Download introduction to cardiovascular system 26. 02. 2014

26. 02. 2014
Kaan Yücel
M.D., Ph.D.
http://yeditepeanatomy1.org
Dr. Kaan Yücel
http://yeditepeanatomy1.org
Introduction to cardiovascular system
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Dr. Kaan Yücel
http://yeditepeanatomy1.org
Introduction to cardiovascular system
Cardiovascular (Circulatory) System transports fluids throughout the body. The heart and blood vessels
make up the blood transportation network, the cardiovascular system.
The vascular system is divided for descriptive purposes into (a) the blood vascular system, which comprises
the heart and blood vessels for the circulation of the blood; and (b) the lymph vascular system, consisting of
lymph glands and lymphatic vessels, through which a colorless fluid, the lymph, circulates. The two systems
communicate with each other and are intimately associated developmentally.
The heart pumps blood throughout the body, and the blood vessels, which are a closed network of tubes
that transport the blood. There are three types of blood vessels:
arteries, which transport blood away from the heart;
veins, which transport blood toward the heart;
capillaries, which connect the arteries and veins, are the smallest of the blood vessels, and are where
oxygen, nutrients, and wastes are exchanged within the tissues.
The walls of the blood vessels of the cardiovascular system usually consist of three layers or tunics:
tunica externa (adventitia)-the outer connective tissue layer;
tunica media-the middle smooth muscle layer (may also contain varying amounts of elastic fibers in
medium and large arteries);
tunica intima-the inner endothelial lining of the blood vessels.
Arteries are usually further subdivided into three classes, according to the variable amounts of smooth
muscle and elastic fibers contributing to the thickness of the tunica media, the overall size of the vessel, and
its function.
a. Large elastic arteries contain substantial amounts of elastic fibers in the tunica media, allowing expansion
and recoil. This helps maintain a constant flow of blood to the heart. An example is the aorta.
b. Medium muscular arteries are composed of a tunica media that contains mostly smooth muscle fibers.
This characteristic allows these vessels to regulate their diameter and control the flow of blood to different
parts of the body. An example is the radial artery.
c. Small arteries and arterioles control the filling of the capillaries and directly contribute to the arterial
pressure in the vascular system.
Veins also are subdivided into three classes.
a. Large veins contain some smooth muscle in the tunica media, but the thickest layer is the tunica externa.
Examples of large veins are the superior vena cava, and the inferior vena cava.
b. Small and medium veins contain small amounts of smooth muscle, and the thickest layer is the tunica
externa. Examples of small and medium veins are superficial veins in the upper and lower limbs and deeper
veins of the leg and forearm.
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Dr. Kaan Yücel
http://yeditepeanatomy1.org
Introduction to cardiovascular system
c. Venules are the smallest veins and drain the capillaries.
The heart has two sides. The right side of the heart (right heart) receives poorly oxygenated (venous)
blood from the body through the superior vena cava (SVC) and inferior vena cava (IVC) and pumps it to the
lungs for oxygenation. The left side of the heart (left heart) receives well-oxygenated (arterial) blood from
the lungs and pumps it into the aorta for distribution to the body. So the suction part is the right side
(venous blood), and pumping part is the left side (arterial blood). The main artery in the body is the aorta.
All the arteries in the body leave from the branches of the aorta. Arteries have also branches themselves.
Some large arteries such as axillary, subclavian, and maxillary are divided into different parts by distinct
muscles. The direction of the blood flow in arteries is from the heart to the body. The direction of the blood
flow in veins is from the body to the heart. Veins drain into other veins; vein A draining into vein B is called
the tributary of the vein B.
One more thing, arteries (also veins) do anastomosis (stoma= mouth). This means a branch of an
artery comes to mouth to mouth and connects with another branch of an artery. This is vital for the sake of
the place where an artery is supplying blood to. If there is a problem in the flow, and it is a site in the body
where anastomosis is occurring, the blood will travel from here in order to bring blood to that area; so that
the tissue does not die.
Lymphatic system: is a network of lymphatic vessels that withdraws excess tissue fluid (lymph) from
the body's interstitial (intercellular) fluid compartment, filters it through lymph nodes, and returns it to the
bloodstream. Lymph nodes, small masses of lymphatic tissue, are located along the course of lymphatic
vessels through which lymph is filtered on its way to the venous system. The lymph carried by lymphatic
vessels reaches to the regional lymph nodes, then into larger lymph nodes and ends up in the venous system
in order to reach its final destination; the right heart.
Functions of the lymphatic system:
1) to maintain the pressure and volume of the interstitial fluid and blood by returning excess water and
dissolved substances from the interstitial fluid to the circulation.
2) lymph nodes and other lymphoid tissues are the site of clonal production of immunocompetent
lymphocytes and macrophages in the specific immune response.
HEART
The heart is the central organ of the blood vascular system, and consists of a hollow muscle; by its
contraction the blood is pumped to all parts of the body through a complicated series of tubes, termed
arteries. The arteries undergo enormous ramification in their course throughout the body, and end in
minute vessels, called arterioles, which in their turn open into a close-meshed network of microscopic
vessels, termed capillaries. After the blood has passed through the capillaries it is collected into a series of
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Dr. Kaan Yücel
http://yeditepeanatomy1.org
Introduction to cardiovascular system
larger vessels, called veins, by which it is returned to the heart. The passage of the blood through the heart
and blood-vessels constitutes what is termed the circulation of the blood.
The heart, slightly larger than a clenched fist, is a double, self-adjusting suction and pressure pump,
the parts of which work in unison to propel blood to all parts of the body.
The heart has four chambers: right and left atria and right and left ventricles. The atria are receiving
chambers that pump blood into the ventricles (the discharging chambers).
The right side of the heart (right heart) receives poorly oxygenated (venous) blood from the body
through the superior vena cava (SVC) and inferior vena cava (IVC) and pumps it through the pulmonary trunk
and arteries to the lungs for oxygenation. The left side of the heart (left heart) receives well-oxygenated
(arterial) blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to
the body.
The right and left brachiocephalic veins are formed by the union of the internal jugular and
subclavian veins. The brachiocephalic veins unite to form the superior vena cava (SVC). The superior vena
cava (SVC) returns blood from all structures superior to the diaphragm, except the lungs and heart. It ends
by entering the right atrium of the heart. The inferior vena cava (IVC) returns blood from the lower part of
the body including the lower limbs right into the right atrium.
The ascending aorta begins at the aortic orifice. Its only branches are the coronary arteries, arising
from the aortic sinuses. The arch of the aorta (aortic arch) is the curved continuation of the ascending aorta.
The usual branches of the arch are the brachiocephalic trunk, left common carotid artery, and left subclavian
artery.
The subclavian artery will continue as axillary artery, and later brachial artey on both arms. The
brachial artery will then divide into two terminal branches: ulnar and radial arteries.
What happens to descending aorta (thoracic aorta) which is the continuation of the arch of aorta is that
after passing through the diaphragm, it becomes the abdominal aorta which finally terminates as common
iliac arteries which will then bifurcate into the external and internal iliac arteries. The external iliac arteries,
after passing below the inguinal ligament, will become femoral arteries. The femoral arteries will supply the
lower limbs. On both sides, these arteries will continue as popliteal arteries which then will branch into
anterior and posterior tibial arteries.
The common carotid artery will divide into external carotid artery and internal carotid artery. The external
carotid artery basically supplies blood to the face and neck, and the internal one to the brain. The other
artery of the brain is the vertebral artery which is a thick branch of the subclavian artery.
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