Vascular Flashcards
arteries
carry blood away from the heart
branch
diverge
fork as they form smaller ones
Veins
carry blood twd the heart
join, merge, and converge into successive layers approaching heart
In pulmonary circulation how do arteries function?
Instead of carrying oxygenated blood they carry deoxygenated blood to the lungs
In pulm ciruit, how do veins function ?
Instead of carrying deoxygenated blood they carry oxygenated blood to from lungs to heart
Lumen
central blood-containing space covered by the tunics
Tunics
the walls of blood vessels, except smallest ones, have three layers and surround the lumen
(coverings)
tunica intima
innermost tunic
intimate contact with the blood in the lumen
What does the tunica intima contain?
simple squamous (endothelium tissue) epithelium that lines the lumen of all vessels
What is the role of the endothelium tissue ?
continuous with the endocardial lining of the heart, and its flat cells fit closely together, forming a slick surface that minimizes friction as blood moves through the lumen.
What is the subendothelial layer and its purpose?
In vessels larger than 1mm, has basement layer and loose connective tissue that supports the endothelium
Tunica media
middle tunic that is mostly circular arranged muscle cells and sheets of elastin
How is the smooth muscle cells activity of the tunica media regulated?
It is regulated by the sympathetic vasomotor nerve fibers of the ANS and bunch of chemicals
What does tunica media regulation cause?
Vasconstriction or vasodilation
Vasoconstriction
lumen diameter decreases as the smooth muscle contracts
vasodilation
lumen diameter increases as the smooth muscle relaxes
Why is the activity of the tunica media important?
Tunica medica is critical in regulating circulatory dynamics because small changes in vessel diameter greatly influence blood flow and blood pressure
What is the bulkiest tunic layer in the arteries and why so?
Tunica media since it chiefly responsible for maintaining blood pressure and circulation
Tunic externa
outermost layer of blood vessel wall
Tunica adventitia
same as tunic externa
means coming from outside
What makes up the tunica externa?
composed largely of loosely woven collagen fibers that protect and reinforce vessel and anchor it to surrounding structures
What is the tunica externa infiltrated with?
nerve fibers, lymphatic vessels, and in larger VEINS, a network of elastic fibers
What does the tunica externa have in large vessels?
Vasa vasorum, tiny system of blood vessels
“vessels of the vessels”
function of vasa vasorum
nourish more external tissues of the blood vessel wall
What gets the most nutrients?
innermost/luminal portion of the vessel obtains nutrients directly from blood in the lumen
What do the tunics all vary?
length, diameter, wall thickness, and tissue makeup
What are the three groups that arteries can be divided into
in regards to relative size and function?
elastic arteries
muscular arteries
arterioles
Elastic arteries
thick-walled arteries near the heart like the aorta and it major branches, and are the largest in diameter and most elastic, low resistance pathways that conduct blood from the heart to medium sized arteries, and for that they are sometimes called conducting arteries
What do elastic arteries have most of than any other arteries?
elastin
What is present in all three tunics, and which tunic has the most?
elastin, tunica media
Function of elastic arteries
pressure reservoirs, expanding and recoiling as the heart ejects blood, so that blood flows continusouly rather than starting and stopping with pulsating rhythm of the heartbeat
How does atherosclerosis impact elastic arteries?
blood flows more intermittently (stop and go)
What would happen to arteries if they weren’t elastic?
Without the pressure smoothing effect of the elastic arteries, the walls of arteries throughout body would experience higher pressures, and would eventually weaken and may balloon or burst
Muscular arteries
distal to elastic arteries
deliver blood to specific body organs (sometimes called distributing arteries for that reason)
size of muscular arteries
internal diameter from that of a little finger to that of a pencil lead
muscular arteries have the thickest what
media tunica
Tunica media in muscular artery traits
more smooth muscle and less elastic tissue than elastic arteries
Since they have a unique tunica media, muscular arteries have more of an active role in what?
vasoconstriction and less stretchable (distensible)
What on each face of tunica media in muscular arteries?
elastic membrane
larger arterioles and their tunics
larger ones have all three, but their tunica media is chiefly smooth muscle with a few scattered elastic fibers
smaller arterioles
lead into cap beds, little more than a single layer of smooth muscle cells spiraling around endothelial lining
arteriole diameter determines what?
