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154 Cards in this Set
- Front
- Back
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Arteries
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Carry blood away from the heart
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Arteries are oxygenated except for
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pulmonary circulation and umbilical vessels of fetus
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Structure of Arteries
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3 tunics: 1) Tunica Intima
2) Tunica Media 3) tunica Externa |
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Elastic (conducting) Arteries
Structure |
Large Lumen=low resistance
Elastin in all 3 tunics large, thick walled |
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Elastic (conducting) Arteries
Function |
Act as pressure reservoirs
expand and recoil as blood is ejected from heart |
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Muscular (distributing) Arteries
Structure |
thick tunica media with more smooth muscle
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Muscular (distributing) Arteries
Function |
deliver blood to body organs
active in vasoconstriction |
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Define Arterioles
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Smalles Arteries, lead to capillary beds
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Arterioles
Function |
control flow into capillary beds via vasodilation and vasoconstriction
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Define Capillaries
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microscopic blood vessels that contact tissue cells and directly serve cellular needs
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Capillaries Function
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exchange of gases, nutrients, wastes and hormones
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Capillaries Structure
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Thin tunica intima
1 cell thick basal lamina pericytes stabalize walls and control permeability |
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Capillaries are found
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everywhere except cartilage, epithelia, cornea and lens
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Continous Capillaries Structure
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tight junctions connect endothelial cells
intercellular clefts allow passage of fluids and small solutes |
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Continous Capillaries Location
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abundant in skin and muscles
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Fenestrated Capillaries structure
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some endothelial cells contain pores
more permeable than continuous capillaries |
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Fenestrated Capillaries Function
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absorption or filtrate formation in small intestines, endocrine glands and kidneys
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Sinusoidal Capillaries Structure
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fewer tight junctions, larger intercellular clefts, large lumens
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Sinusoidal Capillaries Function
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allow large molecules and blood cells to pass between blood and surrounding tissue of liver, bone marrow and spleen
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Define Capillary beds
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interwoven networks of capillaries from the microcirculation between areterioles and venules
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2 types of vessels in capillary beds
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1) Vascular Shunt
2) True Capillaries |
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Vascular Shunt
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directly connects the terminal areteriole and a postcapillary venule
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True Capillaries
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10-100 exchange vessels per capillary bed branch off the metarteriole or terminal arteriole
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Precapillary Sphincters
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regulate blood flow into true capillaries
regulated by local chemcial conditions and vasomotor nerves |
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Venules
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formed when capillary beds unite
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Venules Structure
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very porous
post capillary venules consist of endothelium and a few pericytes larger venules have 1 or 2 layers of smooth muscle cells |
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Venules Function
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allow fluids and WBC's into tissues
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Veins formed when
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venules converge
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Veins Structure
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thinner walls, larger lumens than arteries
thin tunica media and thick tunica externa made of collagen fibers and elastic networks |
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Veins, Adaptations that ensure return of blood to heart
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1) larger diameter lumens offer little resistance
2) Valves prevent backflow |
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Venous Sinuses
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flattened veins with extremely thin walls
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Define Vascular Anastomoses
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interconnections of blood vessels
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Vascular Anastomoses Locations
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not found in retina, kidneys, and spleen
common in abdominal organs, brain and heart |
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Arterial Anastomoses
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provide alternate pathways to a given body region
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Examples of Areteriovenous anastomoses
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vascular shunts of capillaries
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Define Blood Flow
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volume of blood flowing through a vessel an organ or the entire circulation in a given period
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Blood flow measured as
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ML/Min
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blood flow equivalent to
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Cardiac Output (CO) the amount of blood pumped out by the ventricles in a given period of time
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Blood flow varies_________
Constant________ |
through organs
at rest |
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Define Blood Pressure
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force per unit area exerted on the wall of a blood vessel by the blood
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Blood Pressure Expressed as
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mm HG
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Pressure Gradiant
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provides the driving force that keeps blood moving from higher to lower pressure areas
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Define Resistance
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opposition to flow
measure of the amount of friction blood encounters |
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Resistance location
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generally found in the peripheral systemic circulation
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3 Sources of Resistance
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1) Blood Viscosity-"stickiness" of blood, formed elements, and plasma proteins
2) Total blood vessel length-longer the vessel, the greater the resistance 3) Blood vessel diameter- varies inversly w/ 4th power of vessel radius |
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Major determinants of peripheral resistance?
