Circulatory system blood vessels and circulation Flashcards
Arteries carry blood ___ from the heart
Veins carry bood ____ the heart
Capillaries connect the smallest ___ to the smallest ___
Away
Back to
arteries and veins
How many layers do the walls of blood vessels have? What are they?
three
Tunica interna
Tunica media
Tunica externia
Describe the tunica interna
- Inner most layer of the blood vessel wall
- composed of simple squam epi and a basment layer
The tunica interna secretes chemicals that stimulate ____ or ____ of the vessel
dilation or constriction
What appens at the tunica interna when the surrounding tissue becomes inflamed?
The endothelial cells produce cell adhesion molecules that catch leukocytes
Describe the tunica media
- middle layer of blood vessel wall
- consists of smooth muscle, collagen, and elastic tissue
What are the two primary functions of the tunica media?
to strengthen vessels and regulate the diameter of the vessel
Describe the tunica externa
- outer most later of the blood vessel wall
- consists of loose contective tissue
What is the main function of the tunica externa?
to anchor the vessel and provide passage for small nerves and lymphatic vessels
What are Vasa vasorum?
small blood vessels that supply blood to outer part of larger vessels
What are arteries sometimes called resistance vessels?
because of their strong resilient tissue structure
What are the three size classifications of arteries?
Conducting -Biggest
Distributing- middle
Resistance- small
What makes conducting arteries unique?
give and example of two arteries
-They are large
-have an abundance of elastic tissue
aorta and common carotid
Give an example of three distributing arteries
Brachial, femoral, renal, splenic
Arterioles are the ___ arteries and have a tunica ____that is thicker in proportion to other arteries
Smallest
media
What are meta arterioles?
Short vessels that link arterioles to capillaries
How is blood flow in capillaries controlled?
via precapillary sphincters muscle cell sphincters that can open and close to allow for a change in blood flow
What are the two types of arterial sense organs?
baroreceptors-pressure
chemoreceptors-chemical
The carotid sinuses contains ___receptors and transmit signal through the ___ nerve
Baro
glossopharyngeal
The carotid bodies contain ____ receptors and transmit signals through the ___ nerve
Chemo
glossopharyngeal
describe the carotid bodies
oval bodies near the branch of the common carotids
The aortic bodies are ____ receptors and are innervated by the ____ nerve
Chemo
Vagas
What are capillaries?
exchange vessels
sites where gasses, nutrients, wastes, and hormones pass between blood and tissue fluid
What is the composition of capillaries?
endothelium and basal lamina
Where are some places that have no capillaries?
tendons, ligaments, epithelia, cornea, lens of eye
What are capillaries categorized?
by permeability
What are the three types of capillaries?
- Continuous
- fenestrated
- sinusoids
What is the function of pericytes in capillaries?
they wrap around the capillaries and contract using the same contractile protein as muscle
Where are fenestrated capillaries found?
- in organs that need rapid absorption or filtration
- kidneys
What is a capillary bed?
- a network of 10-100 capillaries
- usually supplied by a single arteriole or meta arteriole
How are veins different from arteries?
- greater capacity for blood
- thinner walls and collapse when empty
- have a steady flow with very low pressure
What are post capillary venules?
- the smallest of the veins
- more porous than capillaries
- sight of leukocyte emigration
What size veins contain venous valves?
medium veins 10mm and up
Describe the simplest pathway for circulatory routes
Heart > arteries >
arterioles >capillaries >
venules >veins
Passes through only on network of capillaries
Describe the portal system for circulatory routes
The blood flows through two consecutive capillary
Describe the Arteriovenous
anastomosis (shunt) for circulatory routes
The artery flows directly into a vein bypassing cappilaries
what is an Anastomosis
convergence point between two vessels other than capillaries
Describe the Venous anastomosis for circulatory routes
when one vein empties directly into another
Describe the arterial anastomosis for circulatory routes
when two arteries merge
this can provide alternative routes of blood supply to a tissue
Blood supply to a tissue can be expressed in terms of ____flow and ___
flow and perfusion
What is blood flow?
the amount of blood flowing through and organ, tissue, or vessel at any given time (mL/min)
At rest Blood flow is equal to ___
cardiac output
What is perfusion?
the flow per given volume or mass of tissue in a given time mL/min/g
What is hemodynamics?
physical principlles of blood flow based on pressure and resistance
F∝∆𝑃/𝑅
flow is proportional to the difference in pressure over resistance
- The greater the pressure difference between two points the ___ the flow
- the greater the resistance the ___ the flow
greater
less
Blood pressure is ?
the force the blood exerts against the vessel wall
What is pulse pressure?
the difference between systolic ad diastolic pressure
How is Mean arterial pressure calculated?
Diastolic pressure + (1/3 pulse pressure)
What three main factors determine BP
Cardiac output
Blood volume
Resistance to flow
What is peripheral resistance?
the opposition to flow that blood encounters in vessels away from the heart
What three variables determine resistance?
- Blood viscosity
- vessel length
- vessel radius
What is blood viscosity?
the thickness
determined by
RBC count and albumin concentration
What is the most powerful infulence over flow/resistance?
Vessel radius
the only significant way of controling resistance
how is vessel radius changed?
via vasorelexes
- vasoconstriction
- vasodilation
What is laminar flow?
the fact that blood flows in layers due to vessel wall friction
(Faster in the middle)
Blood flow is proportional to the ______of the radius
What does this mean in terms of flow?
fourth power
small changes in radius can cause large changes in flow ml/min
What are the three reasons for speed decrease from the aorta to the capillaries?
