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ANP 1105 > Chapter 19 - Blood vessels > Flashcards

Chapter 19 - Blood vessels Flashcards

1
Q

What is the difference between arteries, capillaries and veins regarding blood flow?

A

A - blood away from heart (towards capillaries) ; umbilical arteries transport oxygen-poor blood from fetus to placenta
C - exchange vessels, directly serving cellular needs
V - blood to the heart (away from capillaries) - happens when venules join together

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2
Q

What are capillaries called when they unite and what are their characteristics?

A

postcapillary venules
- smaller venules contain only endothelium and pericytes
- very porous; fluids and WBC move into tissue

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3
Q

What are the characteristics of larger venules?

A

have a thin tunica media and tunica externa

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4
Q

What is the composition difference between tunica media and tunica external in venues?

A

TM - thin (little smooth muscle or elastic)
TE - thicker (thick collagen fibers and elastic network)

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5
Q

Why can veins accommodate large amounts of blood relative to low pressure?

A

called capacitance vessels and blood reservoirs because they contain up to 65% of blood supply at any time

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6
Q

Why is blood pressure low in the arteries?

A

so adaptation ensure that blood returns to the heart
- large diameter lumens offer little resistance

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7
Q

What do vessels consist of?

A
  • lumen
  • central blood-containing space
  • wall
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8
Q

What are the layers of wall in vessels?

A
  • tunica intima
  • tunica media
  • tunica externa
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9
Q

what are capillary walls made of?

A

endothelium with thin basal lamina

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10
Q

Why is the structure of the tunica intima important?

A

simple squamous epithelium lines lumen of all vessels
- continuous with the endocardium and reduces friction
- subendothelial layer: basement membrane and loose connective tissue - support endothelium

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11
Q

What are the characteristic of tunica media?

A
  • bulkiest layer in arteries
  • smooth muscles regulate sympathetic vasomotor nerve fibers; vasoconstriction and vasodilation
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12
Q

What are the characteristics of tunica externa?

A
  • mostly collagen fibers to protect wall and anchors to surrounding
  • contains elastics in large veins
  • networks with nerve fibers, lymphatic vessels and blood vessels
  • has vasa vasorum
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13
Q

What are the three groups of arteries?

A
  • elastic arteries
  • muscular arteries
  • arterioles
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14
Q

What are the characteristics of elastic arteries also known as conducting arteries?

A
  • thick walled near the heart: pulmonary truck/ aorta and major branches
  • large lumen = low resistance
  • contains more elastin and smooth tissue(inactive in vasoconstriction)
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15
Q

How do arteries act as pressure reservoirs?

A
  • expand and recoil as blood is ejected from the heart
  • allows for continuous blood flow downstream, even with heart beat
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16
Q

Why are muscular arteries also called distributing arteries?

A
  • deliver blood to specific body organs
  • diameter ranges from pinky finger to pencil lead size
  • thickest tunica media and less stretchy and more vasoactive than elastic fibers
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17
Q

What are the characteristics of arterioles also called resistance vessels?

A
  • smallest of all arteries
  • large one: contains all layers of tunica; small one: contains single layer of smooth muscle around endothelium
  • controls flow into capillary beds via vasodilation and constriction
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18
Q

What are the characteristics of capillaries?

A

smallest blood vessel and act as exchange vessels between blood and interstitial fluid
- consists of only thin tunica intima and single endothelial cells
- RBC pass through in single file

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19
Q

Why do some capillaries have pericytes?

A

P- contractile cells
- can generate new vessels or scar tissue and stabilize wall/ control permeability

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20
Q

Which tissues lack capillaries?

A
  • some tendons/ ligaments
  • avascular cartilage/ epithelia/ cornea/ lens
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21
Q

What are capillary beds?

A

network of capillaries between arterioles and venules

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22
Q

What is microcirculation?

A

flow of blood through capillary bed and arteriole to venule
- capillary drains into postcapillary venule (helps with exchange)

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23
Q

What controls blood flow into capillary beds?

A

local chemicals and arteriolar vasomotor nerve fibers

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24
Q

what does the vascular shunt consist of?

A

metarteriole and thoroughfare channel

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25
Q

What is the function of the intestinal mesenteries?

A

vascular shunts: channel that directly connects terminal arteriole with postcapillary venule

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26
Q

What is the precapillary sphincter?

A

smooth muscle surrounding each true capillary that branches off metarteriole
- acts as valve regulating blood flow
- controlled by local chemicals

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27
Q

Where is most of the blood in the body at any given time and percentage?

