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Anatomy and Physiology > blood vessels > Flashcards

blood vessels Flashcards

1
Q

Bblood vessels

  • examples
  • when aren’t arteries carrying oxygenated blood?
A
  • delivery system of dynamic structures that begins and ends at the heart
  • arteries, capillaries, veins
  • pulmonary circulation and umbilical vessels of fetus
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2
Q

structures of blood vessel walls

A
  • lumen
  • tunica intima
  • tunica media
  • tunica externa

capilaries = endothelium with sparse basal lamina

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3
Q

Tunica intima

A
  • endothelium lines lumen of all vessels
  • continuous with endocardium
  • slick surface reduces friction
  • subendothelial layer in cessels larger than 1 mm = CT basement membrane
  • internal elastic lamina in arteries
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4
Q

Tunica media

A

smooth muscle and sheets of elastin
-sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels (affects blood flow and pressure)

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5
Q

Tunica externa (tunica adventitia)

A
  • collagen fibers protect and reinforce; anchor to surrounding structures
  • contain nerve fibers and lymphatic vessels
  • vaso vasorum of larger vessels nourishes external layer
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6
Q

Elastic arteries

A
  • “conducting arteries”
  • large, thick-walled arteries with elastin in all three tunics
  • aorta and its major branches
  • large lumen offers low resistance
  • inactive in vasoconstriction
  • acts as pressure reservoirs - expand and recoil as blood ejected from heart
  • smooth pressure downstream
  • diameter = 1.5 cm; thickness = 1 mm
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7
Q

muscular arteries

A
  • “distributing arteries”
  • distal to elastic arteries
  • deliver blood to body organs
  • thick tunica media with more smooth muscle
  • active in vasoconstriction
  • diameter = 6 mm; thickness = 1 mm
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8
Q

arterioles

A
  • -“resistance vessels”
  • smallest arteries
  • lead to capillary beds
  • control flow into capillary bed via vasodilation and vasoconstriction
  • diameter = 37 um; thickness = 6 um
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9
Q

capillaries

-walls and size

A
  • microscopic blood vessels
  • walls of thin tunica intima
  • in the smallest, one cell forms entire circumference
  • diameter allows only one rbc to pass at a time
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10
Q

capillaries
-where?
function?

A

in all tissues except cartilage, epithelia, cornea, and lens of eye

  • provide direct access to almost every cell
  • func: exchange of gases, nutrients, wastes, hormones, etc… bt blood and interstitial fluid
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11
Q

Three types of capillaries

A
  • continuous= least permeable; most common; tight junctions; small intercellular cleft; skin and muscle
  • fenestrated = large fenestration; tight junctions; intercellular cleft; kidney and small intestine
  • sinusoid = few tight junctions; pores and intercellular cleft; big lumen; macrophages in lining; liver and bone marrow and spleen and adrenal medulla
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12
Q

blood flow in sinusoid capillaries

A
  • slugginsh –> allows modification

- big molecules and blood cells pass bt blood and surrounding tissues

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13
Q

Microcirculation in capillary beds

A
  • interwoven networks of capillaries between arterioles and venules
  • teminal arteriole –> metarteriole –> throughfare channel –> postcapillary venule
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14
Q

two types of vessels in capillary beds

A
  • vascular shunt (metarteriole to thoroughfare channel) - directly connects terminal arteirole and postcapillary venule
  • true capillaries = 10-100 exchange vessels per capillary bed –> branch off metarteriole or terminal arteriole and return to thoroughfare channel
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15
Q

precapillary sphincters

A
  • regulate blood flow into true capillaries
  • blood may go into true capillaries or to shunt
  • regulated by local chemical conditions and vasomotor nerves
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16
Q

venules

A
  • formed when capillary beds unite
  • smallest postcapillary venules = endothelium and a few pericytes - very porous, allowing fluids and wbcs into tissues
  • larger venules have 1-2 layers of smooth muscle cells
17
Q

veins

  • anatomy
  • pressure
A
  • formed when venules converge
  • have thinner walls, bigger lumens than arteries
  • BP is lower than arteries
  • thin tunica media; thick tunica externa of collagen fibers and elastic networks
  • “capacitance vessels” (blood reservoirs) w/ up to 65% of blood supply
18
Q

