Blood vessels & Blood - Lectures 14-15-16 Flashcards
- walls of blood vessels contain (3)
- inner layer is ___________ –> secretes what? + regulates (3)
- smooth muscle + elastic connective tissue + fibrous connective tissue
- endothelium –> secretes paracrine factors + regulates blood pressure, blood vessel growth and absorption
what is muscle tone?
a state of partial contraction –> smooth muscles always in contraction, never totally relaxed
what are the 3 layers of blood vessel structure?
- tunica intima = most inside
- endothelium: specialized epithelial cells
- under endothelium = 1 layer of basement membrane (layer of collagen to support cells together)
- some elastic components - tunica media:
- lost of smooth muscles for contractions
- some elastic tissues (especially arteries) - tunica externa:
- connective tissues: collagen + fibroblast to hold blood tissues together
ARTERIES:
- 2 main functions
- 2 characteristics
- pressure reservoir
- distribute blood to different tissues and organs using smooth muscles (contract = less blood VS relax = more blood goes through)
- thick layers of vascular smooth muscles
- lots of elastic and fibrous connective tissue
ARTERIOLES:
- main function?
- part of the _________
- characteristic
- generate variable resistance using 80% of smooth muscle
- part of microcirculation
- less elastic + more muscular
METARTERIOLES:
- btw (2)
- branches of ________
- 2 characteristics
- between arterioles and capillaries
- branches of arterioles
- partial smooth muscle layer
- precapillary spincters open and close to direct blood flow to capillaries or venous circulation
CAPILLARIES:
- function?
- has all 3 layers of blood vessels?
- walls are (3)
- what contributes to capillary impermeability? –> characteristics
- primary site of exchange between blood and interstitial fluid! very leaky
- has tunic intima. almost no tunic media and externa
- walls lack smooth muscle + flat layer of endothelium + basal lamina = tunic intima
- pericytes! contractile cells associated with capillaries –> projection hold endothelial cells + secrete paracrine factors that promote growth and differentiation
VEINULE AND VEINS
- main function?
- 2 characteristics
VENULES:
- function?
- 3 characteristics: what type of pattern flow?
VEINS:
- function?
- 4 characteristics: more numerous than arteries? Close/far of body surface? Thin/thick walls? Elastic?
- contain what which prevent backflow?
- volume reservoir
- large lumen + not much smooth muscle and elastic
VENULES: - receive blood from capillaries
- thin exchange epithelium + little connective tissue + convergent pattern of flow
VEINS: - volume reservoir!
- thin walls of vascular smooth muscles + more numerous than arteries + lie closer to body surface + less elastic tissue
- contain one-way valves to prevent backward flow (especially for legs bc hard to push back to heart bc low BP in veins)
what do precapillary sphincters do?
- in most situations, open or closed?
- control if blood goes through capillary bed
- if contracted, blood from arterioles directly go to veinules (no exchange with interstitial fluid)
- if open, artery blood goest through capillaries
- most situations –> closed! only 7% of blood in capillaries
where is vein located in calf muscle? why?
in between muscle cells!
- so when muscle contracts, squeeze vein to help blood go back to heart
Blood pressure is highest in _______ and lowest in ________
- what is pulse pressure? how to calculate?
- decreases over what?
- how to aid venous return (3)
- highest in arteries, lowest in veins
- pulse pressure measures strength pressure wave produced by ventricular contraction
- pulse pressure = systolic pressure - diastolic pressure
- decreases over distance due to friction
1. valves
2. skeletal muscle pump
3. respiratory pump
- what is mean arterial pressure (MAP)? how to calculate?
- hypotension/hypertension compared to MAP
- MAP represents driving pressure –> arterial blood pressure reflects driving pressure for blood flow
- MAP = diastolic pressure + 1/3(systolic pressure - diastolic pressure)
*not just (systolic + diastolic)/2 bc heart spends more time in relaxation than contraction - hypotension lower than MAP, hypertension higher than MAP
blood pressure is estimated by ____________
- _________ sounds?
sphygmomanometry
- Korotkoff sounds
how do arteries act as a pressure reservoir when ventricle contracts? 3 steps ish
- ventricle contracts –> semilunar valve opens + blood ejected from ventricles flows into arteries –> aorta and arteries expand and store pressure in elastic walls!
- aorta = lots of elastic tissues –> when blood comes, expand like a balloon so pressure doesn’t increase too much
how do arteries act as pressure reservoir when ventricle relaxes? 3 steps
isovolumic ventricular relaxation –> semilunar valve shut, preventing flow back into ventricle –> elastic recoil of arteries sends blood forward into rest of circulatory system = maintains driving pressure during ventricular diastole
when person gets older, BP increases or decreases? why?
increases! because elastic tissues get lost –> heart can’t expand that much to BP increases –> heart needs to pump harder
- mean arterial pressure proportional to what (2)
- if flow in exceeds flow out, then blood volume (increase/decrease) and MAP (increase/decrease)
- if flow out exceeds flow in, then blood volume (increase/decrease) and MAP (increase/decrease)
- proportional to cardiac output (CO) and resistance in arterioles
- in > out –> BP increases, MAP increases
- out > in –> BP decreases, MAP decreases
how does blood volume affect blood pressure:
- blood volume constant during day?
