Chapter 20 - Blood Vessels Flashcards

Question

What is the vascular shunt?

Answer 1

- Made of metarteriole and thoroughfare channel - Allow blood to be directly shunted to the venous side

Answer 2

Metarteriole, thoroughfare channel

Answer 3

- Larger venules have all 3 tunics - Companion vessels with arterioles - Formed when capillary beds unite - Very porous; allow fluids and WBC into tissues - Consists of endothelium and a few pericytes - Merge to form veins

Answer 4

- Pulmonary circulation ~18% - Heart ~ 12% - Systemic circulation ~70% --> 55% is within systemic veins

Answer 5

Flattened veins with extremely thin walls (ex: coronary sinus of the heart and dural sinuses of the brain)

Answer 6

- Has 1 artery, 1 capillary bed, and 1 vein - End arteries: Arteries that provide only one pathway through which blood can reach an organ

Answer 7

1.) Venous anastomoses 2.) Arterial anastomoses 3.) Arteriovenous anastomosis (shunt) 4.) Portal system

Answer 8

- Number of arteries, capillary beds, or veins

Answer 9

The joining together of blood vessels - Provide an alternative route in case a vessel is compressed or blocked - Arterial anastomosis is common in joints, abdominal organs, heart --> none in retina, kidneys, spleen - Vascular shunts of capillaries are examples of arteriovenous anastomoses

Answer 10

Other vessels (ex: coronary arteries) that are so small, the function of the arteries may almost be considered end arteries

Answer 11

- Includes 2 or more arteries converging to supply the same body region

Answer 12

- 2 or more veins draining into the same body region - There are more venous anastomoses than arterial anastomoses - Ex: veins that drain upper limb like basilic, brachial, and cephalic veins

Answer 13

- Transports blood from an artery directly into a vein, bypassing the capillary bed - In fingers, toes, palms, and ears --> allow these areas to be bypassed if the body is becoming hypothermic --> bypassing these structures makes them more vulnerable to frostbite

Answer 14

Diameter of the vessel's lumen

Answer 15

Aggregate lumen diameter across total number of a given type of blood vessel if they were positioned side by side - Measures area of lumen - Influences blood flow velocity

Answer 16

- Cross-sectional area --> relatively large - Total cross-sectional area --> Smallest

Answer 17

- Total cross-sectional area --> relatively small

Answer 18

- Cross-sectional area --> relatively large - Total cross-sectional area --> Largest (~60,000 miles or ~4,500cm^2)

Answer 19

- The rate of blood transported per unit time (cm/sec) - Inverse relationship between total cross-sectional area and blood flow velocity --> Capillaries with largest total cross-sectional area --> slowest flow - Changes as it moves through different vessel type --> Fastest in aorta; slowest in capillaries; increases in veins - Ex: flow of a narrow river = faster - Slower rate allows for sufficient time for capillary exchange between body tissues and blood

Answer 20

- Elastic arteries (e.g., aorta) → Fastest - Muscular arteries - Venae cavae - Veins - Arterioles - Venules - Capillaries → Slowest

Answer 21

Volume of blood flowing through vessel, organ, or entire circulation in given period - mL/min - Equivalent to cardiac output (CO- Amount of blood ejected from heart in 1 min) for entire vascular system - Constant at rest - Can vary through individual organs based on needs

Answer 22

Force per unit area exerted on wall of blood vessel by blood - mm Hg - Measured as systemic arterial BP in large arteries near heart - Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas --> BP is highest in arteries as heart contracts and lowest in veins - Measured indirectly by auscultatory method using a sphygmomanometer --> pressure increased in cuff until it exceeds systolic pressure in brachial artery --> pressure released slowly and examiner listens for sounds of Korotkoff (sounds of blood flow) with stethoscope

Answer 23

F = (Pressure of blood coming into vessel - Pressure of blood coming out vessel)/ Resistance = ΔP/ R

Answer 24

R = (Viscosity of blood x length of blood vessel)/ radius of blood vessel^4

Answer 25

- Radius of blood vessel

Answer 26

r^4 --> r^4/2 (bc half is blocked) --> r^4/2^4 = r^4/16 --> 16x less blood is getting to the area

Answer 27

- The friction blood encounters - Opposite to flow - Due to contact between blood and vessel wall

