Lecture Quiz 8 Flashcards
What do arteries do?
Carry blood away from the heart
What do veins do?
Carry blood towards the heart
What do capillaries do?
contact tissue cells and directly serve cellular needs
Describe the components of arterial and venous walls
composed of three tunics: tunica interna, tunica media, and tunica externa
surround the central blood-containing space, the lumen
Describe the tunica interna
endothelial layer that lines the lumen of all vessels
What is found in vessels larger than 1 mm?
a subendothelial layer of connective tissue is present
Describe the tunica media
consists of smooth muscle and an elastic. fiber layer
regulated by the sympathetic nervous system
controls the vasoconstriction and vasodilation of vessels
Describe the tunica externa (tunica adventitia)
contains collagen fibers that protect and reinforce the vessel wall
What is vasa vasorum?
a network of small blood vessels that supply the walls of large blood vessels, such as elastic arteries and large veins
What are elastic arteries?
thick-walled arteries near the heart (aorta and its major branches)
contain elastin
What does the elastic in elastic arteries do?
help withstand and smooth out large blood pressure fluctuations
allow blood to flow fairly continuously through the body
What are muscular arteries?
found distal to elastic arteries deliver blood to organs thick tunica media more smooth muscle less elastic tissue active in vasoconstriction
What are arterioles?
the smalles arteries
lead to capillary beds
control flow into capillary beds via vasodilation and constriction
What is blood pressure defined as?
the force per unit area exerted by blood on the vessel wall
expressed in mm Hg
measured in reference to systemic arterial BP in the large arteries near the heart
What do the differences in BP provide?
the driving force that keeps blood moving from higher to lower pressure areas
What is resistance defined as?
the opposition to flow
measures the amount of friction that the blood encounters as it passes through the vessels
What are the three important sources of resistance?
blood viscosity
total blood vessel length
blood vessel diameter
What is blood viscosity?
represents thickness or stickiness of blood
directly proportional to resistance
R goes up, BF goes down
How does blood vessel length affect resistance?
the longer the vessel, the greater the resistance encountered
How does vessel diameter affect resistance?
changes in vessel diameter are frequent and most significant to peripheral resistance
small-diameter arterioles are the major determinants of peripheral resistance
What is blood flow defined as?
volume of blood flowing through a vessel, an organ, or the entire circulation in a given period of time
measured in mL/min
What does blood flow throughout the entire vascular system equate to?
Cardiac output
How does blood flow compare throughout organs?
varies wildly through individual organs
dependent on its immediate needs
What is blood flow directly proportional to?
change in blood pressure between two points in the circulatory pathway
Describe how change in pressure and blood flow affect each other in terms of up and down
if change in pressure increases, blood flow increases
if change in pressure decreases, blood flow decreases
What is blood flow inversely proportional to?
resistance
Describe how resistance and blood flow affect each other in terms of up and down
If resistance increases, blood flow decreases
What is the equation to calculate blood flow?
pressure gradient/resistance
When is pressure resulted in the vascular system,?
when flow is opposed by resistance
Describe systemic pressure throughout the cardiovascular system
highest in the aorta
declines throughout the length of the pathway
Where is systemic pressure 0 mmHg?
right atrium
Where does the steepest change of systemic pressure occur?
the arterioles
What is blood pressure like in the elastic arteries near the heart?
pulsatile
What is systolic pressure?
the pressure exerted on the arterial walls during ventricular contraction
normal value is less than 120 mmHg
What is diastolic pressure?
lowest level of arterial pressure during a ventricular cycle
normal value is less than 80 mmHg
What is pulse pressure?
difference between systolic and diastolic pressure
P pulse = P systolic - P diastolic
What is mean arterial pressure (MAP)?
the pressure that propels the blood to the tissues
MAP = P diastolic + 1/3 P pulse
What two factors does arterial blood pressure reflect?
their elasticity
the amount of blood force into them at any given time
How is blood pressure maintained?
through cooperation of the heart, blood vessels, kidneys, and the brain
What are the main factors influencing blood pressure?
cardiac output
peripheral resistance
blood volume
BP = CO * PR
What are short-term controls in regulating blood pressure?
mediated by the nervous system and blood-borne chemicals that counteract moment-to-moment fluctuations in blood pressure by altering peripheral resistance
What are long-term controls in regulating blood pressure?