A

systemic veins and venules
- 60%

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28
Q

What is vascular anastomoses, subcategory, and location?

A

interconnection of blood vessels
- interconnected arteries form arterial anastomoses (alternate pathway - collateral channel - to same tissue to ensure continuous blood flow)
- in joints, abdominal organs, brain, heart

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29
Q

What is arteriovenous anastomoses and subcategory and characteristic?

A

shunts across capillary beds (ex. metarteriole-thoroughfare channel)
- venous anastomoses
- so abundant that occluded veins rarely block blood flow or tissue death

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30
Q

What is blood flow and characteristics?

A

amount of blood flowing through vessel, organ, or entire circulation in a given period of time
- equivalent to CO
- flow is based on organ need

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31
Q

What is blood pressure and characteristics?

A

force per unit area exerted on vessel wall by blood
- in mm Hg
- measured as systemic arterial BP in large arteries near heart
- pressure gradient provides driving force that keeps blood moving

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32
Q

What is resistance and characteristics?

A

opposition to flow; measure of friction blood encounters along vessel walls
- mostly in peripheral (systemic) circulation, also called total peripheral resistance (TPR)
- contributing factors: blood viscosity, vessel length and diameter

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33
Q

What is blood viscosity and characteristics?

A

the internal resistance to flow in fluids
- thickness/ stickiness
- contributing factors: too many RBC

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34
Q

What is the total blood vessel length characteristics?

A

constant, but when tissue grows so does its blood supply
- greater vessel length means more resistance

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35
Q

What are the blood vessel diameter characteristics?

A
  • smaller diameter = more resistance (more contact with wall)
  • frequently changes
  • radius reduces by half (resistance rises 16 times); radius doubles (resistance decreases by 1/16)
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36
Q

What is the relationship between blood flow (F) and pressure (P) and the equation?

A
  • if delta P increase, blood flow increase (vice versa)
  • if TPR increases, blood flow decreases (vice versa)
  • F= delta P/ TPR
37
Q

What is the order of blood pressure in various blood vessels from highest to lowest?

A
  • aorta (80 -120)
  • arteries
  • arterioles (steepest fall)
  • capillaries
  • venules
  • veins
  • vena cava (0)
38
Q

What is a vital sign and pressure points?

A

VS - pulse and blood pressure, along with respiratory rate and body temperature
PP - areas where arteries are close to skin

39
Q

What is the difference between systolic and diastolic pressure?

A

SP - pressure when first sounds heard, as blood starts to spurt though artery
DP - pressure at which sounds disappears, as artery no loner constricted, blood flows freely

40
Q

What is the BP range from the beginning to end of the capillary bed and why is low BP desirable?

A

35- 17
- high BP ruptures fragile, thin-walled capillaries
- capillaries are extremely permeable, so even low pressure forces filtrate into interstitial spaces

41
Q

What are the characteristics of venous pressure?

A
  • steady (non pulsatile)
  • low BP causes blood to flow steadily out of cut and helps distribute (cool down) heat
42
Q

What are the 3 functional adaptations that assist venous return?

A
  • muscular pump: contracts/ relaxes skeletal muscle around deep veins to prevent back flow
  • respiratory pump: pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
  • sympathetic venoconstriction: SNS triggers contraction of veins, reducing their capacitance (and blood reservoir) as blood is pushed towards the heart
43
Q

What are the 3 factors regulating BP?

A
  • cardiac output (CO)
  • Total peripheral resistance (TPR)
  • Blood volume
44
Q

what is the calculation to find MAP and CO?

A

CO = SV x HR
MAP = CO x TPR
MAP = SV x HR x TPR

45
Q

What are the 2 mechanisms regulating BP?

A
  • short term: alters TPR and CO
  • long term: alters blood volume (via kidneys)
46
Q

What is the TPR main goals through neural controls?

A
  1. maintain adequate MAP moment-by-moment by altering vessel diameter
  2. after blood distribution to organs as the metabolic demands change (distributing blood to needed organs)
47
Q

What is the difference between baroreceptors reflex and chemoreceptor reflex?

A

BR - neural controlled; monitor changes in stretch of vessel walls (pressure changes)
CR - neural controlled; influenced by higher brain centers and chemoreceptors that monitor blood levels of CO2, H+ and O2

48
Q

What is the cardiovascular center?

A

in medulla receives/ integrates inputs from baroreceptors, chemoreceptors and higher brain centers

49
Q

What is the roll of the cardiovascular center?

