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PHARM 111 > Blood Vessels > Flashcards

Blood Vessels Flashcards

1
Q

What are the major types of blood vessels and their functions?

A
  1. Arteries → carry blood away from the heart
  2. Veins → carry blood towards heart
  3. Capillaries → contact tissue cells & directly serve cellular needs
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2
Q

What is an anastomoses?

A

Special interconnections between blood vessels that form where vascular channels unite → allows an area to be supplied/drained even if one channel is blocked

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3
Q

What are the three layers of arteries and veins?

A
  1. Tunica Intima → deepest layer, has “intimate” contact with blood
  2. Tunica Media → middle layer
  3. Tunica Externa → external layer
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4
Q

What is the Tunica Intima made of? (what are the differences here between arteries and veins?)

A
  • endothelium → simple squamous
  • Subendothelial layer → connective tissue basement membrane present in vessels >1mm
  • (arteries) internal elastic membrane
  • (veins) valves
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5
Q

What is in the Tunica Media?

A

Smooth muscle and sheets of elastin → SNS vasomotor nerve fiver control vasoconstriction and vasodilation for preserving pressure

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6
Q

What is in the Tunica Externa?

A

Collagen fibers protecting and reinforcing

(larger vessels have vasa vasorum → some blood vessels are so large they need their own vessels to supply them)

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7
Q

What is the purpose of the valves in the tunica intima of veins?

A

Ensures unidirectional flow of blood → back flow closes them and pressure pushing opens them

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8
Q

What the sectioned appearance of a typical artery and vein look like?

A

Artery → usually round with a relatively thick wall (tunica media)

Vein → usually flattened or collapsed with a relatively thin wall

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9
Q

What is the difference between the tunica intima in an artery versus a vein?

A

Artery → usually rippled because of vasoconstriction, internal elastic membrane present

Vein → endothelium is smooth, may have valves and NO internal elastic membrane

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10
Q

What are the differences in the tunica media between arteries and veins?

A

Artery → thick, dominated by smooth muscle cells and elastic fibers, external elastic membrane present

Vein → thin, dominated by smooth muscle cells and collagen fibers, does NOT have an external elastic membrane

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11
Q

What are the differences in the tunica externa between arteries and veins?

A

Arteries → collagen and elastic fibers

Veins → collagen, elastic fibers and smooth muscle cells (although not many smooth muscle cells)

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12
Q

What are some of the structural characteristics of capillaries and what is their function?

A

Endothelium with sparse basal lamina, diameter ~8-10um (small → not much bigger than an RBC so there is a lot of peripheral resistance)

Function: exchange materials

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13
Q

What are the three structural types of capillaries?

A
  1. Continuous capillaries
  2. Fenestrated capillaries
  3. Sinusoidal capillaries (sinusoids)
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14
Q

What are some of the properties of continuous capillaries? (6)

A
  1. least permeable and most common
  2. Tight junctions connect endothelial cells
  3. Intercellular clefts allows passage of fluid and small solutes
  4. Often have associated pericytes (support/reinforcement cells)
  5. Pinocytotic vesicles move fluid across endothelial cell
  6. Brain endothelial cells lack intercellular clefts & have tight junctions around entire perimeter
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15
Q

Where would you find fenestrated capillaries?

A

Areas of active filtration or absorption & areas of endocrine hormone secretion → the fenestrations improve permeability

(kidneys, endocrine organs, small intestine)

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16
Q

What are fenestrated capillaries covered by?

A

Usually covered by a thin diaphragm of extracellular glycoproteins (little effect on solute and fluid movement)

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17
Q

What are the characteristics of sinusoid capillaries?

A
  1. most permeable
  2. large intercellular clefts & fenestrations; few tight junctions with incomplete basement membranes
  3. allow large molecules (even cells) to pass across walls
  4. macrophages may extend processes through clefts to catch “prey”
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18
Q

Where would you find sinusoid capillaries?

