artery & vein

Circulatory System
Is a transport system that carries blood and lymph to and from the tissue of
the body.
? Blood vessels :
Blood vessels are
arranged so that blood
delivered from the heart
quickly by arteries
reaches a network of
narrow thin walled
vessels, the blood
capillaries.

:General features of Arteries &Veins
? They are composed three layers called tunics they are
from the lumen outward :
? 1-Tunica intima : The innermost layer that includes the
endothelial lining (a single layer of simple squamous
epithelial tissue ),resting on a basal lamina and the
underlying connective tissue .
? 2-Tunica media : The muscular middle layer (consists
primarily of circumferentially arranged layers of smooth
muscle cells ).
? 3- Tunica adventitia : The outermost connective tissue
layer.



? Arteries :-Are classified into three types on
the basis of size and the characteristics of
the tunica media.
Artery
Vessel Inner layer
(Tunica Intima)
Middle layer
(Tunica Media)
Outer layer
(Tunica Adventitia)
Elastic artery Endothelium
Connective tissue
Smooth muscle
Smooth muscle
Elastic lamellae
Connective tissue Some elastic fibers
Thinner than tunica media
Muscular artery
Large
Endothelium
Connective tissue
Smooth muscle
Smooth muscle
Collagen fiber
Relatively little elastic tissue
Connective tissue Some elastic fibers
Thinner than tunica media
Small Endothelium
Connective tissue
Smooth muscle Prominent internal elastic
membrane
Smooth muscle (8-10 cell layers)
Collagen fibers
Connective tissue Some elastic fibers
Thinner than tunica media
Arteriole Endothelium
Connective tissue
Smooth muscle
Internal elastic membrane
Smooth muscle (1-2 cell layers) Thin , ill-defined sheath of connective
tissue
Capillary Endothelium None None

? Veins :- Generally, the tunica adventitia is
the thickest layer of the wall , and are
classified into three types on the basis of size
and the characteristics of the tunica media :
Veins
Vessel
Inner layer
(Tunica Intima)
Middle layer
(Tunica Media)
Outer layer
(Tunica Adventitia)
Post capillary venule Endothelium None None
Muscular venule Endothelium Smooth muscle
(1 or 2 layers)
Connective tissue
Some elastic fibers
Thicker than tunica media
Small vein Endothelium
Smooth muscle (2 or 3 layers)
Smooth muscle
(2 or 3 layers continuous with
tunica intima)
Connective tissue Some elastic fibers
Thicker than tunica media
Medium vein Endothelium
Connective tissue
Smooth muscle
Internal elastic membrane in some
cases
Smooth muscle
Collagen fibers
Connective tissue Some elastic fibers Much thicker
than tunica media
Large vein Endothelium Connective tissue
Smooth muscle
Smooth muscle (2 – 15 layers)
Cardiac muscle near heart
Collagen fibers
Connective tissue Some elastic fibers Much thicker
than tunica media
:- Capillaries
? Smallest diameter
blood vessels , are
consist of single
layer of endothelial
cells and their basal
lamina