A&p 19

Front 1

Arteries

Back 1

Carry blood away from heart; high O2 blood in systemic circuit, low O2 blood in pulmonary circuit

Front 2

Capillaries

Back 2

Contract tissue cells and directly serve cellular needs (exchange here via diffusion and filtration)

Front 3

Veins

Back 3

Carry blood toward heart; Low O2 blood in systemic circuit, high O2 blood in pulmonary circuit

Front 4

Tunica Intima

Back 4

Endothelium lines lumen of all vessels; In vessels larger than 1mm, subendothelial connective tissue basement membrane is present

Front 5

Tunica Media

Back 5

Smooth muscle and sheets of elastin; Sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels

Front 6

Tunica Externa

Back 6

Collagen fibers protect and reinforce; Larger vessels contain vasa vasorum to nourish layer

Front 7

Elastic (Conducting) Arteries

Back 7

Large thick walled, elastin in all tunics; Aorta and major branches; Large lumen offers low resistance; Act as pressure reservoirs - expand and recoil as blood is ejected from heart

Front 8

Muscular (Distributing) Arteries and Arterioles

Back 8

Distal to elastic arteries - deliver blood to organs; Thick tunica media with more smooth muscle; Active in resistance control (vasoconstriction/vasodilation) - Local blood flow regulation and overall blood pressure control

Front 9

Capillaries

Back 9

Microscopic blood vessels; Endothelium is principal layer; Pericytes help stabilize wall and control permeability; Size allows only single RBC to pass at a time; In almost all tissues; Functions to exchange gases, nutrients, wastes, hormones, etc.

Front 10

Continuous Capillaries

Back 10

Abundant in skin and muscles - tight junctions connect endothelial cells, intercellular clefts allow passage of fluids and small solutes; In brain tight junctions form blood brain barrier

Front 11

Fenestrated Capillaries

Back 11

Some endothelial cells contain pore (fenestrations); More permeable than continuous capillaries; Function in absorption or filtrate formation

Front 12

Sinusoidal Capillaries

Back 12

Fewer tight junction, larger intercelluar clefts, large lumens; Usually fenestrated; Allow passage of large molecules and blood cells between bllod and surrounding tissues; Found in liver, bone marrow, spleen

Front 13

Capillary Beds

Back 13

Interwoven networks of capillaries form microcirculation between arterioles and venules

Front 14

Vascular Shunt

Back 14

Metarteriole - Thoroughfare channel; Directly connects termianl arteriole and postcapillary venule

Front 15

True Capillaries

Back 15

10 to 100 exchange vessels per capillary bed; Branch off the metarteriole or terminal arteriole

Front 16

Precapillary Sphincters

Back 16

Regulate blood flow into true capillaries; Work in tandem with arterioles to modify blood flow through a tissue

Front 17

Capillary Exchange

Back 17

Simple diffusion of O2 and nutrients from blood to tissues; CO2 and metabolic wastes from tissues to blood; Lipid soluble molecule diffuse directly through endothelial membranes; Water soluble solutes pass through clefts and fenestrations; Larger molecules are actively transported in pinocytotic vesicles or caveolae

Front 18

Venules

Back 18

Formed when capillary beds unite; Very porous, allow fluids and WBCs into tissues; Postcapillary venules consist of endothelium and a few pericytes; Larger venules have one to two layers of smooth muscle cells

Front 19

Veins

Back 19

Formed when venules converge; Thinner walls, larger lumens compared with corresponding arteries; Blood pressure lower than in arteries; Thin tunica media and thick tunica extterna consisting of collagen fibers and elastic networks; Called capacitance vessels (blood reservoirs) contain up to 65% of blood supply

Front 20

Blood Flow

Back 20

Volume of blood flowing through a vessel, organ, or entire circulation in a given time period; Measured as ml/min; Equivalent to CO for entire vascular system; Relatively constant when at rest; Varies widely through individual organs based on needs

Front 21

Blood Pressure (BP)

Back 21

Force per unit area exerted on wall of a blood vessel by blood; Expressed in 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

Front 22

Resistance (Peripheral)

Back 22

Opposition to flow; Amount of friction blood encounters; Generally encountered in peripheral systemic circulation; Small diameter arterioles are major determinants of peripheral res.; Abrupt diameter changes or fatty plaques (atherosclerosis) increase resistance; Varies inversely with the fourth power of vessel radius (if radius is doubled, resistance is 1/16 as much)

Front 23

Sources of Resistance

Back 23

Blood viscosity; Total blood vessel length; Blood vessel diameter (most adjustable)

Front 24

Blood Flow (F), BP, and Resistance Relationship

Back 24

F directly proportional to blood (hydrostatic) pressure gradient (^P); If ^P increases, F speeds up; F inversely proportional to R; if R increases, F decreases (F=^P/R); R is more important in influencing local blood flow because it is easily changed by altering blood vessel diameter

