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Bio 157 Lecture > Chapter 20- Blood Vessels > Flashcards

Chapter 20- Blood Vessels Flashcards

1
Q

Three principal categories of blood vessels

A

arteries, veins, capillaries

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2
Q

Walls of arteries and veins have three layers

A

tunica interna, tunica media, tunica externa

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3
Q

Tunica interna

A

Lines the blood vessel and is exposed to blood

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4
Q

Endothelium

A
  • Simple squamous epithelium
  • Selectively permeable barrier
  • Secretes chemicals that stimulate dilation or constriction
  • Normally repels blood cells and platelets to prevent clotting
  • When tissue around vessel is inflamed, endothelial cells produce
    cell-adhesion molecules
  • Causes leukocytes to adhere to surface and congregate in tissues
    where their defensive actions are needed
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5
Q

Tunica media

A
  • Middle layer
  • Consists of smooth muscle, collagen, and elastic tissue
  • Strengthens vessels and prevents blood pressure from
    rupturing them
  • Contraction of muscle controls blood vessel diameter
  • This layer is more prominent in arteries compared with
    veins in general
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6
Q

Tunica externa (tunica adventitia)

A
  • Outermost layer
  • Consists of loose connective tissue that often merges with
    that of neighboring blood vessels, nerves, or other organs
  • Anchors the vessel and provides passage for small
    nerves, lymphatic vessels
  • Vasa vasorum: small vessels that supply blood to outer
    part of the larger vessels
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7
Q

Conducting (elastic or large) arteries

A
  • Biggest arteries
  • Examples: aorta, common carotid, subclavian, pulmonary trunk,
    and common iliac arteries
  • Internal elastic lamina at the border between interna and media
  • External elastic lamina at the border between media and externa
  • Expand during systole, recoil during diastole
  • Expansion takes pressure off smaller downstream vessels
  • Recoil maintains pressure during relaxation, keeps blood flowing
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8
Q

Distributing (muscular or medium) arteries

A
  • Distribute blood to specific organs
  • Examples: brachial, femoral, renal, and splenic arteries
  • Smooth muscle layers constitute three-fourths of wall thickness
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9
Q

Resistance (small) arteries

A
  • Thicker tunica media in proportion to their lumen than
    large arteries and very little tunica externa
  • Arterioles: smallest of the resistance arteries
  • 200 μm diameter; only 1-3 layers of smooth muscle
  • Control amount of blood to various organs
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10
Q

Metarterioles (thoroughfare channels)

A
  • Short vessels that link arterioles directly to venules in
    some places (for example, in mesenteries)
  • Provide shortcuts allowing blood to bypass capillary beds
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11
Q

Aneurysm

A
  • weak point in artery or heart wall
  • Forms a thin-walled, bulging sac that pulsates
    with each heartbeat and may rupture at any
    time
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12
Q

Dissecting aneurysm

A

blood accumulates between tunics of artery and separates them, usually because of degeneration of the tunica media

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13
Q

Most common sites for aneurysm

A

abdominal aorta, renal arteries, and arterial circle at base of brain

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14
Q

symptoms and cause of aneurysm

A
  • Can cause pain by putting pressure on other
    structures
  • Can rupture causing hemorrhage
  • Result from congenital weakness of blood
    vessels, trauma, or bacterial infections
  • Most common cause is atherosclerosis and
    hypertension
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15
Q

Carotid sinuses: baroreceptors

A

In walls of internal carotid artery, monitor blood pressure, allow for baroreflex, innervation is glossopharyngeal n (CN IX

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16
Q

Carotid bodies: chemoreceptors

A
  • Oval bodies near branch of common carotids
  • Monitor blood chemistry, CNIX to brainstem respiratory centers; adjust respiratory rate to stabilize pH, CO2, and O2
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17
Q

Aortic bodies: chemoreceptors

A

One to three bodies in walls of aortic arch, same structure and function as carotid bodies, but innervation is by vagus n.