Answer 28

- Measure of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation - 3 sources of resistance 1.) Blood viscosity 2.) Total blood vessel length 3.) Blood vessel diameter (lumen size)

Answer 29

- Blood viscosity - Blood vessel length

Answer 30

- Resistance of blood to its flow --> the thickness of a fluid - The stickiness of blood due to formed elements and plasma proteins - Increased viscosity --> increased resistance - Depends on percentage of particles in fluid and their interactions --> anemic person has a lower blood viscosity and less resistance - Blood is ~5x more viscous (thicker) than water

Answer 31

- Longer vessel = greater resistance as friction occurs along the length - Weight gain or loss can change vessel length - Weight gain --> associated with angiogenesis (increased resistance) - Weight loss --> associated with vessel regression (decreased resistance)

Answer 32

- Greatest influence on resistance - Blood has laminar flow (different flow rate within vessel) --> flow is faster in center of lumen and slower new vessel wall - Varies inversely with fourth power of vessel radius --> F ∝ r^4 --> if radius is doubled, the resistance is 1/16 as much - Fatty plaques from atherosclerosis can increase resistance - Disrupt laminar flow and cause turbulent flow --> irregular fluid motion = increased resistance

Answer 33

- Blood flow (F) is directly proportional to blood pressure gradient (ΔP = systemic blood pressure gradient = P1-P2) divided by resistance = F ∝ ΔP/R - Systemic blood pressure gradient increases --> blood flow speeds up - R increases, blood flow decreases - F = ΔP/R - R more important in influencing local blood flow

Answer 34

Local blood flow: Blood delivered locally to the capillaries of a specific tissue (bc blood is directed where it is most needed) Dependent on... 1.) Degree of vascularization 2.) The myogenic response 3.) Local regulatory factors (vasoactive chemicals, autoregulation, etc.) 4.) Total blood flow

Answer 35

The contraction and relaxation of smooth muscle within blood vessels i response to changes in stretch of blood vessel wall - Can cause blood flow to be relatively constant - EX: Higher systemic BP --> increase in blood vessel --> increase in stretch of smooth muscle cell in vessel wall --> smooth muscle contract --> vasoconstriction

Answer 36

Vasoactive chemicals: The certain chemicals that change in concentration and stimulate regulation 1.) Vasodilators: substances that cause smooth muscle relaxation and results in vasodilation of arterioles and opening of precapillary sphincters --> increase blood flow into capillary bed 2.) Vasoconstrictors: Substances that cause smooth muscle contraction --> arterioles vasoconstrict and precapillary sphincters close --> blood flow decreases in capillary bed

Answer 37

The idea that a tissue regulates its local blood flow in response to its changing metabolic needs - Initial stimulation is typically inadequate perfusion because of increased metabolic activity of the tissue --> oxygen and nutrients are low and high level of CO2, H+, and K+ - Negative feedback loop controlled intrinsically by modifying the diameter of local arterioles feeding capillaries (independent of MAP, which is controlled as needed to maintain constant pressure) - Reactive hyperemia: A condition in which local blood flow is restored and there is an increase in blood flow to tissue --> ex: cheeks getting warm after cold - Short term regulation as part of the body defense system or because of damaged tissue (organs can also regulate their own blood flow by varying resistance of own arterioles) - Histamine (increases capillary permeability and causes vasodilation) and bradykinin are inflammatory mediators Two types that determine final autoregulatory response --> metabolic controls and myogenic controls

Answer 38

Local - Decreased O2 levels - Decreased nutrient needs - Increased CO2, H+, K+, and lactate levels - Histamine - Bradykinin - Nitric oxide - Prostaglandins Hormones and neurotransmitters - Atrial natriuretic peptide (ANP) - Epinephrine (bound to β2 receptors within coronary and skeletal muscle blood vessels)

Answer 39

Local - increased O2 levels - increased nutrient needs - decreased CO2, H+, K+, and lactate levels - Leukotrienes - Thromboxanes - Endothelins Hormones and neurotransmitters - Angiotensin II - Aldosterone - Antidiuretic hormone (ADH) - Norepinephrine and to a lesser extent epinephrine (bound to Local - Decreased O2 levels - Decreased nutrient needs - Increased CO2, H+, K+, and lactate levels - Histamine - Bradykinin - Nitric oxide - Prostaglandins Hormones and neurotransmitters - Atrial natriuretic peptide (ANP) - Epinephrine (bound to ⍺1 receptor in most blood vessels, including skin and abdominal organs)

