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Anatomy & Physiology > Chapter20 Circulatory > Flashcards

Chapter20 Circulatory Flashcards

1
Q

Capillaries

A

Connect smallest arteries to smallest veins

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2
Q

Tunica interna

A

Consists of simple squamous endothelium that acts as a selectively permeable barrier, secretes chemicals for vasoconstriction/vasodilation, and repels blood cells and platelets

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3
Q

Tunica media

A

The thickest layer that consists of smooth muscle, strengthens vessels and prevents blood pressure from rupturing them, and regulates the diameter of blood vessels

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4
Q

Tunica externa

A

Loose connective tissue that anchors the vessel and provides passage for small nerves and lymphatic vessels

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5
Q

Vasa vasorum

A

Small vessels that supply blood to at least the outer half of the larger vessels

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6
Q

A

Strong, resilient tissues that resist high blood pressure

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7
Q

What are conducting arteries

A

The thickest/strongest arteries that expand during ventricular systole and recoil during ventricular diastole which lessens fluctuations in blood pressure and takes stress off arteries downstream

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8
Q

What are examples of conducting arteries

A

Aorta, common carotid, subclavian, pulmonary trunk, common iliac arteries

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9
Q

What are distributing arteries

A

Distribute blood to specific organs; smooth muscle layers constitute majority of vessel wall

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10
Q

What are examples of distributing arteries

A

Brachial, femoral, renal, and splenic arteries

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11
Q

What are resistance (small) arteries

A

They are arterioles - the smallest arteries - that control the amount of blood that goes to various organs

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12
Q

What are metarterioles

A

Known as thoroughfare channels; short vessels that link arterioles to capillaries and allow blood to bypass capillary bed

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13
Q

What is an aneurysm

A

Thin-walled, bulging sac that pulsates with each heartbeat; may rupture at any time causing hemorrhage

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14
Q

Where are the most common sites of aneurysm

A

Abdominal aorta, renal arteries, arterial circle at the base of the brain

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15
Q

What causes an aneurysm

A

Congenital weakness of blood vessels, trauma, bacterial infections; most common cause is combination of atherosclerosis and hypertension

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16
Q

What happens in the walls of the major arteries above the heart?

A

Blood pressure and composition is monitored, information is transmitted to the brain stem that serves to regulate heartbeat, blood vessel diameter, and respiration

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17
Q

What do the baroreceptors in the carotid sinuses do?

A

Monitors blood pressure, decreases heart rate and causes vasodilation in response to high BP; located in the internal carotid artery

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18
Q

What do the chemoreceptors in the carotid bodies do?

A

Monitor blood composition and transmit signals to brain stem respiratory centers; adjust respiratory rate to stabilize pH as well as CO2 and O2 levels; oval bodies near branch of common carotid

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19
Q

What do the chemoreceptors in the aortic bodies do?

A

They have the same function as carotid bodies (monitoring and adjusting) but are located in the walls of aortic arch near arteries to head and arms

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20
Q

What are capillaries

A

Site where nutrients, wastes, and hormones pass between blood and tissue fluid; known as the “business end” of the cardiovascular system

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21
Q

What are capillaries made of

A

Only endothelium and basal lamina so exchange can occur at a very fast rate

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22
Q

Where are capillaries absent from

A

Tendons, ligaments, epithelia, cornea, and lens of eye

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23
Q

What are the most common capillaries

A

Continuous capillaries

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24
Q

What are continuous capillaries

A

Endothelial cells held together by tight junctions forming a continuous tube with intercellular clefts

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25
Q

What do intercellular clefts do

A

Allow passage of solutes such as glucose, restrict passage of large molecules such as plasma proteins, platelets, and blood cells

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26
Q

What are pericytes

A

They wrap around the capillaries to contract and regulate blood flow

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27
Q

Where are fenestrated capillaries

A

They are found in organs that require rapid absorption or filtration such as the kidneys and small intestines

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28
Q

What are fenestrated capillaries

A

Endothelial cells riddled with holes called filtration pores (fenestrations) that allow passage of only small molecules; retain most proteins and larger particles in bloodstream

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29
Q

What are sinusoids

A

Endothelial cells separated by wide gaps that occur in the liver, bone marrow, and spleen; irregular blood filled spaces with large fenestrations

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30
Q

What do sinusoids do

A

Allow proteins (albumin), clotting factors, and new blood cells to enter circulation