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18
Q

Capillaries

A

Where gasses, nutrients, wastes, and hormones pass
between the blood and tissue fluid
* The “business end” of the cardiovascular system
* Composed of endothelium and basal lamina
* Absent or scarce in tendons, ligaments, epithelia, cornea, and lens of the eye
* Three capillary types distinguished by permeability

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19
Q

Three capillary types distinguished by permeability

A
  • Continuous capillaries
  • Fenestrated capillaries
  • Sinusoids
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20
Q

Continuous capillaries

A
  • Occur in most tissues
  • Endothelial cells have tight
    junctions
  • Form a continuous tube with
    intercellular clefts
  • Allow passage of solutes such as
    glucose
  • Pericytes wrap around the
    capillaries and contain the same
    contractile protein as muscle
  • Contract and regulate blood flow
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21
Q

Fenestrated Capillary

A
  • Organs that require rapid absorption or filtration - Examples: kidneys, small intestine
  • Endothelial cells riddled with holes called filtration pores (fenestrations)
  • Spanned by very thin glycoprotein layer
  • Allow passage of only small molecules
  • Proteins and larger particles stay in bloodstream
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22
Q

Sinusoids

A
  • Found in liver, bone marrow,
    spleen
  • Irregular blood-filled spaces with
    large fenestrations
  • Allow proteins (albumin), clotting
    factors, and new blood cells to
    enter the circulation
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23
Q

Veins

A
  • Thin-walled and flaccid
  • Collapse when empty, expand easily
  • Greater capacity for blood containment than arteries
  • At rest, about 64% of blood is in veins, 15% in arteries
  • Have steady blood flow (unlike pulses in arteries)
  • Have valves to prevent back flow (except in head and
    most of neck region) – formed from tunica interna
  • Subjected to relatively low blood pressure
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24
Q

Postcapillary venules

A
  • Smallest veins (10 to 20 mm diameter)
  • Even more porous than capillaries
  • Also exchange fluid with surrounding tissues
  • Tunica interna with only a few fibroblasts around it
  • No muscle
  • Leukocytes (WBCs) leave bloodstream through venule
    walls
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25
Q

Varicose Vein

A

Standing for long periods promotes blood pooling in the lower limbs and stretches the veins, especially
superficial ones

As veins distend more their walls weaken and become
varicose veins with irregular dilations and twisted
pathways

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26
Q

Simplest and most common route for blood

A

Heart → arteries → arterioles → capillaries → venules → veins (one capillary bed)

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27
Q

Portal system blood flow

A
  • Blood flows through two consecutive capillary networks before
    returning to heart
  • Examples: Between hypothalamus and anterior pituitary; in kidneys; between
    intestines to liver
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28
Q

Anastomosis blood flow

A
  • Convergence between two vessels other than capillaries
    -Arteriovenous anastomosis (shunt)
  • Artery flows directly into vein, bypassing capillaries
    Venous anastomosis (most common)
    Arterial anastomosis (two arteries merge, collateral route of blood supply
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29
Q

Blood pressure

A

-Force that blood exerts against a vessel wall
-Measured at brachial artery using sphygmomanometer
-A close approximation of pressure at exit of left ventricle

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30
Q

Two pressures are recorded for BP

A
  • Systolic pressure
  • Peak arterial BP taken during ventricular contraction (ventricular systole)
  • Diastolic pressure
  • Minimum arterial BP taken during ventricular relaxation
    (diastole) between heart beats
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31
Q

Pulse pressure

A
  • Difference between systolic and diastolic pressure
  • Important measure of driving force on circulation and of stress exerted on small arteries by pressure surges generated by the heart
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32
Q

Mean arterial pressure (MAP)

A
  • Diastolic pressure + (one-third of pulse pressure)
  • Average blood pressure that most influences risk level for edema, fainting (syncope), atherosclerosis, kidney failure, and aneurysm
33
Q

