Click here to load reader
Upload
samiha-haq
View
215
Download
0
Embed Size (px)
Citation preview
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 1/13
Miscellaneous Features of
Arteries and Veins
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 2/13
Arteries and Veins
Histological differences between small, mediumand large sized veins
What is Vasa vasorum
Venous Valves
Histological differences between a typical arteryand vein
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 3/13
Layers of Vessels
Both arteries and veins have are composed of
the same three layers.
Tunica intima/interna
Tunica media
Tunica adventitia
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 4/13
Tunica interna
This is the innermost layer and lines the lumen of the blood vessels.
It consists of areloar simple squamous
epithelium and a thin layer of (basementmembrane) to "stick it to the Tunica media.
The simple squamous epithelium provides asmooth surface for the blood to "slide past."
The tunica intima is continuous with theendocardium, makes-up the capillaries and iscollectively referred to as the endothelium.
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 5/13
Middle Layer
Tunica media
This is the middle layer. It is made
of smooth muscle and elastic fibers. It is
responsible for vasodialation and
vasoconstriction of the blood vessels. It is also
the target tissue for Vasopressin (ADH)
Hormone and plays into blood pressure.
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 6/13
Superficial Layer
Tunica adventitia
This is the most superficial of the layers. It
is made of dense irregular CT with lots of
collagen fibers running in all directions for
strength in many different directions.
In many of the slide preps, you can see the
collagen fibers as squiggly lines in this layer.
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 7/13
Large Veins Medium Veins Small Veins
Tunica intima Endothelial lining
with basement
membrane,
subendothelialconnective tissue
and smooth muscle
cells
Endothelium and a
thin subendothelial
layer, smooth
muscle cells
Endothelium
surrouned by
pericytes,
undifferentiatedmesenchymal cells
Tunica media Thin, consists of
smooth muscle, aswell as collagen
fibers and
fibroblasts
Thin, consists of
circularly arrangedsmooth muscle ,
collagen fibres
Lacks a smooth
muscle media
Tunica adventitia Large, thickest
layer,, made of
collagen fibers,elastic fibers and
fibroblasts
Thinner than large
veins, mostly
collagen fibers, maycontain
longitudinally
arranged collagen
fibers
Longitudinally
arranged collagen
and elastin fibres;muscular venules
contain 1-3 layers
of smooth muscles
Valves No Yes Yes
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 8/13
Differences between arteries and veinsArteries Veins
Tunica media is relatively thicker than in
veins
Tunica media is relatively thin, consisting
of smooth muscle fibers. May contain
collagen fibers and fibroblasts
Tunica adventitia l layer is lesser than in
veins
Tunica adventitia composed solely of
longitudinally arranged collagen fibrers, is
more thicker than in arteries. Large
arteries contain many smooth muscle
layers
Valves absent except semilunar valves of
pulmonary artery and aorta
Valves present to prevent return of waste
materials to tissues
Lumen is relatively narrower than in veins
Lumen is regular
Lumen is wider in vein than arteries
Lumen is irregular
Smooth muscle layer, elastic fiber layer is
more thicker in arteries to provide
pressure for pulsatile movements of heart
for blood flow
Smooth muscle and elastic fiber layer is
less than arteries
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 9/13
Venous Valves
The valves are formed by the loose pocket-
shaped folds of tunica intima, which extend
into lumen of the vein
The opening of pocket point into direction of
flow of blood towards the heart
One to three but usually two pockets form the
valves
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 10/13
Valve structure
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 11/13
How valve prevents backflow of blood
Blood flowing towards heart will pass thepockets.
If the flow reverses, blood will fill the pockets
which will occlude the lumen of the vein andprevent the return of blood into the part of thevein preceding the valve.
The ability of the valves to prevent backflow
depends to some extent on the state of contraction (tone) of the smooth muscle in thewall of the vein.
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 12/13
Vasa vasorum
A network of small blood vessels that supply
larger vessels with blood
Literally means vessels of the vessel
Both oxygenated and deoxygenated blood are
carried to and from larger vessels by these tiny
blood vessels.
8/9/2019 Miscellaneous Features of Arteries and Veins
http://slidepdf.com/reader/full/miscellaneous-features-of-arteries-and-veins 13/13
Why is vasa vasorum needed by large
blood vessels?
Because the large veins and arteries are by
necessity so thick, their outer and middle cell
layers cannot be adequately nourished
without this additional network of blood
vessels