blood vessels easily
Thalassaemia
- mutation in haemoglobin chains
Acquired caused of haemolysis
Autoimmune
- immune system attacks own blood cells
- can be triggered by a blood transfusion due to the presence of foreign antibodies
Mechanical
- fragmentation of erythrocytes by mechanical heart valve or intravascular thrombosis in DIC (disseminate intravascular coagulation)
Haemolytic disease of the foetus and newborn
What is haemolytic disease of the foetus and newborn?/ Rhesus disease
Mother is rhesus negative but the first child is rhesus positive
- mother is exposed to the baby’s blood in pregnancy
- mother recognises and makes antibodies against the baby’s rhesus positive erythrocytes
- mother is sensitised to rhesus positive blood
- first baby is unaffected as it takes time to produce the antibodies
- second rhesus positive baby is affected
- antibodies are produced immediately, and destroys the baby’s erythrocytes
- results in haemolysis of the foetus/ newborn’s red blood cells
- anaemia and jaundice occur
Features of neutrophils:
How numerous in comparison to other leucocytes?
Lifespan?
Which hormone controls rate of production?
Function?
Most numerous white blood cell
10 hours
Phagocytose and kill bacteria
Release
- chemotaxins (signal more white blood cells to come to the site)
- cytokines (inflammatory response)
What is caused by a lack of neutrophils?
Recurrent bacterial infections
Functions of B and T lymphocytes?
Immunity
Some generate antibodies against specific foreign antigens e.g bacteria and viruses
Others are immunological memory - generates immunity and allows vaccination
Features of B lymphocytes:
Where are they formed?
Where are they stored?
What is their function?
Made in bone marrow
Stored in secondary lymphoid organs
Differentiate into plasma cells and produce immunoglobulins when stimulated by a foreign antigen
Features of T lymphocytes
Made in bone marrow
Mature in thymus
Some are CD4 helper cells
- help B cells in antibody generation, responsible for cellular or cell mediated immunity
Some are cytotoxic cells (CD8) - T killer cells
What is acute leukaemia, and what does it cause?
Proliferation of primitive precursor cells usually found in bone marrow
Causes…
- anaemia: pallor and lethargy
- neutropenia: infections
- thrombocytopenia: excessive bleeding
What is acute myeloblastic leukaemia?
malignant proliferation of the precursor myeloblasts in the bone marrow
primarily affects adults
what is high grade lymphoma?
lymphocytes in lymph nodes becoming malignant, very similar to leukaemia
Classified as Hodgkins’s disease and Non-Hodgkins lymphoma
Disease usually of the lymph nodes that spreads to the liver, spleen, bone marrow and blood
How do you test platelet function function?
Prothombrin time
- time taken for a clot to form in a blood sample
Describe the features of platelets
Cytoplasmic enucleate cells
What precursor cells form platelets?
megakaryocytes
Lifespan of platelets
5-10 days
What is the range of normal numbers of platelets?
140-400x10^9/l
What are the complication of reduced numbers of platelets?
Thrombocytopenia
Risk of cerebral bleeding
What are the complications of high levels of platelets?
Thrombocytosis
Arterial and venous thrombosis
Increased risk of heart attack and stroke
What proteins can be found in the blood?
Coagulation proteins
Plasma proteins
What is vitamin K and why is it needed?
Essential for the correct synthesis of coagulation factors 2,7,9 and 10 (remember as 1972)
Describe the circulation of coagulation proteins in the blood
Circulate in their inactive form
Describe the function of coagulation proteins
Make blood clot
Convert soluble fibrinogen into insoluble fibrin
Describe the functions of plasma proteins
Carrier proteins for nutrients and hormones
What are coagulation proteins?
Enzymes made in the liver
Key enzyme is thrombin (makes platelet plug)
How do plasma proteins circulate in the blood
In plasma component
Soluble
Which is the most numerous plasma protein?
Albumin
where is albumin produced
liver
function of albumin
maintain oncotic pressure
sign of a lack of albumin
oedema
what does albumin carry?
fatty acids, steroids and thyroid hormones
what are immunoglobulins
antibodies produced by plasma cells
what are the classes of immunoglobulins?
IgG, IgM, IgA, IgE
most important immunoglobulin class?
IgG
What is haemostasis?
The arrest of bleeding
what are the two components of haemostasis?
coagulation of blood
contraction of damaged blood vessels
why is blood usually fluid inside blood vessels?
the proteins of the coagulation cascade circulate in their inactive state until they are activated by tissue factor
what is tissue factor
a protein present on every cell apart from endothelial cells
what stimulates blood clotting?
when endothelium is punctured, blood comes into contact with tissue factor and clotting occurs
what is the term for when blood clots inside a vessel?
thrombosis
what is the coagulation cascade?
series of proteolytic enzymes that circulate in an inactive state being activated in a cascade sequence to generate thrombin
thombrin cleaves fibrinogen to create fibrin polymerisation i.e a blood clot
what is the significance of thee coagulation cascade having multiple steps?
allows for biological amplification
allows for regulation
not an all or nothing response
can be graduated in response to severity of challenge
function of platelets
responsible for primary haemostasis
adhere to damaged endothelium and aggregate to form a platelet plug that blocks the hole in the vessel
