circulatory system Flashcards
what are the differences between arteries and veins?
arteries have a thick, smooth muscular wall transporting blood under high pressure.
veins have thinner walls and transport blood under lower pressure, but contain more blood by volume
what are the three layers of a blood vessel?
tunica intima - connective tissue, endothelium and basement membrane
tunica media - elastic tissue and muscle
tunica adventitia
when is the maximum arterial pressure measured?
when the ventricle contracts and blood is pumped into the arterial system
when is minimum arterial pressure measured?
when the ventricle is relaxed and blood is returned to the heart via veins
what is meant by pulse pressure?
the difference between systolic and diastolic pressure
where is peripheral resistance the highest?
arterioles
what is the composition of the blood?
55% plasma
45% formed elements
what proteins are present in plasma?
albumin
globulins
fibrinogen
what are the formed elements of the blood?
RBCs (erythrocytes)
platelets (thrombocytes)
white blood cells (leukocytes)
what is the function of albumin?
maintains osmotic pressure and helps transport substances in the blood
what is the relevance of Ca2+ ions in the blood?
important for clotting, signal platelets to aggregate
what are granulocytes?
a group of white blood cells including neutrophils, eosinophils and basophils
what are neutrophils?
granulocytes involved in first response to infection. phagocytic
what do basophils do?
release heparin and histamine
what does haematocrit measure?
volume in the blood occupied by RBCs as a percentage. normal value = approx 45%
what happens when the dissociation curve for Hb shifts left?
at a given PO2 in the tissue, there is decreased release of O2 and affinity for O2 is increased
what happens when the dissociation curve for Hb shifts to the right?
increased unloading of O2, affinity for O2 decreased
what causes a rightward shift of the Hb dissociation curve?
muscle is hot (such as in exercise)
low pH
hypercapnia
high levels of organic phosphates
what is the startling equation?
an equation that describes the role of hydrostatic and oncotic forces in the movement of fluid across the capillary membranes as a result of filtration
when is filtration favoured?
when the blood pressure is greater than the osmotic pressure, fluid moves out of the capillary
when is reabsorption favoured?
when blood pressure is less than osmotic pressure, fluid enters capillary
how do interstitial fluids enter the lymphatic system?
via lymphatic capillaries assisted by osmotic pressure
