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Anatomy 2 > Circulatory System Blood Vessels and Circulation > Flashcards

Circulatory System Blood Vessels and Circulation Flashcards

1
Q

6 Classes of Blood Vessels

A
  1. arteries
  2. arterioles
  3. capillaries
  4. venules
  5. veins
  6. anastomoses
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2
Q

arteries

A

carry blood away from heart
Branch and decrease in diameter

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3
Q

arterioles

A

Are smallest branches of arteries
Connect to capillaries

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4
Q

Capillaries

A

are smallest blood vessels
location of exchange between blood and interstitial fluid

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5
Q

Venules

A

Smallest veins
collect blood from capillaries

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6
Q

Veins

A

return blood to heart
Converge and increase in diameter

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7
Q

Anastomoses

A

Bypass connection between vessels

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8
Q

largest blood vessels to exit heart

A

pulmonary trunk and aorta

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9
Q

Pulmonary trunk

A

carries blood from right ventricle to pulmonary circulation

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10
Q

Aorta

A

carries blood from left ventricle
to systemic circulation

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11
Q

largest blood vessels to enter heart

A

superior and inferior vena cava
pulmonary vein

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12
Q

superior and inferior vena cava

A

carries blood to the right
ventricle from the systemic
circulation

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13
Q

pulmonary vein

A

carries blood to the left
ventricle from the
pulmonary circulation

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14
Q

The Smallest Blood Vessels

A

Capillaries
* Have small diameter and thin walls
* Chemicals and gases diffuse across walls

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15
Q

Arteries, veins, and capillaries

A

– Have different structures
– Have different functions

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16
Q

Walls have 3 layers

A
  1. tunica intima
  2. tunica media
  3. tunica externa
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17
Q

The Tunica Intima/Tunica interna

A
  • Is the innermost layer
  • Includes:
    – the endothelial cell lining
  • Endothelium = simple squamous epithelial-like cells connected by tight junctions
    – With basal lamina of loose connective tissue containing elastic fibers (elastin)
  • Arteries have internal elastic membrane
    – extra layer of elastic fibers on the outer edge
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18
Q

Tunica Media

A
  • Is the middle layer
  • Contains smooth muscle cells in loose connective tissue with sheets of elastin
    – Binds to inner and outer layers
  • Arteries have external elastic membrane
    – extra layer of elastic fibers on the outer edge
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19
Q

Tunica Externa/Tunica adventitia

A
  • Is outer layer
  • Contains collagen rich external connective tissue sheath
  • Infiltrated with nerve fibers and lymphatic vessels
  • Large vessels contain vasa vasorum
  • Arteries = more collagen, scattered elastic fiber bands
  • Veins = extensive fiber networks, bundles of smooth muscle cells
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20
Q

Vasa Vasorum

A
  • Small arteries and veins
  • Found:
    – in walls of large arteries and veins
  • Function:
    – Supply cells of tunica media and tunica externa
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21
Q

Artery Characteristics

A

Elastic and muscular, thick walls
– Elasticity allows arteries to absorb pressure waves that come with each heartbeat
– Muscular layer allows contractility, change diameter

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22
Q

From heart to capillaries, arteries change

A

– from elastic arteries
– to muscular arteries
– to arterioles

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23
Q

Elastic Arteries

A
  • Also called conducting arteries
  • Diameter up to 2.5cm
  • Elastin in all three tunics
    – Elasticity evens out pulse force
  • Stretch (ventricular systole) and rebound (ventricular diastole)
  • Not involved in systemic vasoconstriction
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24
Q

Muscular Arteries

A
  • Also called distribution arteries
  • Are medium-sized (most arteries)
  • Transport blood to organs and tissues
  • Diameter 10mm – 0.3mm
  • More smooth muscle and less elastin in tunica media than elastic arteries
  • Involved in systemic vasoconstriction via sympathetic stimulation
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25
Q

Vasoconstriction

A

The contraction
of arterial
smooth muscle
by the ANS

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26
Q

Vasodilatation

A

– The relaxation of
arterial smooth
muscle
– Enlarging the
lumen

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27
Q

Arterioles

A
  • Also known as resistance vessels
  • Connect blood supply to capillary beds
  • Are small – diameters 300μm – 10μm
  • All three tunics thin with few elastic fibers
  • Involved in local vasoconstriction via endocrine or sympathetic stimulation
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28
Q

Arterial sense organs

A
  • In walls of some major
    vessels, sensory
    structures monitor
    blood pressure and
    chemistry
  • Transmit information
    to brainstem to
    regulate heart rate,
    blood vessel diameter,
    and respiration
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29
Q

