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Ahlulbait University
College of Pharmacy
Human Anatumy
Stage : 1 st
Lab:1
Ass.Lectur:Maryam M. Alhelfy
Functions of the Circulatory System
The many functions of the circulatory system can be grouped into two
broad areas: transportation and protection.
1- Transportation. All of the substances involved in cellular
metabolism are transported by the circulatory system. These
substances can be categorized as follows:
A- Respiratory. Red blood cells called erythrocytes transport oxygen
to the tissue cells. In the lungs, oxygen from the inhaled air
attaches to hemoglobin molecules within the erythrocytes and is
trans-ported to the cells for aerobic respiration. Carbon dioxide
produced by cellular respiration is carried by the blood to the lungs
for elimination in the exhaled air
B- Nutritive. The digestive system is responsible for the mechanical
and chemical breakdown of food to forms that can be absorbed
through the intestinal wall into the blood and lymph vessels. The
blood then carries these absorbed products of digestion through the
liver to the cells of the body.
C- Excretory. Metabolic wastes, excess water and ions, as well as
other molecules in plasma (the fluid portion of blood), are filtered
through the capillaries of the kidneys into kidney tubules and
excreted in urine.
D- Regulatory. The blood carries hormones and other regulatory
molecules from their site of origin to distant target tissues.
2- Protection. The circulatory system protects against injury and
foreign microbes or toxins introduced into the body.
Major Components of the Circulatory System The circulatory system
is frequently divided into the cardiovascular system, which consists of the
heart, blood vessels, and blood, and the lymphatic system, which consists
of lymphatic vessels and lymphoid tissues within the spleen, thymus,
tonsils, and lymph nodes.
Chest Cavity
The chest cavity is bounded by the chest wall and below by the diaphragm. It extends upward into the root of the neck about one fingerbreadth above the clavicle on each side.
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Pericardium
The pericardium is a fibroserous sac that encloses the heart and the
roots of the great vessels. Its function is to restrict excessive
movements of the heart as a whole and to serve as a lubricated
container in which the different parts of the heart can contract. The
pericardium lies within the middle mediastinum.
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Location of the Heart The heart is located in the chest between the lungs behind the
sternum and above the diaphragm. It is surrounded by the
pericardium. Its size is about that of a fist, and its weight is about
250-300 g. Its center is located about 1.5 cm to the left of the
midsagittal plane. Located above the heart are the great vessels: the
superior and inferior vena cava, the pulmonary artery and vein, as
well as the aorta. The aortic arch lies behind the heart.
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Structure of the Heart
The walls of the heart are composed of a thick layer of cardiac
muscle, the myocardium, covered externally by the epicardium and
lined internally by the endocardium. The atrial portion of the heart
has relatively thin walls and is divided by the atrial (interatrial)
septum into the right and left atria. The septum runs from the
anterior wall of the heart backward and to the right. The ventricular
portion of the heart has thick walls and is divided by the ventricular
(interventricular) septum into the right and left ventricles.