chapter 20- blood vessels lecture

tunica intima

tunica intima

innermost layer of the blood vessel, contains the basement membrane and endothelium

basement membrane

where the endothelial cells grow off of

endothelium

the innermost area surrounding lumen made of simple squamous epithelium

tunica media

middle layer of the blood vessel containing circular smooth muscle and external elastical lamina

circular smooth muscle

controls vasodilation/vasoconstriction

external elastica lamina

controls recoiling and expanding of vessels

tunica externa

most external layer, made up of sturdy connective tissue

which blood vessel has a larger lumen?

veins

which blood vessel has valves?

veins

which blood vessel has thicker walls due to withstanding higher pressure?

arteries

large elastic arteries

large and highly elastic arteries made to withstand the systolic pressure of the heart, like the aorta and the pulmonary trunk

muscular arteries

limited elasticity but have a lot of smooth muscle, adapted to constrict or dilate

aterioles

smallest arteries which are important for blood pressure and blood flow and also always slightly contracted due to vasomotor tone

vasa vasorum

smallest arteries that bring blood back to the large elastic arteries

continuous capillaries

single endothelial cell layer making a complete lining and basement membrane with intercellular clefts

fenestrated capillaries

endothelial cell layer has pores in it, but the basement membrane is complete. Located in muscular and nervous systems

sinusoid capillaries

endothelial cell layer and basement membrane both have pores in them. Located in bone marrow of the bones, liver, and spleen

how do capillaries connect to veins

through postcapillary venules

where is most of the blood when the body is at rest?

mostly in the systemic circuit, 55% of blood in the blood in the systemic circuit is in the venous system

where is the blood flow the fastest?

large elastic arteries

where is blood flow the slowest?

capillaries

how do cells receive substances they need?

from the arterial blood to tissue

how do cells get rid of their waste?

from tissue to the venous blood

what are the 3 main substance exchange methods?

diffusion, vesicular transport, bulk flow

diffusion

movement across the permeable capillary membrane down its concentration gradient. through pores in fenestrated capillaries

vesicular transport

some hormones and fatty acids go from blood to the tissues through pinocytosis

bulk flow

movement of large amounts of fluid and dissolved substances through capillary membrane up the concentration gradient

filtration

from arterial blood across capillary membrane to surrounding interstitial fluid

reabsorption

from surrounding interstitial fluid back to the blood of the venous end of the capillary

what are the 2 forces involved in bulk flow?

hydrostatic pressure and colloid osmotic pressure

hydrostatic pressure (HP)

exerted by blood within a capillary, a pushing force. HPb if in the blood, HPif if in the interstitial fluid

colloid osmotic pressure (COP)

created by solutes drawing water towards them via osmosis, a pulling force, COPb if in blood, COPif if in the interstitial fluid

what are the outward forces of net filtration?

COPif and HPb

what are the inward forces of net filtration?

COPb and HPif

what causes filtration?

outward forces exceeding inward forces

what causes reabsorbtion?

inward forces exceeding outward forces

in which vessels is net filtration higher?

in the arteries by 85%, so the remaining 15% goes to the lymphatic system

what are the 3 large physiological factors of circulation?

blood pressure, resistance, and total blood volume

blood pressure

the measure of force exerted by the moving blood against vessel walls

what happens in arteries during systole?

pressure increases and the vessel expands

what happens in arteries during diastole?

pressure decreases and vessel recoils

what does blood pressure create?

a pressure gradient for thats needed for circulation

pulse pressure (PP)

difference between systolic and diastolic BP, measuring the elasticity of vessels so if PP increases arteries must allow for the added pressure

what makes up the cushings triad?

high PP, bradychardia, and irregular breathing; indicates head trauma

what is mean arterial pressure (MAP)

the average of both systolic and diastolic pressures, considered to be the perfusion pressure for the body

what is the formula for mean arterial pressure (MAP)?

diastolic pressure + (pulse pressure/3) = MAP

what is normal MAP?

70-110 mmHg, shows adequate tissue perfusion

low MAP= <60 mmHg is inadequate perfusion

high MAP causes edema

what is the average pressure in the arterial end of capillary

40 mmHg (higher for filtration)

what is the average pressure in the venous end of capillary?

20 mmHg (lower to allow for reabsorbtion)

what is venous return?

volume of blood returning to the right side of the heart through the systemic circuit, should be equal to CO

what are the three techniques that help VR?

skeletal muscle pump, respiratory muscle pump and gravity

skeletal muscle pump

during muscle contraction, muscle bellies “milk” blood up to the heart, think of walking and flexing the calf muscle

respiratory muscle pump

breathing muscles in the thoracic cavity do the dame function of “milking” blood towards the heart

gravity

having elevated feet is the best way to promote venous rate, crossing legs compresses venous return

what is resistance (R)?

the amount of friction blood finds flowing through a vessel

what are the 3 contributing factors towards resistance?

1. blood viscosity- the thicker the blood, the more resistance there will be

2. blood vessel length- if the blood vessels are longer, the resistance will increase and BP may increase

   1. blood vessel radius- the blood closest to the walls of the vessels will have more resistance. Vasoconstricted vessels will also have higher resistance than vasodilated vessels

what is total blood flow?

amount of blood moving through vessels in a given period. Dependent on both resistance and pressure gradient

what do we use to measure total blood flow?

pulse, since it displays the the expansion and recoil of blood vessels

how does our body regulate blood pressure?

through negative feedback loops

where are the receptors that control BP?

baroreceptors (stretch receptor) and chemoreceptors (chemical sense receptor) are both in the aortic arch, baroreceptors are in coronary sinus and chemoreceptors are in the carotid body

where is the control center for BP?

medulla oblongata (cardiovascular center)

what are the two subdivisions of the cardiovascular center

cardiac center and vasomotor center

what happens in the cardiac center of the cardiovascular center?

the cardio acceleratory center gets triggered with a high CO, BP, and + inotropic and chronotropic features

the cardioinhibitory center gets triggered with a low BP, CO, and - chronotropic features

what happens in the vasomotor center of the cardiovascular center?

under sympathetic control, so causes most vessels to constrict except for those who need blood during fight or flight response like muscles

what are the effectors for BP?

the heart (alters CO and BP, speeds up contractions), vessels (alters pressure and flow of blood)

how do smaller tissues regulate their own blood flow?

with a mini negative feedback loop, if the blood has low oxygen levels and high levels of waste, vasodilation will be triggered so oxygen delivery will increase. when levels regulate then the vessels will stop dilating.