- Greater distance
- smaller radii of arterioles create more resistance
- farther from the heart equals more and more vessels thus area becomes more and more
Why does velocity increase from the capillaries to the vena cava?
(3 reasons)
- veins are larger so less resistance
- lots of blood in smaller channels
- blood in veins never reaches full velocity again
____are the most significant point of control over peipheral resistance and flow
arterioles
Why do arterioles have significant control over peripheral resistance?
- they outnumber all other types of arteries
- they are more muscular thus more capable of changing radius
How much of the total peripheral resistance do arterioles produce?
50%
What are the three ways of controling vasomotor activity?
- Local control
- Neural control
- Hormonal control
What type of vasomotor control is autoregulation and what is it?
Local control
the ability of the tissues to regulate their own blood supply
if a tissue is inadequately perfused it will increase perfusion
What type of vasomotor control are vasoactive chemicals and what are they? give some examples
local control
Substances secreted by platelets, endothelial cells, and perivascular tissues to stimulate vasomotor response
- Histamine, bradykinin, prostaglandins = vasodilation
- Prostacyclin and nitric oxide = vaso constrictors
What type of vasomotor control is reactive hyperemia and what is it?
Local control
Blood flow will increase above normal is blood flow is cut off and then restored
What type of vasomotor control is angiogenesis and what is it?
Local control
growth of new blood vessels
Which medulla center exerts sympathetic control over blood vessel regulation
describe its role
the vasomotor center
Stimulates most vessels to constrice apart from the cardiac muscle which relaxes
the vasomotor center integrates the three autonomic reflexes
what are the three autonomic reflexes that the vasomotor center integrates?
Baroreflexes
chemoreflexes
medullary ischemic reflexes
What is a baroreflex describe its functions
An automatic negative feedback response to change in blood pressure
increase in bp detected, the signal is sent to the brainstem and results in
1) inhibition of symapthetic cardiac and vasomotor neurons
2) excitation of the vagal fibers the slow heart rate
decreases in bp have opposite effect
are baroreflexes good for long term regulation of high bp?
no because they reset to compensate for steady bp levels weather high or low
What is a chemoreflex describe its functions
an automatic response to changes in blood chemistry pH, O2, CO2
When high or low levels are detected, via chemoreceptors, respiration rates are then adjusted accordingly to correct the levels
Do chemoreflexes effect vasomotion?
yes they will work to constrict vessels to increase BP thus allowing for more lung perfusion and gas exchange
What is the Medullary ischemic reflex describe its functions
automatic response to a drop
in perfusion of the brain
when low blood supply is detected BP is raised via cardiac and vasomotor centers
what two ways do hormones influence BP?
- vasoative effects
- regulation of water balance
How does Angiotensin II effect BP?
I—potent vasoconstrictor
– Raises blood pressure
– Promotes Na+ and water retention by kidneys
– Increases blood volume and pressure
How does Atrial natriuretic peptide effect BP?
—increases urinary sodium
excretion
– Reduces blood volume and promotes vasodilation
– Lowers blood pressure
How does ADH effect BP?
promotes water retention and raises BP
– Pathologically high concentrations; also a vasoconstrictor
(aka vasopressin)
How do Epinephrine and norepinephrine effect BP?
– Most blood vessels
• Bind to 𝛼-adrenergic receptors—vasoconstriction
– In cardiac muscle blood vessels
• Bind to 𝛽-adrenergic receptors—vasodilation
What are the three routes that chemicals can pass through capillary walls?
- through endothelial cells
- intercellular clefts
- filtration pores
What four mechanisms are involved in capillary exchange?
- diffusion
- transcytosis
- filtration
- reabsorption
How much of the fluid filtered by the capillaries gets reabsorbed?
85%
15% is absorbed into the lymphatic system and returned to the blood
What five things does venous return rely on?
- Pressure gradient
- gravity
- skeletal muscle pump
- thoracic pump
- cardiac suction
What is circulatory shock?
any state in which cardiac output is
insufficient to meet the body’s metabolic needs
What are the three principal forms of Low venous return (LVR) shock?
- Hypovolemic shock-loss of blood volume
- Obstructed venous return shock
- venous pooling (vascular) shock
what is Neurogenic shock
loss of vasomotor tone,
vasodilation
– Causes from emotional shock to brainstem injury
What is Septic shock
– Bacterial toxins trigger vasodilation and increased capillary
permeability
what is Anaphylactic shock
– Severe immune reaction to antigen, histamine release,
generalized vasodilation, increased capillary permeability
what is Compensated shock
– Several homeostatic mechanisms bring about
spontaneous recovery
• Example: If a person faints and falls to a horizontal
position, gravity restores blood flow to the brain
what is Decompensated shock
– When compensation fails
– Life-threatening positive feedback loops occur
– Condition gets worse causing damage to cardiac and
brain tissue
What does blood flow to the brain fluctuate less than any other organ?
because blood deprivation can lead to loss of conciousness and even death
What are Transient ischemic attacks (TIAs)
—brief episodes of
cerebral ischemia
– Caused by spasms of diseased cerebral arteries
– Dizziness, loss of vision, weakness, paralysis, headache, or
aphasia
– Lasts from a moment to a few hours
– Often early warning of impending stroke
What is a Stroke, or cerebral vascular accident (CVA)
– Sudden death of brain tissue caused by ischemia
• Atherosclerosis, thrombosis, ruptured aneurysm
– Effects range from unnoticeable to fatal
• Blindness, paralysis, loss of sensation, loss of speech
common
– Recovery depends on surrounding neurons, collateral
circulation
Why is BP in the lungs so low?
it allows for increased time for gas exchange and prevents fluid accumulation
