Blood vessels and circulation Exam1 Flashcards
what are the characteristics of arteries
away from heart
- aorta
- arteries
- large, medium, small
- arterioles
What do capillaries do
exchange
what are the characteristics of veins
toward heart
- venules
- veins-large, medium, small
- vina cava -inferior and superior
what does the vessel wall consist of
tunica intima or tunica interna -endothelium and underlying connective tissue tunica media -smooth muscle and elastic fibers tunica externa or tunica adventitia -connective tissue
what is the smooth muscle in the tunica media responsible for?
vasoconstriction
does the tunica extera offer protection:
creates tough outer covering that resists puncture
what do large arteries tend to have?
what do medium/small arteries have?
very thick internal elastic layer while some medium/smaller arteries have a proportionally large muscular layer
why do veins have a larger radius relative to arteries at same distance from heart?
it allows for similar flow in veins with lower pressure and velocity than the matched artery
what is involved in controlling the perfusion of capillary eds, local and systemic?
local controls
- oxygen
- carbon dioxide
- K+
- nitric oxide
systemic control
- norepinephrine
- epinephrine
- vasopressin (ADH)
- angiotensin
define perfusion.
blood flowing into capillary beds
are precapillary sphincters involved in control of blood flow?
precapillary sphincters control the flow of blood into a capillary bed thus controlling the level of perfusion of that bed and the tissue it supplies.
what is a metarteriole?
a metarteriole is a more direct passage through the capillary bed
with less perfusion do you get more blood flow through the metarteriole?
with less perfusion more blood would flow through the metarteriole
an arteriovenous anastomosis is a direct connection that serves for a bypass for what?
an arteriovenous anastomosis is a direct connection between the arteriole and venule that serve as a bypass for the capillary bed
explain what regulates the level of perfusion at a local level?
the level of perfusion of capillary beds is under primarily local controls from chemical signals, through sympathetic signals (nerves and hormones) can regulate perfusion in some situations.
list the local effectors of vasodilation and vasoconstriction
vasodilators
- low O2 and or high CO2 - lactic acid - nitric oxide (NO) from endothelium - high K+ or H+ in interstitial fluid - local inflammation (e.g. histamine, NO)
vasoconstrictors
- prostaglandins - throwboxanes - endothelin
what is the endothelin and what produces it as well as releases it?
endothelin is a chemical messenger produced and released by endothelium
is adenosine a vasodilator?
adenosine is also listed as a vasodilator it may by an important local vasodilator for the heart
where are baroreceptors and chemoreceptors located?
baroreceptors and chemoreceptors in the arteries superior to the heart
specifically where are baroreceptors and what are their functions?
there are baroreceptors )fundamentally stretch receptors) in the aortic arch and carotid sinuses.
- they trach blood pressure for flow of blood to
the body (aortic arch) and brain (carotid sinus)
what do chemoreceptors form?
there are chemoreceptor cells clustered to form aortic bodies (where corotids branch from aorta) and carotid bodies (where internal and external carotids branch )
peripheral chemoreceptors in these blood vessels detect oxygen, carbon dioxide and PH levels in the blood
what do the peripheral chemoreceptors detect in the blood?
peripheral chemoreceptors in these blood vessels detect oxygen, carbon dioxide and PH levels in the blood
-the pressure, blood gas and PH information is
all transmitted to the brain stem via the vagus
(X) and glossopharngeal (IX) cranial nerves
what can these receptors affect? how does it affect it?
signals from these receptors can affect the ananomic nervous system drive to the heart to increase blood pressure (baroreceptors) and respiratory rythms (chemoreceptors) to keep blood gases and PH within normal reange
what are the 3 main types of capillaries?
continuous capillaries
fenestrated capillaries
sinusoids
describe continuous capillaries.
structure of a continuous capillary: small gaps between endothelial cells called intercellular clefts that let fluid in and out of the capillary
*specialized continuous capillaries in the brain have tight junctions between epithelial cells rather than clefts to form the blood-brain barrier
describe fenestrated capillaries
structure of fenestrated capillaries: capillaries with pores that span the epithelial cells
-these make these capillaries more porous than
continuous capillaries
-found in choroid plexus of brain, most classical
endocrine organs, intestines and kidneys
describe sinusoids
structure of sinusoids: flattened or irregularly shaped with large gaps between adjacent epithelial cells
-allows for greater exchange with surrounding
tissues
-found in liver spleen and bonemarrow
do arteries act as a reserve for pressure?
do veins act as a reserve for blood volume?
Arteries act as a reserve of pressure within the cardiovascular system, but veins act as reserve for blood volume
what has to happen for your blood to start circulating faster?
when you need to get blood circulating faster constriction of larger veins will greatly increase venous return helping to boost cardiac output
what portion of the nervous system controls vasoconstriction of veins?
sympathetic innervation controls the vasoconstriction of veins
do most tissues have a simple pathway?
most tissue have the simple pathway
is there a portal system in the hypothalamus and pituitary?
there is a portal system in the hypothalamus and pituitary
what is the portal system between the liver and intestine called?
the hepatic portal system
where are AV shunts most commonly found?
AV shunts are most common in fingers and toes for conserving heart
does the blood supply to and from the brain have lots of anastomoses?
the blood supply to and from the brain has lots of anastomoses
what are the differences in arterial and venous systemic circulation?
Arterial
- conduit between heart and capillaries
- pressure reservoir
- damp oscillations in pressure and flow
- control distribution to capillary networks
Venous side
- conduit between capillaries and heart
- volume reservoir
- low pressure aided by various mechanisms
* one way valves
* skeletal muscle pumping
* respiratory pumping
Is TPR affected by arterial diameter?
Total Paripheral Resistance (TPR)
Arteriole diameter -big factor in TPR
why are baroreceptors called different things according to where they are found?
baroreceptors in the arterial side monitor blood pressure and sometimes are called high pressure baroreceptors while those in the venous side (primarily right atrium and a few large veins ) are called low pressure baroreceptors.