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Home , Arteriole, Vascular resistance, Vasoconstriction, Venule

Over 60,000 Cardiovascular System – Vessels miles of vessels Cardiovascular System: Vessels Vessel Anatomy: per human body (branch / diverge / fork)

Elastic Muscular Arteries

Vessel Types: (nutrient 1) Arteries (away from heart) exchange) 2) Capillaries 3) (toward heart)

Veins

(join / merge / converge)

Cardiovascular System – Vessels Cardiovascular System – Vessels

Blood Vessel Anatomy: Anatomy: Only tunic present in capillaries Vessels composed of distinct tunics :

O2-rich; CO2-poor 1) Pulmonary circuit Tunica intima • (simple squamous epithelium) (short, low pressure loop) • ( elastic fibers) O2-poor; CO2-rich (long, high pressure loop) 2) Systemic circuit • / elastic fibers • Regulates pressure / circulation • Sympathetic innervation Lumen O2-poor; O2-rich; Vasa CO2-rich CO2-poor 3) vasorum • Loose collagen fibers • Nerves / & blood vessels • Protects / anchors vessel % / volume not fixed: Function: • Alteration of size 1) Circulate nutrients / waste • Alteration of stimulation = Tunica media 2) Regulate • Combination of two above Vasomotor relaxation = Tunica externa Costanzo (Physiology, 4th ed.) – Figure 4.1

Cardiovascular System – Vessels Relative tissue Cardiovascular System – Vessels Relative tissue

makeup makeup

Blood Vessel Anatomy: Blood Vessel Anatomy:

Arteriosclerosis:

Arteries: Hardening / stiffening of arteries Capillaries:

Endothelium Endothelium

Elastic tissue Elastic tissue Elastic

Fibrous tissue Fibrous tissue Fibrous Smooth muscle Smooth Major groups: muscle Smooth D = Diameter T = Thickness 1) Capillaries: 1) Elastic Arteries (conducting arteries): D: 9.0 m D: 1.5 cm • Location of blood / tissue interface T: 1.0 m • Large, thick-walled (near heart) T: 1.0 mm • Stabilized by (smooth muscle cells) •  [elastic fibers] (pressure reservior) Types of Capillaries: 2) Muscular Arteries (distributing arteries): • Deliver blood to organs D: 6.0 mm T: 1.0 mm •  [smooth muscle] (vasoconstriction)

3) Arterioles: • Control blood into capillaries D: 37.0 m T: 6.0 m A) Continuous 2) Fenestrated 3) Sinusoidal: • Neural / hormonal / local controls • Uninterrupted lining • Oval pores present • Holes / clefts present • Found throughout body • Located in high absorption / • Allow passage of large (most common type) filtration regions (e.g., ) molecules (e.g., liver)

Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Table 19.1 Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Table 19.1 / Figure 19.3

1 Cardiovascular System – Vessels Cardiovascular System – Vessels Relative tissue makeup

Blood Vessel Anatomy: Blood Vessel Anatomy:

Leukocyte

Capillaries: Veins: margination

Capillaries do not function independently – Instead they

Endothelium

Elastic tissue Elastic Fibrous tissue Fibrous Major groups: muscle Smooth form interweaving networks called beds 1) Venules: Vascular True capillaries Not all capillaries are perfused D: 20.0 m shunt with blood at all times… • Formed where capillaries unite T: 1.0 m • Extremely porous

2) Veins (capacitance vessels): D: 5.0 mm • Large lumen; “volume” sink T: 0.5 mm • Low pressure environment

Terminal Postcapillary Precapillary sphincters Venous sinuses: arteriole Specialized, flattened veins • 10 - 100 capillaries / bed • Sphincters control blood flow composed only of endothelium; supported by surrounding tissues a) Vascular shunt through capillary bed b) True capillaries Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 19.4 Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figures 19.3 / 19.5

Cardiovascular System – Vessels Vascular anastomoses: Blood Vessel Anatomy: Regions where vessels unite, forming interconnections

Heart Heart

Venous anastomoses are common; blockages collateral rarely lead to tissue death Arteriovenous channels anastomosis Arterial anastomoses provide alternative channels for blood to reach locations • Joints • Abdominal organs • Brain

Retina, , & kidney have Great saphenous limited collateral circulation vein harvest Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 19.2

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must Would you want be kept moving… Pathophysiology: Most common form to find this pipe : of in your house?

