Microscopic Structure Of BV Flashcards
Large elastic arteries leave the
heart and branch to form
muscular arteries.
muscular arteries branch further
and enter—— , where they
branch much further to form
organs
arterioles
arterioles branch into the
smallest vessels, the———
capillaries
capillaries are
the site of exchange between
blood and surrounding tissue.
smallest vessels
Capillaries then merge to form
venules
Venules merge further into—-
and then———sized
veins.
small
medium
small
and then medium vein leave organs, form
————which eventually
bring blood——
larger veins
back to the heart.
In the basic structure of any vessel there are three layers:
1) tunica intima (the inner layer)
2) tunica media
3) tunica adventitia /externa (The Outer layer)
tunica intima
the inner layer: Endothelial cells and sub-endothelial connective tissue
tunica media
elastic fibers and smooth muscles (thicker than intima )
tunica adventitia /externa
The Outer layer: A connective tissue layer , continues with the connective tissues surrounding the blood vessel.
Mention large elastic arteries?
the ascending / arch / descending aorta
large size arteries ,and because of the ———they are also called elastic arteries
large amount of elastic fibers
muscular arteries.
the tunica media of these arteries have
large amounts of smooth
muscles
muscular arteries further divided into arterioles , which have a
very thin tunica media
The capillaries is only an
endothelium supported by a basement membrane , no other layers
small and then medium—sized veins (Have—- amount of muscles in Tunica media )
Less
The most important feature in Large size veins (e.g. IVC) is the presence of
smooth muscle fibers in tunica externa (only in this type of veins)
Walls of both arteries and veins have a—————,
tunica intima, tunica media, and tunica externa (or adventitia)
endoca
artery has a thicker ——and relatively narrow——-.
tunica media
lumen
vein has a larger——— and its——- is the thickest layer.
lumen
tunica externa
The tunica intima of veins is often folded to form
valves.
True or false
Capillaries have only an endothelium, with no subendothelial layer or other tunics.
T
line the tunica intima
Simple squamous endothelial cells
tunica intima has
-endothelial cells
-subendothelial loose
connective tissue
tunica intima is separated from the tunica media by
internal elastic lamina (IEL)
internal elastic lamina (IEL)
prominent sheet of elastin.
The media (M) contains
elastic lamellae and fibers (EF) and multiple layers of smooth muscle
The tunica media is—— in large arteries than veins, with relatively more elastin.
thicker
Elastic fibers are also present in the tunica adventitia (A), which is relatively —-in large veins.
thicker
Vasa vasorum (V) are seen in
adventitia of the aorta.
The connective tissue of the adventitia always merges with the
less dense connective tissue around it.
large elastic arteries
tunica media consists mainly
elastic fibers
if muscular arteries
tunica media consists mainly
Smooth muscles fibers
larger vessels, as the
aorta
Walls of the larger vessels contain in the tunica adventitia a
supply of
microvasculature to bring O2 and nutrients to local cells too far from the lumen to be
nourished by blood there.
-small sympathetic
nerves (N) for control of vasoconstriction.
constitute the vasa vasorum (vessels of
vessels).
arterioles (A), capillaries and venules (V)
The largest arteries contain
1-considerable elastic material and expand with blood when
the heart contracts.
2-thick tunica media (M)
consisting largely of many well developed elastic lamellae.
Strong pressure of blood pulsating into such arteries during systole
expands the arterial wall,
reducing the pressure and allowing strong blood flow to continue during diastole.
intima (I) of the empty aorta is typically—— and the adventitia (A) contains
folded
vasa vasorum.
medium sized artery shows a—— tunica media (M) consisting largely——
thick
smooth muscle fibers.
Why so large sized arteries need elastic
the fibers ?
?
Microvasculature arises to?
nutritional
needs of one organ or parts of one organ
Microvasculature consists of blood vessels of
less than 0.5 mm
diameter.
Microvessels include
arterioles
metarterioles( arterioles smaller
branches)
Microvessels include arterioles and their smaller
branches called metarterioles in which the layer
of smooth muscle cells is dispersed as bands of
cells that act as?
precapillary sphincters.
The distal portion of the metarteriole, sometimes
called a ——— and it lacks—-
thoroughfare channel,
any smooth
muscles
muscle cells.
The wall of capillaries lacks
smooth muscle cells
altogether.
The precapillary sphincters allow blood to enter
the ——in a ——manner for
maximally efficient exchange of nutrients,
wastes, O2, and CO2 across the capillary wall.
the bed of capillaries
pulsatile
Capillaries and the metarteriole converge as
——-, the last component of the
microvasculature.
Blood enters microvasculature
well—oxygenated and leaves poorly oxygenated.
postcapillary venules
——-make up the microvasculature where in almost every organ, exchange takes place between blood and the interstitial fluid of the tissues.
Arterioles (A), small capillaries (C) and venules (V)
Arterioles are microvessels with a tunica intima (I) that consists only of the ——- in which the cells may have——
endothelium
rounded nuclei.
Arterioles have tunica media (M) with only———-, and usually——, inconspicuous adventitia (Ad).
one or two layers of smooth muscle
thin
Capillaries consist only of an endothelium rolled as a tube, across which molecular exchange occurs between blood and tissue fluid.
T
Capillaries are normally associated with perivascular contractile cells called ——which have a variety of functions. The more—— nuclei belong to endothelial cells.
pericytes (P)
flattened
Capillary—- wall of one endothelial cell covered by an external lamina (arrows).
Endothelial cells have numerous—— vesicles and their edges overlap and are bound tightly together with——-
thin
transcytotic vesicles
occluding junctions (J).
Pericytes can proliferate to form ——-when a capillary is transformed into an——
smooth muscle cells
arteriole or venule after tissue injury and repair.
Types of capillaries
(a) : Continuous capillaries,
(b) : Fenestrated capillaries
(c) : Sinusoids
Continuous capillaries, the most common type, have?
tight, occluding junctions sealing the intercellular clefts between all the endothelial cells to produce minimal fluid leakage
Continuous capillaries,
All molecules exchanged across the endothelium must cross the cells by
diffusion or transcytosis.
Fenestrated capillaries have——-, but perforations (fenestrae) through the endothelial cells——
tight junctions
allow greater exchange across the endothelium.
Fenestrated capillaries,
external lamina is
continuous in both a and b
Fenestrated capillaries are found in organs where molecular exchange with the blood is important, such as
1) endocrine organs,
2) intestinal walls, and
3) choroid plexus.
Sinusoids usually have a
1) wider diameter
2) discontinuities between the endothelial cells, large fenestrae through the cells,
3) partial, discontinuous basement membrane.
Sinusoids are found in organs where ———and cells occurs readily between tissue and blood, such as in
exchange of macromolecules
bone marrow, liver, and spleen.
Continuous capillary
tight or occluding junctions
Numerous transcytotic vesicles are evident (small arrows).
Fenestrated capillaries are specialized for uptake of molecules such as——— or
for outflow of molecules such as in the—-
hormones in endocrine glands
kidney’s filtration system.