Answer 40

Ventricular systole (contraction) when artery is maximally stretched (systolic pressure)

Answer 41

During ventricular diastole (relaxation) when artery recoils no further (diastolic pressure)

Answer 42

The additional pressure placed on the arteries when the heart is resting (diastolic bp) to when the heart is contracting (systolic bp) - Pulse pressure = Systolic bp - diastolic bp - A measure of the elasticity and recoil of arteries as it is a pressure wave caused by the expansion and recoil of arteries --> healthy arteries expand and recoil easily - Highest closest to the heart and decline with increasing distance - Radial pulse (taken at wrist) is commonly used - Pressure points where arteries close to body surface can be compressed to stop blood flow

Answer 43

- Pressure results when flow is opposed by resistance in the body - Highest in the aorta and declines throughout pathway - 0 mm HG in right atrium --> the end point where blood returns to the heart

Answer 44

1.) Elasticity (compliance or distensibility) 2.) Volume of blood forced into them at any time

Answer 45

Pressure exerted in aorta during ventricular contraction - About 120 mm Hg or less in normal adult - Pressure when sounds first occur as blood starts to spurt through artery - Artery is maximally stretched during ventricular systole

Answer 46

Lowest level of aortic pressure - Normally less than 80 mm Hg - Pressure when sounds disappear because artery is no longer constricted and recoils no further in ventricular diastole --> blood flowing freely

Answer 47

Throbbing of arteries

Answer 48

The average measure of BP in the arteries - Pressure that propels blood to tissues MAP = Diastolic pressure + (1/3) pulse pressure - Decline with increasing distance from heart Ex: BP= 120/80 --> MAP= 80 + ((1/3)x(120-80)) --> 80+(1/3)(40) --> 93 mm Hg - Takes into account the fact that diastolic pressure usually lasts slightly longer than systolic pressure - Numeric value for how well body tissues and organs are perfused --> high MAP value --> possible edema - During stress, cardioacceleratory center increases heart rate and stroke volume via sympathetic --> ESV decreases and MAP increases

Answer 49

- Ranges from 17 to 35 mm Hg - By the time the blood preaches capillaries, fluctuations between systolic and diastolic BP disappear - ~40 mm Hg on atrial end of capillary - ~20 mm Hg on venous end of capillary - Venous and atrial end pressure of capillary is used to determine net filtration pressure for capillary exchange

Answer 50

- changes little during cardiac cycle - Small pressure gradient (~15 mm Hg) - Low pressure bc of cumulative effects of peripheral resistance --> bp energy lost as hear during each circuit --> ~20 mm Hg in venules and almost 0 mm Hg by the time the blood is transported through the IVC - Venous return of blood to the heart depends on... 1.) Pressure gradient 2.) Skeletal muscle pump 3.) Reparatory pump

Answer 51

Contraction of skeletal muscles "milks" blood toward heart - Valves prevent blood backflow - Assists with movement of blood primarily within limbs - Circulates blood faster and more efficiently when more active - Extended inactivity --> blood pooling --> higher risk for deep vein thrombosis

Answer 52

- Pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand - Assists with movement of blood within thoracic cavity

Answer 53

Sympathetic control

Answer 54

1.) Cooperation of heart, blood vessels, and kidneys 2.) Supervision by brain

Answer 55

1.) Cardiac output (CO) 2.) Peripheral resistance (PR) 3.) Blood volume

Answer 56

- Autonomic reflexes involving nuclei within the medulla oblongata

Answer 57

- Within medulla oblongata

Answer 58

Cardiac center --> Regulates heart activity and cardiac output 1.) Cardioacceletory center: Sympathetic division pathways extend from the cardioacceletory center to both SA and AV node --> causes release of NE from ganglionic neurons --> increases firing rate of SA and shortens the AV delay - Also extends to myocardium to cause more forceful contractions and increase stroke volume 2.) Cardioinhibitory center: Parasympathetic decreases heart rate --> CO decreases - Doesn't extend to myocardium Vasomotor center: Controls degree of vasoconstriction/dilation --> thus, resistance - Unlike the heart, blood vessels don't have dual innervation and are typically only innervated by sympathetic division --> sends steady impulses via sympathetic efferents to blood vessels - NE released from ganglionic neurons here - Recieves input from baroreceptors, chemoreceptors, and higher brain centers