Atherosclerosis: Blood Flow: Formation of (small, patchy thickenings) Volume of blood flowing past a on wall of vessel; intrude into lumen point per given time (ml / min)

1) Endothelium injured 3) Fibrous plaque forms The velocity of blood flow is not related to proximity of heart, but depends • Infection / • Collagen / elastin fibers on the diameter and cross-sectional area of blood vessels deposited around dying or 2) Lipids accumulate / oxidize dead foam cells • LDLs collect on tunica intima 4) Plaque becomes unstable Foam cells: • Calcium collects in plaque v = Q / A Macrophages engorged • Vessel constricts; arterial wall with LDLs; form frays / ulcerates (= thrombus) v = Velocity (cm / sec)

Link Q = Flow (mL / sec) Outcome: A = Cross-sectional area (cm2) Statins: • Myocardial -lowering 2 drugs • A = r • Angioplasty / Stent Bypass surgery Costanzo (Physiology, 4th ed.) – Figure 4.4

2 Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must Hemodynamics: be kept moving… v = Q / A

Blood Flow: A man has a cardiac output of 5.5 L / Volume of blood flowing past a min. The diameter of his is point per given time (ml / min) estimated to be 20 mm, and the total cross-sectional area of his systemic capillaries is estimated to be 2500 cm2. The velocity of blood flow is not related to proximity of heart, but depends on the diameter and cross-sectional area of blood vessels What is the velocity of blood flow in the aorta relative to the velocity v = Q / A of blood flow in the capillaries? Blood velocity is highest in the aorta cm3 (1 cm) and lowest in the A = r2 A = (3.14) (10 mm)2 A = 3.14 cm2 capillaries Capillaries (5500 mL) Vein 5.5 L / min 5500 cm3 / min vcapillaries = vaorta = 2500 cm2 3.14 cm2 800x difference

vcapillaries = 2.2 cm / min vaorta = 1752 cm / min Randall et al. (Eckert Animal Physiology, 5th ed.) – Figure 12.23

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

Blood flow through a blood vessel or a series of blood vessels is Heart determined by blood pressure and peripheral resistance generates initial pressure

Blood Pressure: Force per unit area on wall of vessel (mm Hg)

• The magnitude of blood flow is directly proportional to the size of the pressure difference between two ends of a vessel

Blood Flow (Q) = Difference in blood pressure ( P)

• The direction of blood flow is determined by the direction of the pressure gradient Vessel resistance generates Always moves from high to low pressure pressure gradient

Costanzo (Physiology, 4th ed.) – Figure 4.8

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

Blood flow through a blood vessel or a series of blood vessels is (difference in voltage) determined by blood pressure and peripheral resistance (current) Difference in blood pressure ( P) Blood Flow (Q) = Peripheral Resistance: Peripheral resistance (R) Amount of friction blood encounters (electrical resistance) passing through vessels (mm Hg / mL / min) Analogous to Ohm’s Law (V = I x R OR I = V / R)

• Blood flow is inversely proportional to resistance encountered in the system

Q = P / R 1 A man has a renal blood flow of 500 Blood Flow (Q) = mL / min. The renal atrial pressure R = P / Q is 100 mm Hg and the renal venous Peripheral resistance (R) pressure is 10 mm Hg. 100 mm Hg – 10 mm Hg R = What is the of 500 mL / min The major mechanism for changing blood flow in the the kidney for this man? cardiovascular system is by changing the resistance of blood vessels, particularly the arterioles R = 0.18 mm Hg / mL / min

3 Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

The factors that determine the resistance of a blood vessel to The total resistance associated with a set of blood vessels also depends blood flow are expressed by Poiseuille’s (pwä-zwēz) Law: on whether the vessels are arranged in series or in parallel

A) Series resistance: Powerful relationship! R = Resistance 8Lη Slight diameter change η = of blood R = Sequential arrangement (e.g., pathway within single organ) equals r4 L = Length large resistance change r = Radius

1) Blood viscosity 2) Vessel Length 3) Vessel Diameter Arteriolar resistance is the greatest which equates to the area with the greatest decrease in pressure