Arteriosclerosis

A

stiffening of arteries due to deterioration
of elastic tissues of artery walls

34
Q

Atherosclerosis

A

build up of lipid deposits that become
plaques (a form of arteriosclerosis)

35
Q

Hypertension

A
  • High blood pressure
  • Chronic resting BP >140/90
  • Consequences:
  • Can weaken arteries, cause aneurysms, promote atherosclerosis
36
Q

Hypotension

A
  • Chronic low resting BP
  • Caused by blood loss, dehydration, anemia
37
Q

BP determined by three variables

A
  • Cardiac output
  • Blood volume
  • Resistance to flow
38
Q

Peripheral resistance

A

opposition to flow that blood encounters in
vessels away from the heart

39
Q

Blood viscosity (thickness)

A
  • RBC count and albumin concentration raise viscosity the most
  • Low viscosity with anemia and hypoproteinemia speeds flow
  • High viscosity with polycythemia and dehydration slows flow
40
Q

Resistance depends on three variables:

A

Blood viscosity (thickness), Vessel length, Vessel radius

41
Q

Vessel length

A

farther liquid travels through tube, the more cumulative friction it encounters; pressure and flow decline with distance

42
Q

Vessel radius

A
  • Most powerful influence on blood flow
  • Only significant way of controlling
    resistance
43
Q

Laminar flow

A

flows in layers, faster in center
* Blood flow (F) proportional to fourth power of
radius (r), 𝐹 α 𝑟4
* Small changes in blood vessel radius can
cause large changes in flow (mL/min)

44
Q

Local control

A

Autoregulation; vasoactive chemicals; shear stress; reactive hyperemia; angiogenesis

45
Q

Three ways of controlling vasomotor activity

A

local, neural, hormonal

46
Q

Neural control

A
  • Vasomotor center of medulla oblongata has sympathetic ANS control over
    blood vessels
  • Integrating center for baroreflexes, chemoreflexes and medullary ischemic reflex
47
Q

Hormones influence blood pressure

A
  • Some through their vasoactive effects
  • Some by regulating water balance
48
Q

Aldosterone – secreted from adrenal cortex

A
  • Promotes Na+ retention by the kidneys
  • “Salt-retaining hormone”
  • Supports blood pressure
  • Water follows sodium osmotically
  • Na+ retention promotes water retention
48
Q

Epinephrine and norepinephrine (adrenal medulla)

A

Both are vasoconstrictors and raise blood pressure

48
Q

Angiotensin II

A
  • Raises blood pressure
  • Potent vasoconstrictor
49
Q

Natriuretic peptides – secreted by the heart

A

Lower blood pressure by: Antagonizing aldosterone; increase Na+ excretion
by the kidney which reduces blood volume
- Promoting vasodilation

50
Q

Chemicals pass through capillary
wall by three routes

A
  • Endothelial cell cytoplasm
  • Intercellular clefts between
    endothelial cells
  • Filtration pores (fenestrations) of
    fenestrated capillaries
51
Q

Mechanisms involved in routes of Fluid Exchange Across the Capillary Wall

A

Diffusion, transcytosis, filtration,
and reabsorption

52
Q

Hydrostatic pressure

A

-Physical force exerted against a surface
by a liquid
-Blood pressure in vessels is
hydrostatic pressure
-Capillaries reabsorb about 85% of the
fluid they filter
-Other 15% is absorbed by lymphatic
system, returned to blood

53
Q

Lymphedema (one type of edema)

A

-accumulation of excess fluid in a tissue
-fluid filters into tissue faster than it is absorbed

54
Q

The flow of blood back to the heart relies on

A

pressure gradient, gravity, skeletal muscle pump, thoracic pump, cardiac suction

55
Q

Pressure gradient

A

Blood pressure is most important force in venous
return

56
Q

Gravity

A

Drains blood from head and neck

57
Q

Skeletal muscle pump

A

Contracting limb muscles squeeze blood out of
compressed part of vein; valves

58
Q

Cardiac suction

A

During contraction of the ventricles, valves are
pulled downward and atrial space expands, slight
suction draws blood into atria from venae cavae
and pulmonary veins

