blood vessels, arteries, and arterioles (1)

arteries function and composition

carry blood away from heart to tissues

composition

* lined with endothelial cells
* elastin fibres
* smooth muscle
* elastin fibres
* connective tissue coat - collagen fibres

arterioles function and composition

smaller branches of arteries

composition

* lined with endothelial cells
* smooth muscle
* connective tissue coat - collagen fibres

capillaries function and composition

smaller branches of arterioles - large surface area

smallest vessel

exchanges nutrients, fluid, and gases with surrounding cells

composition

* endothelial cells

venules function and composition

formed when capillaries rejoin

return blood to heart

veins function and composition

formed when venules merge

returns blood to heart

composition

* venous valve - promotes on way blood flow
* endothelium cells
* smooth muscle - elastin fibres
* connective tissue coat - collagen fibres

blood vessel wall division

Tunica interna (intima)

Tunica media

Tunica external (adventitia)

Tunica interna (intima) composition and function

innermost layer of cells - mostly comprised of endothelium

smooth - minimises friction

present in all blood vessels

Tunica media composition and function

middle layer

thickest layer

smooth muscle in circular arrangement - innervated by SNS

Tunica external (adventitia)

outermost layer

thin layer of connective tissue

* protective layer and anchors cell to surroundings

contains elastic and collagen fibres

contains nerves

blood vessel - arteries division

elastic arteries

muscular arteries

elastic arteries characteristics

thick walled

muscular

highly elastic (in tunica intima and tunica media)

large diameter - allows low resistance conduction of blood flow

elastic arteries function

pressure reservoir

conduits for blood flow: passageway from heart to tissues

walls stretch during cardiac systole and recoil during diastole

* allows arteries to take on large volume of blood ejected from heart
* when no longer encountering force that drives stretch - the blood pressure in the walls is pushed into the system
* even though 0 mmHg of pressure is generated by the ventricle the arteries are still driving blood through the system

muscular arteries composition

medium sized

tunica media has more smooth muscle and less elastin

close to surface, allowing pulse to be felt

muscular arteries function

distributing arteries

vessels supply blood to individual organs

innervated by sympathetic nervous system

blood vessels - arterioles composition

highly muscular

highly innervated

* circular smooth muscle that receive sympathetic innervation
* brings about contraction and change in diameter

arterioles function

major resistance vessels

radius is vessel can be adjusted independently

* distribute cardiac output depending on body’s momentary needs
* regulate arterioles blood pressure

arteriolar resistance types

vasoconstriction

vasodilation

vasoconstriction definition and function

narrowing of a vessel

decrease in radius

increases resistance and decreased blood flow

result of increased SNS activity

vasodilation definition and function

enlargement of vessel circumference

increase in radius

decreased resistance and increase blood flow

decreased SNS activity