Cardiovascular
System
BY: Wang Qiao Zhi
Objectives：
 Recognize the general structures of blood
vessels.
 Distinguish the structure of medium-sized
artery and large artery; small artery and
small vein.
Recognize the 3 layers of heart wall, the
structure of capillary.
General characters of blood vessels:
1. tunica intima
endothelium,
subendothelium,
internal elastic membrane
2.tunica media
most importante layer
each structure is often fit for
it’s function
3.tunica adventitia
LCT, small arteries and veins,
nerves, fat cells
external elastic membrane
★ Identify blood vessels according to:
 lumen is hollow;
structurally：endothelial
cells line in the vessel’s
interior surface;
 contents ：blood cells in
lumen generally .
Subject to the first two conditions, the structures is identified
as the blood vessels.
How to distinguish arteries and veins？
Veins have thinner walls than their accompanying
arteries, and the lumen of the vein is larger than that of
the artery.
the lumen of veins is collapsed and irregular.
the lumen of arteries is more regular, round or oval.
slides:
1. Medium-sized artery & vein (中等动静脉)
2. Small artery & vein (小动静脉)
3. Large artery /elastic artery （大动脉）
4. Heart（心脏）
1. Medium-sized artery & vein
1) Lower magnification (×4)
V
A
You can find two
large blood vessels
cross sections, among
these with thicker
wall and small lumen
is medium-sized
artery; thinner wall
and large or irregular
lumen is mediumsized vein.
Three layers of Medium-sized artery:
• Internal elastic lamina (thick
pink wave line)and external
elastic lamina are delimits the
three layers.
Above the internal elastic
lamina is tunica intima.
Between them is tunica
media.
Below external elastic lamina
is tunica adventita.
Lower magnification (×10)
tunica
intima
endothelium
Simple squamouse epithelium
subendothelial layer
shrank during tissue
preparation,and cannot be
seen easily.
internal elastic lamina
scalloped , pink wave
line (delimit tunica intima
from tunica media).
Higher magnification (×40)

tunica media
(1) 10-40 layers of
concentrically-arranged
smooth muscle cells.
(2) elastic & collagen fibers
can be seen in this layer.

tunica adventitia
external elastic laminae
-more thicker
Several layers
discontinousely (compare
to innner-elastic menbrane).
MV
adventitia
 internal and external
elastic lamina are not
clear
 the adventitia of
veins is thicker than
the media.
 tunica media is thin,
with a few elastic
fibers and smooth
muscles
 Adventitia contain
smooth muscle cells.
2.Small artery & vein：
small artery：
appear round;
small lumen;
thick wall;
rich muscle.
small vein：
appear flattened or
collapsed
big or irregular lumen;
thin wall;
less muscle.
A
B
Features of small artery and small vein
Three layers are not obversly.
Internal and external elastic
laminae are absent or very thin.
small artery: several layers of
SMC in media
small vein: one or two layers
of SMC in media
The adventitia merge with
surrounding CT .
V
A
3.Large artery /elastic artery:
compare to Medium-sized artery:
 the internal elastic lamina and
external elastic lamina cannot be
seen clearly
three layers cannot be
distingushed obviousely
tunica media consists of elastic
membranes instead of smooth
muscle.
tunica intima: thicker than medial-sized artery
(subendothelial layer is thicher )
internal elastic lamina can not be seen easily.
Higher magnification (×40)
tunica media :40-70 layers of elastic membranes
tunica adventitia:
loose connective
tissue,small blood
vessels ,nervers and fat
cells can be seen .
4.Heart:
1) Layers of heart:
Endocardium
Myocardium
Epicardium
 Endocardium
 Endothelium
 Subendothelial layer
(thin sheet of c.t.. )
 Subendocardial layer
c.t with Purkinje fibres
Purkinje fibres

shorter and
broader than
commom cardiac
muscle cells
 Cytoplasm is
Pale-stained(less
myofibrils)
Myocardium
common cardiac muscles,
rich in capillaries.
Only one layer of
endothelial cells
(cross-section)
The red blood cells
can transverse like a
line (longitudinalsection)
Epicardium (compare with the Endoardium)
 mesothelium
 more c.t (adipose cells)
 small blood vessels
QUIZ
Which organ is showing:
A :medium
sized vein
A
B
B:mediumsized artery
Which layer or structures are showing?
internal
elastic lamina
tunica media
external
elastic lamina
Which structure
is showing?
capillary
Which structures
are showing?
Small artery
Which structure
is showing?
left:small vein
right: small artery
Which organ and
Which layer?
Medial-sized artery
Tunica media
Which organ is showing?
Medial-sized
artery
Which organ is showing ?
Large artery
Larger artery
medical-sized artery