varies in change to response to changing neural, hormonal, and local chemical influences
What happens when the arterioles constrict?
the tissues served are largely bypassed
What happens when the arterioles dilate??
blood flow into the local capillaries increases dramatically
What the smallest blood vessels? They r microscopic
capillaries
Capillaries consist of what?
thin tunica intima, and sometimes one endothelial cell forms the entire circumference of the capillary wall
Pericytes
at strategic points along the outer surface of some capillaries are these spider shaped, smooth muscle-like cells that stabilize the capillary wall and help control capillary permeability
cap size
large enough to allow red blood cells in single file
Tendons and ligaments are what?
poorly vascularized
Cartilage and epithelia lack?
caps, but receive nutrients from blood vessels through nearby connective tissues
AVASCULAR cornea and lens of eye receive nutrients from what?
aqueous humor
What are capillaries role ideally suited for?
exchange of materials such as gases, nutrients, hormones .. . between the blood and interstitial fluid
what are the three structures of capillaries?
continuous
fenestrated
sinusoid
Continuous capilliaries
abundant in skin and muscles, most common
Continuous in the sense that their endothelial cells are joined together by tight junctions
What do tight junctions in continuous caps do?
providing an uninterrupted lining, but these junctions usually incomplete and leave gaps of unjoined membrane, intercellular clefts
Intercellular clefts in continuous caps
gaps of unjoined membranes (tight junctions) that are large enough to allow limited passage of fluids and small solutes
Brain caps in cont caps
tight junctions are complete and extend the entire perimeter of endothelial cells, constituting structural basis of blood brain barier (no intercellular cleft makes it unique)
Fenestrated caps
are like continuous variety except that the endothelial cells in fenestrated capillaries are riddled with oval pores, or fenestrations (fenestra=window)
What covers fenestrations?
delicate membranes, or diaphragm
What does fenestrated have differently from continuous cap structure?
more permeable to fluids and small solutes than cont caps
Where are fenestrated capillaries found?
anywhere active capillary absorption or filtrate formation occurs
example location fenestrated caps
small intestines receive nutrients from digested food, and those in endocrine organs allow hormones rapid entry into the blood, kidneys-open pores where rapid filtration of blood plasma is essential
Sinusoid caps (sinusoids)
highly modified, leaky caps found only in the liver, bone marrow, spleen, and adrenal medulla
sinusoids desrciption
large, irregularly shaped lumens and are fenestrated
sinusoids endothelial have
fewer tight junctions and larger intercellular clefts than ordinary capillaries
What do the structural adaptations in sinusoids allow?
large molecules and even blood cells to pass between the blood and surrounding tissues
sinusoids in liver
endothelial is discontinuous, and lining includes stellate macrophages (hepatic macrophages)
purpose/f(x) of stellate macrophages
remove and destroy any bacteria
sinusoids in spleen
phagocytes located just outside the sinusoid stick cytoplasmic extensions through the intercellular clefts into the sinusoid lumen to get their prey
How does blood flow in sinusoids?
sluggishly through sinusoid channels since it allows time for it be modified in various ways.
Capilary beds
caps form these interweaving networks
Microcirculation
blood flow from arteriole to a venule
What blood vessels comprise the cap bed?
vascular shunt
true capillaries
vascular shunt
metarteriole-thoroughfare channel
a short vessel that directly connects the arteriole and venule at opposite ends of the beds
True capillaries
actual exchange vessels
terminal arteriole
feeding bed leads into a metarteriole that is continuous with the thoroughfare channel that joins the postcapilary venule
metarteriole
vessel structurally intermediate btw an arteriole and a capillary
thoroughfare channel
intermediate btw a capilary and a venule
postcapillary venule
drains the bed
What determines amount of true capillaries?
organ or tissue served
how the true cap situate in the body?
branch off the metarteriole, the proximal end of shunt, and return to the thoroughfare channel (distal end of shunt); but sometimes they derive from the terminal arteriole and empty into the venule
precapillary sphincter
cuff of smooth muscle fibers that surrounds the root of each true capillary at the metarteriole
precap sphincter function
acts as a valve to regulate blood flow into the capillary
Blood flow through a terminal arteriole flows
through true cap or through the shunt
What happens when the precapillary sphincters are relaxed/open?