A

Liver, spleen, bone marrow (allowing RBCs to get through), adrenal medulla

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19
Q

What are the four capillary transport mechanisms and what can get through them?

A
  1. Diffusion through plasma membrane (lipid soluble substances)
  2. Movement through intercellular clefts (water-soluble substances)
  3. Movement through fenestrations (water-soluble substances)
  4. Transports via vesicles (large substances)
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20
Q

What are the two types of vessels in capillary beds and what do they do?

A
  1. Vascular shunt: directly connects terminal arteriole & post-capillary venule
  2. True capillaries: where the actual exchange happens; 10-100 exchange vessels per capillary bed
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21
Q

What does a pre-capillary sphincter do and what is it regulated by?

A

Regulate blood flow into true capillaries; when sphincters are open blood flows through true capillaries, when they are closed, blood flows through met-arteriole through-fare channel (bypassing true capillaries)

Regulated by local chemical conditions and vasomotor nerves

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22
Q

Are there sphincters on both ends of the through-fare channel?

A

NO → there are no sphincters on the post-capillary end because so that blood does not flow backwards from there

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23
Q

Summary of blood vessel anatomy

A
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24
Q

Are there more veins or arteries?

A

Veins → 60%; most of your blood is in the venous system with a large reserve because of how much bigger they are

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25
Q

Out of 20L of fluid filtered through capillary beds each day, how much is reabsorbed at the venous end and where does the rest go?

A

17L of fluid/day is reabsorbed into capillaries at venous end

3L of fluid/day & any leaked proteins are removed by the lymphatic system

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26
Q

What are the two types of pressures that move fluid?

A
  1. Hydrostatic pressure → due to fluid pressing against a boundary; in blood vessels this is due to BP
  2. Osmotic pressure → due to non-diffusible solutes that cannot cross boundary; in blood vessels this is due to plasma proteins
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27
Q

Which of the two pressures is a pushing force? Which is a pulling force?

A

Pushing force → hydrostatic pressure

Pulling force → osmotic pressure

28
Q

What is HPC

A

Capillary hydrostatic pressure = capillary blood pressure

Tends to force fluids through capillary walls

Greater at arterial end of capillary than venule end

29
Q

What is HPif

A

Interstitial fluid hydrostatic pressure

Pushes fluid into capillaries

Usually assumed to be ZERO because of lymphatic vessels → picks up extra fluid so that it can’t push back

30
Q

What is OPc

A

Capillary colloid osmotic pressure (oncotic pressure)

Created by non-diffusable plasma proteins which draw water towards themselves

pulls fluid into capillary

31
Q

What is OPif

A

Interstitial fluid osmotic pressure

Low due to low protein content

pulls fluid out of capillary

32
Q

What is NFP and how do you calculate it?

A

NFP = Net filtration pressure

To determine pressure driving fluid out of capillary at any given point, calculate NFP

NFP = outward forces - inward pressures

NFP = (HPc + OPif) - (HPif + OPC)

33
Q

Where does the net filtration happen?

A

Arteriolar end of capillary

NFP = 10 mm Hg → fluid moves out in the arterial end into the interstitial space

34
Q

Where does net reabsorption occur?

A

Venous end of a capillary

NFP = -8 mm Hg → reabsorption is occurring and fluid moves from interstitial space into capillary

35
Q

Why isn’t NFP the same at the arteriole and venule end of capillary beds?

A

The lymphatic system is cleaning out extra fluids

36
Q

What does F represent?

A

Blood flow → volume of blood flowing through a vessel, organ, or entire circulation in a given period (mL/min or L/min)

Equivalent to CO for entire vascular sustem

Relatively constant when at rest; varies widely through individual organ based on needs

37
Q

What is represented by BP, how is it measured, and what provides the driving force ?

