19) Blood Vessels Flashcards
1-13 quiz, 14- lecture notes
long term regulation of blood pressure is guided by renin, a hormone released from the ___
kidneys
filtration results when substances are forced through capillary walls by ___ pressure.
hydrostatic
the smallest blood vessels are called ___
capillaries
the presence of plasma proteins in blood increase its ___ pressure as compared to tissue fluids.
osmotic
when contraction of the smooth muscle in a blood vessel wall occurs, the vessel is referred to as being in condition of ___
vasoconstriction
___ are vessels with large lumens that serve as blood reservoirs
veins
___ are composed of smooth muscle that encircles the entrances of capillaries and thus can control the distribution of blood within tissues
pre capillary sphincters
oxygen and carbon dioxide move easily through most areas of cell membranes because they are soluble in ___
lipids
the ___ of an artery wall is largely composed of connective tissue
tunica externa
vessels that carry blood away from the heart
arteries
the peak blood pressure driven by ventricular contraction is called
systolic pressure
the process called ___ provides the most important means of transfer of biochemicals through capillary walls
diffusion
short term regulation of blood pressure is primarily controlled by the ___
nervous system
types of vessels
*arteries- carry blood away from ventricles of heart, they branch, diverge and fork
*arterioles- receive blood from arteries, carried to capillaries
*capillaries- sites of exchange of substances between blood and body cells
*venules- receive blood from capillaries
*veins- carry blood towards ventricles of hear, they join, merge and converge
structure of blood vessel walls
*lumen- central space containing blood
*tunica intima- innermost layer
*tunica media- middle layer
*tunica externa- outermost layer
tunica intima
*innermost layer
*endothelium- simple squamous epithelium, lines lumin of vessels, continuous with endocardium, slick surface
*subendothelial layer- connective tissue basement membrane
tunica media
*middle layer
*mostly smooth muscle and sheets of elastin
*sympathetic vasomotor nerve fibers innervate this layer
*vasoconstrict- decreases lumen diameter
*vasodilate- increases lumen diameter
*bulkiest layer responsible for maintaining blood flow and blood pressure
tunica externa
*outermost layer
*composed of loose collagen fibers, protect and reinforce wall, anchor to surrounding structures
*infiltrated with nerve fibers, lymphatic vessels, larger veins also contain elastic fibers
three types of arteries
*elastic arteries
*muscular arteries
*arterioles
elastic arteries
*thick walled w/ large, low-resistance lumen
*elastin found in all three tunic
*contains substantial smooth muscle, active in vasoconstriction
*act as pressure reservoirs, expand and recoil as blood is ejected from heart, continuous blood flow
muscular arteries
*distributing arteries deliver blood to body
*accounts for most of named arteries
*thickest tunica media with more smooth muscle, less elastic tissue
*active in vasoconstriction
arterioles
*smallest of all arteries
*larger contain all three tunica, smaller are single layer smooth muscles surrounded by endothelial cells
*control flow into capillary beds via vasodilation & vasoconstriction
*lead to capillary beds
capillaries
*microscopic vessels allow exchange of gasses and substances
*so small only allows single RBC to pass
* thin tunica intima, one cell forms entire circumference
intracellular clefts
small gaps in endothelial cells, allow fluid and solutes to pass through capillaries
three types of capillaires
*continuous capillaries
*fenestrated capillaries
*sinusoidal capillaries
continuous capillaries
*abundant in skin, muscles, lungs, and CNS
*form blood brain barrier in brain, enclosed with tight junction, no intercellular clefts
fenestrated capillaries
*found in areas involved in active filtration (kidneys), absorption (intestines), or endocrine hormone secretion
*endothelial cells contain pores like swiss cheese (fenestrations)
*increased permeability
sinusoidal capillaries
*fewer tight junctions, fenestrated with large intercellular clefts (incomplete basement membranes)
*only in liver, bone marrow, spleen, and adrenal medulla
*blood flow is sluggish, allows modification of large molecules & blood cells, pass between blood & tissue
*contains macrophages to capture foreign invaders
precapillary sphincters