Answer 59

- Carotid sinus - aortic arch - within right atrium

Answer 60

- Carotid body - Aortic body

Answer 61

- Specialized sensory nerve endings that respond to stretch - Increased blood pressure stimulates baroreceptors to increase input to vasomotor center --> inhibits vasomotor and cardioacceleratory centers to cause arteriole dilation and venodilation --> stimulates cardioinhibitory center - If MAP is low --> reflex vasoconstriction --> increased CO --> increased blood pressure

Answer 62

- Within each carotid artery, near artery's initial bifurcation - Transmit nerve signals to cardiovascular center through glossopharyngeal nerve (CN IX - 9) - Monitor bp changes in head and neck and are more sensitive to changes than those in arch - Best for short term changes

Answer 63

Peripheral sensory receptor or specialized cells that detect specific chemicals in fluid - Most important in regulating repsoration - Negative feedback loop - Stimulated by high CO2 levels, low pH, and very low O2 levels - Increased firing stimulates vasomotor center --> increases nerve signals along sympathetic pathways to blood vessels --> increases resistance and venous return --> bp and blood flow increase and blood flow to lungs for gas exchange --> blood gas levels return to normal - Causes increase in bp by signaling cardioacceletory center --> increase CO and also signaling vasomotor center --> increase vasocontriction

Answer 64

- At the bifurcation of each common carotid as it splits into an external carotid and internal carotid artery - Sends sensory input to cardiovascular center via glossopharyngeal nerve (CN IX - 9)

Answer 65

- Sends sensory input to cardiovascular center via vagus nerve (CN x -10)

Answer 66

- Transmit nerve signals to the cardiovascular center through vagus nerve (CN x -10) - Helps regulate systemic bp - best for short term change

Answer 67

- Subtypes of receptors in the smooth muscle cells within tunica media

Answer 68

- Contract in response to NE --> vasoconstriction - Most blood vessels in the body

Answer 69

- Relax in response to epinephrine --> vasodilation - Ex: coronary arteries and arteries supplying skeletal muscle

Answer 70

1.) Increased peripheral resistance as vessels constrict since there are more with ⍺1 than β2 2.) Larger circulating blood volume --> vasoconstriction of veins shifts blood from venous reservoirs 3.) Redistribution of blood flow --> More blood flow reaches skeletal muscle and heart

Answer 71

- BP measures cardiovascular --> Heart + blood vessels BP = CO x PR - CO depends on blood volume

Answer 72

- CO x SV x HR - SV controlled by venous return (EDV) --> affected by preload, contractility with Ca2+, and afterload - Normal = 5.0 - 5.5 L/min - Determined by venous return, and neural and hormonal controls - Resting heart rate maintained by cardioinhibitory venter via parasympathetic vagus nerves

Answer 73

- Neural controls of peripheral resistance - Maintain MAP by altering blood vessel diameter --> if low blood volume all vessels constrict except those in heart and brain and alters blood distribution - Operate via reflex arcs that involve... 1.) Baroreceptors 2.) Cardiovascular center of medulla 3.) Vasomotor fibers to heart and vascular smooth muscle 4.) Sometimes input form chemoreceptors and higher brain centers

Answer 74

Counteract fluctuations in blood pressure by altering peripheral resistance and CO - Neural controls - Hormonal controls

Answer 75

- Reflexes in medulla - Hypothalamus and cerebral cortex can modify arterial pressure via relays to medulla - Hypothalamus increases blood pressure during stress - Hypothalamus mediates redistribution of blood flow during exercise and changes in body temperature

Answer 76

- Via changes in peripheral resistance and cardiac output - Cause increased np - Epinephrine and norepinephrine from adrenal gland --> increased CO and vasoconstriction - Anginotensin II stimulates vasoconstriction - High ADH levels causes vasoconstriction - Atrial natriuretic peptide causes decreased blood volume by antagonizing aldosterone

