Download Elastic Arteries

Cardiovascular system
Department of Histology and Embryology
Medical college in Three Gorges University
• The circulatory system comprises both the
cardiovascular and lymphatic system.
The cardiovascular system:
heart
blood vessels: capillaries
arteries
viens
Histology of the heart
• There are three layers in the wall of the
heart :
•
(1)Endocardium:epithelium
subepithelial layer
subendocardial layer
•
(2)Myocardium: cardiac muscle
•
(3)Epicardium: connective tissue
mesothelium
Endocardium 心内膜
It provide smoothing lining for the chambers of the heart
endocardium
subepithelial
layer
Purkinje fibers
Endocarditis: inflammation which most caused by bacteria
Myocardium 心肌膜 myocarditis
Pumping action, involuntary like SM
Epicardium: the visceral layer of the serous pericardium
Epicardium:connective tissue and mesothelium
• Arteries:
Arteries are blood vessels that carry blood
away from the heart.
1. Classification of arteries:arteries are of
three types:
elastic arteries (conduction arteries)
muscular arteries( distributing arteries)
arterioles
• 2. Basic structure of arteries:
The wall of an arteries is made up of three
layers:
(1) tunica intima 内膜: inner layer
(a) endothelial lining
(b) subendothelial connective tissue
(c) internal elastic lamina: a membrane
formed by elastic fibers.
• 2. Tunica media中膜: or middle layer,which
is outside the tunical intima. The media may
consist predominantly of elastic tissue or of
smooth muscle.Some connective tissue is
usually present. On the outside the media is
limited by a membrane formed by elastic
fibers.This is the external elastic lamina.
• 3. Tunica adventitia外膜: the outmost layer
of arteries. This coat consist of connective
tissue in which collagen fibers are
prominent. This layer presents undue
stretching or distension of the artery.
• Elastic Arteries:
• The feature of elastic arteries is the media
which have predominently elastic
membrane known as fenestrated membrane,
or occupy much of the tunica media.
Between the elastic membranes there is
some loose connective tissue. Some smooth
muscle cells may be present.
• Muscular arteries:
Muscular arteries are characterized by a thick
tunica media that is composed mostly of smooth
muscle cells. The musles is arranged circulary
made up mainly of smooth muscle.This muscle is
arranged circulary. Between groups of muscle
fibers, come connective tissue is present. This may
contain some elastic fibers.
Vasa vasorum
Arterioles
• When traced distally, muscular arteries
progressively decrease in calibre till they
have a diameter of about 100 um.They then
become continuous with arterioles. The
larger or muscular arterioles are 100 to 50
um in diameter.
• Arterioles less than 50 um in diameter are
called terminal arterioles. Muscular
arterioles can be distinguished from true
arteries:
(1) by their small diameter
(2) by the fact that they do not have an
internal elastic lamina.
• Veins:
• The basic structure of veins is similar to that
of arteries.The tunica intima, media and
adventitia can be disinguished specially in
large veins.the structure of veins differs
from that of arteries in the following
respects:
• (1) The wall of a vein is distinctly thinner
than that of an artery having the same sized
lumen.
• (2) the tunica media contains a much larger
quantity of collagen than in arteries. Elastic
tissue
• (3) Vein is easily compressed, usually
collapsed
• (4) In arteries the tunic media is usually
thicker than the adventita.In contrast the
adventitia of veins is thicker than the media.
• Capillaries:
• Arising from the terminal ends of the
arterioles are capillaries ,which form, by
branching and anastomosing,a capillary bed
(network ) between the artrioles and the
venules. The richness of the capillary
network is related to the metabolic activity
of the tissue.
• General structure of capillaries:
Capillaries composed of a single layer of
endothelial cells, are the smallest blood
vessels.
The average diameter of a capillary is 8 um.
The wall of a capillary is formed essentially
by endothelial cells which are lined on the
outside by a basal lamina secreted by the
endothelial cells.
• Overlying the basal lamina there may be
isolated branching perivascular cell
(pericytes) and a delicate network of
reticular fibers and cells.
• Classification of capillaries:
(1)Continuous capillaries:
The endothelial cell is continuous, no
pores or fenestrated in their walls.
The basement membrane is completedly.
Distribution: connective tissue ,muscle,
nervous tissue
• (2) Fenestrated capillaries: fenestrated
capillaries possess pores (fenestrate) in
their walls that are covered by pore
diaphrgms.
• The pores are 60-80 nm in diameter, ridged
by an ultra thin diaphragm. diffusion of
substances takes place through the
numerous fenestrate in the capillaries wall.
• Distribution: kindney, small intestine
• (3) Sinusoidal capillaries:
• Sinusoidal capillaries or sinusoids may
discontinuous endothelial cells and basal
lamina and contain many large fenestrate
without diaphragms,enhancing exchange
between blood and tissue.
• Distribution: liver and spleen