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31
Q

What are capillary beds

A

Organized networks of capillaries supplied by a single arterioles or metarteriole; transition to venules or drain into a thoroughfare channel at the distal end

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32
Q

What are precapillary sphincters

A

They control which beds are well perfused

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33
Q

What happens when precapillary sphincters are relaxed

A

Capillaries are well perfused with blood and engage in exchanges with tissue fluid

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34
Q

What happens when precapillary sphincters contract

A

Blood bypasses capillaries, flows through thoroughfare channel to venule

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35
Q

What do veins have more of than arteries

A

Greater capacity for blood containment than arteries

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36
Q

Describe veins compared to arteries

A

Thinner walls, flaccid, less muscular, elastic tissue; collapse when empty, expand easily; have steady blood flow; merge to form larger veins; subjected to relatively low blood pressure

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37
Q

What are the smallest veins

A

Post capillary venules

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38
Q

What do post capillary venules do

A

Receive blood directly from capillaries or by distal end of thoroughfare channels

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39
Q

Describe postcapillary venules

A

Porous; fluid exchange with surrounding tissues; most leukocytes emigrate from bloodstream through venule walls

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40
Q

Describe muscular venules

A

Receive blood from postcapillary venules; 1 or 2 layers of smooth muscle in tunica media

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41
Q

Describe medium veins

A

Tunica interna forma venous valves; skeletal muscle pump propels venous blood back toward the heart

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42
Q

Describe venous sinuses

A

Veins with especially thin walls, large lumens, and no smooth muscle; dural venous sinus of brain and coronary sinus of the heart; not capable of vasomotion

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43
Q

Describe large veins

A

Some smooth muscle in all 3 tunics; tunica externa thickest layer and contains longitudinal bundles of smooth muscle; vena cavae, pulmonary veins, internal jugular veins, renal veins

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44
Q

What are varicose veins

A

Blood pools in lower legs of people who stand for long periods stretching the veins

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45
Q

What is the physiology of varicose veins

A

Cusps of valves pull apart in enlarged superficial veins, further weakening the vessels. Blood back flows and further distends vessels, their walls grow weak and develop into varicose veins

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46
Q

What can contribute to varicose veins

A

Hereditary weakness, obesity, pregnancy

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47
Q

What is the simplest and most common circulatory route?

A

Heart to arteries to arterioles to capillaries to venules to veins; passes only one network of capillaries from time it leaves the heart until the time it returns

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48
Q

Describe a portal system

A

Blood flows through 2 consecutive capillary networks before returning to the heart; found between hypothalamus and anterior pituitary as well as in kidneys between intestines and liver

49
Q

Describe arteriovenous anastomosis

A

Shunt; artery flows directly into vein by passing capillaries

50
Q

What is venous anastomosis

A

One vein empties directly into another

51
Q

What is arterial anastomosis

A

Two arteries merge providing collateral routes of blood supply to a tissue; coronary circulation and common around joint

52
Q

Define blood flow

A

The amount of blood flowing through an organ, tissue, or blood vessel in a given time (mL/min); at rest, total flow is equal to the cardiac output (5.25 L/min)

53
Q

Define perfusion

A

The flow per given volume or mass of tissue in a given time (mL/min/g)

54
Q

What is perfusion important for

A

Delivery of nutrients and oxygen, and removal of metabolic wastes

55
Q

How are pressure and flow related

A

The greater pressure difference between 2 points, the greater the flow; the greater the resistance the less the flow

56
Q

Describe blood pressure

A

The force that blood exerts against a vessel wall; use sphygmomanometer at brachial artery

57
Q

What are the two pressure recorded when taking blood pressure

A

Systolic - peak arterial BP taken during ventricular systole - and diastolic - minimum arterial BP taken during ventricular diastole between heart beats

58
Q

What is the normal BP in a healthy adult

A

120/75 mm Hg

59
Q

What is peripheral resistance

A

Opposition to flow that blood encounters in vessels way from the heart

60
Q

What are the 3 variables that effect resistance

A

Blood viscosity, vessel length, vessel radius

61
Q

What effects blood viscosity

A

RBC count, albumin concentration, anemia and hypoproteinemia (decrease viscosity), polycythemia and dehydration (increase viscosity)

62
Q

What effect does vessel radius have on peripheral resistance

A

Most powerful resistance; vasoreflexes changes laminar flow (flows in layers, faster in center)

63
Q

How does blood velocity change from aorta to capillaries and why

A

Decrease due to greater distance, smaller radii, and farther from heart (total cross sectional area gets greater and greater)

64
Q

How does velocity change from capillaries to vena cava and why?