Answer 77

- Natrium = sodium - Helps put Na+ in urine --> wherever Na+ goes, water will follow - Stimulates vasodilation --> decrease peripheral resistance - Increases urine output --> decreases bp

Answer 78

- Counteracts fluctuations in blood pressure by altering blood volume via kidneys - Baroreceptors quickly adapt to chronic high or lo bp so are ineffective - Kidneys regulate arterial blood pressure --> direct renal mechanism and incirect renal (renin-angiotensin-aldosterone) mechanism

Answer 79

- Alters blood volume independently of hormones - Increased BP or blood volume causes elimination of more urine --> reduces BP - Decreased BP or blood volume causes kidneys to conserve water --> BP rises and MAP rises

Answer 80

1.) Kidney receptors detect low blood pressure or are stimulated by the sympathetic decision - Renin enzyme is released from the kidney 2.) Renin converts angiotensinogen into angiotensin I - Angiotensinogen: A plasma protein that is continuously produced by the liver and circulates within the blood --> an inactive hormone 3.) ACE (Anginotensin Converting Enzyme- enxyme in capillaries of the lung) converts angiotensin I (an inactive hormone) into Angiotensin II (active hormone) - Most conversion occurs within blood vessels of lungs 4.) Angiotensin II increases blood pressure by... - Causing vasoconstriction --> thus, increase in peripheral resistance and increase bp - Stimulating thirst center within hypothalamus --> an increase in fluid intake is an increase in BP - Decreasing urine formation through the stimulus of aldosterone and antidiuretic hormone --> Aldosterone increases absorption of Na+ and water in kidney while ADH increases water absorption in kidney

Answer 81

- Blood flow changes from 5.25 L/mm --> 17.5 L/mm - Blood flow to coronary arteries of heart increase by 3-fold for sufficient O2 (250 --> 750 mL/min) - Skeletal muscle blood flow increases by 11-fold (1,100 --> 12,500 mL/min) - Percent of blood flow to skin increases to almost 5x resting level (400 mL -->1,900 mL/min) to dissipate heat - Less total blood flow distributed to abdominal organs

Answer 82

Increase - Brain - Heart - Skin - Skeletal muscles Decrease - Kidney - Abdominal organs - Other (400 mL/min)

Answer 83

- Pulse and blood pressure, along with respiratory rate and body temperature

Answer 84

- Delivery of O2 and nutrients to, and removal of wastes from, tissue cells - Gas exchange (lungs) - Absorption of nutrients (digestive tract) - Urine formation (kidneys)

Answer 85

- Vasodilation of arterioles and relaxation of precapillary sphincters occur in response to declining tissue O2 or substances from metabolically active tissues (H+, K+, adenosine, and prostaglandins) and inflammatory chemicals - Causes relaxation of vascular smooth muscle - Causes release of Nitric Oxide (a powerful vasodilator) by endothelial cells - Endothelins released from endothelium are potent casoconstritors - NO and endothelins balanced unless blood flow inadequate, then NO wins

Answer 86

- Myogenic responses keep tissue perfusion constant despite most fluctuations in systemic pressure - Vascular smooth muscle responds to stretch 1.) Passive stretch: Increased intravascular pressure --> promotes increased tone and vasoconstriction 2.) Reduced stretch --> promotes vasodilation and increases blood flow to the tissue

Answer 87

- Occurs when short-term autoregulation can't meet tissue nutrient requirements - Include angiogenesis

Answer 88

When the number of vessels to a region increases and existing vessels enlarge - Common in heart when coronary vessel occluded, or throughout body in people in high-altitude areas - Over weeks to months to increase potential perfusion - Ex: skeletal muscle (bc of aerobic training), adipose tissue (weight gain), coronary vessels (blockage)

Answer 89

Blood flow through capillaries - Slow, intermittent flow - Reflects on/off opening and closing of precapillary sphincters

Answer 90

1.) Diffusion 2.) Vesicular transport 3.) Bulk flow (filtration/reabsorption)