Health Problems with Arteries

A

aneurysm
arteriosclerosis
atherosclerosis
stroke

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30
Q

Aneurysm

A

– Pressure of blood
exceeds elastic
capacity of wall
– Causes bulge or
weak spot prone
to rupture
– Caused by chronic
high blood
pressure or
arteriosclerosis

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31
Q

Arteriosclerosis

A

– Variety of pathological conditions causing
changes in walls that decrease elasticity
(“thickenings”)
* Focal calcification = smooth muscle
degenerates, replaced by calcium salts
* Atherosclerosis (common type of
arteriosclerosis)

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32
Q

Atherosclerosis

A

lipid deposits

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33
Q

Stroke

A

cerebrovascular accident (CVA)
– Interruption of arterial supply to portion of brain due to embolism or atherosclerosis
– Brain tissue dies and function is lost

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34
Q

Capillaries

A
  • Only vessels with thin enough wall structure to allow complete diffusion
    – Designed to allow diffusion to/from the tissue
  • Diameter 8 μm
    – Consists of tunica intima only
    – endothelium + basal lamina
  • Human body contains 25,000 miles of capillaries
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35
Q

Capillary Structure

A
  • Endothelial tube, inside thin basal lamina
  • No tunica media
  • No tunica externa
  • Diameter is similar to red blood cell
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36
Q

Capillary Function

A
  • Location of all exchange functions of cardiovascular system
  • Materials diffuse between blood and interstitial fluid
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37
Q

Types of Capillaries

A

Continuous capillaries
Fenestrated capillaries
Sinusoids

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38
Q

Continuous capillaries

A
  • Normal diffusion to all tissues; majority type
  • Complete endothelium, tight junctions
  • Functions:
  • Permit diffusion of: water, small solutes, lipid-soluble materials
  • Block: blood cells and plasma proteins
  • e.g., the blood–brain barrier
    Are found in all tissues except: epithelia and cartilage
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39
Q

Fenestrated capillaries

A
  • Pores/fenestrations span endothelium
  • High volume fluids or large solute transfer
  • Permit rapid exchange of water and larger solutes between plasma and interstitial fluid
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40
Q

Fenestrated capillaries are found in

A

– choroid plexus
– endocrine organs
– kidneys
– intestinal tract

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41
Q

Sinusoids

A

– Gaps between endothelial cells
– Cell or large protein exchange
– Permit free exchange of water and large plasma proteins between blood and interstitial fluid
– Phagocytic cells monitor blood at sinusoids

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42
Q

Sinusoids are found in

A

– liver
– spleen
– bone marrow
– endocrine organs

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43
Q

Capillaries Networks

A
  • Organized into Capillary bed or capillary plexus
  • Connect 1 arteriole and 1 venule
  • Not enough total blood to fill all capillaries at once
    – Flow through capillary bed must be controlled based on need via precapillary sphincters
    – Metarterioles (thoroughfare channels)
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44
Q

Capillary Sphincter

A
  • Guards entrance to each capillary
  • Opens and closes, causing capillary blood to flow in pulses
44
Q

Anastomoses

A
  • Bypass routes between vessels
    – Bypass the capillary bed
  • Not present in retina, kidney, or spleen
  • More common in veins
45
Q

Veins vs. Arteries

A
  • Are larger in diameter
  • Have thinner walls
  • Carry lower blood pressure
46
Q

Veins

A
  • Collect blood from capillaries in tissues and organs
  • Return blood to heart
  • Can serve as blood reservoir
  • Thin walls but large lumens
  • Thin tunica media = little smooth muscle or elastin
  • Tunica externa = elastin and smooth muscle
  • Tunica intima = valves to prevent back-flow
47
Q

Three Vein Categories

A
  1. venules
  2. medium-sized veins- diameter 2-9 mm
  3. large veins- diameters up to 3 cm
48
Q

venules

A

– very small veins
* Average diameter 20 μm
– collect blood from capillary beds
– Small venules lack tunica media

49
Q

Vein Valves

A
  • Valves = Folds of tunica intima
  • Prevent blood from flowing backward
  • Pressure from heart drives blood flow in arteries, but pressure in veins often too low to oppose gravity
  • Compression pushes blood toward heart
    – Skeletal muscle movement required to “squish” blood through veins
50
Q

Valves in the Venous System

A

Valves in tunica
intima insure one
way movement

51
Q

Health Problems with Veins

A
  • Resistance to flow (gravity, obesity) causes pooling above valves, veins stretch out
    – Varicose veins
    – Hemorrhoids
52
Q

Blood Reservoirs in
Venous System

A
  • Venous system contains 65-70% total blood volume
  • Can constrict during hemorrhage to keep volume in capillaries and arteries near normal
53
Q