The total resistance is equal to the sum of the individual resistances

 viscosity =  resistance  length =  resistance  diameter =  resistance

Costanzo (Physiology, 4th ed.) – Figure 4.5

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

The total resistance associated with a set of blood vessels also depends Ideally, blood flow in the cardiovascular system is streamlined on whether the vessels are arranged in series or in parallel 1) Laminar Flow: Characterized by parabolic velocity profile B) Parallel resistance: • Flow is 0 velocity at wall; maximal at center Simultaneous arrangement (e.g., pathway among various circulations) • Layers of fluid slide past one another Blood ~ 4x Viscosity: more viscous Adding a new resistance to the Measure of the resistance to sliding than water circuit causes total resistance between adjacent layers to decrease

No loss of pressure in major arteries What would you expect to happen to blood viscosity  viscosity in as vessel diameter decreases? capillaries – Why? Increasing the resistance in one circuit causes total resistance Fahraeus – Lindqvist Effect: to increase () Relative viscosity of blood decreases with Hematocrit decreasing vessel diameter RBCs The total resistance is less than any of the individual resistances (< 0.3 mm ~ 1.8x water)

Reduced energy required to drive blood through Plasma Skimming Exit to smaller

Costanzo (Physiology, 4th ed.) – Figure 4.5 Costanzo (Physiology, 4th ed.) – Figure 4.6 vessels

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

Ideally, blood flow in the cardiovascular system is streamlined The capacitance of a blood vessel describes the volume of blood a vessel can hold at a given pressure 1) Laminar Flow: Characterized by parabolic velocity profile • Flow is 0 velocity at wall; maximal at center Volume (mL) • Layers of fluid slide past one another Compliance = Blood ~ 4x (mL / mm Hg) Pressure (mm Hg) Viscosity: more viscous Measure of the resistance to sliding than water Compliance = slope of line between adjacent layers Compliance is high in veins Unstressed (large blood volumes @ low pressure) volume 2) Turbulent Flow: Blood moves in directions not aligned with axis of blood flow • More pressure required to propel blood Compliance is low in arteries Stressed • Noisy (stethoscope) (low blood volumes @ high pressure) volume

Anemia Reynolds Number: Total = Unstressed volume + Stressed volume Indicator of whether flow will be Thrombi laminar or turbulent Changes in compliance of the veins cause redistribution of blood between arteries and veins Arterial pressure increases in  Re = turbulence (> 2000) Factors affecting Reynolds Number: elderly due to lower compliance • Venoconstriction 1) Viscosity ( viscosity =  Reynolds number) 2) Velocity ( velocity =  Reynolds number) Costanzo (Physiology, 4th ed.) – Figure 4.6 Costanzo (Physiology, 4th ed.) – Figure 4.7

4 Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

As noted earlier, blood pressure is not equal throughout system Although mean pressure is high and constant, there are pulsations of aortic (and arterial) pressure

~ 100 mm Hg 1

High initial pressure: Dicrotic notch • Large volume of blood entering aorta • Low compliance of 1 aortic wall

Systolic Pressure: Dicrotic notch: Pressure from ventricular contraction Brief period following closure of aortic valve Diastolic Pressure: where pressure drops due to retrograde flow Pressure from ventricular relaxation

Costanzo (Physiology, 4th ed.) – Figure 4.8 Costanzo (Physiology, 4th ed.) – Figure 4.9

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must Hemodynamics: be kept moving… Pathophysiology:

Although mean pressure is high and constant, there are Several pathologic conditions alter the arterial pulsations of aortic (and arterial) pressure pressure curve in a predictable way

Arteriosclerosis:

Pulse Pressure: Systolic pressure – Diastolic pressure  compliance =  systolic pressure C = V / P

• Reflective of volume Aortic :

Mean Arterial Pressure: Why is it not Diastolic pressure + 1/3 pressure + 1/2 ?