A

Increases due to larger veins/less resistance, large amount of blood forced into smaller channels, noteworthy that it never regains velocity of large arteries

65
Q

What are arterioles role in peripheral resistance

A

Most significant point of control over peripheral resistance and flow; best positioned to regulate flow into capillaries, most numerous control points, more muscular in proportion to their diameters; highly capable of changing radius

66
Q

What are vasoreflexes

A

Quick and powerful ways of altering blood pressure and flow; vasoconstriction and dilation

67
Q

What are the 3 ways of controlling vasomotor activity

A

Local control, neural control, hormonal control

68
Q

What are the components of local control

A

Auto regulation, vasoactive chemicals, reactive hyperemia, angiogenesis

69
Q

What is autoregulation

A

Ability of tissue to regulate their own blood supply

70
Q

What is the metabolic theory of autoregulation

A

If tissue is inadequately perfused, wastes accumulate, stimulating vasodilation which increases perfusion; blood stream delivers oxygen and removes metabolites, when wastes removed vessels constrict

71
Q

What are vasoactive chemicals

A

Substances secreted by platelets, endothelial cells, and peri vascular tissue to stimulate vasomotion; histamine, prostacyclin, nitric oxide

72
Q

What is reactive hyperemia

A

If blood supply is cut off and then restored, flow increase above normal

73
Q

What is angiogenesis

A

Growth of new blood vessels; controlled by growth factors and inhibitors; occurs in regrow that of uterine lining, around coronary artery obstructions, in exercised muscle, and malignant tumors

74
Q

Describe neural control

A

Vessels under remote control by CNS and ANS; vasomotor center exerts sympathetic control over blood vessels

75
Q

What effect does the vasomotor center have on vessels

A

Stimulates most vessels to constrict, but dilates vessels in skeletal and cardiac muscle to meet demands of exercise; vasomotor center is the integrating center for 3 autonomic reflexes: baroreflexes, chemoflexes, medullary ischemic reflex

76
Q

Describe the baroreflex

A

Automatic, negative feedback response to a change in BP

77
Q

What detects the increases and decreases in BP

A

Carotid sinuses

78
Q

Where are baroreflex signals sent

A

to brainstem

79
Q

What type of BP change are baroreflexes important for

A

Short-term; not cases of chronic hypertension

80
Q

Described the chemoreflex

A

Autonomic, response to changes in blood chemistry (pH, O2, and CO2 concentrations)

81
Q

where are chemoreceptors found

A

Aortic and carotid bodies in aortic arch, subclavian arteries, and external carotid arteries

82
Q

What is the primary role of the chemoreflex

A

adjust respiration to changes in blood chemistry

83
Q

What is the secondary role of the chemoreflex

A

Vasomotion: Hypoxemia, hypercapnia, and acidosis stimulate chemoreceptors causing widespread vasoconstriction, increases in BP, lung perfusion, and gas exchange; also stimulates breathing

84
Q

Describe the medullary ischemic reflex

A

Autonomic response to a drop in perfusion of the brain; Medulla oblongata monitors its own blood supply and activates corrective reflexes when ischemia is detected

85
Q

How does the medulla oblongata activate corrective reflexes

A

Cardiac and vasomotor centers send sympathetic signals to heart and blood vessels which increases heart rate and contraction force, causes widespread vasoconstriction, and raises BP and restores normal perfusion to the brain

86
Q

What is angiotensin II

A

A type of hormonal control that is a potent vasoconstrictor; it raises blood pressure by promoting Na+ and water retention by kidneys and increases blood volume and pressure

87
Q

What is aldosterone

A

Hormonal control that promotes Na+ retention by kidneys which promotes water retention; maintains BP

88
Q

What is Natriuretic peptide

A

Hormonal control that increases urinary sodium excretion by reducing blood volume and promoting vasodilation; lowers blood pressure

89
Q

What is ADH

A

Hormonal control that promotes water retention and raises BP

90
Q

What is epinephrine and norepinephrine

A

Hormonal control that causes most blood vessels to vasoconstrict except skeletal and cardiac muscle blood vessels that vasodilate

91
Q

What are two purposes of vasomotion?