Blood flow

A

volume of blood flowing through a vessel in given period
– Total body flow = Cardiac output

54
Q

Blood Pressure

A

force per unit area exerted on vessel by blood (mmHg)
– Blood flows from high pressure → low

55
Q

Resistance

A

opposition to blood flow, friction
– Incr. blood viscosity = incr. resistance
– Incr. vessel length = incr. resistance
– Decr. vessel diameter = incr. resistance

56
Q

Pressure (P)

A

– The heart generates P to overcome resistance
– Absolute pressure is less important than pressure gradient

57
Q

The Pressure Gradient

A

The difference between pressure at the heart and pressure at peripheral capillary beds

58
Q

Flow (F)

A
  • Is proportional to the pressure difference (P)
  • Is inversely proportional to resistance (R)
59
Q

Vascular Resistance (R)

A

– Due to friction between blood and vessel walls
– Depends on vessel length, diameter and blood viscosity
* Adult vessel length is constant
* Vessel diameter varies by vasodilation and vasoconstriction
– R increases exponentially as vessel diameter decreases

60
Q

Vasoconstriction

A

– Decr. Flow
– Incr. Blood Pressure
– Incr. Resistance

61
Q

Vasodilation

A

– Incr. Flow
– Decr. Blood Pressure
– Decr. Resistance

62
Q

Measuring Blood Pressure

A
  • Blood pressure changes throughout body
    – Greatest in arteries leaving heart, lowest in veins returning to heart
    – Measured at brachial artery using
    sphygmomanometer
  • Person’s BP measures
    – Systolic pressure/diastolic pressure (from
    ventricles)
    – “Normal”: 120/80 mmHg
63
Q

pressures in the systemic circuit

A

systolic pressure, diastolic pressure, pulse pressure

64
Q

Systolic pressure

A

peak arterial pressure during ventricular systole

65
Q

Diastolic pressure

A

minimum arterial pressure during diastole

66
Q

Pulse pressure

A

difference between systolic pressure and diastolic pressure

67
Q

Abnormal Blood Pressure

A

hypertension or hypotension

68
Q

hypertension

A

abnormally high blood pressure
– Arterial pressure > 130/90 mmHg
– Causes incr. workload for heart
– Untreated = enlarged left ventricle requires more O2 heart can fail

69
Q

hypotension

A

abnormally low blood pressure
– Caused by blood loss, dehydration, anemia
– No specific numerical criterion for hypotension

70
Q

Mechanisms of Venous Return

A

pressure gradient
muscular compression of peripheral veins
the respiratory pump
cardiac suction

71
Q

venous return

A

flow of blood back to the heart, is achieved by pressure gradient, muscular compression, respiratory pump, cardiac suction

72
Q

Pressure gradient

A

Overall, venous pressure gradient toward heart
(venules ~13mmHg to venae cavae ~7mmHg)

73
Q

Muscular compression of peripheral veins

A

Compression of skeletal muscles pushes blood toward heart (one-way valves)

74
Q

The respiratory pump

A

– Inhaling decreases thoracic pressure
– Exhaling raises thoracic pressure
– Thoracic cavity action

75
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

76
Q

Capillary Exchange

A
  • Vital to homeostasis
  • Functions to feed tissues and remove wastes
  • Due to filtration and diffusion
  • Dependent on good blood flow and pressure
77
Q

capillaries move materials across capillary walls by:

A
  1. Diffusion
  2. Transcytosis
  3. Filtration
  4. Reabsorption
78
Q

Diffusion

A
  • Movement of ions or molecules:
    – from high concentration to lower concentration
    1. Small ions transit through endothelial cells
    – e.g. Na+, K+, Ca2+, Cl−
    2. Large ions & small organics pass between endothelial
    cells or through fenestrated capillaries
    – E.g. glucose, amino acids
    3. Lipids pass through endothelial membrane
    – e.g. steroid hormones
    4. Large water-soluble compounds diffuse at fenestrated
    capillaries
    – e.g. in intestine
    5. Large plasma proteins diffuse only at sinusoids
    – e.g. in liver
79
Q

Transcytosis

A
  • Transcytosis is a vesicle-mediated transport
  • Material picked up on one side of membrane by pinocytosis or
    receptor-mediated endocytosis
  • Transport vesicles move material across epithelial cell
  • Material discharged on other side by exocytosis
  • Accounts for only a small fraction of solute exchange across the
    capillary wall
  • Important for fatty acids, albumin, and some hormones such as
    insulin
80
Q

Filtration and Reabsorption

A
  • Fluid filters out of arterial end of capillary and reabsorbed
    osmotically at venous end of capillary
    – Accelerates distribution of nutrients
    – Flushes out toxins and pathogens
  • Balance between osmosis and hydrostatic pressure
  • Hydrostatic pressure
  • Colloid osmotic pressure (COP)
81
Q