A

consist of three groups of neurons in the medulla that work together to adjust CO (via HR and SV) and TPR (via vessel diameter) to regulate MAP
- has inhibition and contractile centers

50
Q

What is the vasomotor center?

A

sends impulses via sympathetic vasomotor fibers to blood vessels (mainly arterioles)
- continuous moderate constriction is called vasomotor tone

51
Q

Where are baroreceptors located?

A

carotid sinus, aortic arch, and walls of large arteries of neck and thorax

52
Q

How are chemoreceptors in the aortic arch and large arteries stimulated by and what do they stimulate?

A
  • rise in blood CO2 or drop in bloop pH or O2
  • send AP to cardiovascular center at high frequency to increase CO and MAP by: simulating the cardio acceleratory center (increase HR and SV) and the vasomotor center (increase TPR via vasoconstriction)
53
Q

What influence does the higher brain center have?

A

hypothalamus and cerebral cortex can modify arterial pressure via relays to the cardiovascular center in the medulla
- hypo mediates fight/ flight and increased blood flow in exercise

54
Q

What regulates MAP?

A

short term - hormone regulation via TPR
long term - via changes in blood volume

55
Q

What is the function of the adrenal medulla hormones?

A

E and NE from adrenal gland increase CO and vasoconstriction
- angiotensin 2 stimulates vasoconstriction, release of adenosine and ADH (all increase blood volume)

56
Q

what is atrial natriuretic peptide (ANP)?

A

decreases MAP by antagonizing aldosterone, causing decreased blood volume; also by causing generalized vasodilation

57
Q

What is ADH - vasopressin?

A

stimulates kidneys to conserve water
- also stimulates vasoconstriction

58
Q

How do the kidneys regulate MAP?

A
  1. direct renal mechanisms
  2. indirect renal mechanism (renin-angiotensin- aldosterone system)
59
Q

What is the direct renal mechanism?

A

alters blood volume independent of hormone
- rise in blood pressure or volume causes kidneys to eliminate more water in the body (reducing BV and P)
- fall in P causes kidneys to conserve more water (increases BV and P)

60
Q

What is the indirect renal mechanism?

A

use of the renin-angiotensin-aldosterone system
- drop in MAP triggers kidneys to release enzymes called renin into blood
- catalyzes conversion of angiotensinogen to angiotensin 1
- angiotensin-converting enzyme (ACE) converts angiotensin 1 to angiotensin 2

61
Q

How does angiotensin 2 act to increase MAP and ECF volume?

A
  • triggers aldosterone secretion (kidneys conserve Na+ and water)
  • causes ADH conserve water
  • activates hypothalamic thirst center (increased water intake)
  • acts as a potent vasoconstrictor to increase TPR (directly increases MAP)
62
Q

What is primary hypertension?

A
  • 90% of hypertensive people have it
  • no underlying cause identified; results from genetics or environment
  • no cure
  • risk factors: obesity, genetics, diet, age, stress, smoking, diabetes mellitus
63
Q

What is secondary hypertension?

A
  • 10% of hypertensive people
  • due to identifiable disorders (obstructed renal arteries, kidney disease)
  • treatment available
64
Q

What is hypertension?

A

systolic BP above 130 or diastolic BP above 80
- slowly damages heart and vessels (silent killer)
- causes heart failure, vascular disease, renal failure and stroke
- heart must work harder

65
Q

What is hypotension?

A

low BP between 90/60 mm Hg
- may cause inadequate blood flow to tissues
- associated with long life and lack of cardiovascular illness

66
Q

What is tissue perfusion (blood flow through body tissue) involved in?

A
  • delivery of o2 and nutrient to and removal of wastes from tissue cells
  • gas exchange (lungs)
  • absorption of nut (digestive system)
  • urine formation (kidney)
67
Q

What is the rate of tissue/ organ perfusion dependent on?

A

metabolic needs to meet supply and demands
- regulated by intrinsic controls (autoregulation) that acts automatically in the smooth muscle of arterioles

68
Q

What is the extrinsic controls?

A

sympathetic and endocrine
- act on smooth muscles of arterioles to maintain MAP (not to regulate tissue perfusion)
- SNS and certain hormones reduce flow to regions that least need it (constriction) to maintain MAP

69
Q

What is the difference between intrinsic and extrinsic controls?

A

IC - uses paracrine or properties of muscle tissue (autoregulation or local control)
EC - uses hormones

70
Q

How do organs regulate their own blood flow and what allows it to happen?

