Cardiovascular System II Flashcards
Arteries Function
Carries blood away from the heart
Arterioles Function
Carries blood to capillary beds/regulates blood pressure
Capillaries Function
Exchange network for blood/interstitial fluid
Venules Function
Collects blood from capillary beds
Veins Function
Returns blood to the heart
Features of the Capillary Bed
Entry to capillary bed has precapillary sphincter to constrict blood flow into capillary bed
Containts Arteriovenous anastomosis
Increased density of capillary beds in structures that need high O2 delivery (smooth muscle)
Function of Arteriovenous Anastomosis
Blood vessel used to transport blood quickly, bypassing the capillary bed
Used if capillary bed is damaged
Distribution of Blood Volume (%)
Systemic Venous System - 64%
Systemic Arterial System - 13%
Systemic Capillaries - 7%
Heart - 7%
Pulmonary Circuit - 9%
3 Layers of Blood Vessel Structure
Tunica intima
Tunica media
Tunica externa
Has endothelium lining inside
Differences between veins and arteries
No smooth muscle in veins
Veins have valves,, arteries don’t
Tunica Intima Features
Inner layer
Encompasses endothelial lining
Connective Tissue Layer
Elastic membrane to provide passive elasticity to arteries, to withstand high blood pressure
Endothelium Function
Releases vasoactive substances which affect vascular tone, blood pressure and blood flow
Maintains vascular homeostasis
Releases Nitric Oxide (vasodilator)
Releases Endothelin (vasoconstrictor)
Tunica Media Features
Contains concentric sheets of smooth muscle in loose connective tissue
Encircles endothelium that lines the lumen
Binds to inner and outer layers
Tunica Externa Features
Anchors vessel to adjacent tissue
Contains collagen, elastic fibers, smooth muscle cells
Contains Vasa Vasorum (smaller arteries and veins in larger arteries and veins)
Types of Arteries
Elastic Arteries (e.g. Aorta)
Muscular Arteries (e.g. Femoral Artery)
Arterioles
Characteristics of Arteries
Elastic contain great amount of elastic fibers = more elasticity
Muscular contains more smooth muscle = greater control of vasoconstriction/dilation
Arteries have no tunica intima/externa = focus on blood flow regulation
3 Types of Capillaries
Continuous
Fenestrated
Sinusoid
Capillary Features
No Tunica media/externa
Similar diameter to RBC
Continuous Capillary Features
Found in all tissues
Have complete endothelial lining
Permit diffusion of water, small solutes and lipid-soluble materials
Fenestrated Capillary Features
Have pores in endothelial lining
Permit rapid exchange of water and larger solutes (e.g. hormones)
Found in Endocrine Organs, Kidneys, Intestinal Tract
Sinusoid Capilary Features
Have gaps between adjacent endothelial cells
Permit free exchange of water and large plasma proteins
Found in Liver, Spleen, Bone Marrow, Endocrine Organs
Main differences of veins from arteries
Larger diameter
Thinner Walls
Lower blood pressure
Valves
Venous Valves Features
Folds of tunica intima
Prevents blood from flowing backwards
Weakened walls of veins near valves = varicose veins
Skeletal Muscle Pump Definition
Contraction of Skeletal Muscle that aids the opening/closing of valves
When a muscle contracts, the valve superior to the muscle opens whilst the valve inferior to the muscle closes
Relationship between blood flow and cardiac output
Total capillary blood flow = cardiac output
Flow is proportional to pressure gradient/resistance (^P/R)
Pressure Gradient Definition
Difference in Pressure from one end of a vessel to the other
Total Peripheral Resistance Definition
Resistance of entire cardiovascular system
Overcame by Circuilatory Pressure
Factors affecting total peripheral resistance
Vascular Resistance
Blood Viscosity
Turbulence
Vascular Resistance Definition
Resistance due to friction between blood and vessel walls
Factors affecting Vascular Resistance
Vessel Length
Vessel Diameter
Normal Blood Pressure
120/80
Hypertension Definition
Abnormally high blood pressure
Greater than 140/90
Hypotension Definition
Abnormally low blood pressure
Less than 90/60
Responses to Exercise
Increased Heart Rate
Increase in Systolic Blood Pressure
Redistribution of Blood Flow
Parasympathetic ANS Regulation of Heart Rate
Slows Heart Rate by inhibiting SA and AV Node
Via Vagus Nerve
Sympathetic ANS Regulation of Heart Rate
Increases Heart Rate by stimulating SA and AV Node
Via Cardiac Accelerator Nerves
Ways to change stroke volume
Increased Sympathetic ANS activation
Increased end diastolic volume, leading to increased stretch of sarcomeres
Relationship between contraction and stroke volume
Increased force of contraction = increased stroke volume