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Small diameter arterioles
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Blood Flow (F) relationship to Blood pressure gradiant
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directly proportional
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If Blood pressure gradiant increases, (F)
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Blood Flow decreases
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Blood flow is ______ to peripheral resistance (R)
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Inversly
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If (R) increases blood flow
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decreases
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(F)=
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P/R
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(R) is more important in influencing local blood flow because
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it is easily changed by altering blood vessel diameter
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Systemic Blood Pressure results when Flow is
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opposed by resistance
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Systemic Blood Pressure is highest in the
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aorta
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Systemic blood pressure is 0 mm Hg where
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right atrium
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Steepest drop of systemic blood pressure occurs where
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arterioles
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Arterial blood pressure reflects 2 factors
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1) Elasticity of arteries close to heart
2) Volume of blood forced into them at any time |
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Blood pressure near heart is
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pulsatile
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Systolic Pressure
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pressure exerted during ventricular contraction
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Diastolic Pressure
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lowest level of areterial pressure
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Blood Pressure Expressed as
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mm HG
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Pressure Gradiant
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provides the driving force that keeps blood moving from higher to lower pressure areas
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Define Resistance
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opposition to flow
measure of the amount of friction blood encounters |
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Resistance location
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generally found in the peripheral systemic circulation
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3 Sources of Resistance
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1) Blood Viscosity-"stickiness" of blood, formed elements, and plasma proteins
2) Total blood vessel length-longer the vessel, the greater the resistance 3) Blood vessel diameter- varies inversly w/ 4th power of vessel radius |
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Major determinants of peripheral resistance?
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Small diameter arterioles
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Blood Flow (F) relationship to Blood pressure gradiant
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directly proportional
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If Blood pressure gradiant increases, (F)
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Blood Flow decreases
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Blood flow is ______ to peripheral resistance (R)
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Inversly
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If (R) increases blood flow
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decreases
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Pulse Pressure
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difference between systolic and diastolic pressure
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Mean Arterial Pressure (MAP)
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pressure that propels the blood to the tissues
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Equation for MAP
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MAP=Diastolic pressure + 1/3 pulse Pressure
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Pulse Pressure and Map both decline
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with increasing distance from the heart
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Capillary Blood pressure ranges from
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15-35 mm Hg
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High capillary BP would
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rupture thin walled capillaries
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Venous Blood pressure measures about
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15 mm Hg
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Venous Blood pressure changes
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little during cardiac cycle
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3 Factors Aiding in Venous Return
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1) Respiratory Pump
2) Muscular Pump 3) Vasoconstriction of Veins under sympathetic control |
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Respiratory Pump
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pressure changes created during breathing move blood toward the heart by squeezing abdominal veins as thoracic veins expand
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Muscular Pump
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contraction of muscles "milk" blood toward the heart and valves prevent backflow
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Maintaining blood pressure requires:
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cooperation of the heart, blood vessels, and kidney supervision by the brain
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Main Factors influencing BP
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Cardiac Output
Peripheral Resistance Blood Volume |
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F=
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P/R
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CO=
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P/R
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BP=
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CO x R
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BP varies directly with
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CO, R and blood volume
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Cardiac Output determined by
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Venous return and neural, hormonal controls
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Resting heart rate is maintained by
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the cardioinhibitory center via the parasympathetic vagus nerve
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Stroke Volume controlled by
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Venous Return
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During stress the cardioaccelaratory center
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increases heart rate and stroke volume via sympathetic stimulation'; ESV decreases and MAP increases
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Define Vasomotor Center
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cluster of sympathetic neurons in the medulla that oversee changes in blood vessel diameter
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Vasomotor Center Function
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maintains vasomotor tone
receives inputs from baroreceptors, chemoreceptors, and higher brain centers |
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Control of BP
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Short term-Nerual and Hormone Controls
Long Term-Renal Regulation |
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Short term-Nerual and Hormone Controls
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counteract fluctuations in blood pressure by altering peripheral resistance
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Long Term-Renal Regulation
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counteracts fluctuations in blood pressure by altering blood volume
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Neural Controls of BP
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maintain MAP by altering blood vessel diameter
alter blood distribution in response to specific demands |
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Neural Controls of BP operate via
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reflec arcs that involve baroreceptors
vasomotor centers vasomotor fibers vascular smooth muscles |
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Baroreceptor Initiated Reflexes location
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carotid sinus
aortic arch walls of large arteries of neck and thorax |
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Baroreceptors: Increased BP
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stimulates baroreceptors to increase input to the vasomotor center which inhibits the vasomotor center, causing arteriole dilation and venodilation
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Baroreceptors: Decrease BP
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inhibits baroreceptors to stimulate cardioacceleratory center, causing increased CO and vasoconstriction
