A&P2: Circulation Flashcards
What are the micro/macroscopic vessels?
arteries and veins- macro
arterioles/capillaries/venules- micro
What are the 3 wall layers (external to internal)?
Externa (adventitia)
Media
Interna (intima)
Tunica externa (adventitia) is composed of what tissue?
Connective tissue composed of collagen fibers
Small amounts of elastic fibers present
What is the function of the tunica externa (adventitia)?
anchor vessels
What does the tunica media consist of (external to internal)?
external elastic lamina (membrane) Smooth muscle (some elastic fiber)
Tunica media containing external elastic laminas are only found in ? structure?
arteries
Where are window-like openings located that help with diffusion?
Tunica Media- elastic lamina
Tunica Interna- elastic lamina
What part of the vessel regulates the diameter of vessel lumen?
What NS innervates this?
tunica media smooth muscles
nervi vasorum innervated by sympathetic
What are the layers of the Tunica Interna (intima)
internal elastic lamina (arterial) basement membrane layer (arterial and venous) endothelial layer (arterial and venous)
What does the internal elastic lamina of the Tunica Interna consist of?
Only found in arteries
Window openings for diffusion
What part of the Tunica Interna (intima) is responsible for physical support to epithelial layer, has tensile strength (coil/recoil) and anchors endothelium to tunica media
Tunica Interna- Basement layer
What is the function of the endothelium layer of the Tunica Interna (intima)?
lining of vessel lumen
proliferates for repair (angiogenesis)
Participates in inflammatory response
Produces a lot of stuff
What does the Tunica Interna (intima) produce and what is the production used for?
Von Willebrand factor- platelet adhesion
Tissue plasminogen- promotes fibrinolysis
Thromboxane- vasoconstrictor prostaglandin
Nitric oxide- vasodilator
Prostacyclin- prostaglandin vasoDILATOR
Endothelin- vasoconstrictor
What are the two major types of arteries?
elastic
muscular
Where are elastic arteries found?
closest to heart
>10mm diameter
withstand high pressure
Elastic arteries have the highest percentage of ____ fibers
elastic
Give 6 examples of elastic arteries
aorta pulmonary trunk/arteries brachiocephalic subclavian common carotids common iliacs
What is the purpose of elastic arteries?
propel blood during ventricle diastole
Elastic arteries are aka what 2 names?
pressure reservoir- artery wall expansion allowing for momentary storage of mechanical energy
conducting arteries- conduct blood from heart to medium sized arteries
What do muscular arteries help adjust?
helps adjust rate of blood flow
muscular artery tunica media layer contains more ___fibers but less ____ fibers.
These rely on _____ to push blood forward
more smooth and less elastic (no recoil) allowing for greater vasoconstriction/dilation
musculature
Give 3 examples of muscular arteries
axillary
brachial
femoral
Muscular arteries are aka ______ arteries and utilize musculature for what 2 purposes?
distributing arteries
constrict/dilate to adjust pressure towards arterioles
Where can anastomoses develop?
between arteries, arterioles, venules or veins
Define arteriovenous fistula
anastomoses between two different types of vessels
Collateral circulation is the product of what 2 events?
neovascularization or angiogenesis
What are the 3 layers of capillaries?
Tunica externa- very thin
Tunica media- 1-2 muscle layers
Tunica intima- thin
What part of the circulatory system provides vascular tone?
Arterioles- tunica media
1-2 muscular layers in constant partial contraction due to sympathetic NS
Arterioles play a key roll in ______ overall
Arterioles are aka ?
blood pressure
resistance vessels
arteriole vasoconstriction leads to systemic _____
arteriole vasodilation leads to systemic _____
increase
decrease
What are the regulators of blood flow to systemic capillary beds?
arterioles
arteriole “back pressure” builds and is put into ? circulation?
systemic
Define metarterioles
short vessels connecting arteriole ->capillary network
What are the 2 parts of metarterioles?
arteriole-metarteriole junction- normal tunica junction allowing vasoconstriction/dilation
metarteriole-capillary junction- no tunica, only single circumferential sphincter (pre-capillary sphincter)
Pre-capillary sphincters regulate blood flow from ____ to ____
metarterioles into capillaries
when pre-capillary sphincter is closed, how does blood flow into venule?
arteriole -> metarteriole -> thoroughfare channel -> venule
Where can the exchange of nutrients and waste products only occur?
capillary
post capillary venule
List 3 examples/places where capillaries wouldn’t be found? How do they exchange nutrients/wastes?
avascular tissue: cornea, eye lens, cartilage
Diffusion
What are the sizes of capillaries in comparison to the size of blood cells?
