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blood vessels
structure and function
72
Anatomy
Undergraduate 1
09/27/2008

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Cards

Term
What are the three layers in an artery
Definition
tunica interna, tunica media, tunica externa
Term
What are the five type of blood vessels
Definition
arteries, arterioles, capillaries, venules, veins
Term
what does the tunica interna do
Definition
it surrounds the lumen
Term
What is the tunica interna made up of
Definition
simple squamous cells and a basement membrane
Term
What does the tunica media consist of
Definition
smooth muscle
Term
what does the tunica media allow for
Definition
vasoconstriction and vasodilation
Term
what causes vasoconstriction or vasodilation
Definition
signals from the ans and vasodilating chemicals
Term
What does the tunica externa consist of
Definition
collagen and elastic fibers
Term
what is the function of the tunica externa
Definition
It anchors the blood vessel to the surrounding tissue
Term
What are the two groups of arteries
Definition
elastic and muscular/distributing
Term
What type of arteries are the largest and what are some examples
Definition
elastic arteries including the aorta, common carotid artery
Term
What type of fiber do the walls of elastic arteries contain a lot of
Definition
elastic fibers
Term
What do the walls of elastic fibers do when the heart pumps blood into them
Definition
they expand
Term
What do the walls of elastic arteries do when the heart relaxes
Definition
it recoils
Term
What does the expansion and recoiling of elastic arterial walls do to blood flow
Definition
it helps the blood move onward
Term
What type of arteries are medium sized
Definition
muscular/distributing arteries
Term
What do muscular arteries branch off from
Definition
elastic arteries
Term
What is the distinguishing factor in muscular arterial anatomy
Definition
It has a thick tunica media due to the abundance of smooth muscle fibers
Term
Where do muscular arteries distribute blood to
Definition
skeletal muscle and internal organs
Term
What are arterioles
Definition
very small arteries
Term
What layers do large arterioles contain
Definition
tunica interna, tunica media, tunica externa
Term
What layers do smaller arterioles contain
Definition
tunica interna, incomplete tunica media
Term
What do arterioles regulate and how
Definition
they regulate blood flow into the capillaries by regulating resistance
Term
What is resistance
Definition
opposition to blood flow do to friction between the blood and the vascular wall
Term
How do arterioles regulate resistance
Definition
through vasoconstriction and vasodilation
Term
What are capillaries and what do they connect
Definition
they are microscopic blood vessels that connect arterioles to venules
Term
What is microcirculation
Definition
the flow of blood from arterioles to venules through capillaries
Term
What layers do capillaries contain
Definition
tunica interna
Term
What is the function of capillaries
Definition
the exchange of nutrients, wastes, and gases between blood and cells via the interstitial fluid
Term
What do capillaries form
Definition
a complex network of capillary beds
Term
Where are capillary beds not found
Definition
lens of eye, cartilage, epidermis
Term
What do arterioles empty into
Definition
metarterioles
Term
Where do metarterioles lead into and what are they continuous with
Definition
they lead into the capillary bed and are continuous with the thoroughfare channel
Term
What distinguishes metarterioles from the thoroughfare channel
Definition
metarterioles contain scattered muscle fibers. the thoroughfare channel only contains tunica interna
Term
What do true capillaries branch off of
Definition
metarterioles and the thoroughfare channel
Term
What are precapillary sphincters
Definition
rings of smooth muscle that control the flow of blood into the capillary
Term
What happens when precapillary sphincters contract
Definition
blood flow to capillary is decreased or stpps completely
Term
How often does blood flow into a capillary
Definition
intermittently at about five to ten times a minute
Term
What is the exception to intermittent capillary blood flow
Definition
actively contracting muscles
Term
What percentage of capillaries have blood flowing through them at any given time
Definition
25%
Term
What are the three types of capillaries
Definition
continuous, fenestrated, sinusoid
Term
What type of capillary is the most common and least permeable
Definition
continuous capillaries
Term
What is the arrangement of cells in a continuous capillary
Definition
they form and uninterrupted lining with only small intercellular clefts. Do not contain pores through cells
Term
What are intercellular clefts
Definition
the spaces between neighboring endothelial cells
Term
What are continuous capillaries permeable to
Definition
water, small lipid soluble substances, small solutes, ions
Term
What are fenestrated capillaries characterized by
Definition
numerous oval pores in the endothelial cells
Term
What do oval pores in fenestrated capillaries allow for
Definition
greater permeability of fluids and small solutes
Term
Where are fenestrated capillaries found and why
Definition
intestines and kidneys, they are active sites for capillary reabsorption and filtration
Term
What are sinusoid capillaries characterized by
Definition
large fenestrations and large intercellular clefts
Term
What can pass through sinusoid capillaries
Definition
large substances such as hormones and red blood cells
Term
What can pass through sinusoid capillaries
Definition
large substances such as hormones and red blood cells
Term
Where are sinusoid capillaries found
Definition
liver, spleen, bone marrow, endocrine glands
Term
What are Kupffer cells
Definition
stationary macrophages in the sinusoid capillaries of the liver that clean the blood as it passes through
Term
What layers do veins typically have
Definition
tunica interna, tunica media, tunica externa
Term
How do veins compare arteries in terms of layers and lumen
Definition
Veins have a larger lumen and thinner walls.
Term
Which layer is the largest in veins
Definition
tunica externa
Term
What are venous valves composed of
Definition
folds of tunica interna
Term
What is the function of venous veins
Definition
to prevent the backflow of blood
Term
Why are valves necessary in some veins and not in the arteris
Definition
Veins have lower pressure
Term
Where are venous valves usually found
Definition
in the limbs where the upward movement of blood is opposed by gravity
Term
What vessels do venules collect blood from
Definition
capillaries
Term
What do venules drain into
Definition
veins
Term
What are varicose veins due to
Definition
leaky faulty veins that cause pooling of blood and the distension of the vein
Term
What are hemorrhoids
Definition
varicose veins that are located in the anal canal
Term
What is an anastomosis
Definition
the union of two or more blood vessel branches that service the same area
Term
What do anastomoses allow for
Definition
collateral circulation
Term
What is collateral circulation
Definition
the flow of blood via an alternate route through an anastomosis during an occlusion
Term
What happens when blood is needed from the veins
Definition
it is diverted from them by vasoconstriction
Term
What is collateral circulation
Definition
the flow of blood via an alternate route through an anastomosis during an occlusion
Term
Which arteries do not have anastomoses
Definition
end arteries
Term
Which blood vessels contain the majority of blood
Definition
systemic veins and venules
Term
What do veins and venules serve as
Definition
blood reservoirs
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