% of blood everywhere

A 
capillaries = 5%
heart = 8%
pulmonary blood vessels = 12%
systemic arteries and arterioles = 15%
systemic veins and venules = 60%
19
Q

vein adaptations to ensure return of blood to heart despite low pressure

A
  • big diameter lumens offer little resistance
  • venous valves prevent backflow of blood (most abundant in veins of limbs)
  • venous sinuses = flattened veins with extremely thin walls (coronary sinus of the heart and dural sinuses of the brain)
20
Q

dimmensions of capillary, venule and vein

A

capillary: D = 9 um; T = 0.5 um
venule: D = 20 um; T = 1 um
vein: D = 5 mm; T = 0.5 mm

21
Q

vascular anastomoses

A
  • interconnections of blood vessels
  • Arterial anastomoses provide alternate pathways (collateral channels) to a given body region (joinds, abdominatl orgains, brain, and heart –> NOT retina, kidney or spleen)
  • Venous anastomoses are common
22
Q

Blood flow

A
  • volume of blood flowing through a vessel, organ, or entire circulation in given period
  • measured in ml/min
  • CO for entire system
  • constant at rest
  • varies widely through individual organs based on needs
23
Q

blood flow vs blood pressure vs resistance

A
  • blood flow (F) is directly proportional to blood pressure gradient (delta P)
  • Blood flow inversely proportional to peripheral resistance (R)
  • F = (delta P)/(R)
  • R is more important in influencing local blood flow because its easily changed by altering blood vessel diameter
24
Q

Resistance

  • definition
  • sources
A
  • opposition to flow
  • amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation
  • 3 sources:
    1. blood viscosity
    2. total blood vessel length (every 2.2 lb of adipose tissue contains 400 miles of blood)
    3. blood vessel diameter
25
Q

factors affecting resistance that remain relatively constant

A

blood viscosity

  • “stickiness” of blood due to formed elements and plasma proteins
  • increased viscosity = increased resistance

blood vessel length
-longer vessel = greater resistance encountered

26
Q

how does blood vessel diameter impact resistance (use math)?

A

resistance varies inversely with the fourth power of vessel radius

-e.g. if radius doubles, resistance is 1/16 what it used to be

27
Q

Atherosclerosis

A
  • increase in plaque in blood vessels
  • increases resistance
  • disrupts laminar flow and causes turbulent flow
  • irregular fluid motion –> increased resistance
28
Q

Blood pressure

A
  • force per unit area exerted on wall of blood vessel by blood
  • pressure results when flow is opposed by resistance
  • mm Hg
  • measured as systemic arterial BP in large arteries near heart
  • Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas
29
Q

systemic blood pressure

A
  • highest in aorta
  • declines throughout pathway
  • 0 mm Hg in right atrium
  • steepest drop occurs in arterioles
30
Q

Arterial blood pressure

-what it reflects

A

reflects 2 factors of arteries close to heart:

  • elasticity (compliance or distensibility)
  • volume of blood forced into them at any time

-BP near heart is “pulsatile”

31
Q

Arterial BP

  • systolic pressure
  • diastolic pressure
  • pulse pressure
A

Systolic = pressure exerted in aorta during ventricular contraction (about 120 mm Hg in normal adult)

Diastolic = lowest level of aortic pressure

Pulse pressure = dif bt systolic and diastolic pressure
-“pulse” = throbbing of arteries

32
Q

Mean arterial pressure

A
  • pressure that propels blood into tissues
  • MAP = diastolic pressure + 1/3 pulse pressure
  • pulse pressure and MAP both decline with increasing distance from heart
  • BP: 120/80 and MAP = 93 mm Hg near heart
33
Q

capillary blood pressure

A
  • ranges from 17 to 35 mm Hg
  • low capillary pressure is desirable
  • high BP would rupture the thin walls
  • most are very permeable, so low pressure forcesfiltrate into interstitial spaces
34
Q

venous BP

A
  • changes little during cardiac cycle
  • smallest pressure gradient: about 15 mm Hg
  • low pressure due to cumulative effects of peripheral resistance (energy of blood pressure lost as heat during each circuit)
35
Q

Factors aiding venous return

A
  1. muscular pump: contraction of skeletal muscles “milks” blood toward heart; valves prevent backflow
  2. Respiratory pump: pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
  3. Venoconstriction: under sympathetic control pushes blood toward heart
36
Q

Maintaining BP

  • requirements
  • factors influencing BP
A

Requirements

  • cooperation of heart, blood vessels, and kidneys
  • supervision by brain

Main factors influencing BP

  1. Cardiac output (CO)
  2. Peripheral resistance (PR)
  3. Blood volume
    - change in one variable quickly compensated for by change in another

Anatomy and Physiology (50 decks)

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