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What are two major functions of arteries?

-rapid transit passageways for blood from the heart to the tissues
-a pressure reservoir to provide the driving force for blood when the heart is relaxing


What is the structure of arteries?

-total cross-sectional area is lower than those of the downstream arterioles and capillaries=so blood can travel faster there


What are the tissue layers in arteries?

-endothelial lining
-thick smooth muscle layer
-collagen and elastin


What is the purpose of elastin and collagen fibres arteries?

elastin-elasticity so the walls behave like a ballon
collagen- tensile strength against the high pressure of blood ejected from the heart


What is the main function of arteries?

passageway from heart to organs serve as pressure reservoir


What are the tissue layers in arterioles?

-highly muscular, well innervated walls small radii
-less smooth muscle than arteries
-some connective tissue= mainly collagen almost no elastin


What is the main function of arterioles?

-primary resistance vessels, determine distribution of cardiac output
-variably distribute the cardiac output among the systemic organs depending on the body's needs
-to help regulate bodywide arterial blood pressure


What are the tissue layers in capillaries?

-very thin walled, large total cross sectional area
-only endothelial layer (+basement membrane as all of them have= all the tubes)


What is the main function of capillaries?

-site of exchange, determine distribution of extracellular fluid between plasma and interstitial fluid
-diffusion into interstitial fluid


What are the tissue layers in veins?

-thin walled compared to arteries, highly distensible= can be stretched, large radii
-smooth muscle with collagen= not very elastic


What is the main function of veins?

-passageway to heart from organs, serve as blood reservoir


What is the main driving force of blood flow in arteries?

-mean pressure=average pressure responsible for driving blood forward
- not halfway between diastolic and systolic
-as 2/3 are spent in diastole and 1/3 in systole


What do arteries do in systole?

they stretch to accommodate the extra blood


What do arteries do in diastole?

-the smooth muscle naturally flexes back (elastin) as less blood is in arteries then


3What is the pressure in arterioles in comparison to the arteries?

-much lower and arterioles convert the pulsating blood into steady flow


What are the metabolic factors in vaso-regulation?

O2-decreased, during exercise= local concentration drops=relaxation of smooth muscle=more flow
CO2-increased when increases activity=relaxed smooth muscle of arterioles
pH-increased acid-more as exercise more=relaxation of smooth muscle
K+-increase= more K during exercise as Na/K+ pump can't keep up= relaxation of arteriole smooth muscle


What are the chemical factors in vaso-regulation?

adenosine-release when increased activity= relax arteriole smooth muscle=more flow
NO-causes vasodilation by inducing relaxation of arterial smooth muscle
histamine-released by local immune cells when injured=increase in blood flow to the are= relax smooth muscles


What are the physical factors in vaso-regulation?

stretch-more stretch= vasoconstriction, less stretch= vasodilation


What are the autonomic nervous innervation factors in vaso-regulation?

-sympathetic nerve influence
NE -vasoconstriction


What are the hormonal factors in vaso-regulation?

angiotensin II-


What is total peripheral resistance?

-how dilated arterioles are
-many factors determine the constriction and dilation


How fast is the blood in capillaries in comparison to all the other blood vessels?

-the slowest


What is the total cross sectional area of capillaries in comparison to other blood vessels?

-largest, there are so many of them! billions!


What is capillary blood pressure?

-the hydrostatic pressure exerted by blood in the inside of the capillary wall
-forces the fluid out
-lower mean blood pressure here


What is plasma colloid osmotic pressure?

-force caused by the colloidal dispersion of blood proteins, it arises as the plasma proteins remain in the plasma and don't cross into the interstitial fluid
-thus there is osmotic difference causing water movement from the interstitial fluid into the capillaries by osmosis


What is interstitial fluid hydrostatic pressure?

-the fluid pressure exerted on the outside of the capillary wall by the interstitial fluid, this pressure tends to force fluid into capillaries


What is the interstitial fluid colloid osmotic pressure?

-results from the small fraction of plasma proteins that leak across the capillary walls into the interstitial fluid (normally returned to the blood via the lymphatic system), this protein concentration is very low= so this pressure close to zero can change when proteins leak in= like histamine=promotes fluid moving into capillaries


How does blood flow increase in veins?

- as the blood gets closer to the heart the overall cross sectional area decreases so the flow increases


Why are veins so stretchable?

-collagen and not much elastin=stretch easily
-smooth muscle doesn't have myogenic tone= easily stretched


How are veins the blood reservoir?

-when demand for blood low, blood stays in veins that can stretch a lot
-in rest conditions veins have 60% blood in a body