blood flows through true capillaries and takes a role in exchanges w/ tissue cells
What happens when precap sphincters are constricted/closed?
blood flows through the shunts and bypasses the tissue cells
What regulates the amount of blood entering a cap bed?
local chemical conditions and arteriolar vasomotor nerve fibers
when bed is flooded with blood or completely bypassed it depends on what?
conditions in body or specific organ
Venules
Capillaries untie to form
What is the smallest venule?
postcapillary venule
What does postcapilary venule consist of?
entirely endolethium around which the pericytes congregate , extremely porous, and fluid and white blood cells move easily from the bloodstream through their walls
larger venules
have one or 2 layers of smooth muscle cells (tunic media and thin tunica externa)
Veins are formed by
venules
vein anatomy
3 distinct tunics, thinner walls and their lumens r larger than those corresponding arteries. Lumens split like
what is there relatively little of in veins?
smooth muscle/elastin in tunica media that poorly developed and tends to be thin even in largest veins
Tunica externa in veins
is heaviest wall layer, consisting of thick longitudinal bundles of collagen fibers and elastic networks; often several times thicker than tunica media
Large veins (venue cava) tunica externa size
even thicker due to longitudinal bands of smooth muscle
Why are veins called capacitance vessels and blood reservoirs?
hold 65% of body’s blood supply at any time, even so they are partially filled normally
Why can the vein walls be thinner than arteries’ without danger to of bursting ?
blood pressure in veins is low
what adaptation of low pressure do to veins and why so?
Ensure that veins returns blood back to heart same rate it was pumped into circulation
larger lumen in lumen offer little resistance to blood flow
Venous valves
prevent back flow
formed from folds of the tunica intima, resemble semilunar valves of the heart in both structure and f(x)
Where venous valves most abundant?
in veins of limbs, where gravity opposes the upward bloodflow
Where are venous valves unlikely found?
absent in veins of thoracic and abdominal body cavities
varicose veins
veins that are twisted and dilated due to incompetent (leaky) valves
Venous sinuses
coronary sinus
dural venous sinuses
highly specialized, flattened veins with extremely thin walls composed only of endothelium
What venous sinuses supported by?
tissues surrounding them rather than additional tunics
Vascular anastomoses
blood vessels from special interconnections
arterial anastomoses
most organs receive blood from more than one arterial branch and arteries supplying the same area merge and form alternate paths
Alternate paths in anastomoses
collateral channels direct blood to certain body region
What happens if there a branch is cut or there is clot?
collateral channels can provide enough blood to area often
Where do arterial anastomoses occur?
around joints where active movement may hinder blood flow through one channel, and also they common in abdominal organs, heart, and brain
What organs do not have anastomoses?
arteries that supply the retina, kidneys, and spleen or they have poorly developed collateral circulation
What happens to the organs that do not have anastomoses when blood flow is interupted?
cells that supply such vessel die
arteriovenous anastomoses
metarteriole-thoroughfare channel shunts of capillary beds that connect arterioles and venules
what interconnects more freely veins or arteries?
veins interconnect more freely
what are more common and abundant arterial or venous anastomose?
venous anastomoses are more common and abundant
Blood flow
volume of blood flowing through a vessel, an organ, or the entire circulate in a give period (ml/min)
= to Cardiac output and is constant during resting
Blood pressure
force/area exerted on a vessel wall by the contained blood (mm Hg)
bp and pressure gradient
the differences in bp within vascular sys that provides driving force that keeps blood moving always high to low throughout body
Resistance
is opposition to flow and measure of the amount of friction blood encounters as it passes through the vessels
peripheral resistance
most friction is dealt with in the peripheral (systemic) circulation
3 sources of resistance in
blood viscosity, vessel length, and vessel diameter
blood viscosity
internal resistance to flow that exists in all fluids (viscosity) and is related to the thickness or stickiness in fluid
why is blood more viscous than h2o?
blood has formed elements and plasma proteins, it flows more slowly under same conditions
what can increase blood viscosity/resitance?
