Lecture 10 Flashcards
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?
- wide
- 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
prostaglandin-
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?
hot-vasodilation
cold-vasonstriction
stretch-more stretch= vasoconstriction, less stretch= vasodilation