=  systolic pressure Costanzo (Physiology, 4th ed.) – Figure 4.9 Costanzo (Physiology, 4th ed.) – Figure 4.10

Cardiovascular System – Vessels Cardiovascular System – Vessels To stay alive, blood must To stay alive, blood must Hemodynamics: be kept moving… Hemodynamics: be kept moving…

As noted earlier, blood pressure is not equal throughout system As noted earlier, blood pressure is not equal throughout system Pulsations in large arteries greater than aorta ~ 100 ~ 100 • Pressure wave travels faster than blood ~ 100 ~ 100 ~ 50 ~ 20 ~ 4 2 mm Hg mm Hg • Pressure waves reflected at branch points 2 mm Hg mm Hg mm Hg mm Hg mm Hg Pressure remains high: Pressure remains high: Largest Profile similar in • High elastic recoil of • High elastic recoil of drop pulmonary system artery walls artery walls but with much lower • Pressure reservoir • Pressure reservoir pressures (25 / 8) Energy 1 2 1 2 consumed 3 to overcome Dramatic drop in pressure: frictional forces • High resistance to flow 4 3 4 Pressure continues to drop: • Frictional resistance to flow • Filtration of fluid out of Blood return assisted by: capillaries • Large lumen ( resistance) • Valves

Costanzo (Physiology, 4th ed.) – Figure 4.8 Costanzo (Physiology, 4th ed.) – Figure 4.8 • Muscular pumps

5 Note: Cardiovascular System – Vessels Cardiovascular System – Vessels Equation deceptively simple; Blood Pressure Regulation: Blood Pressure Regulation: in reality, cardiac output and peripheral resistance are not independent of each other Factors Affecting Blood Pressure: (Pa) is the driving force for blood flow, and must be maintained at a high, constant level Blood Volume * ( Blood Volume =  BP) Difference in blood pressure ( P) Blood Flow (Q) = Peripheral resistance (R) Mean Arterial Pressure (P ) = Cardiac Output (Q) x Peripheral a Resistance (R)

Cardiac Output * Vessel Diameter * ( CO =  BP) ( D =  R =  BP)

Blood Viscosity ( V =  R =  BP) Pa is regulated by two major systems that work via negative feedback to maintain ~ 100 mm Hg Peripheral Vessel Length Mean Arterial Pressure (P ) = Cardiac Output (Q) x ( L =  R =  BP) a Resistance (R) Vessel Elasticity ( VE =  R =  BP) * Variables that can be readily manipulated

Cardiovascular System – Vessels Cardiovascular System – Vessels

Blood Pressure Regulation: System 1 Blood Pressure Regulation:

Baroreceptor mechanisms are fast, neurally mediated reflexes that attempt Baroreceptor mechanisms are fast, neurally mediated reflexes that attempt

to keep Pa constant via changes in cardiac output and vessel diameter to keep Pa constant via changes in cardiac output and vessel diameter

Baroreceptors:  Pa (+) (+) Function: • Mechanoreceptors (respond to stretch) •  Pa =  stretch =  firing rate •  Pa =  stretch =  firing rate (integration center; medulla) (-) (+) While sensitive to absolute level of pressure, they are most sensitive rates of changes in pressure cardiovascular centers in Location: medulla • Carotid sinus (increase / decrease in P ) Decrease in a Increase in HR / contractility (+) • Glossopharyngeal nerve (IX) (-) (-) (-) (-) vessel diameter ( CO) • Aortic arch (increase in Pa) ( PR) • Vagus nerve (X)

Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figures 18.4 / 19.22 Costanzo (Physiology, 4th ed.) – Figure 4.31

Cardiovascular System – Vessels Cardiovascular System – Vessels Valsalva Maneuver: Blood Pressure Regulation: Expiring against a closed glottis; used Blood Pressure Regulation: System 2 to test integrity of baroreceptor reflex

Baroreceptor mechanisms are fast, neurally mediated reflexes that attempt - II-aldosterone system is a slow, hormonally mediated

to keep Pa constant via changes in cardiac output and vessel diameter response to keep Pa constant via changes in blood volume

 Pa (-) Detected by mechanoreceptors in afferent arterioles Released by juxtaglomerular cells (kidney) (integration center; medulla) (+) Decapeptide; (-) no biological activity

cardiovascular centers in medulla (Produced by liver) ( / kidneys) Increase in Decrease in HR / contractility (-) (+) (+) (+) (+) vessel diameter ( CO) ( PR)

Costanzo (Physiology, 4th ed.) – Figure 4.31 Costanzo (Physiology, 4th ed.) – Figure 4.33

6 Cardiovascular System – Vessels Cardiovascular System – Vessels

Blood Pressure Regulation: Blood Pressure Regulation:

Renin-angiotensin II-aldosterone system is a slow, hormonally mediated Additional mechanisms aid in regulating mean arterial pressure

response to keep Pa constant via changes in blood volume A) Peripheral chemoreceptors C) Antidiuretic (ADH) (carotid bodies / aortic arch) ()

• Respond to  P with vasoconstriction (adrenal cortex) (kidney) (hypothalamus) (blood vessels) O2 and increased aka

B) Central chemoreceptors (medulla oblongata) • Respond to an  serum osmolarity and a  in blood pressure • Respond to primarily to  P and  pH CO2 • Triggers vasoconstriction (V1 receptors) Brain becomes ischemic D) Atrial natriuretic peptide (ANP)  PCO and  pH (atria)  Blood Volume 2 Increased sympathetic outflow

BIG RED BUTTON

Intense arteriolar vasoconstriction in peripheral capillary beds • Respond to an  in blood pressure

Redirects blood • Triggers vasodilation and  H2O excretion Costanzo (Physiology, 4th ed.) – Figure 4.33 to brain

Cardiovascular System – Vessels Cardiovascular System – Vessels

Microcirculation: Functions of the arterioles, capillaries, Microcirculation: lymphatic vessels, and veins

Fluid movement across a capillary wall is driven by the Heart Starling pressures across the wall Exchange across capillary wall:

capillary (lipid soluble) (water soluble) :

Pc c Fluids Solutes O2 / CO2 J = K [(P – P) – ( – )] v f c i c i Kf interstitial fluid Directly through Aqueous clefts endothelium between cells Pi i Jv = Fluid movement (mL / min)

Kf = Hydraulic conductance (mL / min  mm Hg) Water permeability of capillary wall (structural property) P = Capillary hydrostatic pressure (mm Hg) Capillary fluid pressure • Simple diffusion drives exchange of c gases and solutes Pi = Interstitial hydrostatic pressure (mm Hg) Interstitial fluid pressure

• Fluid transfer across membrane occurs c = Capillary osmotic pressure (mm Hg) Capillary osmotic pressure (due to [protein]) via osmosis i = Interstitial osmotic pressure (mm Hg) Interstitial osmotic pressure (due to [protein]) • Hydrostatic pressure Starling • Osmotic pressure forces Direction of fluid movement (Jv) may be into or out of capillary Filtration = Net fluid movement is out of capillary and into interstitial fluid ((+) number) Microcirculation Absorption = Net fluid movement is into capillary and out of interstitial fluid ((-) number) Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 19.2

Cardiovascular System – Vessels Cardiovascular System – Vessels

In a skeletal muscle of an individual, the In a skeletal muscle of an individual, the following Starling pressures were measured: following Starling pressures were measured:

Pc = 30 mm Hg Pc = 30 mm Hg

Pi = 1 mm Hg Pi = 1 mm Hg Kf = 0.5 mL / min  mm Hg Kf = 0.5 mL / min  mm Hg c = 26 mm Hg c = 26 mm Hg

i = 3 mm Hg i = 3 mm Hg What is the direction and magnitude What is the direction and magnitude of fluid movement across this capillary? of fluid movement across this capillary?

Jv = Kf [(Pc – Pi) – (c – i)] Jv = 0.5 (6) Jv = 0.5 [(30 – 1) – (26 – 3)] Pc = +30 c = -26 +6 Jv = 0.5 [29 – 23] Jv = 3 mL / min (filtration) Jv = 0.5 (6) Jv = 3 mL / min (filtration) Pi = -1 c = +3

7 Cardiovascular System – Vessels Cardiovascular System – Vessels

Microcirculation: Microcirculation:

Fluid movement across a capillary wall is not Lymphoid system returns excess fluid to bloodstream equal along the length of a capillary Additional Functions: • Produce / maintain / distribute  Lymph node biopsy • Distributes / nutrients / waste products

Arterial end Lymph nodes filter fluids (99% purified)

+10 Pc = +35 c = -26 Pc = +17 c = -26 -8 Flow of Lymph:

• Originate as pockets Venous end • Large diameters / thin walls • One-way valves (external)

Pi = 0 c = +1 Pi = 0 c = +1

Lymphatic ducts Lymphatic Trunks Jv = 0.5 (2) What happens to the fluid not returned to the capillary? Jv = 1 mL / min (net filtration) Lymphatic capillaries Lymphatic vessels Collecting Vessels