polycythemia (excessive numbers of red blood cells)
Blood vessel length
the longer the vessel, the greater the resistance
blood vessel diameter
changes frequently and alters peripheral resistance
laminar flow or streamlining
the relative speed and position of fluid in diff regions of the tube’s cross sectioning remain constant
The smaller the tube the great the friction since more fluid contacts the tube wall where its movement is blocked
How does resistance vary?
inversely with the fourth power of the vessel radius
why do the arterioles change dramatically in diameter?
they respond to neural and chemical curls, are major determinants of peripheral resistance unlike the large arteries close to the heart
turbulent flow
irregular fluid motion where blood from the different laminae mixes, increasing resistance dramatically, is onset by arteriosclerosis
What is blood flow directly proportional to?
to difference in blood pressure between two point in circulation which is bp, hydrostatic pressure, gradient. When pressure increases, bf speeds up
Blow flow is inversely propotional to?
PERIPHERAL RESISTANCE R in systemic circulation; if resistance increases, BF decreases
What does pressure result from?
when flow is opposed by R
What vessel offers the greatest resistant to blood flow?
arterioles
arterial blood pressure
how much the elastic arteries close to the heart can stretch (compliance/distensibility)
volume of blood forced into them at any time
Why is blood pressure pulsatile and what does that word even mean?
the amount of blood leaving and entering heart are not equal/constant, and that means a rise and fall in a reg fashion in the elastic arteries near the heart
ventricular contraction
systolic pressure
blood moves into the arterial bed since the pressure in the aorta is higher than the pressure in the more distal vessels
WHAT HAPPENS DURING DIASTOLE? diastolic pressure
the aortic valves closes preventing blood from flowing back into the heart; wall of aorta recoil maintaining sufficient pressure tp keep blood flowing fwd to its lowest levels
pulse pressure
the difference btw systolic and diastolic pressure
Mean arterial pressure (MAP)
aortic pressure fluctuates up and down with each heartbeat is important to this
the pressure that propels blood to the tissues
why low cap pressures necessary?
capillaries are fragile and high pressures rupture them
most capillaries are extremely permeable and thus even the low capillary pressure can force solute containing fluids (filtrate) out of blood stream into the interstitial space
venous blood pressure
is different from arterial bp
steady and changes very little during cardiac cycle
what happens when a vein is cut and how is it different than artery being cut?
different than artery
for vein, blood flows evenly from wound
for artery, spurts blood
This is because veins have lower pressure, high R
muscular pump
skel muscle activity
as skel muscle surrounding deep veins contract and relax, they “milk” blood two the heart and once blood passes each successive valve like the circles in inferno, it can’t flow back
fainting after standing for long time periods cuz it reduces venous return
resp pump
moves blood up two heart as pressure changes in the ventral body cavity during breathing
As we inhale, abdominal pressure increases, squeezing local veins aand forcing blood two the heart
at the same time, the pressure in the chest decreases allowing thoracic veins to expand and speeding blood entry into right atrium
Sympathetic venoconstrction
reduces volume of blood in veins (capacitance vessels)
as the layer of smooth muscle around veins constricts under sympathetic ctrl, venous volume is reduced and blood is pushed two the heart
What do muscle pumpp, resp pump, and sympathetic venoconstriction do?
increase venous return which increases SV by the Frank-starling mechanism thus increasing CO
what maintains blood pressure?
cns, CO, R, blood volume
blood varies ______ with CO (and blood volume) and R
directly
what is in charge of heart most of the time (resting heart rate that is )
cardioinhiborty center of medulla oblongatta
short-term regulation of bp
by nervous system and bloodborne hormones alters bp by changing peripheral resistance and CO
long-term reg bp
alters blood volume via kidneys
Short term regulation functions how
neural ctrls alter both CO and R
2 main goals of neural curls of peripheral R
maintainin adq MAP by changing blood vessel diameter on a moment basis, under low blood volume, all vessels except those supplying heart and brain are constricted to allow as much blood as possible to flow to those two vital organs
altering blood distribution to respond to specific demands of various organs
How do most neural curls operate ?
via reflex arcs involving barorecptors and associated afferent fibers; these reflexes are integrated in the cardiovascular center of the medulla, and their output travels via autonomic fibers to the heart and vascular smooth muscle.
