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The Vascular Tree

sophietevans Level 2 Diploma of Higher Education Englisch 45 Karten

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  1. 1What is the function of the cardiovascular system?To perfuse tissues with sufficient blood to meet their differing and changing needs. This includes the delivery of oxygen and nutrients, and the removal of CO2 and other cellular wastes.
  2. 2How is the pressure to counteract inertia and promote fluid transport generated in the cardiovascular system?The heart provides the kinetic energy through systole, while the blood vessels provide the resistance against blood flow. This interaction generates pressure.
  3. 3Once blood starts moving through the cardiovascular system, what form of energy does the pressure energy dissipate as?Heat/friction.
  4. 4Which factors does blood flow depend on?A pressure gradient, the resistance of the vessels, blood viscosity, vessel length, and vessel radius.
  5. 5Which factors that influence blood flow can be considered constant?Vessel length and blood viscosity.
  6. 6What is a pressure gradient?A pressure gradient is developed along a tube that provides resistance to the pump at the origin, as energy is lost as heat through friction with the tube/vessel walls. It is both a product of, and required by, blood flow.
  7. 7What is the calculation for vessel resistance?Resistance = 1 / radius^4
  8. 8Halving the diameter of a blood vessel would increase its resistance by what factor? What does this mean for pressure?It would increase resistance by 16x, meaning that a pressure increase of 15x would be necessary to maintain flow - a large increase.
  9. 9Where is the greatest drop in pressure in the cardiovascular system? What is the benefit of this?The greatest drop of pressure occurs in the arterioles as they offer the most resistance. They are a physiological bottleneck, which is significant for control (i.e. of perfusion of different tissues).
  10. 10Which structural layers do arteries possess that veins don't? Why is this?Arterial vessels possess internal and external elastic laminae, unlike veins, because they are exposed to large pressures generated in the ventricles which they must be protected against, and because their role is in transport of blood to tissues so they must be able to maintain a pressure gradient via elastic recoil between systoles.
  11. 11What does the vascular shunt consists of?A metarteriole and a venous thoroughfare channel.
  12. 12What is the point of precapillary sphincters?Precapillary sphincters are sensitive to the metabolic needs of the tissues downstream from them. They can respond by opening (smooth muscle dilation) and allowing blood to flow through an arterial bed, or by closing (smooth muscle contraction) and forcing blood to only move through the vascular shunt.
  13. 13Which arteriole does an arterial bed branch from?The terminal arteriole.
  14. 14What proportion of vessels are closed at rest?Up to 95%.
  15. 15Which factors to precapillary sphincters respond to in order to influence flow through the microcirculation?Autonomic nervous stimulation, blood pressure, local metabolities (CO2, K+), and circulating hormones.
  16. 16Describe the structure of a continuous capillary, and suggest where one might be found.A continuous capillary has very tight endothelial cell junctions and an intact endothelial lining. This is the most common capillary type, and is found in the blood-brain barrier as the tight endothelial junctions do not allow most substances through. They are also found in skeletal muscle.
  17. 17Describe the structure of a fenestrated capillary, and suggest where you might find one.Fenestrated capillaries contain fenestrations - small pores which allow for more rapid exchange by sacrificing a degree of control over exchange. There are less tight inter-cell junctions between endothelial cells. They are found in the kidneys and intestines as they allow for exchange (e.g. absorption, filtration, reabsorption etc).
  18. 18Describe the structure of a sinusoid capillary, and suggest where you might find one.Sinusoid capillaries retain the least control over exchange, in order for movement of cellular components and even cells to be possible. They have an incomplete endothelial cell lining and basement membrane, and are present in the bone marrow and liver for haematopoiesis and processing of blood, respectively.
  19. 19Describe the forces influencing fluid exchange in capillaries.Pressure on blood will push it forward, but also hydrostatic pressure will push it towards the periphery of the capillary, while interstitial forces will push it back, and osmotic pressure force fluid in and out of capillaries depending on composition of fluids.