Why is this relationship important?
capillaries= 5-10um RBC= 8 um
Causes RBCs to pass in single file and buys more time for nutrient exchange (perfusion)
what forms the union between arterial and venous blood flow?
capillaries
What are the 3 types of capillaries?
What wall layers do they have?
continuous
fenestrated
sinusoid
single endothelial layer basement membrane.
Define capillary bed
10-100 capillaries that arise from single metarteriole that increase surface area
Define vasomotion and its purpose
contraction/relaxation of pre-capillary sphincters
5-10/min @ rest
What regulates the blood flow through capillary beds?
vasomotion
tissue would become ischemic w/out it
Vasomotion is due to local chemicals released by endothelial cells, what do they respond to?
O2 level
CO2 level
lactic acid
H levels
define continuous capillary and it’s characteristics
where are they found?
majority of capillaries
continuous tube interrupted by intercellular clefts- this is where small molecule exchange occurs
Located in: CNS, skin, muscles, lungs
define fenestrated capillaries and their characteristics.
Where are they found?
fenestrations= cytoplasmic holes for large particle diffusion. Still have INTRAcellular clefts
Located in: kidneys, villi, choroid plexuses of brain ventricles, eye ciliary processes, some endocrine glands (hypothalamus, pituitary, pineal gland, thyroid)
Define sinusoid capillaries and their characteristics?
Where are they found?
Least common type
Incomplete/absent basement membrane
Unusually large fenestrations and intercellular clefts for RBC and protein passage
Contain specialized cells to serve unique purpose in their location (specialized phagocytes in liver sinusoids)
Liver, spleen, marrow, nodes (lymph carrying only), endocrine glands (adrenal, pituitary, thyroid)
What type of capillaries does the pituitary have?
Fenestrated
Sinusoids
Define portal system
Give two examples
Parts of the body where blood passes from one capillary network to another, transporting products in high concentrations
hepatic system (liver) hypophyseal system (pituitary)
Why is the hepatic portal systems important?
Allows liver “first-pass” at blood from stomach, spleen, pancreas, mesenteric and gallbladder before systemic circulation, cleaning some blood with specialized phagocytes in liver sinusoids
What are postcapillary venules and what is their function?
Small veins that receive blood directly from capillary beds
Significant site of nutrient/waste exchange (only other one other than capillaries)
Define diapedesis and where does it occur
venule walls are porous which allow for phagocytic WBCs to pass to inflamed/infected tissue
postcapillary venules
What are the two sites of nutrient/waste exchange?
capillaries
post-capillary venules
Define mascular venules and what is their function?
thicker walled venules that prevent metabolic exchanges with interstitial fluids
What are the two most distensible elements of the entire vascular system?
walls of postcapillary and mascular venules
Why is the distensibility of the postcapillary and mascular walls important?
Blood reservoirs
Blood volume can increase by 360%
Veins lack what 2 laminae?
internal and external elastic laminae
Vein have a high capacitance, meaning?
Capacity to distend to store high volumes of blood
Where are vein valves highly prevalent?
What are they made of?
Which way do they face?
Limbs
Thin tunica interna (intima)
Towards the heart
When does blood flow backwards in veins?
during ventricle diastole
Define vascular sinus
Give one example
Vein w/ thin endothelial wall and no smooth muscle
Surrounding dense CT replaces tunica media/externa to provide support
Coronary sinus
Difference superficial veins and deep veins
reside in subcutaneous layer
superficial and deep veins connect via perforating veins, reside between skeletal muscles
Difference of superficial/deep veins between upper/lower limbs
Upper- larger superficial veins, some bypass deep veins and dump into venae cavae
Lower- Deep veins are larger and are principle return pathway to heart
How does blood pass from superficial to deep veins?