One-way valves (internal) Randall et al. (Eckert Animal Physiology, 5th ed.) – Figure 12.37 Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 20.1

Cardiovascular System – Vessels Cardiovascular System – Vessels

Microcirculation: Pathophysiology: • Lymph from right side of • Lymph from left side of Flow of Lymph: body above diaphragm head, neck, and thorax (swelling) results from an increase Thoracic Duct: in interstitial fluid volume • Begins inferior to diaphragm Forms when the volume of fluids filtered out of the capillaries exceeds the • Empties into left subclavian vein ability of the lymphatics to return it to circulation

Elephantiasis Right Lymphatic Duct: Jv = Kf [(Pc – Pi) – (c – i)] • Empties into right subclavian vein Causes: 1) Increased capillary hydrostatic pressure • Arteriole dilation • •

2) Decreased capillary osmotic pressure • Severe liver failure (limited protein synthesis) • Protein malnutrition 4) Impaired lymphatic drainage • Prolonged standing 3) Increased hydraulic conductance • Removal / irradiation of lymph nodes Cisterna chyli: • Severe burn • Parasitic infection Chamber that collects lymph from • (leaky vessels) abdomen, pelvis, and lower limbs Similar to Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 20.2

Cardiovascular System – Vessels Cardiovascular System – Vessels

Special Circulations: Special Circulations:

Blood flow is variable between one organ and another, depending The mechanisms that regulate blood flow are categorized as on the overall demands of each organ system local (intrinsic) control and neural / hormonal (extrinsic) control

Local controls are most important mechanism for regulating 1) Local control: coronary, cerebral, skeletal muscle, pulmonary, Interorgan differences in blood and renal circulation flow results from differences A) in vascular resistance • Maintenance of constant blood flow in face of changing arterial pressure Blood flow to specific organs can increase or decrease depending on Myogenic Hypothesis: metabolic demands Q = P / R When is stretched, it contracts What about the lungs? Changes in blood flow to an individual organ are achieved by  BP  BP =  smooth muscle stretch = vasoconstriction altering arteriolar resistance =

ALTERNATIVELY

 BP =  BP =  smooth muscle stretch = vasodilation

Marieb & Hoehn (Human Anatomy and Physiology, 8th ed.) – Figure 19.13

8 Cardiovascular System – Vessels Cardiovascular System – Vessels

Special Circulations: Special Circulations:

The mechanisms that regulate blood flow are categorized as The mechanisms that regulate blood flow are categorized as local (intrinsic) control and neural / hormonal (extrinsic) control local (intrinsic) control and neural / hormonal (extrinsic) control

Local controls are most important mechanism for regulating Neuronal / hormonal controls are most important 1) Local control: coronary, cerebral, skeletal muscle, pulmonary, 2) Neuronal / Hormonal controls: mechanism for maintaining circulation and renal circulation B) Active hyperemia A) Neuronal • Blood flow to an organ is proportional to its metabolic activity • Sympathetic innervation of vascular smooth muscle

C) Reactive hyperemia (Repayment of oxygen ‘debt’) B) Hormonal • Blood flow to an organ is increased in response to a period of decreased blood flow

Vasodilator metabolites

Histamine Metabolic Hypothesis: • arteriodilator; venoconstrictor • local vasoconstriction • local vasodilators / vasoconstrictors

O delivery to a tissue is matched + + + + •  Pc = local edema 2 CO2 H K lactate CO2 H K lactate to O consumption by altering Back to resting… 2 O Fluid arteriole resistance 2 • arteriodilator; venoconstrictor

•  Pc = local edema Tissues Tissues Tissues

Cardiovascular System – Vessels

Pathophysiology:

Circulatory refers to any condition in which the blood vessels are inadequately filled

A) B) Vascular Shock C) Cardiogenic Shock Large-scale blood loss Abnormal expansion of Heart malfunctions vascular beds due Thready pulse to extreme vasodilation

(  HR;extreme vasoconstriciton)

• Acute hemorrage • Myocardial • Severe vomiting / diarrhea • Anaphylaxis (allergies) • Extensive burns • Failure of ANS regulation • Septicemia (bacteria)

9