These just regulate blood volume
What does high blood pressure do to baroreceptors?
increases stimulation of baroreceptors in the aortic arch and carotid sinuses
stimulus is processed by the cardiovascular center
What does high blood pressure result in in regards to the nervous system?
increase in parasympathetic activity - decreases heart rate and contractility leads to decrease of CO and therefore BP sympathetic activity decreased decrease in peripheral resistance decrease BP
What does declining BP do to baroreceptors?
decreases rate of firing
stimulus is processed by the cardiovascular center
What does declining blood pressure result in in regards to the nervous system?
sympathetic stimulation vasoconstriction increase in peripheral vascular resistance increase in heart rate and contractility increase CO BP rises back to normal
How have baroreceptors adapted to chronic increased BP?
stimulates the kidneys to elimnate water, thus reducing BP
How have baroreceptors adapted to chronic reduced BP?
stimulates the kidneys to increase blood volume and VP
kidneys act directly and indirectly to maintain long-term blood pressure
What does the direct renal mechanism lead to in increased BP?
increase urine production
lower blood volume
decrease BP
What does the direct renal mechanism lead to in reduced BP?
renin-angiotensin mechanism
renin is released by the kidneys
renin converts blood-born angiotensinogen into angiotensin I
angiotensin-converting enzyme (ACE) further converts angiotensin I into angiotensin II
What effects does angiotensin II have?
potent vasoconstrictor which increases resistance and BP
stimulates aldosterone and ADH secretion
these enhance renal reabsorption and lead to water retention
BV leads to preload increase and SV, CO, BP increase
What do capillary walls consist of?
thin tunica interna, one cell thick
lumen only allows one RBC to pass at a time
What are continuous capillaries?
abundant in the skin and muscles
have endothelial cells that provide an uninterrupted lining
adjacent cells held together with tight junctions
What allows passage of fluids in continuous capillaries?
intercellular clefts of unjointed membranes
What are fenestrated capillaries?
found wherever active capillary absorption or filtrate formation occurs
characterized by fenestrations (pores) and are more permeable to solutes and fluids than other capillaries
What are sinusoids?
highly modified, leaky, fenestrated capillaries with large lumens
allow large molecules (proteins and blood cells) to pass between the blood and surrounding tissues
Where are sinusoids found?
liver
bone marrow
lymphoid tissue
some endocrine organs
What are metarterioles?
a thoroughfare channel connecting an arteriole directly with a postcapillary venule
Describe the capillary pathway
microcirculation of interwoven networks of capillaries consists of vascular shunts
true capillaries that branch off the metarteriole
return to the thoroughfare channel at the distal end of the bed
review in book worded horribly in notes
What are precapillary phincters?
contain smooth muscle cells
surround each true capillary
regulate blood flow into it
What regulates blood flow through the capillary bed?
vasomotor nerves
local chemical conditions
it can either bypass or flood the capillary bed
What are venules?
formed when capillary beds unite
What happens in capillary exchange?
O2, CO2, nutrients, and metabolic wastes diffuse between the blood and interstitial fluids along concentration gradients
What passes FROM blood TO tissues in capillary exchange?
O2
nutrients
What passes TO blood FROM tissues in capillary exchange?
CO2
metabolic wastes
What types of molecules travel through what type of passageways in capillary exchange?
water-soluble solutes pass through clefts and fenestrations
lipid-soluble molecules diffuse directly through endothelial membranes
What is capillary filtration subjective to?
direction and the amount of fluid flow depend upon the difference between hydrostatic pressure and colloid osmotic pressure
What is capillary hydrostatic pressure?
the pressure of blood on the capillary walls
forces fluids through the capillary walls
Describe hydrostatic pressure throughout a capillary bed
because of the resistance, HPc is greater at the arterial end of a bed than at the venular end
very little fluid in interstitial space, so HPc on capillary wall by interstitial fluid is very small
What is osmotic pressure?
the pull of water exerted by large non-diffusible molecules
What causes capillary osmotic pressure?
non-diffusible plasma proteins
these draw water to themselves
What is interstitial osmotic pressure?
Created by the few proteins in the interstitial space
small
How is net filtration pressure calculated?
NFP = P out - P in = (HPc + OPi) - (HPi + OPc)
What happens when NFP is positive? Negative?
positive - filtration takes place
negative - reabsorption takes place
What is the lymphatic system?
excessive fluid is filtered from the capillaries and is returned to general circulation via the lymphatic system
What are lymphatic capillaries?
blind ended and extremely porous capillaries that lie in the interstitial spaces
aid in reabsorption of interstitial fluid
assemble into lymphatic ducts
Where do lymphatic capillaries travel to?
pass through lymph nodes and drain into subclavian veins
What are lymph nodes?
a site of immune defense
Describe the right lymphatic duct
drains lymph from the right side of the body above the diagram
Describe the thoracic duct
drains the lymph from the left side of the body above the diaphragm and all the body below the diaphragm
What are venules?
formed when capillary beds unite
What forms veins?
formed by converging venules