One way valves in penetrating vessels and prevent reverse flow
What type of light waves pass into/through our superficial veins?
skin absorbs red-light waves, allows blue light to pass through to vein surfaces
What two structures have become known as blood reservoirs? What are the AKA?
What action reduces their volume capacity?
Systemic veins and venules
Capacitance vessels
Vasoconstriction
What is the text’s definition of the primary purpose of the cardiovascular system?
Circulate gases, nutrients, wastes and substances to/from cells of the body
Substances can enter/leave capillaries by what three mechanisms?
diffusion- concentration gradients
transcytosis- large molecule movement
bulk flow- pressure gradient
O2 and nutrients are usually in higher concentrations where?
Where does it diffuse to?
arterial blood
Diffuses-> interstitial fluids
CO2 and wastes are in higher concentrations where?
Where do they diffuse to?
interstitial fluid
Diffuses->blood (venous)
What is slower, diffusion or bulk flow?
Diffusion
Most areas of the brain have ___ capillaries
continuous w/ tight junctions forming blood-brain-barrier
What areas of the brain lack the blood-brain-barrier
hypothalamus
pineal gland
pituitary gland
Define transcytosis
What is this method used to move? Give examples
small quantities slowly cross capillary walls
endocytosis-lateral transport-exocytosis
Large, lipid soluble molecules
Insulin, Abs (maternal circulation->fetal circulation)
Define bulk flow
2 pressure driven mechanisms- filtration and reabsorption
Passive process that moves large amount of fluids in/out of capillaries
Bulk flow is driven by ____?
How long does it stay in effect?
Pressure, not concentration
more efficient than diffusion
As long as pressure difference exists
Define Bulk Flow (filtration) and Bulk Flow (reabsorption)
BFF- pressure moves fluids from blood w/in capillaries to interstitial fluid
BFR- pressure moves fluids from interstitial-> blood
What two pressures promote Bulk Flow Filtration?
Blood hydrostatic pressure
Interstitial fluid osmotic pressure
What is the one main pressure that normally promotes reabsorption?
blood colloid osmotic pressure
Describe net filtration pressure
balance of filtration and reabsorption pressures
Determines if blood/interstitial fluids remain same or change
Where is Net Filtration Pressure measured?
Both arterial AND venous end of capillary
Define Starlings Law of capillaries
Volume of fluid and solutes reabsorbed is near the volume of fluid and solutes filtered
What is the Net Filtration Pressure equation
NFP=(BHP-IFOP) - (BCOP+IFHP) BHP= blood hydrostatic press IFOP= interstitial fluid osmotic press BCOP= blood colloid osmotic press IFHP= interstitial fluid hydrostatic press.
If NFP is positive it promotes ____
If it’s negative it promotes ____
\+= filtration - = reabsorption
Define BHP
Blood Hydrostatic Pressure
Pushes fluid/solutes out of capillaries -> interstitial space
Define IFOP
Interstitial Fluid Osmotic Pressure
Pulls fluid/solutes out of capillaries->interstitial fluid
Why is the IFOP usually small?
Normally, only small amounts of protein is present in interstitial fluid
Define BCOP
Blood Colloid Osmotic Pressure
Caused by colloidal suspension of proteins in plasma
Pulls fluid/solutes from interstitial->capillaries
Define IFHP
Interstitial FLuid Hydrostatic Pressure
Pushes fluid/solutes out interstitial space->capillaries
When/why is IFHP usually 0mmHg?
noncontributory unless pathologic
Define flow of liquids in filtration
fluid moves from capillary into interstitial space
Define flow of liquids in reabsorption
fluid moves from interstitial fluid into capillaries
Define the purpose of the lymphatic system
accessory route for excess fluid and some solutes to flow back into blood circulation from interstitial spaces.
