chapter 21 Flashcards
The vascular system consists of
arteries, capillaries and veins. These vessels must be resilient and flexible to withstand pressure and move with tissues
Function of vascular system
exchange of material between blood and tissues
transporting blood between the capillaries and the heart
Three layers of a vessel
- tunica intima
- tunica media
- tunica externa
tunica intima
smooth, innermost layer made of endothelium and a surrounding layer connective tissue
tunica media
middle layer, made of smooth muscle and external elastic membrane; structure varies pending vessel; important for maintenance of normal bp in arteries
smooth muscle allows
arteries to constrict or dilate but is too thick to allow difussion between tissues and blood
tunica externa
fibrous connective tissue, strong t prevent rupture or larger arteries, thinner in veins
Arteries and veins run
side by side, arteries have thicker walls and higher bp than veins
has small rounds lumen (internal space)
collapsed artery
has a large, flat lumen
vein
lining contracts
veins
lining does not contract
lining folds
artery
more elastic
arteries
have valves
veins
Arteries
responsible for vasodilation and vasoconstriction; blood travels through elastic arteries, muscular arteries and arterioles, lrgest vessels that carry blood away from heart
Elastic arteries
conducting arteries
artery walls are resillient due to
elastic fibers in the tunica media
elastic rebound
cushions the sudden rise in pressure during ventricular systole and the recoil during ventricular diastole slows the drop in pressure
Muscular Arteries
medium sized arteries with thick tunica media, distribution arteries, distributes blood to skeletal muscles and organs
examples of muscular arteries
exernal carotid artery, brachial artery, mesenteric artery and femoral
major arterial pressure points
common carotid, radial, brachial, femoral, popliteal, posterior tibial, dorsal pedal
arterioles
small arteries; resistance vessels with poorly defined tunica externa
tunica media consists of
smooth muscle to allow vasoconstriction/dialation in response to O2 levels
arterioles have more resistance to blood flow because
more pressure is required to push blood through a small diameter
capillaries
exchange vessels, only vessels that permit exchange between blood and tissue, one cell layer thick
blood flow is slowest in capillaries to
allow time for two-way exchange
There are no capillaries in
cartilage and epithelial tissue
capillaries prevent
blood loss and keeps plasma proteins in the blood
Fenestrated capillaries
contain pores that allow rapid exchange
sinusoids
large and more permeable than other capillaries to allow exchange of larger molecules like protein and blood cells to leave and enter blood stream
precapillary sphincters
regulated by smooth muscle cells, found at the beginning of each network, regulate blood flow into capillary network based on the needs of tissue
collaterals
multiple arteries supplying one capillary bed; the fusion exemplifies an arterial anastomosis to provide alernate routes of blood flow
metarteriole
precapillary arteriole
thoroughfare channel
normal passageways of capillary bed
vasomotion
blood flow in capillaries occurs in pulses
veins
collect blood from tissues and organs and return it to the heart; LARGER in diameter than arteries, thinner walls because no blood pressure
venules
small veins that collect blood from capillary beds
medium sized veins
few smooth muscle cells with a sturdy tunica externa
large veins
all three layers present
valves
present in venules and medium veins of the limbs that have to fight gravity to return blood to the heart; prevent backflow
varicose vein
swollen and distended veins found in superficial veins of the legs…prego=blood pools in veins, valves no longer work=stretched
hemorrhoids
constipation or child birth…vessels in digestive tract irritated and swollen
exchange in capillaries, 3 steps
- diffusion=gasses move from greater to lesser concentration
- filtration=high pressure forces plasma out of caps to tissue distributing nutrients
- colloid osmotic pressure=attracting pressure caused by proteins in blood, when blood reaches venous end, proteins pull tissue fluid/waste into capillaries
venoconstriction
systemic veins constrict to shunt blood to arteries, this maintains normal bp during blood loss
venous reserve
blood reserved in liver, skin and lungs…taken to general circulation after blood loss
pressure and resistance
increased pressure=increased flow, increased resistance=decreased flow
blood pressure
arterial pressure pressure is highest in arterial circulation due to the elevated resistance of the arterioles
capillary hydrostatic pressure
fluid pressure
venous pressure
low pressure of venous system
vascular resistance
friction between blood and the wall of the vessel; length and diameter of vessel affect resistance
vessel length
longer blood vessels experience more friction which increases resistance
vessel diameter
smaller diameters increase friction slowing the flow of blood; diameter has more of an affect on resistance than does vessel length
viscosity
normal blood viscosity is dependent on the presence of protein and RBC friction, too much increases friction, too little lower friction
turbulence
upsetting the flow of blood die to sudden changes in vessel diameter or vessel wall damage
blood pressure
the force blood exerts against the walls of the blood vessels
filtration in capillaries depends on
blood pressure
pressure is measured in
mmHg
systolic pressure
blood pressure when the left ventricle is contraction, higher of the two numbers
normal range: 120mmHg or below
diastolic pressure
when left ventricle is relaxed, the lower bp #
normal range: 80mmHg or below
pulse pressure
the difference between the systolic and dyostolic pressures
mean arterial pressure (MAP)
diastolic pressure + (pulse pressure / 3)
**Hypertension
high blood pressure
Hypotension
low blood pressure
brachial artery
most common place to take normal bp. readings. pressure decreases as distance from the heart increases
capillary beds
bp decreases as it travels through the capillary beds of the organs and tissues. it is high enough for filtration but low enough to prevent rupture