A

intrinsically by varying the diameter (thus resistance) of their arterioles
- based on local tissue conditions
- form autoregulation because no nerves or hormones

71
Q

What is the types of intrinsic mechanisms determine final autoregulatory responses?

A
  • metabolic (chemical)
  • myogenic (physical)
72
Q

What are the metabolic controls and what are the effects of changing the levels or local chemicals?

A

increase in tissue metabolic activity due to
- decreased O2 or increased metabolic factors

  • direct relaxation of arterioles and precapillary sphincters
  • NO and inflammatory chemicals (vasodilator)
  • endothelin (vasoconstrictor)
  • NO and endo is balanced but when not enough blood, NO is more powerful
73
Q

Myogenic controls: what is myogenic responses and what are the factors that change it?

A

vascular smooth muscle responds to changes in intravascular pressure to keep perfusion relatively constant
- if pressure increases: vessel walls stretch (smooth muscle contracts to constrict the vessel and reduce flow)
- if pressure decreases: vessel walls stretch less (smooth muscle relaxes/ dilates vessel, allowing blood flow)

74
Q

Why does long-term autoregulation happen and what are the effects?

A

when short-term controls can’t meet tissue demands
- existing vessels enlarge and new vessels form (angiogenesis); takes months
- common in heart when coronary vessels partially occluded; throughout people in high altitude

75
Q

What is active hyperemia in regards to skeletal muscle?

A

blood flow increases in direct proportion to metabolic activity, a form of metabolic regulation
- local controls override sympathetic vasoconstriction; blood flow increases 10X

76
Q

How does velocity change throughout the systemic system and what is speed related to?

A
  • aorta: fastest
  • capillaries: slowest
  • veins: increases again

total cross-sectional area
- capillaries have the largest, so it moves the slowest allowing for proper exchange

77
Q

What is vasomotion and what is it due to?

A

intermittent flow of blood through capillaries
- alternating dilation and constriction of arterioles and precapillary sphincters in response to local chemical conditions (intrinsic control)

78
Q

What are the 4 routes molecules move through capillaries?

A
  1. liquid-soluble molecule: endothelial cell membrane (respiratory gases)
    2/3. water-soluble molecules: intercellular cleft or fenestrations (amino acids/ sugar)
  2. larger molecule: actively transported in vesicles via endocytosis and transcytosis (proteins)
79
Q

Explain what bulk flow is, the filtration, reabsorption and results?

A

continuous movement of fluid across capillary walls mixes blood plasma and interstitial fluid
F: 20 L of fluid filters from cap at arteriolar end to interstitial space
R: 17L of fluid reabsorbed
R: maintain composition of inter fluid ensure proper fluid balance

80
Q

What is the difference between hydrostatic pressure and osmotic pressure?

A

HP - fluid pressing against a boundary until it “pushes” some of the fluid across the boundary
OP - non-diffusible solutes that cannot cross the boundary. “pulls” fluid a cross the boundary

81
Q

what is edema and how does it affect capillary filtrate?

A

an abnormal increase in interstitial fluid volume
- rise in outward directed pressures, leading to more filtrate (high NFP)
- drop in inward directed pressure (high NFP)

82
Q

How is capillary hydrostatic pressure increased?

A

through fast fluid build up
- due to incompetents venous valves, localized vessel blockage, cong. heart failure or high BP

83
Q

How is osmotic pressure increased?

A

due to inflammatory response
- inflammation increases capillary permeability and allows proteins to leak into interstitial fluid

84
Q

How is capillary colloid osmotic pressure decrease hinder fluid return to blood?

A

Hypoproteinemia (low protein levels): results from malnutrition, liver disease or glomerulonephritis

85
Q

What is the venous system?

A

consists of two main circulations
- pulmonary: short loop that runs from heart to lungs and back
- systemic: long loop to all parts of body and back

86
Q

What is the difference in depth between arteries and veins?

A

A - run deep
V - run superficial and deep; most veins share same name with artery but superficial veins don’t share names

87
Q

Is the venous pathway more interconnected then the arteriole?

A

Yes

88
Q

How is the venous drainage system different in the brain and digestive system?

A

B: blood from brain enters dural venous sinuses (rather than veins)
DS: blood enters hepatic portal system, passing through the liver before getting to the heart

89
Q

What are the 3 types of capillaries?

A
  • continuous (least permeable - skin, muscle, lungs, CNS)
  • fenestrated (pores - active filtration and absorption - kidney)
  • sinusoid (most permeable - liver, bone marrow, spleen and adrenal medulla)

ANP 1105 (12 decks)

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