Front 25

Systemic BP

Back 25

Pumping action of heart generates blood flow; Pressure results when flow is opposed by resistance; Systemic pressure is highest in aorta, declines throughout pathway, and is 0 mm Hg in right atrium; Steepest drop occurs in arterioles

Front 26

Arterial BP

Back 26

Reflects two factors of arteries close to hear - elasticity and volume of blood forced into them at any time; BP near heart is pulsatile

Front 27

Elasticity

Back 27

The ability to recoil, which creates additional push on blood during ventricular diastole - compliance is level of distensibility

Front 28

Systolic Pressure

Back 28

Pressure exerted during ventricular contraction

Front 29

Diastolic Pressure

Back 29

Lowest level of arterial pressure, just before next ventricular systole

Front 30

Pulse Pressure

Back 30

Systolic pr. - diastolic pr.

Front 31

Mean Arterial Pressure (MAP)

Back 31

Pressure that propels blood to tissues; MAP = Diastolic pressure + 1/3 pulse pressure; Pulse pressure and MAP both decline with increasing distance from ventricles

Front 32

Capillary BP

Back 32

Ranges from 15 to 35 mm Hg; Low capillary pressure is desirable - high BP would rupture fragile, thin walled capillaries , most are very permeable, low pressure forces filtrate into interstitial spaces

Front 33

Venous BP

Back 33

Changes little during cardiac cycle; Small pressure gradient about 15 mm Hg; Low pressure due to cumulative effects of peripheral resistance

Front 34

Factors Aiding Venous Return (Increases EDV)

Back 34

One way flow valves/vein diameter; Respiratory pump pressure changes created during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand; Muscular pump contraction of skeletal muscles milk blood toward heart and valves prevent backflow; Venoconstriction caused by sympathetic output reduces volume capacity

Front 35

Maintaining BP

Back 35

F = ^P/PR and CO = ^P/PR; BP = CO x PR (CO depends on blood volume); BP varies directly with CO, PR, and blood volume; Changes in one variable are quickly compensated for by changes in other variables

Front 36

Vasomotor Center

Back 36

Cluster of sympathetic neurons in medulla that oversee changes in blood vessel diameter; Part of cardiovascular center; Maintains vasomotor tone (moderate constriction of arterioles); Receives inputs from baroreceptors, chemoreceptors, and higher brain centers

Front 37

Baroreceptors

Back 37

Located in carotid sinuses and aortic arch

Front 38

BP Control

Back 38

Short term neural and hormonal controls - counteract fluctuations in BP by altering R; Long term renal regulation - counteracts fluctuations in BP by altering blood volume

Front 39

Blood Flow Tissue Perforation

Back 39

Involved in delivery of O2, gas exchange in lungs, absorption of nutrients in digestive tract, and urine formation in kidneys; Rate of flow is precisely right amount to provide for proper function

Front 40

Autoregulation

Back 40

Auto adjustment of blood flow to each tissue in proportion to its requirements at any given point in time; Controlled intrinsically by modifying diameter of local arterioles feeding papillaries; Independent of MAP, which is controlled as needed to maintain constant pressure; Metabolic and Myogenic autoregulation

Front 41

Metabolic Autoregulation

Back 41

Hyperemia; Vasodilation of arterioles and relaxation of precapillary sphincters occur in response to declining tissue O2 and substances from metabolically active tissues and inflammatory chemicals; Release of NO from vascular endothelial cells causes vasodilation; Vasoconstriction due to sympathetic stimulation and endothelin (produced by endothelium)

Front 42

Skeletal Muscle Blood Flow

Back 42

At rest, myogenic and general neural mechanisms predominate; During muscle activity F increases in direct proportion to metabolic activity (active or exercise hyperemia), local controls override sympathetic vasoconstriction; Muscle F can increase 10x or more during physical activity

Front 43

Skin Blood Flow

Back 43

Supplies nutrients to cells; Helps maintain body temperature; Provides blood reservoir; Flow to venous plexuses below skin surface - varies from 50 ml/min to 2500 ml/min depending on body temp., controlled by sympathetic nervous system reflexes initiated by temperature receptors and central nervous system

Front 44

Lung Blood Flow

Back 44

Pulmonary circuit unusual - pathway is short, arteries/arterioles are thin walled with large lumens (like veins), arterial resistance and pressure are low (24/8 mm Hg)

Front 45

Heart Blood Flow

Back 45

During ventricular systole coronary vessels are compressed, myocardial blood flow ceases, stored myoglobin supplies sufficient oxygen; Control is probably myogenic; During strenuous exercise coronary vessels dilate, F increases 3 to 4 times

Front 46

Hypotension

Back 46

Low BP; Systolic pressure below 100 mm Hg; Often associated with long life and lack of cardiovascular illness

Front 47

Hypertension

Back 47

High BP; Sustained elevated arterial pressure of 140/90 or higher - may be transient adaptations during fever, physical exertion, emotional upset; Often persistent in obese people;