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43 Cards in this Set
- Front
- Back
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What are the functions of the vascular system?
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Transport O2 and nutrients and waste products (e.g. lactic acid and CO2)
Transport defence cells, hormones, growth factors Regulate distribution of blood Blood pressure and temperature Wound healing |
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What are the 3 layers of blood vessels?
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Tunica intima
Tunica media Tunica adventitia |
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What is the tunica intima composed of?
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Endothelium (simple squamous epithelium on basement membrane)
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What is the tunica media composed of?
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Smooth muscle and connective tissue
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What is the tunica adventitia composed of?
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Connective tissue - collagen and elastin
Sometimes vaso vasorum - blood vessels supplying vessel wall (lymphatics and nerves too) |
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Give examples of elastic arteries
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Aorta
Pulmonary artery |
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Give examples of muscular arteries
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Most arteries, size variation
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Describe the structure of elastic arteries
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Tunica intima - thin, endothelium with layer of collagenous tissue rich in elastin, myointimal cells (atherosclerosis) and fibroblasts
Tunica media - broad, elastin, collagen and smooth muscle fibres Tunica adventitia - relatively thin, vasa vasorum - lymphatics, nerves, elastin and type 1 collagen |
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What is the function of elastic arteries?
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Shock absorption in response to high pulse pressure - distension during systole, recoil during diastole
Maintains smooth blood flow and blood pressure |
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Describe the structure of muscular arteries
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Two well defined elastic sheets - internal elastic lamina between tunica intima and media, external elastic lamina between tunica media and adventitia
Tunica media usually equal to or smaller then tunica adventitia Tunica adventitia - collagen and elastin, broad |
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What is the function of muscular arteries?
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Control or adjust blood flow distribution and blood pessure by nervous control and vasodilation/constriction respectively
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Describe the structure of arterioles
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Lumen diameter usually <0.3mm and fewer than 6 layers of smooth muscle
Tunica intima and adventitia layers quite insignificant |
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What is the function of arterioles?
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Regulate blood pressure and blood flow to capillary beds
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What does increased vasoconstriction in arterioles cause?
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Increased peripheral resistance -> increased blood pressure
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How do arteries protected by the skull differ?
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Thin t. media (no need for protection, already protected)
Thick inner elastic lamina |
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How are arteries in the penis specialised?
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Helicine arteries
Extensively branched and coiled Smooth muscle cushions - valves for erection |
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How do umbilical arteries differ?
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No inner elastic lamina
Inner longitudinal and outer circular smooth muscle layer |
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How are arteries in the lung specialised?
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Less elastin and muscle due to lower pressure in pulmonary circulation
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Describe the structure of capillaries
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Endothelium, basement membrane and CT
Diameter of 3-10µm Flattened cells pericytes present - progenitor CT cells: fibroblasts, macrophages, smooth muscle - contractile or regulatory |
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What does the density of capillaries in a tissue represent?
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How metabolically active a tissue is
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What are the 3 different types of capillaries?
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Continuous
Fenestrated Sinusoidal |
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Describe where continuous capillaries are found and how exchange occurs
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Lungs, muscle, skin, exocrine glands, nervous tissue
Passive diffusion - gases, ions and small molecules Pinocytic vesicles - proteins and some lipids Intercellular passage - via intercellular space between endothelial cells |
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Describe where fenestrated capillaries are found and how exchange occurs
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Kidneys, intestines, endocrine glands
Pores - much greater permeability, macromolecules smaller than plasma proteins Fewer, if any, pericytes |
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Describe where sinusoidal capillaries are found and how exchange occurs
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Spleen and liver
Large spaces between endothelial cells allowing large particles like RBCs and proteins to pass through |
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Name numbers
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1 - arteriole
2 - metarteriole 3 - precapillary sphincters 4 - thoroughfare channel 5 - venule 6 - arteriovenous shunt |
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What is a metarteriole?
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Connects a terminal arteriole and venule
Capillary bed branches off arteriole end and reemerge into thoroughfare channel |
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What happens if the precapillary sphincters close?
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Blood bypasses capillary bed through arteriovenous shunts
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What happens if the arteriovenous shunt smooth muscle or metarteriole smooth muscle contracts?
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Blood flows into capillary network
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Why is the arteriovenous shunt contraction/precapillary sphincter shutting an important mechanism?
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For tissue with intermittent blood flow e.g. digestive system
Temperature regulation |
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Describe the 3 types of venules
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Postcapillary venules - drain several capillaries, wider diameter, blood almost stagnant but inflammation, allergies, temperature
Collecting venules - larger diameter and greater number of pericytes Muscular venules - 3 layer structure, 1-2 muscle layers |
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What are valves in veins made up of?
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Fibroelastic infolding of tunica intima
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Why are veins considered blood reservoirs?
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Up to 65% of body's blood in veins
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Describe small/medium and large veins
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Small/medium - t. media 2-3 layers of smooth muscle and t. adventitia contains longitudinal collagen fibres
Large - NO VALVES, t. intima some elastic fibres, t. media poorly developed with circular muscle except vena cava where it is longitudinal, t. adventitia very thick with vaso vasorum, lymphatics, collagen, elastin |
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How are veins that have to cope with high hydrostatic pressure specialised?
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Thick tunica media
e.g. teat veins, limb veins |
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How are veins specialised in protected regions?
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No tunica media
e.g. bones, penile erectile tissue |
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Do endothelial cells retain their ability to repair and divide throughout life?
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Yes
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How do endothelial cells respond to injury?
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Produce Vascular Endothelial Growth Factor (VEGF) which acts on VEGF receptor
- manipulated by tumours |
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How do veins respond to age?
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Loss of elasticity, thickening, fragmentation, atherosclerotic plaques, calcification of t. media
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What are the 3 forms of control of blood vessels?
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Neural control - sympathetic postganglionic fibres - noradrenaline - α-1 adrenergic receptors = vasoconstriction - β-2 adrenergic receptors (blood vessels in skeletal muscle) - vasodilation
Endocrine - catecholamines from adrenal medulla - vasoconstriction (except skeletal muscle) Autoregulation - local control in response to local O2/lactic acid concentrations |
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Which vessel?
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Elastic artery
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Which vessel?
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Muscular artery
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Which vessel?
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Small and medium veins
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Which vessel?
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Large vein
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