  20. 20What is oedema?Build up of fluid in the interstitial space.
  21. 21Why does oedema not occur more often, given the tendency for fluid to move out of capillaries due to the net forces?The lymphatic system returns lost fluid to the circulation via the subclavian veins, at a rate of ~2L/day.
  22. 22Write an equation for the net outflow into the extracellular fluid.Net outflow = net filtration - net absorption
  23. 23What is the pressure gradient in the venous circulation?~20 mmHg.
  24. 24Which force is the venous pressure gradient not large enough to oppose?Hydrostatic forces.
  25. 25What is the muscular pump?Given that the pressure gradient in the venous circulation alone is not enough to return blood to the heart, the skeletal muscles, particularly those of the legs, aid the process by squeezing blood up the veins during contraction. The blood only travels towards the heart because of the presence of valves, which ensure unidirectional flow.
  26. 26What is the respiratory pump?The venous pressure gradient is not sufficient alone to overcome hydrostatic forces in order to return blood to the heart. The respiratory pump aids blood return (inadvertently) as when the intrathoracic volume increases during inspiration, the great veins are expanded. This accommodates a larger volume of blood to fill them, and then reduction of the thoracic volume during expiration compresses the vessels and aids return to the right atrium.
  27. 27List the 4 main factors that mean arterial pressure is determined by.Blood volume, cardiac output, vessel resistance, and distribution of blood between the arterial and venous aspects of the circulation.
  28. 28Which long-term mechanism is the blood volume controlled by?The renin-angiotensin system, which also recruits aldosterone and antidiuretic hormone in order to conserve Na+ and therefore H2O and raise blood pressure.
  29. 29What is the equation for the factors that cardiac output is controlled by?Cardiac output = heart rate x stroke volume
  30. 30What might heart rate be altered by?Autonomic stimulation, and/or the presence of epinephrine.
  31. 31What is Starling's Law?Starling's Law states that the heart will always try to pump what is returned to it. So, a greater preload (set by the end-diastolic volume), increased contractility (e.g. caused by epinephrine), and increased afterload (the pressure against which ventricles pump), all increase blood pressure.
  32. 32What is the preload?The volume of blood in the ventricles which helps to determine the contractility of the muscle. It is set by the end-diastolic volume.
  33. 33What is afterload?The pressure developed in the ventricles in order to eject blood against the pressure of the arteries, predominately the aorta, so that the aortic valve will open.
  34. 34What factor is vessel resistance determined by?Vessel radius, so the activity of the smooth muscle cells in the walls of arterioles.
  35. 35Which factors is smooth muscle cell activity in the arteriole walls affected by?Direct response to stretch, response to local metabolites and circulating hormones (e.g. adrenaline, ADH, renin-angiotensin II, and endothelium-derived factors), and autonomic activity (e.g. the baroreceptor reflex).
  36. 36Which are the capacitance vessels?The great veins, such as the femoral veins and vena cavae.
  37. 37What is the distribution of blood between venous and arterial vessels predominately determined by?Dilation or constriction of the capacitance vessels, which hold ~65% of circulating blood.
  38. 38Constricting the great veins will shift a significant volume of blood to the arterial side of the circulation. What other ratio determines the distribution of blood?The plasma:interstitial fluid distribution, determined by osmotic/hydrostatic forces.
  39. 39What is hypertension defined as?Systolic/diastolic pressures >140/90 mmHg.
  40. 40Pathogenesis of hypertension is multi-factorial. What does this mean?There are both genetic and environmental predispositions to its pathogenesis.
  41. 41What type of disease is hypertension?Chronic.
  42. 42List some other conditions that hypertension is involved in.Atherosclerosis, ischaemic heart disease, stroke, and diabetes.
  43. 43Which produces a sharper increase in mortality: an increase in systolic pressure or an increase in diastolic pressure?An increase in systolic pressure.
  44. 44Consumption of which mineral increases blood pressure?Salt.
  45. 45What factor does blood pressure 'naturally' rise with?Age!

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Beschreibung
From the 01/10/13 Human Physiology lecture.
Erstellt von
sophietevans · Jan 2014
Aktualisiert
28 Aug 2016
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