intro to blood Flashcards
what is the average circulating volume of blood in a typical adult male (70kg)?
5L
1L - lungs
3L - systemic venous circulations (veins have a greater capacity to hold blood than arteries due to thinner walls)
1L - in heart and arterial circulation
what are 5 functions of blood?
carriage of plasma
clotting - platelets
defence - white blood cells
carriage of gas - red blood cells
thermoregulation
describe the composition of plasma
makes up 4% of body and contains 95% water
what 3 categories of proteins is plasma subdivided into?
Albumin
- creates oncotic pressure
- transports fat-soluble vitamins and steroid hormones.
Globulins (3 types) :
a, ß, (alpha and beta transport like albumin)
while g, (gamma acts as antibodies)
Fibrinogen and other clotting factors
what is colloid oncotic pressure?
a form of osmotic pressure induced by proteins in the blood because they displace water
which then favours the movement of water and solutes into the capillary.
what is capillary hydrostatic pressure?
Capillary hydrostatic pressure (blood pressure) is an opposing pressure
it favours the movement of water and solutes out of the capillary into the interstitial space
what is hypoproteinaemia?
low levels of circulating plasma proteins.
what 4 things can hypoproteinaemia be caused by?
Live disease
Prolonged starvation
Intestinal disease
Nephrosis kidney disease
what characteristic do all types of hypoproteinaemia share?
oedema/swelling (build-up of fluid) in the interstitial space due to loss of oncotic pressure because of the loss of plasma proteins.
what is haematopoiesis?
process where all mature blood cells are produced from undifferentiated stem cells (pluripotent) found in bone marrow
what type of blood cells do stem cells give rise to?
erythroblast
- reticulocyte (not mature RBC)
-> erythrocyte (mature RBC)
megakaryocyte - platelets
WBC - neutrophil, monocyte, basophil, eosinophil
what are myeloid cells?
all blood cells except lymphocytes
what are the most abundant blood cells?
erythrocytes 4-6x10^12/L with a 120-day lifespan
highly flexible
biconcave (increases surface area-to-volume ratio to carry more gas)
non-nucleated cells with a diameter of 7-8 micrometres.
They are densely packed with haemoglobin (protein for O2 transport).
Why does arterial blood have a bright red colour while venous blood has a bluish/purplish colour?
when oxygen binds to the iron atoms on haemoglobin it becomes oxyhaemoglobin and takes on a brighter colour
when it loses oxygen it becomes deoxyhaemoglobin and takes on a darker bluish/purplish colour.
what is erythropoiesis?
a process is controlled by the hormone erythropoietin
it gets increasingly secreted when oxygen delivery to kidneys is reduced (hypoxia).
how is erythropoietin secreted?
85% kidney
15% liver
Why is erythropoietin secretion increased when oxygen delivery to kidneys is reduced (hypoxia)?
the role of erythropoietin is to stimulate the maturation process of red blood cells in the bone marrow which takes about 2-3 days to mature.
increasing the amount of erythropoietin
-> speeds up growth of RBCs
-> an increase in the delivery of oxygen
-> restore oxygen delivery (negative feedback loop)
Why is renal disease associated with anaemia (deficiency in the number of red blood cells)?
the kidney secretes 85% of the hormone erythropoietin which is responsible for stimulating the maturation process of red blood cells in the bone marrow.
So lack of kidney function = less erythropoietin secretion = less red blood cells.
what are leukocytes (WBC)?
nucleated cells involved in defence against pathogens.
They are larger than red blood cells and are approximately 1 x 10^10/L
what are neutrophils?
the most abundant white blood cells with a half life of 10 hours, and the body produces approximately 100bn of them per day.
what are basophils
Basophils are the least abundant white blood cells
what is the difference between a monocyte and a macrophage?
Monocytes (5%) are circulating cells in the plasma.
After they migrate to connective tissue
They become macrophages (live for 3 months) which phagocytose pathogens
what is leukopoiesis?
the process by which white blood cells form.
what is leukopoiesis controlled by?
a cocktail of cytokines such as:
Colony Stimulating Factors (CSF) - responsible for stem cell proliferation and differentiation.
Interleukins - mediates communication between cells.
what are cytokines?
proteins or peptides released from mature white blood cells.
They stimulate both mitosis and maturation of leukocyte
Why is the cytokine cocktail that is responsible for leukopoiesis considered dynamic?
it changes its composition in response to infection, which stimulates an increased formation of a specific type of white blood cell.
Explain the differential stimulation of leukopoiesis in response to Bacterial and Viral infection.
In response to infection, all white blood cell production is increased.
Bacterial infection - there is a higher formation of neutrophils.
Viral infection - there is a higher formation of lymphocytes.
what does a differential white cell count show?
the proportion of white blood cells in the blood to allow you to differentiate between infection types.
what are platelets? lifespan, abundancy, function
membrane-bound cell fragments from megakaryocyte cells, rarely nucleated, are 2-4 microns in diameter.
10-day lifespan
least abundant in the composition of blood at 140-440 x 109/L.
They form the foundations of blood clotting, by adhering to damaged vessel walls and exposed connective tissue.
what hormone governs the formation of platelets?
thrombopoietin
what is a haematocrit?
a measurement of the percentage of red blood cells to the whole blood
it’s 40-50%, but it’s less in women and higher in men.
what happens to the haematocrit in dehydration?
increases because the fluid component of blood decreases.
what happens to the haematocrit under the influence of erythropoietin?
increases because it stimulates the growth of red blood cells.
what is jaundice?
the condition caused by the build-up of bilirubin in the blood due to liver malfunction.
what is bilirubin?
yellow substance in the blood
It forms as a product of red blood cell breakdown, which gets recycled under normal circumstances by the liver.
what is viscosity?
how thick or sticky blood is compared to water
what is the viscosity of plasma and whole blood compared to water?
plasma - 1.8x thicker than water
whole blood - 3/4x thicker than water
what 3 factors does viscosity depend on?
Haematocrit - 50% increase in haematocrit = increase in viscosity by 100%
Temperature - increased temperature = decreased viscosity.
1 degrees changes viscosity by around 2%
Flow rate - decreased flow rate = increased viscosity