What are the chemical inputs in neural ctrl?
chemoreceptors and higher brain centers also influence the neural ctrl mech
what ctrls diameter of blood vessel????
cardiovascular centers and vasomotor centers
vasomotor fibers
the vasomotor center transmits fibers impulses at a fairly steady rate along the sympathetic efferents
what do the vasomotor fibers do?
fibers exit T1 through L2 levels of spinal cord and innervate the smooth muscle of blood vessels, mainly invervate arterioles
vasomotor tone
arterioles are almost always state of moderate constriction
what does any increase in sypmthatetic activity do?
yields generalized vasoconstriciton and raises bp
modify inputs of cardiovascular center
baroreceptors
chemoreceptors
higher brain receptors
baroreceptors
pressure sensitive mechanoreceptors that respond to changes in arterial pressure and stretch
arterial blood pressure increase activates it
stretch receptors
they decrease BP
chemoreceptors
receptors that respond to changes in blood lvld of co2, H+, O
where are baroreceptors located?
carotid sinuses
AORTIC ARCH
walls of nearly every large artery of the neck and thorax
carotid sinuses
which are dilations in the internal carotid arteries that provide the major blood supply to the brain
arteriolar vasodilation
decreased output from vasomotor center allows arterioles to dilate. as r falls, MAP does
venodialtion
decreased output from vasomotor center makes veins dilate which shifts blood to the venous reservoirs; this decreases venous return and CO
Decreased CO
impulses to the cardiac centers inhibit sympathetic activity and stimulate parasympathetic activity, reducing HR and contractile force. As CO decreases so does MAP
what do barorecptors in the carotid sinus reflex do?
protect blood supply to your brain
barorepctors in aortic reflex?
help maintain adq bp in your systemic circuit
How chemrecptors activated?
When CO2 lvld rises or pH falls or oxygen content of the blood drops sharply
where are the chemrecpts activated and how
aortic arch and large arteries of the neck transmit impulses to the cardioacceltry center which then increases cardiac output,and to the vasomotor center that causes reflex vasoconstriction.
what are the most prominent chemrecptors?
carotid and aortic bodies located close by the baroreceptors in carotid sinuses and aortic arch
chemosrepctors play a larger role in
regulating resp rate than bp
WHAT mediates long term regualtion
renal mechanisms
kidneys help regulate
blood volume
what is a major determinant in blood volume?
CO
What does a sudden drop in BP signals?
internal bleeding and blood volume too low to support normal circulation
direct renal mechanisms
alters blood volume independently of hormones (they don’t rely on hormones to change blood volume)
as blood volume decreases, what else does?
arterial bp decreases
indirect renal mechanism
renin-angiotensin-aldosterome mechanism regulates bp
vital signs (vitals)
pulse, BP, resp rate, and body temp
pulse
transmitted through the arterial tree, artery against a firm tissue is how it is felt
pressure points
pulse points, they are compressed to stop flow into distal tissue during hemorrhage
hemmorrhage
bleeding
systolic pressure where hear what is happening
first point at which a small amount of blood is spurting through constricted artery
sounds of Korotkoff
cuff pressure reduction when sounds get louder and disntct
diastiolic pressure when heard
when sound goes away
tissue perfusion 4 things it does
delievering oxygen and nutrients to tissue cells and removing waste from them
exchangig gases in the lungs
absorbing nutritents from digest tract
forming urine in kidneys
autoregulation
the automatic adjustment of blood flow to each tissue in proportion to the tissues requirements at any instant
What can cause essential/ primary hypertension?
