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19 Cards in this Set
- Front
- Back
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Describe the tunica interna |
-innermost and in direct contact with blood -composed of endothelial layer: continuous with the endocardial layerof the heart and made of a thin layer of flattened cells. Involveddirectly in various porcesses within the vessel e.g. asdjustingvessel calibre and capillary permeability -contains basement membrane which supports epithelial layer andanchors the endothelium to the connective tissue -the outermost layer is is the internal elastic lamina: thin sheet ofelastic fibres with variably-sized openings which allow diffusion ofsubstances through the interna to the media. |
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Describe the tunica media |
-muscular and connective tissue layer; generally thickest -composed mainly of smooth muscle and elastic fibres -smooth muscle fibres surround the lumen and control vessel diameter -sympathetic stimulation typically causes contraction -chemicals such as H+, NO, and lactic acid cause vasodilation -smooth muscle also regulates vascular spasm in the event of injury toprevent blood loss -also contains the external elastic lamina, composed of a network ofelastic fibres |
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Describe the tunica externa |
-composed of elastic and collagen fibres -contains lots of nerves -contains the vasa vasorum: network of small blood vessels whichsupply the vessel wall (seen in larger arteries) -also help anchor the vessel to the surrounding tissues |
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Describe elastic arteries |
-largest diameter arteries in the body, but with relatively thinvessel walls -have well defined internal and external elastic laminae, and a thicktunica media with lots of elastic fibres – called elastic lamellae -elastic arteries include; aorta, pulmonary trunk, and thebrachiocephalic, subclavian, common carotid, and common iliacarteries -the role of elastic arteries is to stretch and then propel bloodalong the vessel (stored potential energy) |
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Describe muscular arteries |
-these are medium sized arteries. They contain more smooth muscle andless elastic fibres -walls are typically thick due to the amount of smooth muscle in thewalls -the amount of smooth muscle means they are more able to vasodilateand vasocontract. -they have a well defined internal elastic lamina but a thin externalelastic lamina |
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Describe arterioles |
-microscopic vessels that flow into capillaries -thin tunica interna and thin internal elastic lamina -the terminal end of an arteriole – metarteriole – tapers as itapproaches the capillary bed. Where the arteriole meets thecapillaries is a junction – precappilary sphincter – whichmonitors the flow of blood into the capillaries; other cells regulatethe resistance -a key role of arterioles is to regulate the resistance. Reducing thediameter increases the friction between the blood and the vesselwalls, and therefore increases resistance -the tunica externa contains unmyelinated sympathetic nerve fibres toregulate diameter |
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Describe capillaries |
-interplay between the arterial, venous and lymphatic vessels -branched interconnected vessels covering an enormous surface area tosupply the individual body cells -branching increases surface area -primary function is to exchange substances between the blood andinterstitial fluid -the number of capillaries in different regions depends on themetabolic demand of the tissues is supplies e.g. the muscle, brainand liver have a high metabolic demand and a more extensive networkof capillaries. -blood is directed through capillaries as required by peristalsis(vasomotion) -lack tunica media and tunica externa |
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What are the three types of capillaries? |
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Describe the three mechanisms of exchange at capillaries |
Diffusion - simple substances, suchas O2, CO2, glucose, amino acids and hormones, leave capillaries bydiffusion - requires gradient - most proteins and RBCscannot pass through continuous or fenestrated capillaries as theyare too large. They can, however, fit through sinusoids e.g. inhepatocytes and red bone marrow - some capillaries allowonly small amount of exchange e.g. capillaries of the blood-brainbarrier Trancytosis - substances are enclosedin pinocytic vesicles and then transported by exocytosis - mainly used for large,lipid-insoluble molecules such as insulin Bulk flow -determined by pressures - filtration is enabledby blood hydrostatic pressure and interstitial fluid osmotic pressure - the main pressurepromoting reabsorption into the blood vessels, is colloid osmoticpressure - the balance of thesepressures is called Net Filtration Pressure - normally the exchangebetween the blood and interstitial fluid is about equal –Starling's Law of capillaries |
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Describe venules |
-thin walls which do not readily maintain shape -they drain the capillary blood and begin the return of the blood tothe heart -the venules which collect blood directly from the capillaries arecalled postcapillary venules. They are very porous are significantsites of exchange along with the capillaries -as the postcapillary venules move away from the capillaries, theyacquire one or two layers of smooth muscle - called muscular venules -muscular venules have thicker walls preventing exchange -the thin walls of the postcapillary and muscular venules maked themhighly distensible, allowing them to act as resevoirs for blood |
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Describe veins |
- generally have thinwalls - composed of the samelayers as arteries, though the thickness's are different: tunicainterna is thinner, tunica mediai is thinner, tunica externa isthickest - veins lack internal andexternal elastic laminae - not designed towithstand high pressure - lumen is larger andblood pressure is considerably lower - most contain one-wayvalves which are folds of the tunica interna - a vascular sinus is avein with a thin endothelial wall that has no smooth muscle to alterdiameter e.g. coronary sinus of the heart - some veins run inparallel and connect via venous channels called anastomotic veins –particularly in the limbs - the subcutaneous layeris a major source of veins – superficial veins |
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List 5 potential consequences of hypertension What percentage of cases is idiopathic (essential hypertension)? |
coronaryartery disease, stroke, heart failure, renal disease, and peripheralvascular disease. ~90% |
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List 7 causes of secondary hypertension |
- alcohol - obesity - preganancty (preeclampsia) - coarctation of the aorta - endocrine disease - renal disease - drugs |
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How do diuretics lower BP |
- lower BP by depletingsodium stores, thereby reducing reabsorption - reduces blood volumeand therefore cardiac output. When CO returns to normal (6-8 weeks),peripheral vascular resistance is reduced -thiazide diuretics act on distal convoluted tubule andinhibit Na+-Cl- symport. -loop diuretics (e.g. fusosemide) are more powerful than thiazides.They increase urine Ca2+ |
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How do ACE inhobitors lower BP |
-inhibit conversion of angiotensin 1 to 2 |
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How do calcium channel antagonsists lower BP |
-Arteriolar vascular tone depends on free intracellular Ca2+concentration. -Calcium channel blockers reduce transmembrane movement of Ca2+ - reduce the amount reaching intracellular sites and therefore reducevascular smooth muscle tone. |
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How do beta blockers lower BP |
(1)Reduce cardiac out put (2) inhibit renin release and AT-II andaldosterone production, and lower peripheral resistance (3) maydecrease adrenergic outflow from the CNS |
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How do alpha 2 agonists lower BP |
-Centrally acting alpha2-agonists stimulate presynapticalpha2-adrenergic receptors in the brain stem, which reducessympathetic nervous activity |