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Baroreceptors in the carotid sinues reflex
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protect the blood supply to the brain
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Baroreceptors in the aortic reflex
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help maintain adequate blood pressure in the systemic circuit
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Chemoreceptor Initiated Reflex
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chemoreceptors respond to rise in CO2, drop in pH or O2
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Chemoreceptors located in
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carotid sinus, aortic arch, large arteries of the neck
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Chemoreceptors Increase BP via
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vasomotor center and cardioacceleratory center
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Hormonal Controls of BP:
Norepinephrine and Epinephrine |
cause generalized vasoconstriction and increase cardiac output
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Hormonal Controls of BP:
Angiotensin II |
generated by kidney release of renin, cause vasoconstriction
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Hormonal Controls of BP:
Atrial Natriuretic Peptide |
causes blood volume and BP to decline, causes generalized vasodilation
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Hormonal Controls of BP:
Antidiuretic Hormone |
causes intense vasoconstriction in cases of extremely low BP
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Influence of Higher Brain Centers:
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higher brain centers can modify BP via relays to medullary centers
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Long Term Mechanism:
Renal Regulation |
step in to control BP by altering blood volume
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Long Term Mechanism:
Renal Regulation Increased BP |
leads to elimination of water
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Long Term Mechanism:
Renal Regulation Decreased BP |
leads to retention of water
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Renin-Angiotensin Mechanism
5 Steps |
1) decreased arterial BP causes renin release
2) renin causes production of angiotensin II 3) angiotensin II causes aldosterone secretion 4) aldosterone causes renal reabsorption of NA and decreases urine formation 5) angiotensin II stimulates ADH release |
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Blood pressure peaks
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in the morning due to hormone levels
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Vital signs
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pulse
blood pressure respiratory rate body temperature |
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Pulse
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pressure wave caused by the expansion and recoil of arteries
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Measuring blood pressure
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pressure is increased in cuff of sphygmomanometer until it exceeds systolic pressure in brachial artery
pressure released slowly and examiner listens for sounds of Korotkoff with stethoscope sounds first occur as blood starts to spurt through the artery, sounds disappear when the artery is no longer constricted and blood is flowing freely |
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Hypotension
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low blood pressure
Systolic < 100 mm Hg |
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Orthostatic Hypotension
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temporary low BP and dizziness when suddenly rising from a sitting or reclining position
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Chronic Hypotension
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hint of poor nutrition and warning sign for Addisons diseas or hypothyroidism
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Accute Hypotension
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important sign of circulatory shock
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Hypertension
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high blood pressure
>140/90 |
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Hypertension can occur with
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fever, physical exertion or emotional upset
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Prolonged hypertension major cause of
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heart failure, vascular disease, renal failure, and stroke
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Elevated diastolic pressure indicates
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progressive occlusion
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Primary/Essential Hypertension causes
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Hereditary, diet, Obesidy, age, stress, diabetes mellitus, and smoking
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Secondary Hypertension causes
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kidney disease, arteriosclerosis, hyperthyroidism and cushings syndrome
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Blood flow involved in
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delivery of O2 and nutrients
removal of wastes from tissue gas exchange (lungs) absorption of nutrients (digestive tract) Urine formation (kidneys) |
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Velocity of blood flow changes
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as it travels through the systemic circulation
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Velocity of blood flow is fastest
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in the aorta
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Velocity of blood flow is slowest
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in the capillaries
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Slow capillary flow allows for
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adequate time for exchange between blood and tissues
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Autoregulation
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automatic adjustment of blood flow to each tissue in proportion to its requirements at any given point in time
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Autoregulation is controlled how
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intrinsically by modifying the diameter of local arterioles feeding the capillaries
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2 types of Autoregulation
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Metabolic
Myogenic |
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Autoregulation: Metabolic Effects
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relaxation of vascular smooth muscle
release of NO from vascular endothelial cells |
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NO is the major factor causing
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vasodilation
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Long Term Autoregulation: Angiogenesis
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# of vessels to a region increases and existing vessels enlarge
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Angiogensis common in cases of
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occluded vessel
people who live in high altitude areas |
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How are lipid soluble molecules, water soluble molecules, and larger molecules exchanged through capillaries
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1) Lipid soluble diffuse directly through endothelial membranes
2) Water soluble pass through clefts and fenestrations 3) Larger molecules actively transported in pinocytic vescicles or caveole |
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Capillary Colloid Osmotic Pressure OPc
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Created by nondiffusable plasma proteins which draw water toward themselves
26 mm Hg |
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Interstitial fluid Osmotic Pressure
OPif |
low 1 mm Hg to low protein content
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Net Fitration Pressure
NFP |
comprises all the forces acting on a capillary bed
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NFP equation
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NFP=(HPc - HPif) - (OPc - OPif)
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At the arterial end of a capillary bed what forces dominate
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Hydrostatic
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At the Venous end of a capillary bed what forces dominate
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Osmotic
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Excessive fluid in capillary beds returned to blood via
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lymphatic system
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Circulatory Shock
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any condition in which blood vessels are inadequately filled or blood cannot circuilate normally
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3 Types of circulatory shock
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1) Hypovolemic Shock
2) Vascular Shock 3) Cardiogenic Shock |
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Hypovolemic Shock
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resultrs from large scale blood loss
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Vascular Schock
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results from extreme vasodilation and decreased peripheral resistance
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Cardiogenic Shock
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results when inefficient heart cannot sustain adequate circulation
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