A

Generalizes raising or lowering of BP throughout entire body; Selectively modifying perfusion of a particular organ and rerouting blood from one body region to another

92
Q

What are capillaries

A

only place where exchanges between blood and surrounding tissue occur

93
Q

Define capillary exchange

A

two-way movement of fluid across capillary walls; water, oxygen, glucose, amino acids, lipids, minerals, antibodies, hormones, wastes, carbon dioxide, ammonia

94
Q

Mechanisms for capillary exchange

A

Diffusion, transcytosis, filtration and reabsorption

95
Q

When can diffusion occur in capillary exchange

A

Only if solute can permeate plasma membrane of endothelial cell (lipid soluble); use filtration pores and intracellular clefts; Large particles such as proteins are held back

96
Q

Describe transcytosis in capillary exchange

A

Endothelial cells pick up material on one side of plasma membrane, transport vesicles cross cell, and discharge material on other side; important for fatty acids, albumin, and some hormones (insulin)

97
Q

Define filtration and reabsorption

A

Fluid filters out of arterial end of capillary and osmotically reenters at venous end

98
Q

Define hydrostatic pressure

A

physical force exerted against a surface (capillary wall) by a liquid (blood) that drives fluid out of a capillary; high on arterial end of capillary, low on venous end

99
Q

What are the opposing forces to hydrostatic pressure

A

Colloid osmotic pressure (COP) and Oncotic pressure

100
Q

What is COP

A

draws fluid into capillary; results from plasma proteins (albumins) - more in blood than surrounding tissue fluid

101
Q

What is oncotic pressure

A

net COP (blood COP - tissue COP); this pressure draws H20 into capillary by osmosis

102
Q

What is edema

A

Accumulation of excess fluid in a tissue; fluid filters into a tissue faster than it is reabsorbed

103
Q

What are the 3 primary causes of edema

A

Increased capillary filtration (kidney filtration, histamine release, old age, poor venous return), Reduced capillary reabsorption (hypoproteinemia, liver disease, dietary protein deficiency), and Obstructed lymphatic drainage or surgical removal of lymph nodes (fluid accumulation distal to obstruction)

104
Q

What are some consequences of edema

A

Tissue necrosis, pulmonary edema, cerebral edema, circulatory shock or severe edema

105
Q

What is venous return

A

flow of blood back to heart

106
Q

What are the mechanisms of venous return

A

Pressure gradient, Gravity, skeletal muscle pump, thoracic (respiratory) pump, and cardiac suction

107
Q

How does exercise increase venous return

A

Heart beats faster and harder, increasing CO and BP; Vessels of skeletal muscles, lungs and heart dilate to increase flow; increased respiratory rate, increased action of thoracic pump; increased skeletal pump

108
Q

What occurs with inactivity

A

Venous pooling - accumulation of blood in the limb

109
Q

What is circulatory shock

A

Any state in which cardiac output is insufficient to meet body's metabolic needs

110
Q

What are some examples of circulatory shock

A

Cardiogenic shock, Low venous return (hypovolemic shock, obstructed venous return shock, venous pooling shock), neurogenic shock, septic shock, anaphylactic

111
Q

What are the two types of responses to circulatory shock

A

Compensated shock and decompensated shock

112
Q

What is compensated shock

A

several homeostatic mechanisms bring about spontaneous recovery; example is fainting

113
Q

What is decompensated shock

A

Triggered when compensated shock mechanism fails; life-threatening positive feedback loop occurs; Condition gets worse causing damage to cardiac and brain tissue

114
Q

What is the brains role in its own regulation of BP and chemistry

A

Regulates its own blood flow to match changes in BP and chemistry

115
Q

What are transient ischemic attacks

A

brief episodes of cerebral ischemia caused by spasms of diseased cerebral arteries

116
Q

What is a CVA or stroke?

A

Sudden death of brain tissue caused by ischemia

117
Q

What is the state of arterioles in skeletal muscles at rest

A

Arterioles constrict, most capillary beds shut down

118
Q

What is the state of arterioles in skeletal muscles when exercising

A

Arterioles dilate in response to epinephrine and NE, precapillary sphincters dilate due to muscle metabolites like lactic acid, CO2, blood and flow can increase 20 fold

119
Q

Is capillary pressure high or low in the lungs

A

Low pulmonary pressure so that there is more time for has exchange

Anatomy & Physiology (6 decks)

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