Usually smaller proteins or large molecules that can’t cross capillary membrane. Large part in returning nutrients from GI tract to circulation.
Some bacteria enter circulation here
What 4 areas do not have lymph drainage?
superficial skin
CNS
endomysium of muscles
bones
List the lymph drainage pathway for the lower part of the body
Lower body portion L head/neck L arm L side of thorax All drain->thoracic duct
List the lymph drainage pathway for the R side of the body
R head/neck
R arm
R thorax
All flow into smaller R duct
Where do the major lymph ducts meet and drain?
Thoracic duct->junction of L Internal jugular vein and L SubClav vein
R duct->junction of R internal jugular vein and R subclavian vein
What is Poiseuilles equation and what are the parts of the equation
equation describing blood flow and its relationship to know parameters
Pi= ratio of circle circumf to diameter Tri-P= difference in pressure r4= radius of vessel to 4th power eta= blood viscosity lambda= blood vessel length
What are the 5 variables that influence blood flow and pressure?
CO Compliance Blood volume Blood viscosity Blood vessel length/diameter
Define compliance
Ability of a compartment to expand and accommodate increased content
greater compliance=greater accommodation
What effect does hardened arteries have on flow/pressure/rate?
Compliance- reduced
Resistance to blood flow- increased
BP- increased
Flow rate- decreased
How does blood volume effect pressure and flow?
vol dec= press and flow dec
vol inc= press and flow inc
What happens to flow and rate during hyer/hypovolemia
hypo= dec press, dec flow hyper= inc press, inc flow
What are the 4 components of blood
RBCs
WBCs
Platelets
Plasma- fluid
What does bloods viscosity do to resistance and flow?
inc visc= inc resistance
low visc= low resistance
high visc= slower flow
lower visc= faster flow
How does blood vessel length/diameter impact resistance and flow
inc length= inc resistance and dec flow
inc diameter= dec resist, inc flow
If an artery/arteriole constricts by 1/2 its radius, how much does the resistance to the flow increase?
16xs
If artery/arteriole dilate to twice it normal size, what happens to resistance and flow?
resist- dec by 1/16th
flow inc by 16xs
Flow can be related to what other two factors?
Cross-sectional area
Linear velocity of flow
Define cross-sectional area
Inversely proportional to velocity of flow
Where is velocity of flow the slowest? Fastest?
Slow- capillaries (greatest aggregate cross-sectional area)
Fast- large vessels (smallest aggregate cross-sectional area)
Where is the greatest velocity of flow found at? Lowest?
Highest- center of vessel
Lowest- vascular wall
What causes streamlining of laminar flow?
shear stress produced as blood flows past stationary walls
How is turbulent flow characterized in laminar flow?
irregularities in flow pattern
whorls
vortices
eddies
Define venous return
What causes it?
Volume of blood flowing back to heart through systemic veins
L ventricle contraction
What happens to venous return if the pressure in the R atria or ventricle increases?
Venous return decreases
What 3 mechanisms help return blood to the R side of the heart?
L ventricle contraction
Skeletal muscle pump
Respiratory pump
Define milking in venous return
Leg muscles contract (standing on tip toes) causing vein to compress pushing blood through proximal valve
Distal valve closes when blood pushes against it from muscle contraction occurring above it.
Muscle relaxation, proximal valve closes, distal opens
Define respiratory pump components and characteristics
Inhalation- increases abdominal cavity pressure, compresses abdominal veins and pushing blood volume through thoracic cavity to heart
Exhalation- diaphragm moves up increasing thoracic press, dec abdominal pressure, closes valves to prevent back flow from thoracic veins
Blood pressure is created by ____
Define hydrostatic pressure
Ventricle contraction
pressure exerted on walls of vessel by blood
What are the 3 things that factor into BP
CO
Blood volume
Cardiac resistance
What type of feedback signals control BP? How are the corrections made?
interconnected negative feedback
HR, SV, systemic vascular resistance, blood volume
Cardiovascular center in medulla oblongata regulates what things?
HR, SV, contractility, vessel diameter.