59
Q

Thoracic (respiratory) pump

A
  • Inhalation expands thoracic cavity
  • Thoracic pressure on the inferior vena cava (IVC) decreases
  • Abdominal pressure on the IVC increases
  • Blood is forced upward toward heart
  • Blood flows faster with inhalation
  • Central venous pressure
  • Direct measurement of BP in the right atrium and vena cava
  • Fluctuates during respiration due to thoracic pump
  • Inhalation: 2 mm Hg
  • Exhalation: 6 mm Hg
60
Q

Circulatory shock

A

any state in which cardiac output is insufficient to meet body’s metabolic needs

61
Q

Cardiogenic shock

A

Inadequate pumping of heart (MI)

62
Q

Obstructed venous return shock

A

tumor or aneurysm compresses a vein

63
Q

Low venous return (LVR) shock

A

Cardiac output low because too little blood returns to heart; three types
-Hypovolemic shock, Obstructed venous return shock, Venous pooling (vascular) shock

64
Q

Hypovolemic shock

A

most common; Loss of blood volume - trauma, burns,
dehydration

65
Q

Venous pooling (vascular) shock

A

Long periods of standing, sitting, or widespread vasodilation

66
Q

Neurogenic shock

A
  • Loss of vasomotor tone, vasodilation
  • Causes range from emotional shock to brainstem injury
67
Q

Septic shock

A

Bacterial toxins trigger vasodilation and increased capillary permeability

67
Q

Anaphylactic shock (severe immediate allergic reaction)

A

Severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability

67
Q

Venous pooling occurs with inactivity

A
  • Venous pressure not enough to force
    blood upward
  • With prolonged standing, CO may be low
    enough to cause dizziness
  • Prevented by tensing leg muscles, activate
    skeletal muscle pump
  • Jet pilots wear pressure suits
68
Q

Transient ischemic attacks (TIAs)

A
  • Brief episodes of cerebral ischemia
  • Caused by spasms of diseased
    cerebral arteries, can be early
    warning of a stroke
69
Q

Stroke, or cerebral vascular
accident (CVA)

A
  • Sudden death of brain tissue
    caused by ischemia
  • Atherosclerosis, thrombosis,
    ruptured aneurysm
  • Effects range from unnoticeable to
    fatal
  • Blindness, paralysis, loss of
    sensation, loss of speech
    common
  • Recovery depends on surrounding
    neurons, collateral circulation
70
Q

hemorrhagic stroke

A

when a blood vessel bursts within the brain

71
Q

ischemic stroke

A

a blood clot blocks the blood flow in an artery within the brain

72
Q

Skeletal Muscles At Rest

A
  • Arterioles constrict
  • Most capillary beds shut down
  • Total flow about 1 L/min
73
Q

Skeletal muscles during exercise

A
  • Arterioles dilate in response to muscle
    metabolites such as lactate, CO2, and
    H+
  • Blood flow can increase up to 20-fold
  • Blood diverted from digestive and
    urinary organs
74
Q

Special Circulatory Routes: Brain

A

Total blood flow to the brain fluctuates less than that of any other organ (700 mL/min)
* Seconds of deprivation causes loss
of consciousness
* Four to 5 minutes causes
irreversible brain damage
Brain regulates its own blood flow
Cerebral arteries dilate as systemic BP drops, constrict as BP rises

75
Q

Lungs circulatory route

A

Low pulmonary blood pressure (25/10 mm Hg)
* Flow slower, more time for gas exchange
* Oncotic pressure overrides blood (hydrostatic) pressure
* Pulmonary capillaries absorb fluid (almost no filtration)
* Prevents fluid accumulation in alveoli
Unique response to hypoxia
* Pulmonary arteries constrict in diseased area
* Redirects flow to better ventilated region

Bio 157 Lecture (4 decks)

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