Download cardiovascular system

cardiovascular system
It is a network of tubular passages runs through the connective tissues,
through which the more fluid components of the extracellular
environment flow. The fluid is either blood forming blood vascular system
which is formed of heart,the cardiovascular system consist of heart,
arteries ,arterioles, capillaries, venules , and veins
The main function of the circulatory system
1-deliver oxygenated blood to cells and tissue and to return venous blood
to the lungs for gaseous exchange
2-distributes nutrients, hormones to all parts of the body; collects wastes
produced
during cellular metabolism.
Histological structure of the typical artery and vein
The wall of the typical artery and vein consist of three layers (tunics)
1-Inner,
tunica
intima:consist
of
simple
squamous
epithelium(endothelium)and the underlying subendothelial connective
tissue
2-Middle ,tunica media:- composed mainly of smooth muscle fibers
Interspersed among the smooth muscle fibers are a variable amount of
elastic and reticular fibers
3-Outer, tunica adventitia:- contains primarily collagen (type I) and elastic
fibers
Muscular artery and vein
Types of arteries
There are three types of arteries in the body according to the
histological structure
1-Elastic arteries :- are the largest vessels in the body include aorta
and their branches , the brachiocephalic , common carotid ,
subclavian ,vertebral ,pulmonary trunk , common iliac artery ,and
charactirized by
a-Exhibit resilience and flexibility during blood flow
b-Walls greatly expand during systole (heart contraction ) and during
diastole (heart relaxation) walls recoil and force blood forward
histological structures of elastic arteries
 Tunica intima consist of endothelium, basement membrane,
underlying subendothelial connctive tissue
 Tunica media is very thick and composed of predominant elastic fibers
with less amount of circular smooth muscle fibers , the wall of elastic
artery visible elastic membrane is the internal elastic lamina which
located between tunica intima and tunica media.
 tunica adventitia composed of collagen and elastic fibers
Elastic artery
 2-Muscular arteries(distributing arteries) :- Control of blood
flow through vasoconstriction or vasodilation of lumina by
autonomic nervous system
histological structur of muscular arteries
 Tunica intima consist of endothelium, basement membrane,
underlying subendothelial connctive tissue.
 Tunica media composed of predominant circular smooth
muscle fibers (more than 25 layer) and a less amount of elastic
fibers and theirs two elastic membranes, internal elastic
membrane between tunica intima and tunica media , external
elastic membrane between tunica media and tunica adventitia.

tunica adventitia composed of collagen and elastic fibers.
3-Arterioles
are the small blood vessels with one to five layers of smooth
muscle in tunica media.
Note: Terminal arterioles deliver blood to smallest blood vessels
(capillaries).
 Capillaries sites of metabolic exchanges between blood and tissues.
 Capillaries connect arterioles with venules.
 Capillary wall is two layers ,tunica intima and tunica adventitia.
 Venules consist of one layer ,tunica intima (there is no tunica media
and tunica adventitia)
Histological structure of large vein( portal vein)
 The tunica intima consist of endothelium , basement membrane ,
subendotheliual connective tissue.
 Tunica media is thinner and consist of smooth muscle in circular
orientation .
 The tunica adventitia characterized by thick in which the smooth
muscle fibers show longitudinal orientation.
Note:Small and medium size veins particularly in the extremities have
valves.
Vasa vasorum
Small blood vessels supply tunica media and tunica adventitia and
found in the walls of large arteries and veins
large vein
Types of capillaries
Capillaries are the smallest blood vessels ,their average
diameter is about 8µm which is about the size of erythrocyte (red
blood cell) ,there are three types of capillaries
1-Continuous capillaries :-are the most common ,they are found in
,muscle , connective tissue ,nervous tissue , skin ,respiratory organs
and exocrine glands . In this capillaries the endothelial cell are joined
and form an uninterruptid and solid endothelial lining
2-Fenestrated capillaries:-Are vessels characterized by large
openings or fenestration (pores) in the cytoplasm of endothelial cells
designed for rapid exchange of molecules between blood and tissue ,
they are found in endocrine tissues and glands ,small intestine and
kidney glomeruli
3-Sinusoidal capillaries :- Are blood vessels that exhibit irregular
,tortuous paths characterized by wider diameter ,slow down the flow
of blood and endothelial junction rare in sinusoidal capillaries and
wide gaps exist between individual endothelial cell because a
basement membrane underlying the endothelium is either
incomplete or absent , a direct exchange of molecules occurs between
blood and cells ,its found in the liver ,spleen and bone marrow
Lymph vascular system
 Lymphatic system consists of lymph capillaries and lymph vessels and
this system starts as blind-ending
 These vessels collect the excess interstitial fluid (lymph) from the
tissues to the venous blood via large lymph vessels
 The structure of large lymphatic vessels is similar to that of venous
except that their walls are much thinner
 The contraction of surrounding skeletal muscles forces the lymph to
move forward and the lymph vessels contain more valves to prevent a
backflow of collected lymph
 Lymph vessels are found in the all tissues except the central nervous
system ,cartilage , bone and bone marrow , thymus , placenta ,and
teeth
Heart :- It is a hollow muscular organ consisting of groups of cardiac
muscle cells surrounded by highly vascularized connective tissue.
These muscle bundles comprise the myocardium, constituting the
walls of atria & ventricles. On the inner & outer surfaces the
myocardium is lined by the endocardium & epicardium, respectively.
Histologicaly ,the wall of the heart consist of three layers
1- an inner, endocardium :-consist of simple squamous endothelium,
basement membrane and subendothelial connective tissue ,deeper to
the endocardium is the subendocardial layer of connective tissue
contain blood vessels and purkinje fibers and this layer attaches to the
endomysium of the cardiac muscle
2-A middel layer myocardium:- is the thickest layer and consist
cardiac muscle fibers
3-An outer layer epicardium:- consist of simple squamous
mesothelium and an underling subepicardial connective tissue which
contain coronary blood vessels ,nerves, adipose tissue
Heart
Pacemaker of the heart :- are specialized or modified cardiac muscle
fibers located in the sinoatrial (SA) node and atrioventricular (AV
)node in the wall of the right atrium of the heart , because the fibers
in the SA nod depolarize and repolarize faster than those in the AV
node ,the SA node sets the pace for the heartbeat (Pacemaker)
Intercalated disks (gap junction bind all cardiac muscles fibers) and
Purkinje fibers are conducted impulses of the heart .
Atrial natriuretic hormone (heart as endocrin gland)
Cardiac muscles in the atrium exhibit dense granules in their
cytoplasm contain atrial natriuretic hormons ,thes hormone release in
response to the atrial distension (blood hypertension), which lead to
inhibiting the release of renin (by specialized cells in the kidney ) and
aldosterone (from the adrenal gland cortex) ,this induces to lose more
sodium and water (diuresis) as a result the blood volume and blood
pressure reduce
heart wall
Arteriovenous anastomoses :- are special areas of the skin of the
nose , lips and pads where the arteriole opens directly into venule
without going through the capillary bed , this provides an alternative
channel of blood supply and regulation of heat loss.