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Temple A&P > Lecture: Blood Vessels and Circulation > Flashcards

Lecture: Blood Vessels and Circulation Flashcards

1
Q

What are the 3 layers of a blood vessel?

A

from inside to outside:
tunica interna (tunica intima)
tunica media
tunica externa (tunica adventitia)

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2
Q

Describe the composition of the tunica interna (tunica intima).

A

endothelium: simple squamous epithelium
- continuous layer of cells throughout system
- layer in contact with the blood

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3
Q

What are the 4 functions of the tunica interna (tunica intima)?

A

1) selectively permeable barrier
2) secretion of chemicals
3) repels blood cells and platelets
4) inflammation

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4
Q

Describe the composition of the tunica media.

A

smooth muscle (amount varies)
elastic tissue
collagen

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5
Q

What are the 2 functions of the tunica media?

A

1) strengthens vessels / prevents rupture

2) vasomotion (vasoconstriction / vasodilation)

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6
Q

Describe the composition of the tunica externa (tunica adventitia).

A

loose CT

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7
Q

What are the 3 functions of the tunica externa (tunica adeventitia)?

A

1) protects and anchors blood vessel
2) passage for nerves & lymphatic vessels
3) smalls vessels called vaso vasorum supply blood to outer walls of larger vessels

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8
Q

What are the 3 categories of arteries?

A

1) conducting arteries (elastic, large)
2) distributing arteries (muscular, medium)
3) resistance arteries (arterioles, small)

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9
Q

Comment on the composition of conducting arteries. Give some examples of conducting arteries.

A

largest diameter
elastic tunica media
ex. aorta, pulmonary trunk, common carotid, subclavian, common illiac

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10
Q

What is the function of conducting arteries?

A

reduce effects of BP surgers

  • expand during systole, recoil during diastole
  • helps maintain blood flow
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11
Q

Comment on the composition of distributing arteries. Give some examples of distributing arteries.

A

thicket smooth muscle

ex. brachial, femoral, renal, splenic

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12
Q

What is the function of distributing arteries?

A

distribute blood to specific organs and adjust flow based on demand

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13
Q

Describe the composition of resistance arteries.

A

smooth muscles layers variable;

little elastic tissue

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14
Q

Define: arterioles.

A

smallest resistance vessels

lead into capillary bed

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15
Q

Define: metarterioles.

A

link arterioles to capillaries

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16
Q

What is the function of resistance arteries? What vital signs does it influence?

A

primary control of blood flow
most responsible for PR
significantly affects BP

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17
Q

Describe the composition of capillaries.

A

single layer of endothelial cells

small lumen

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18
Q

What is the function of capillaries?

A

to exchange materials, accomplished by their close proximity to nearly all cells

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19
Q

What are the 3 types of capillaries?

A

1) continuous
2) fenestrated
3) sinusoid

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20
Q

Describe the composition of continuous capillaries.

A

present in most tissues, such as skeletal muscle;
tight junctions hold endothelial cells together
intracellular clefts
pericytes

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21
Q

Define: intracellular clefts

A

spaces between endothelial cells in continuos capillaries;
allow small molecules (ex. glucose) to pass through;
retrain larger molecules such as plasma proteins and formed elements

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22
Q

Define: perictyes

A

contractile proteins in continuous capillaries

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23
Q

Describe the composition of fenestrated capillaries.

A

endothelial cells covered in filtration pores (fenestrations);
greater permeability
allow rapid passage of small molecules but retain formed elements

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24
Q

What are some examples of organs/tissues perfused by fenestrated capillaries?

A

kidneys
endocrine glands
small intestine
choroid plexus

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25
Q

Describe the composition of sinusoids.

A

a.k.a. discontinuous capillaries;
irregular, blood-filled spaces;
endothelial cells have large filtration pores (fenestrations) through which formed elements can pass

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26
Q

What are some examples of organs/tissues perfused by sinusoids?

A

liver
bone marrow
spleen

27
Q

Define: capillary beds.

A

networks of capillaries;
not all are perfused at any given time;
they drain into a distal continuation of the metarteriole called a thoroughfare channel, which then leads to a venule

28
Q

Define: capillary sphincter.

A

smooth muscle cell that wraps around the opening to each capillary and regulates blood flow

29
Q

Describe the composition of postcapillary venules.

A

smallest veins
only tunica intima
often have pericytes
extremely porous

30
Q

Describe the composition of muscular venules.

A

thin tunica media

thin tunica externa

31
Q

Describe the composition of medium veins.

A 
have all 3 tunics
-thin tunica media
-thick tunica externa
-large lumen
-tunica intima folds inward, forming valves;
relatively thin wall vessel
-BP much lower, collapses when empty;
blood "reservoirs" (large % of total blood supply)
32
Q

Where are venous valves found/ not found in the body?

A

abundant where upward flow opposed by gravity;

not present in small/large veins, abdominal/thoracic cavities, and the brain

33
Q

Describe the composition of large veins. Name some examples of large veins.

A

v. thin tunica intima, v. thick tunica externa;

ex. venae cavae, pulmonary, internal jugular, renal

34
Q

Describe the 5 different types of circulatory routes.

A

1) simple pathway: 1 network of capillaries
2) portal system: 2 networks of capillaries (ex. kidneys, hypophyseal portal system)
3) arteriovenous anastomosis (a.k.a. shunt): artery directly to vein
4) venous anastomosis: alternative drainage
5) arterial anastomosis: collateral supply

35
Q

Define: anastomosis.