A

BP = blood pressure → force per unit area exerted by blood on blood vessel wall

Measured as systemic arterial BP in large arteries near heart

Pressure gradient provides driving force that keeps blood moving

38
Q

What is R defined as and what does it measure?

A

R = peripheral resistance

Measures amount of friction blood encounters as it travels the length of a vessel

39
Q

What are 3 sources of peripheral resistance?

A
  1. blood vessel diameter
  2. total blood vessel length
  3. blood viscosity
40
Q

What is the relationship between blood flow, pressure and resistance?

A

F = (delta P)/R

41
Q

What is the relationship between blood flow and total cross sectional area?

A

Blood flow velocity is inversely related to total cross-sectional area

42
Q

What is the difference between systolic and diastolic pressure?

A

Systolic = peak pressure generated during ventricular contraction

Diastolic = lowest level of arterial pressure (during ventricular relaxation)

43
Q

What is MAP?

A

MAP = mean arterial pressure

Pressure that propels blood to tissues

MAP = diastolic pressure + ⅓ pulse pressure

44
Q

What is pulse pressure?

A

The difference between systolic and diastolic pressure

45
Q

What happens to pulse pressure and MAP when distance from the heart increases?

A

Both decrease

46
Q

What are the 3 factors aiding venous return?

A
  1. Respiratory “pump”: pressure changes created during breathing move the blood towards the heart
  2. Vasoconstriction of veins under sympathetic control
  3. Muscular pump: contraction of skeletal muscles “milk” the blood towards heart
47
Q

What are the short-term mechanisms for controlling blood pressure?

A
  1. Neural controls → input from chemoreceptors and higher brain centers operate via reflex arcs
  2. Hormonal controls → many different ones
48
Q

List the variable affected and the net effect on blood pressure for the following hormonal controls:

  1. Epinephrine and NE
  2. Angiotensin II
  3. Atrial natriuretic peptide (ANP)
  4. Antidiuretic hormone (ADH)
  5. Aldosterone
A
  1. increases CO and peripheral resistance → increase blood pressure
  2. increases peripheral resistance by vasoconstriction → increase blood pressure
  3. decreases peripheral resistance (vasodilation), decreases blood volume (increasing water and salt loss) → DECREASE blood pressure
  4. Increases peripheral resistance and blood volume → increase blood pressure
  5. increases blood volume → increases blood pressure
49
Q

What are the two ways that the kidneys regulate arterial BP?

A
  1. Direct renal mechanism
  2. Indirect renal mechanism (renin-angiotensin)
50
Q

Explain the direct renal mechanism of regulating BP

A

Alters blood volume independently of hormones

Decrease in arterial pressure decreases filtration by kidneys which decreases urine formation and increases blood volume to increase mean arterial pressure

51
Q

Explain the indirect renal mechanism for regulation of BP

A

Also known as the renin-angiotensin (aldosterone) mechanism

  1. Decrease in arterial pressure inhibits baroreceptors
  2. SNS activity increases and increases renin release from kidneys
  3. Renin converts angiotensin to angiotensin I, which is then converted to angiotensin II by ACE
  4. Angiotensin II does 4 things:
    1. Stimulates adrenal cortex to secrete aldosterone which increases Na+ reabsorption by kidneys and triggers H2O reabsorption by kidneys, increasing blood volume and MAP
    2. Stimulates ADH release by posterior pituitary to promote reabsorption of H2O by kidneys to increase blood volume and thereby MAP
    3. Stimulates thirst in the hypothalamus, increasing water intake and thereby blood volume and then MAP
    4. Stimulates vasoconstriction, increasing peripheral resistance and MAP
52
Q

What are the factors that increase MAP? (7)

A
  1. Activity of muscular pump and respiratory pump
  2. Decreases release of ANP
  3. Fluid loss from hemorrhage and excessive sweating
  4. Crisis stressors: exercise, trauma and increased body temperature
  5. Increased vasomotor tone
  6. Dehydration, high hematocrit
  7. Increased body size
53
Q

What is a pulse?