regulates capillary blood flow in certain parts of the body
exchange in capillaries
*water and other substances leave capillaries due to net outward pressure (filtration)
*water enters capillaries venular ends because of net inward pressure (osmosis)
*substance move in and out along length of capillaries according to their concentration gradient
venules
*microscopic vessels continue from the capillaries
*endothelium, very porous, allow fluids and WBC into tissue
*large venules have one or two layers of smooth muscle cells
veins
*carry blood toward heart
*have all three tunics, thinner walls with larger lumens compared to arteries
*large lumen, good storage vessels (65% of blood supply)
*blood pressure lower than arteries
*venous valves- prevent backflow, abundant in veins of limbs
*venous sinuses- flattened veins with extremely thin walls, (e.g. coronary sinus in heart, dural sinuses in brain)
blood pressure
*force of blood exerted against the inner walls of the blood vessels
*pressure in arteries of the systemic circuit
*measured in units of mm Hg (mercury)
arterial blood pressure
*rises with ventricular contraction
*systolic pressure- maximum pressure achieved during ventricular contraction
*falls with ventricular relaxation
*diastolic pressure- minimum pressure in the arteres before the next ventricular contraction
pulse pressure
difference between systolic and diastolic blood pressure
factors that influence Arterial Blood Pressure
*cardiac output
*blood volume
*peripheral resistance
*blood viscosity
stroke volume
*volume of blood discharged from the ventricle with each contraction
*difference between EDV and ESV
*normal 70mL
end-diastolic volume (EDV)
volume of blood in each ventricle at end of ventricular diastole
end-systolic volume (ESV)
volume of blood in each ventricle at end of ventricular systole
cardiac output
*stroke volume per minute
*stroke volume x heart rate = cardiac output
*if stroke volume or pulse increases, so does cardiac output
*if stroke volume or pulse decreases, so does cardiac output
blood volume
*equals the sum of formed elements (cells and platelets) and plasma volume
*BP directly proportional to volume of blood in cardiovascular system
*low blood volume = low BP (e.g. hemmorage, dehydration)
peripheral resistance
*friction between blood and walls of blood vessels
*BP must overcome this force
*contraction of smooth muscles, increases peripheral resistance
*dilation of smooth muscles, decreases peripheral resistance
*recoil of arteries maintains blood pressure during diastole
viscosity
*greater viscosity= greater resistance of blood flow
*blood cells and plasma proteins increase viscosity
*BP rises with increased viscosity, BP drops with decreased viscosity
control of blood pressure
*determined by cardiac output and peripheral resistance
*BP = CO x PR
*
preload
*measure of degree of ventricular stretch when heart is at end of diastole (EDV)
*grater the EDV, the greater the preload
Frank-Starling law of the heart
relationship between fiber length before contraction and the force of the contraction
end systolic volume influenced by
Preload
Contractility
Afterload
contractility
amount of force generated by contraction of the heart muscle, influenced by autonomic innervation and hormones
afterload
*the amount of force that the ventricle must produce to open the semilunar valves to eject blood
*increased arterial BP, increases afterload
*afterload increases, the heart must work harder to eject blood.
venous blood flow
*blood flow through the venous system partially result of heart action
*muscular pump- skeletal muscle moves blood to heart
*respiratory pump- pressure changes during breathing moves blood towards heart
*sympathetic venoconstriction- smooth muscle constricts, pushing blood toward heart
central venous pressure (CVP)
*blood from veins return to heart to the right atrium
*CVP is the pressure in the right atrium
*if heart is beating weakly, pressure will back up in increase venous network
*if heart is beating forcefully, pressure will decrease in the atria and venous network
pulmonary circuit
*arteries carry blood from the heart to the lungs
*veins carry blood to heart from lungs
*slight net outflow of fluid from capillaries due to right ventricular contraction
*small amount of water keeps alveoli moist, promotes gas exchange
* osmotic pressure draws extra water out of alveoli
systemic circuit
*aorta and its branches-oxygen rich
*veins return blood from right atrium-oxygen poor