veins-pressure
decreases further and approaches zero as blood enters the right atrium
pulmonary bp
see notes, pg. 6
elastic rebound
arteries recoil to their original dimensions during ventricular diastole
elasticity of large arteries
normal elasticity lower systolic pressure and increase diastolic pressure
elasticity in the aortic wall
absorbs some of the force of ventricle systole and recoils to maintain diastolic pressure when there is no blood flow
- venous return, “starlings law”
the heart pumps only the blood it receives, if venous return decreases, cardiac muscle fibers will not be stretched, cannot contract as forcefully
- resistance to blood flow
decreases as it travels through larger veins; increases velocity of blood
- constriction of veins
smooth muscle allows veins to constrict and force blood toward the heart and valves prevent backflow
- skeletal muscle pump, contraction of leg muscles…
squeeze the veins to force blood to the heart
- respiratory pump
inhillation and exhillation of the lungs expand and compress veins to return blood to heart
- heart rate and force
if heart rate and force increase, blood pressure increases (exercise)
- peripheral resistance
vessels offer to the flow of blood (resistance to blood flow)
- blood loss
small loss of blood (donation) temp. drop in pressure, followed by a rapid compensation in the form of a rapid heart rate and greater vasoconstriction
Diffusion
movement of ions from an area of greater concentrationto an area of lesser concentration
Use Diffusion
water, ions and small molecules such as glucose
some ions diffuse through channel in plasma membrane
Na+, K+, Ca+, CI-
large water souluable compounds diffuse through
fenestrated capillaries
Plasma proteins are
senusoid, which are very permeable
Filtration
- driven by hydrostatic pressure
- water and small solutes forced through capillary wall
- leaves larger solutes in blood stream
reabsorption
- the result of osmotic pressure
- equals pressure to prevent osmosis
- caused by suspended blood PROTEINS that are too lrg to cross capillary walls
net capillary colloid osmotic pressure is the difference between:
- blood colloid osmotic pressure
- interstitial fluid colloid osmotic pressure
(pulls water and solutes into a capillary from interstitial fluid)
*both control filtration and reabsorption through capillaries
forces water out of solution
net hydrostatic pressure
forces water into solution
net osmotic pressure
capillary exchange at arterial end
fluid moves out of capillary and into interstitial fluid
capillary exchange at venous end
fluid moves into capillary and out of interstitial fluid
transition point between filtration and reabsorption is closer to
venous end
capillaries filter more than
they absorb
excess fluid enters
lymph vessels
hemorrhaging
increases reabsorption of interstitial fluid
dehydration
accelerates reabsorption
increase in hydrostatic or decrease in colloid osmotic pressure within vessels causes fluid to
move out of blood and build up periphreal tissues=edema (swelling)
autoregulation of blood flow
factors that promote the dilation of precapillary sphincters are called vasodilators; relax the smooth muscle
local vasodilators:
decrease tissue O2 levels increasee Co2 nitric oxide release from endothelial cells increase in potassium or hydrogen ions chemicals release during inflammation elevated local temp
local vasoconstrictors
prostaglandins and thromboxanes; stimulate platelet aggregation and constrition of damaged vessels
baroreceptor reflexes
cardiovascular reflex that responds to change in pressure
chemoreceptor reflexes
cardiovascular reflex respond to changes in chemicals in blood
antidiuretic hormone
causes vasoconstriction that elevates bp, reabsorbs water from kidneys adding to blood volume
angiotensin II
responds to fall in renal bp, stimulates production of aldosterone, stimulates secretion of ADH, stimulates thirst, cardiac output, constriction of atrioles
erythropoetin
responds to a drop in blood O2 levels, causes vasoconstriction and stimulates the production and maturation of RBCs
Natriuretic peptide
respond to excessive stretching of arterial wall during diastole; reduces blood volume and pressure by sodium exchange in the kidneys, increase urine production
Norepiniphrine
stimulates vasoconstriction; raises bp
epinephrine
stimulates vasoconstriction; increases heart rate and force of contraction increasing bp
cardiovascular response to light exercise
- extensive vasodilation occurs increasing circulation
- venous return increases with muscle contraction
- cardiac output increases
Cardiovascular response to heavy exercise
- activates sympathetic nev. system
- cardiac output increases to maximum
- restricts blood flow to non essential organs
- redirects blood flow to heart, lungs and muscles
- blood supply to brain is not affected
**circle of willis (fig 21-24)
circle of arteries around the pituitary gland
**Hepatic portal circulation
blood from abdominal digestive organs and spleen circulate through the liver before returning to the heart
Purpose + anastomosis
fetal circulation
- umbilical vein carries oxygenated blood from placenta to fetus
- umbilical arteries carry oxygen deficient blood from the fetus to placenta
- placenta contains fetal and maternal blood vessels that are close to one another but do not mix, but allows gases, wastes and nutrients in and out
ductus venosus
from the placenta the blood is taken to the inferior vans cava, after birth, these fetal vessels constrict and become nonfunctional
foramen ovale
opening in the interatrial septum that permits some blood flow from the R. atrium to L. atrium in the fetal heart, bypassing the R. ventricals
ductus arteriosus
a short vessel that diverts most of the blood in the pulmonary artery to the aorta and then to the body, bypassing lungs
when an infant is born, the intake of O2 and inflation of lungs
closes a flap over the foramen ovale and constricts the ductus arteriosis
Pulse
heartbeat found at an atrial site; the force of ventricular contraction transmitted through the arterial wall
Pulse sites, 7
radial=wrist, thumb side carotid=neck temporal=temple femoral=top of thigh popliteal=back of knee dorsal pedis=top of foot apical=the heart
