Lab7-cardiovascular system.pdf

Biology Department
Stage: 3
rd
Practical Histology
Lab= 7
Cardiovascular System

Students should be able to:
1) Describe the histological structure of the heart
wall.
2) Classify arteries and veins, identify and
describe their histological structure.
3) Describe and identify different types of
capillaries.

Cardiovascular system
The circulatory system consists of blood and lymphatic vascular
systems.
The blood vascular system composed of:
■ Heart: an organ whose function is to pump the blood.
■ Arteries: carry the blood, with its nutrients
and oxygen, to the tissues.
■ Veins: they convey the blood to heart to be pumped again.
■ Capillaries: through whose walls the interchange between blood and
tissues takes place.
Cardiovascular system act to distribute hormones and
nutrients to cells and tissue and transport waste material to
excretory organs.

The Heart Chambers:
1-The right and left
ventricles pump
blood to the lungs and
the rest of the body
respectively
2- Right and left atria
receive blood from the
body and the
pulmonary veins
respectively.

Heart Wall
The heart is a muscular organ, its
wall consists of 3 layers, the
internal (endocardium), the
middle (myocardium) and the
external (epicardium).
1 Endocardium
consists of a lining endothelium
( single layer of squamous cells )
& subendothelial layer of C.T
containing (Purkinje) fibers in
the ventricles the conducting

Heart Wall Cont.
2 Myocardium:
Is the thickest layer,
consists of cardiac
muscle cells.
The myocardium in
ventricles is much
thickerthaninatrium?
than in atrium ?
M

Heart Wall Cont.
3 Epicardium
simple squamous epithelium
(mesothelium) supported by a
thin layer of connective tissue
contains considerable adipose
tissue.
A- Fibrous layer
B- Parietal layer
C- Visceral layer (Pericardium),
the serous membrane in which
the heart lies.
In the space between the pericardium's
visceral layer (epicardium) and its
parietal layer is a small amount of
lubricant fluid that facilitates the
heart's movements.
Epicardium or visceral pericardium.

Epicardium

Epicardium or visceral pericardium.

Purkinje fibers
Are modified cardiac
muscle fibers located
under the endocardium,
-have larger diameter than
cardiac muscle fibers & the
sarcoplasm has a large
amount of glycogen so
they are less intensely
stained.
Purkinje fibers have fewer
myofibrils than cardiac
muscle fibers & distributed
peripherally.
Function: transmit
impulses to the cardiac
muscle cells located at the
apex of the heart.

Arteries
artery has a relatively thick wall & a
small lumen. The wall of artery
consists of the following layers.
1- Tunica intima :
• an inner layer of endothelium, a
subendothelial layer of delicate
fibro-elastic connective tissue
• internal elastic lamina of
membrane.
2- Tunica media : consists chiefly
of smooth muscle fibers, circularly
arranged. A loose network of fine
elastic fibers is interspersed
among the smooth muscle cells,
the amount of elastic fiber increase
as the diameter of the artery
increases.
3- Tunica adventitia : composed
3 Tunica adventitia : composed
of C.T which contains nerves &
blood vessels .

1 Arterioles They are less than 0.5 mm in diameter,
their wall consist of:
Tunica intima: Consist of endothelium ,subendothelial layer
is very thin and internal elastic lamina is lacking except
in largest arterioles.
Tunica media composed of 1-5 layers of smooth. m. cells.
T. adventitia is thinner than T. media

2 Muscular arteries :
Include small & medium-sized arteries,
The wall of the muscular arteries are relatively thick, having large
amount of muscle in T. media.
A-Small artery:

2-Muscular artery cont.
B- Medium sized artery:
•Tunica media is composed of smooth muscle.
• Internal elastic lamina:Single, fenestrated, elastic sheet; lies internal to the
smooth muscle of the tunica media.
• External elastic lamina: Multiple elastic sheets; lie external to the smooth
muscle of the tunica media.
•Vasa vasorum are confined to the adventitial layer.

3 Large elastic arteries
They are also called conducting arteries,
which include aorta and its large branches.
T. intima is thicker than the muscular art. The endothelial cells are polygonal
in shape, a small bundle of smooth muscle cells are present in deeper portion
of the intima. A distinct internal elastic lamina is difficult to seen.
Tunica media is characterized by numerous distinct elastic lamina 40-60 in
number, arranged concentrically, between these lamina are smooth muscle,
fibroblasts, and affine elastic network.
IEL
T.adventitia is a thin coat & cannot be
sharply distinguished from surrounding
connective tissue.
Vasa vasorum : are blood vessels of
TM
blood vessels that present in adventitia
of large vessels.
Vasa vasorum

Veins
Have relatively thin walls and large lumens. The wall of vein consists
of the following layers:-
Tunica intima : comosed of endothelium & thin layer of fine
collagenous & elastic fibers.
Tunica media : consists of
a thin layer of circularly arranged
smooth muscle & is much
Thinner than in arteries.
Tunica adventitia : consists of
a wide layer of connective tissue
& is much thicker than
the tunica media.

1 Venules
T. intima composed of endothelium only.
T. media: may contain only a few layers
of smooth m. cells.
T. adventitia is the thickest layer and composed of C.T.

2 Small and medium sized veins
With the exception of the main trunks, most veins are small or medium
sized.
• T. intima consists of endothelium , the sub-endothelial tissue is very thin,
which may be some times absent.
• T. media consists of small bundles of smooth m. cells.
• T. adventitia is a well developed C.T layer.
Small vein

3 Large veins
T. intimai is little l thicker than medium-sized i d veins.
T. media is poorly developed, smooth muscle fibers are much reduced or
absent.
the adventitia is the thickest layer & consists of collagen & elastic fibers &
many longitudinal muscle fibers.

Capillaries:
Small blood vessels with
average diameter of 7-9
micrometer
subdivided into three
types
Continuous capillaries
most common type, found
in connective tissue, muscle
tissue & nervous tissue
Fenestrated capillaries
:found in endocrine glands,
small intestine &
glomerulus's l of kidney.
Sinusoids are large
capillaries (30-40 microns)
found in liver, spleen and
bone marrow

References
‣ Junqueira, L.C and Carneiro, J. (2010) Basic
Histology, text and atlas, 12 th Edition.
McGraw-Hill, Inc.
‣ Gartner and Hiatt: Color Textbook of
Histology, 3rd ed. Philadelphia, W.B.
Saunders, 2007.
‣ Victor p. Eroschenko. (1993). diFiore’s Atlas
of Histology with functionalcorrelations,7th
ed. (Egyptian Edition);Elias Modern press.
‣ http://biology.about.com/library/organs/heart/
p gy y g
blpurkinje.htm