Controls neural, hormonal, local negative feedback that help regulate BP
What are the 3 sub-components to the cardiovascular center of MO?
Cardio-stimulatory center
Cardio-inhibitory center
Vasomotor center- vasoconstrictor and vasodilator center
Where does the CV center receive input from?
Cerebral cortex
limbic system
hypothalamus
What type of info does the CV receive from sensory receptors?
Proprioceptors- monitor movement
Baroreceptors- pressure/stretch changes
Chemoreceptors- chemical concentration
Vascular tone is controlled by what part of the NS?
Sympathetic
What are the negative feedback loops the NS uses to regulate BP?
Baroreceptor reflexes
Chemoreceptor reflexes
Where are baroreceptors located?
Where are the two most important chemoreceptors located?
Baro- ascending and arch of aorta, carotid arteries
Chemo- carotid arteries and aortic arch
Function of carotid sinus reflex?
Location?
regulate BP to brain
above branch of R/L carotid arteries after they branch from common carotid
What cranial nerve innovates the carotid sinus reflex?
sinus baroreceptor->sensory axons in glossopharyngeal nerves (CN IX) then into CV center
Purpose of aortic reflex
What cranial nerve is involved
baroreceptor in ascending and arch of aorta
regulates systemic BP
Impulses reach CV from sensory axons in vagal nerves (CN X)
Where are chemoreceptors located?
Which concentration changes to they detect?
Close to baroreceptors: carotid bodies and aortic bodies
O2, CO2 and H+
List 3 things that stimulate the chemoreceptors
Hypoxia- reduced plasma O2
Acidosis- increased H+ concentration
Hypercapnia- increased CO2 in plasma
Stimulation of chemoreceptors causes what cascade of events?
Impulse to CV center
Increased Symp stimulation to arterioles and veins causing vasoconstriction
Constriction increases BP
How do hormones help regulate HR
altering CO
changing systemic resistance
adjusting total blood volume
List 5 examples of hormonal changes to HR
RAA system Epi ADH ADP/ANH Erythropoietin
When/why is the RAA system activated?
blood volume/flow to kidneys decreases
increases BP by increasing water retention
What effect do epi/norepi have on BP?
Both increase CO by increasing rate and contractile force
Vasoconstriction or arterioles and abdominal organs
Vasodilation of arterioles in cardiac/skeletal muscles
How does ADH regulate BP?
Released from hypothalamus in response to dehydration or decreased blood volume
Causes vasoconstriction
Promotes water retention in kidneys
How does Atrial Natriuretic Peptide/Hormone effect BP?
Lowers BP by vasodilation
Promotes loss of Na and H2O in Urine to reduce BP
How does erythropoietin effect BP?
Released by kidneys when blood/O2 is decreased
EP stimulates RBC production in bone marrow
Acts as a vasoconstrictor
Where does auto-regulation of BP take effect at?
Capillary beds regulating vasomotion
What 2 stimuli cause auto-regulation changes in blood flow?
Physical changes
Vasodilation/constriction chemicals
When does a myogenic response happen and what does it do?
Autoregulation of BP
Occurs in arteriole smooth muscles when stretched or relaxed
What are the cells that can release chemicals to alter vessel diameter?
WBS platelets smooth muscle fibers macrophages endothelial cells
What are the vasodilation chemicals?
K+ H+ Lactic acid adenosine NO kinins histamine
What are the vasoconstriction chemicals?
Thromboxane A2
serotonin
endothelins
What response do pulmonary microvasculatures have to decreased O2?
constrict to push blood to areas that are more effectively ventilated by fresh air
What are the sounds heard during manual BP called?
Korotkoff sounds
Define Mean Arterial Pressure
Average blood pressure in arteries
Roughly 1/3 of the way between systolic and diastolic
Considered more accurate measure of perfusion pressure
What is the Mean Arterial Pressure equation and norm?
MAP= Dias. BP + (systol-diastol/3)
70-110
Below 60= inadequate perfusion
Normal heart weight
Athlete heart weight
Norm- 300g
Athlete- 500g