Answer 91

Random movement of molecules down concentration gradient - Move from high concentration in the blood into ISF and then into tissue cells where the concentration is lower - O2 and nutrients --> Blood to tissues - CO2 and metabolic wastes --> from tissue to blood - Lipid-soluble molecules diffuse rectly through endothelial membranes - Very small solutes (water-soluble solutes) (O2,CO2, glucose, ions, et.c) and fluids may diffuse via the endothelial cells or intercellular clefts - Larger solutes (water-soluble solutes) (ex: small proteins) must pass through the fenestrations in fenestrated capillaries or gaps in sinusoids - Larger molecules (ex: larger proteins) are actively transported in pinocytotic vessels (small membrane-bound sacs in endothelial cells that transport stuff across cell via a type of endocytosis called pinocytosis) or caveolae

Answer 92

Occurs when endothelial cells use pinocytosis to form fluid-filled vesicles and those are transported to the other side fo the cells and released by exocytosis - Substances may be moved either from the blood into the ISF or vise versa - Used by larger solutes (ex: insulin)

Answer 93

The movement of large amounts of fluids and their dissolved substances in one direction down a pressure gradient - Important in determining relative fluid volumes in blood and interstitial space - Direction and amount of fluid flow depend on two opposing forces --> hydrostatic and colloid osmotic pressures Two main types: 1.) Filtration: A process that occurs on the arterial end of a capillary in which the fluid bulk flows out of the blood through the openings of capillaries (ex: intracellular clefts, fenestrations) - Fluids and small, dissolved solutes flow through easily - Formed elements and proteins are generally blocked 2.) Reabsorption: Occurs at venous end of a capillary and is the movement of fluid by bulk flow in the opposite direction --> back into blood

Answer 94

Physical force exerted by a fluid on a structure - Can include blood hydrostatic pressure (HPb)/ blood pressure: Force exerted per unit area by the blood as it presses against the internal surface of the vessel wall - Promotes filtration from the capillary - Main hydrostatic pressure 1.) Capillary hydrostatic pressure (HPc) (capillary blood pressure) - Tends to force fluids through capillary walls - Greater at arterial end (35 mm Hg) of bed than at venule end (17 mm Hg) 2.) Interstitial fluid hydrostatic pressure (HPif): The force of the interstitial fluid on the external surface of the blood vessel - Pressure that would push fluid into the vessel - Usually assumed to be 0 because of lymphatic vessels

Answer 95

Refers to the pull of water back into a tissue by the tissues concentration of proteins (colloid) - Blood colloid osmotic pressure (COPb): The force that draws fluid back into the blood due to proteins in the blood (ex: albumin) - Opposes hydrostatic pressure --> COP promotes reabsorption - Ranges from 26 - 28 mm Hg - Also called oncotic pressure 1.) Capillary colloid osmotic pressure/ oncotic pressure (OPc) --> Created by non diffusible plasma proteins, which draw water toward themselves - ~26 mm Hg 2.) Interstitial fluid osmotic pressure (OPif) - Low (~1 mm Hg) due to low protein content - Can range from ~ 0-5 mm Hg

Answer 96

- NFP comprises all forces acting on capillary bed --> based on idea that hydrostatic and osmotic forces work against one another to regulate filtration and reabsorption of materials in capillary wall - NFP = (HPc - HPif) - (OPc - OPif) - Difference between net hydrostatic pressure (bw blood and ISF) and net colloid osmotic pressure (bw blood and ISF) - Net fluid flow out at arterial end - Net fluid flow in at venous end - More leaves than is returned - Excess fluid is returned to blood via lymphatic system --> capillary only absorbs ~ 86% of fluid that's passed from blood to ISF --> lymphatic picks up excess 15% and returns it to blood after filtering - If NFP at venous end is (-) --> reabsorption is occurring so fluid moves from ISF into capillary - If NFP is (+) --> outward pressure

Answer 97

Pulmonary circulation: Short loop that runs from heart to lungs and back to heart - Pulmonary trunk divides into L and R pulmonary artery --> divide into smaller arteries and then form arterioles - CO2 diffuses from blood --> alveoli (air sacs) - O2 moves from alveoli --> blood - Capillaries drain into venules and then pulmonary veins - Pulmonary arteries have less elastic connective tissue and wider lumens than systemic arteries - Compared to systemic circulation, pulmonary vessels are short with less resistance to blood flow because lungs are closer to heart --> lower bp Systemic circulation: Long loop to all parts of body and back to heart

Chapter 20 - Blood Vessels Flashcards

(121 cards)