A

Pressure wave caused by expansion and recoil of arteries

54
Q

When do you hear Korotkoff sounds?

A

Korotkoff sounds are created by pulsatile blood flow through compressed artery

Blood flow is silent when arterial blood flow is stopped and when the artery is no longer compressed

55
Q

What is blood flow (tissue perfusion) involved in?

A
  • Delivery of O2 and nutrients to cells
  • removal of wastes from cells
  • gas exchange in lungs
  • absorption of nutrients
  • urine formation
56
Q

What are the types of auto-regulation of blood flow?

A
  1. Metabolic = chemical
  2. Myogenic = physical
  3. Long-term (weeks/months) = increase in size and # of blood vessels
57
Q

What are the metabolic controls of blood flow?

A
  1. Vasodilation in response to decrease in O2 in tissues, increase in CO2, H+ and metabolic factors, and inflammatory chemicals like histamine, kinins and prostaglandins
  2. Vasoconstriction in response to SNS stimulation and endothelins (mechanism not well understood)
58
Q

What is NO?

A

NO = Nitric oxide

Potent muscle relaxant released from vascular endothelial cells during vasodilation

59
Q

How do myogenic controls of blood flow work?

A

Myogenic responses of vascular smooth muscle keep tissue perfusion constant despite most fluctuations in systemic pressure

Passive stretch promotes increased tone and vasoconstriction to help resist stretch, prevent bursting and increase peripheral resistance

Decrease in stretch promotes vasodilation and increases blood flow to tissue to restore adequate blood flow

60
Q

Explain the long term auto-regulation of blood flow by angiogenesis. When is this common?

A

Occurs when short-term auto-regulation cannot meet tissue requirements

Increases the # of vessels to the region and enlarges existing vessels

Common in the heart when coronary vessels are occluded or throughout the body of people living in high altitude areas

61
Q

How is blood flow to the skeletal muscles adapted during muscle activity?

A

Blood flow is increased in direct proportion to metabolic activity of the muscles

Local controls of decreased O2, increased CO2, H+, and other metabolic factors override sympathetic vasoconstriction (can increase 10x or more)

62
Q

What are the metabolic and myogenic controls regulating blood flow to the brain? What is that blood flow supposed to be at all times?

A

Metabolic: decrease in pH and increase in CO2 causes marked vasodilation

Myogenic: decreased MAP causes cerebral vessels to dilate (prevents syncope at MAP <60mmHg), increased MAP causes cerebral vessels to constrict (prevents cerebral edema at MAP >160mmHg)

Blood flow to the brain is constant at 750mL/min

63
Q

How is blood flow to the skin changed according to body temperature?

A
  • as body temperature increases, hypothalamic signals decrease vasomotor stimulation of skin vessels; heat radiates from skin
  • Sweat causes vasodilation via bradykinin in perspiration (stimulates NO release)
  • as body temperature decreases, blood is shunted deeper to more vital organs
64
Q

How is blood flow to the lungs different from most tissues?

A

The pathway is short, arteries are thin walled and arterial resistance and pressure are low

Auto-regulatory mechanism is opposite of most tissues: Low O2 causes vasoconstriction and high O2 causes vasodilation

65
Q

What is the difference in blood flow during ventricular systole and diastole?

A

During ventricular systole coronary vessels are compressed; myocardial blood flow ceases and stored myoglobin supplies sufficient oxygen

During ventricular diastole, high aortic pressure forces blood through coronary circulation

66
Q

What happens to blood flow in the heart during strenuous excersize?

A

Coronary vessels dilate in response to local accumulation of vasodilators (adenosine) → increases blood flow to heart by 3-4x

Cardiac cells use 65% of O2 delivered so when the coronary vessels dilate, more blood flow = more O2 (most tissues use ~25% O2 delivered)

PHARM 111 (5 decks)

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