- if blood volume increase, pressure (increase/decrease). explain
- if blood volume decrease, pressure (increase/decrease). explain
- relatively constant!
- if blood volume increases, pressure increases –> kidney is responsible for removing excess fluid volume
- if blood volume decreases, pressure decreases –> lost fluid volume compensated through drinking or intravenous infusion + vasoconstriction and sympathetic stimulation of heart
- increase blood volume leads to increase blood ________
- how to compensate ? 2 pathways
increase blood volume leads to increase blood pressure
1. compensation by cardiovascular system –> vasodilation + decrease cardiac output –> decrease BP to normal
2. compensation by kidneys –> excretion of fluid in urine –> decrease blood volume –> decrease blood pressure to normal
resistance in arterioles is influenced by:
1)_________ reflexes –> branches into 2 –> what receptors?
2) _________ control
- which of the 2 is more powerful?
1) systemic reflexes –> in all blood vessels
a) autonomic nervous system –> SNS induces smooth muscle contraction (exception: vasculature of erectile tissue) –> NE on alpha receptors = vasoconstriction
b) hormones: adrenal medulla secretes 80% Epinephrine vs 20% NE –> a receptors with low affinity = vasoconstriction
2) local control –> more important than systemic effects! can override them
2 ways local control can influence resistance in arterioles?
1) ________ _________ adjusts blood flow
- vascular smooth muscle vs stretched vascular smooth muscle
2) _________ signals influence vascular smooth muscle
- secreted by what?
- 3 examples
- active hyperemia vs reactive hyperemia (another flashcard)
- myogenic autoregulation: no need for systemic signal –> when blood comes, vessels expand/stretch –> induces contractions
- vascular smooth muscle regulates its own state of contraction
- stretched: mechanically gated Ca2+ channels –> contracts to resist stretching - paracrine signals influence vascular smooth muscle
- by vascular epithelium or nearby cells
- nitric oxide (induce smooth muscle relaxation through cGMP) + kinins and histamines are potent vasodilators
active vs reactive hyperemia
ACTIVE: matches blood flow to increased metabolism
- increase of tissue metabolism –> need more O2 + produces more CO2 –> release of metabolic vasodilators into ECF –> arterioles dilate –> decrease resistance = more blood flow –> O2 and nutrients supply to tissue increases as long as metabolism is increased
REACTIVE: follows a period of decreased blood blow
- blocked blood flow –> metabolic vasodilators accumulate in ECF –> arterioles dilate but occlusion prevents blood flow –> than unblock –> decrease resistance increases blood flow (increase blood flow at that area (opposite of hemorrhage)) –> as vasodilators wash away, arterioles constrict and blood flow returns to normal
blood distribution varies according to what?
- governed by 2
- possible bc arterioles are arranged in __________: flow in aorta = flow in __________
- individual arterioles regulate _____ flow –> compensated by remaining __________
- cerebral blood flow stays nearly __________
- according to metabolic need of individual tissues
- by local control mechanisms (can override systemic factors) + homeostatic reflexes
- arranged in parallel!: flow in aorta = flow in arterioles
- regulated their own flow –> compensated by remaining arterioles
- constant
distribution of blood in body at rest:
- which 2 organs are pretty stable? vs which organs are variable?
- brain (14%) and kidneys (20%) (to remove waste) are pretty stable
- heart (4%), liver and digestive tract (27%), skeletal muscle (21%), skin (5%), bone and other tissues (9) are variable
blood flow through individual blood vessels is determined by the vessel’s what?
- formula for blood flow –> what is the biggest variation/change in the formula!
- determined by vessel’s resistance to flow!
- blood flow = deltaP / Resistance
- resistance = 8Ln/pi*r^4
- radius!!!! what changes the most because of 4th power while length and viscosity remain pretty constant
what center regulated the cardiovascular function?
- the ____________ reflex controls blood pressure
- 4 steps of the reflex arch
- cardiovascular control center (CVCC)
- baroreceptor reflex
- receptor –> afferent –> CNS/medulla –> efferent –> effectors (heart and blood vessels)
- where are baroreceptors (mechanoreceptors)? (2)
- produce _________/______ action potential to _____ _______
- changes in pressure reflected by changes in ________ of _______ ________
- in carotid arteries and aorta
- produce continuous/tonic action potential in brain stem
- changes in frequency of action potential
- ALWAYS FUNCTIONING!