Hydrostatic pressure

A

drives fluid out of capillary
High on arterial end of capillary, low on venous end

82
Q

Colloid osmotic pressure (COP)

A

draws fluid into capillary
Results from plasma proteins (albumin)—more in blood
Oncotic pressure = net COP (blood COP − tissue COP)

83
Q

At arterial end of capillary

A

– fluid moves out of capillary
– into interstitial fluid

84
Q

At venous end of capillary

A

– fluid moves into capillary
– out of interstitial fluid

85
Q

Edema

A

Buildup of fluid in the tissues, due to:
– Too much filtration
– Less reabsorption
– blocked lymphatics

86
Q

Total peripheral blood flow

A

equals cardiac output

87
Q

Blood pressure overcomes

A

friction and elastic forces
to sustain blood flow

88
Q

If blood pressure is too low:

A

– vessels collapse
– blood flow stops
– tissues die

89
Q

If blood pressure is too high:

A

– vessel walls stiffen
– capillary beds may rupture

90
Q

Cardiovascular Regulation

A
  • Flow, BP, and resistance must be controlled to
    insure delivery of nutrients and removal of
    wastes in tissues
  • Changes blood flow to a specific area:
    – at an appropriate time and area
    – without changing blood flow to vital organs
91
Q

3 Regulatory Mechanisms of cardiovascular regulation

A
  1. Autoregulation
  2. Neural Mechanism
  3. Hormonal Regulation
92
Q

Autoregulation

A

ability of tissues to regulate
their own blood supply
– causes immediate, localized homeostatic adjustments
– Single capillary bed: action at a precapillary sphincter
- local vasodilators & local vasoconstrictors

93
Q

Local vasodilators

A

(increase blood flow)
* Incr. CO2 or decr. O2
* Lactic acid, Incr. K+ or H+
* Inflammation: histamine, Nitric oxide (NO)
* Elevated temperature

94
Q

Local vasoconstrictors

A

(decrease blood flow)
* Prostaglandins
* Thromboxanes
* Endothelins

95
Q

Neural Mechanisms

A

Remote control of vessels by the central and autonomic
nervous systems
- cardiovascular (CV) centers
- baroreceptor reflexes
- chemoreceptor reflexes

96
Q

Cardiovascular (CV) centers

A

– cardiac and vasomotor centers of medulla oblongata
– adjust cardiac output (CO) and peripheral resistance
– Cardiac Center
– Vasomotor Center

97
Q

cardiac center

A
  • Cardioacceleratory center: sympathetic = incr. CO
  • Cardioinhibitory center: parasympathetic = decr. CO
98
Q

vasomotor center

A

exerts sympathetic control
* Stimulates most vessels to constrict, but dilates vessels
in cardiac muscle to meet demands of exercise

99
Q

Baroreceptor reflexes

A
  • Respond to changes in blood pressure
  • Trigger cardiovascular center
100
Q

Chemoreceptor reflexes

A
  • Respond to changes in blood and CSF CO2 and
    O2, pH
  • Trigger respiratory and cardiac center
101
Q

Hormonal regulation

A
  1. Antidiuretic Hormone (ADH)
  2. Angiotensin II
  3. Erythropoietin
  4. Atrial Natriuretic Peptides (ANP)
102
Q

Antidiuretic Hormone (ADH)

A

– From pituitary gland in response to low blood volume
– Causes vasoconstriction and water conservation at kidney

103
Q

Angiotensin II

A

– From kidney in response to low BP
– Causes:
* Na+ retention and K+ loss at kidney
* Stimulates release of ADH, stimulates thirst,
Stimulated CO
* Stimulates arteriole constriction

104
Q

Erythropoietin

A

– From kidney in response to low O2
– Stimulates production and maturation of RBCs

105
Q

Atrial Natriuretic Peptides (ANP)

A

– From atria in response to stretching/high BP
– Causes:
* Increase Na+ and H2O loss at kidney
* Reduced Thirst
* Blocks ADH release
* Stimulates vasodilation

106
Q

Aging and the
Cardiovascular System

A
  1. Decreased hematocrit
  2. Increased blood clots (thrombus) formation
  3. Blood-pools in legs
    – due to venous valve deterioration
  4. Reduction in max cardiac output
  5. Increased arteriosclerosis
107
Q

Blood flow to active vs. inactive tissues must be differentially controlled by

A

autoregulation, neural
regulation, and hormone release

108
Q

Cardiac output (CO) cannot increase

A

indefinitely

Anatomy 2 (8 decks)

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