the circulatory system Flashcards

1
Q

circulatory system functions

A

-unicellular organisms- meet metabolic needs using simple diffusion and convection
-evolution increases size and complexity of CVS
-maintains step IC:EC concentration gradient to deliver nutrients and remove waste from centrally located cells
-fast convection system circulating fluids between surfaces
-primary function is the distribution of gases and molecules for nutrition growth and repair
-secondary functions are fast chemical signalling (hormones ), dissipation of heat and mediates inflammation and host defence responses to invading microbes

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2
Q

what are the 3 functional parts of the CVS and how are they used

A

-heart, blood and blood vessels
-heart: pump (pressure)
-blood : fluid
-blood vessels: set of containers- arteries, veins, capillaries
-blood visits heart 2x during circulation

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3
Q

what kind of demand changes require regulation

A

-sleep/awake
-body position/ intrathoracic pressure
-rest/exercise, acceleration/ deceleration
-digestion
-emotional stress, thermal stress

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4
Q

how does the heart being a dual-pump work

A

-heart pumps blood in two serial circuits
-left heart; systemic circulation:
=parallel pathways from left to right
=usually flows through a single capillary bed (extensive)
=two capillary beds in series e.g. kidneys
=capillary beds in parallel and series e.g. spleen
-right heart; pulmonary circulation
=single pathway from right to left side of heart

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5
Q

what’s vasculature

A

-arteries- the distribution system, under higher pressure (major arteries to minor arteries to arterioles)
-microcirculation- diffusion and filtration system
-veins- collection system, returns heart under low pressure venules to minor veins to major veins

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6
Q

what are the 4 building blocks in vascular wall

A

-endothelial cells (internal)
-elastic fibres
-collagen fibres
-smooth-muscle cells

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7
Q

what are the 3 layers of blood vessel cells walls

A

-intima (tunica interna)
-media (tunica media)
-adventitia (tunuca externa)

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8
Q

why is it important that in capillaries only the intimal layer is resting on a basement membrane

A

-pressure in veins is low which causes back flow

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9
Q

variation in structure of blood vessels

A

-veins have a large capacity of blood but can’t upstanding a large amount of pressure
-lots of elastic fibres in aorta which is important for the pulsatile blood from the heart

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10
Q

what do elastic arteries have

A

-high compliance as walls can stretch easily without tearing
-recoil of elastic fibres forced blood to move even when there ventricles are relaxed

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11
Q

what do muscular arteries consist of

A

-vascular smooth muscle cells arranged circumferentially
-capable of greater vasoconstriction/ vasodilation to adjust blood flow rate
-vascular tone- partial contraction maintains vessel pressure and efficient flow

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12
Q

what are arterioles

A

-smooth muscle enables blood flow regulation to capillary network
-intermittent flow through capillary bed due to periodic contraction of VSMC
-terminal regions- met arterioles (shortcuts)
-precapillary sphincters monitor blood flow to capillary (mesenteric/cerebrak circulation- not innervated but sensitive to local tissue conditions)

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13
Q

what does venules consist of

A

-post capillary venules are porous - act as exchange sites for nutrients and waste
-muscular venules have thin smooth muscle cell layer (less muscular than arterioles)- can expand and contract which is excellent reservoirs for blood
-thin walls allows expansion

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14
Q

what leads to varicose veins

A

-defective and leaky valves which allows back flow

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15
Q

what do capillaries consist of

A

-endothelial cells and basement membrane
-very gappy so many substances can pass through

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16
Q

starlings forces

A

equations: Jv= Kf[(Pc-Pi)-(piec-piei)]
Jv= fluid movement
Kf= hydraulic conductance
Pc= capillary hydrostatic pressure
Pi= interstitial hydrostatic pressure
piec= capillary oncotic pressure
piei= interstitial oncotic preste
oncotic is colloid osmotic pressure

17
Q

starling pressures across capillary wall

A

-Pc declines along length of capillary through fluid filtration
-net filtration becomes net absorption
-arteriole filtration exceeds venular absorption

18
Q

how does the lymphatic system play a role In the maintenance of blood of volume

A

-fluid collected by lymphatic system returns to the cvs via subclavian veins