A

point of convergence between 2 blood vessels other then capillaries

36
Q

Define: flow.

A

vol. of blood through an organ, tissue, or vessel in a given amt. of time;
expressed in ml/min

37
Q

Define: perfusion.

A

flow per given volume or mass of tissue;

expressed in ml/min/g

38
Q

Define: pressure.

A

force of blood exerted on vessel wall;

expressed in mmHg

39
Q

Define: hemodynamics.

A

study of physical principles of blood flow; based on pressure and resistance
F ≈ ΔP / R
where F = blood flow, ΔP = difference in pressure, R = resistance to flow

40
Q

How does blood pressure vary throughout the body / circulatory system?

A

highest pressure immediately after systole;
highest pressure proximal to heart;
arteries > capillaries > veins

41
Q

What 3 factors is blood pressure influenced by?

A

elasticity of arteries: recoil maintains pressure and facilitates flow;
blood volume;
kinetic energy of blood stretching the aorta

42
Q

Define: pulse pressure (PP).

A

measure of pressure surges

PP = SBP - DBP

43
Q

Define: mean arterial pressure (MAP).

A

avg. of pressures

MAP = DBP + 1/3 (PP)

44
Q

BP depends on what 3 organs coordinated by what 1 organ?

A

brain

  • heart
  • blood vessels
  • kidneys
45
Q

What are the 3 main variables determining blood pressure?

A

1) cardiac output
2) blood volume
3) resistance to flow

46
Q

Define: resistance.

A

measure of friction encountered by blood through vessels;

opposition to flow

47
Q

Define: peripheral resistance.

A

opposition to blood flow encountered away from the heart, generally from smaller vessels and arterioles

48
Q

What are 3 sources of resistance?

A

1) blood viscosity
2) blood vessel length
3) blood vessel diameter (most dynamic)

49
Q

Define: blood viscosity. What contributes to it? What is its relationship to resistance and flow?

A

“thickness” of blood;
results from RBC and albumin;
directly proportional to resistance (which is usually constant);
inversely proportional to flow

50
Q

What effect does blood vessel length have on friction, resistance, and flow?

A

longer distance = more cumulative friction;
directly proportional to resistance;
inversely proportional to flow

51
Q

What are the terms for blood vessel diameter changes? What effect does this have on peripheral resistance?

A

vasoreflexes: vasodilation & vasoconstriction;

constantly alters peripheral resistance

52
Q

Differentiate laminar and turbulent flow.

A

laminar flow: layered flow, faster in center and slower near the walls;
turbulent flow: at higher velocities, flow becomes rougher and lateral mixing occurs

53
Q

What is the most significant variable of Poiseuille’s Law?

A

vessel radius (to the fourth power!)

54
Q

What are the 3 reasons that arterioles are the most significant point of control over peripheral resistance and blood flow?

A

1) location proximal to capillary beds makes them best positioned to regulate flow into the capillaries
2) greatly outnumber any other class of arteries
3) more muscular in proportion to their diameters than any other class of blood vessel, and are highly capable of changing radius

55
Q

Name the 3 mechanisms for regulating pressure and flow.

A

1) local control
2) neural control
3) hormonal control

56
Q

Explain local control.

A

autoregulation;
myogenic control: vasoreflexes
metabolic control;
-CO2, H+, K+, lactic acid
-vasoactive chemicals: histamine, prostaglandins, bradykinin;
angiogenesis: growth of new blood vessels

57
Q

Define: autoregulation.

A

ability of tissues to regulate their own blood supply;

corresponds to local control

58
Q

Define: angiogenesis.

A

growth of new blood vessels;

corresponds to local control

59
Q

Explain neural control.

A 
vasomotor center in medulla sends sympathetic impulses to smooth muscle, constricting most vessels, but dilating some cardiac and skeletal muscles;
regulated by 3 autonomic reflexes
1) baroreflex
2) chemoreflex
3) medullary ischemic reflex
60
Q

Define: baroreflex.

A 
autonomic, negative feedback response in response to BP (detected by baroreceptors);
BP increase inhibits SNS, including cardiac and vasomotor centers;
BP increase excites vagal fiber;
effects:
-reduce HR
-reduce cardiac output
-dilates vessels
-reduces BP
61
Q

Define: chemoreflex.

A

autonomic response to chemical changes;
chemoreceptors activated by low pH, low O2, and high CO2;
primary role of chemoreceptors = adjust respiration;
secondary role = vasomotor
-vasoconstriction
-increases perfusion

62
Q

Define: medullary ischemic reflex.

A

autonomic response to brain hypoperfusion;
cardiac and vasomotor centers increase HR & contractile force and cause widespread vasoconstriction;
these centers also receive input from higher brain centers: stress, arousal, anger can stimulate them and raise BP

63
Q

Name 6 hormones and their effects on vascular smooth muscle.

A

1) Angiotensin II: vasoconstriction
2) Aldosterone: sodium retention by kidneys
3) Atrial natriuretic peptide: increases sodium excretion
4) Antidiuretic hormone: water retention
5 & 6) epinephrine and norepinephrine: vasoconstriction in most vessels; vasodilation in coronary and skeletal muscle blood vessels

64
Q

Explain how blood flow can be redirected.

A

local vasoconstriction of an artery;
downstream of site of constriction, pressure decreases;
upstream of site of constriction, pressure increases;
blood takes path of least resistance

Temple A&P (15 decks)

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