Heredity, Diet, Obesity, Age, Diabetes mellitus, and stress, smoking increase blood pressure
Hypertension: secondary hypertension causes
CHAPS
Cushing's syndrome Hyperaldosteronism [aka Conn's syndrome] Aorta coarctation Phaeochromocytoma Stenosis of renal arteries
Posterior mediastinum: contents
DATES
Descending aorta Azygos and hemiazygous veins Thoracic duct Esophagus Sympathetic trunk/ganglia
Thoracoacromial trunk: branches
"Cadavers Are Dead People": Clavicular Acromial Deltoid Pectoral
Thoracoacromial artery branches
ABCD:
Acromial
Breast (pectoral)
Clavicular
Thoracoacromial artery branches
"CAlifornia Police Department": Clavicular Acromial Pectoral Deltoid
Branches of Internal Iliac Artery
"I Love Going Places In My Very Own Underwear": Ileolumbar Lateral sacral Gluteal (superior and inferior) Pudendal (internal) Inferior vesicle (uterine in females) Middle rectal Vaginal Obturator Umbilical
Internal iliac artery: anterior branches
What Bill admitted to Hilary: "I Milked Our Insatiable Intern's Udders Under the Desk": Inferior gluteal Middle rectal Obturator Inferior vesical artery Internal pudendal artery Umbilical U/D=Uterine artery (female)/ Deferential artery (male)
Internal iliac artery: posterior branch
PILS: Posterior branch Iliolumbar Lateral sacral Superior gluteal
External jugular vein: tributaries
PAST: Posterior external jugular vein Anterior jugular vein Suprascapular vein Transverse cervical vein
> Vascular endothelium: simplified cross-section
LIMA: Lumen Intima Media Adventitia
> Aortic arch: major branch order
"Know your ABC'S": Aortic arch gives rise to: Brachiocephalic trunk left Common Carotid left Subclavian · Beware though trick question of 'What is first branch of aorta?' Technically, it's the coronary arteries.
> Lung lobe numbers:
right vs. left Tricuspid heart valve and tri-lobed lung both on the right side.
Bicuspid and bi-lobed lung both on the left side.
> Ulnar nerve to ulnar artery and radial nerve to radial artery relations Think
“peripheral nerves”:
The ulnar nerve is “ulnar” to the ulnar artery.
Radial nerve is “radial” to the radial artery.
> Superior thyroid artery branches
"May I Softly Squeeze Charlie's Girl?": Muscular Infrahyoid Superior laryngeal Sternomastoid Cricothyroid Glandular
> Female pelvic organs’ blood supply
“3 organs, each get 2 blood supplies”:
Uterus: uterine, vaginal.
Rectum: middle rectal, inferior rectal [inferior rectal is the end of pudendal].
Bladder: superior vesical, inferior vesical.
> Liver: side with ligamentum venosum/ caudate lobe vs. side with quadrate lobe/ ligamentum teres
“VC goes with VC”:
The Venosum and Caudate is on same side as Vena Cava [posterior]. Therefore, quadrate and teres must be on anterior by default.
> Saphenous veins:
path of great vs. small at malleolus “MAGdelaine has varicose veins” [The saphenous veins are important for varicose veins]:
Medial maleolus, Anterior to maleolus, and Great saphenous go together.
Then the opposites of these go together: Small saphenous is posterior to the lateral maleolus.
> Internal jugular vein: tributaries
"Medical Schools Let Confident People In": · From inferior to superior: Middle thyroid Superior thyroid Lingual Common facial Pharyngeal Inferior petrosal sinus
> Heart valves: order in circuit
“First learn a Tricycle, then learn a Bicycle”:
Flow through Tricuspid first, then Bicuspid.
> Thoracic cage: relations to the important venous structures
Behind the sternoclavicular joints: the brachiocephalic veins begin.
Behind the 1st costal cartilage on the right the superior vena cava begins.
Behind the 2nd costal cartilage on the right the azygos vein ends.
Behind the 3rd costal cartilage on the right the superior vena cava ends.
> Descending abdominal aorta: seven divisions
"Sometimes Intestines Get Really Stretched Causing Leakage": Suprarenals [paired] Inferior mesenteric Gonadal [paired] Renals [paired] Superior mesenteric Celiac Lumbar [paired]
> Portal-systemic anastomoses:
main 2 places that retroperitoneals connect into systemic
RetroPeritoneals hook up with Renal and Paravertebral veins.
> Maxillary artery branches
"DAM I AM Piss Drunk But Stupid Drunk I Prefer, Must Phone Alcoholics Anonymous": Deep auricular Anterior tympanic Middle meningeal Inferior alveolar Accessory meningeal Masseteric Pterygoid Deep temporal Buccal Sphenopalatine Descending palatine Infraorbital Posterior superior alveolar Middle superior alveolar Pharyngeal Anterior superior alveolar Artery of the pterygoid canal
> Carotid sheath contents
"I See 10 CC's in the IV": I See (I.C.) = Internal Carotid artery 10 = CN 10 (Vagus nerve) CC = Common Carotid artery IV = Internal Jugular Vein
