Cardiovascular system

The cardiovascular system consists of the heart, blood vessels, and the approximately 5 liters of blood that the blood vessels transport. Responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the body’s hardest-working organ — the heart, which is only about the size of a closed fist. Even at rest, the average heart easily pumps over 5 liters of blood throughout the body every minute.

The cardiovascular system of the head and neck includes the vital arteries that provide oxygenated blood to the brain and organs of the head, including the mouth and eyes. It also includes the veins that return deoxygenated blood from these organs to the heart. Among these blood vessels are several unique and important structures that have evolved to help maintain the continuous flow of blood to the brain. The human brain is so powerful and metabolically active that it uses about 20% of all of the oxygen and glucose taken in by the body each day. Any interruption in the blood flow to the brain very quickly results in the decline of mental function, loss of consciousness, and eventually death if not corrected.

The external carotid artery flows upward on the side of the head to branch into various structures in the neck, face, jaw, scalp, and base of the skull. The main vessels that originate from this artery are: (1) the superior thyroid artery, to the hyoid bone, larynx, and thyroid gland; (2) the lingual artery, to the tongue, muscles of the tongue, and salivary glands below the tongue; (3) the facial artery, to the pharynx (throat), palate, chin, lips, and nose; (4) the occipital artery, to the scalp on the back of the skull and various muscles in the neck; and (5) the posterior auricular artery, to the ear and scalp over the ear. The external carotid artery terminates by division into the maxillary and superficial temporal arteries. ...

The cardiovascular system of the upper torso includes the heart and most of the major blood vessels of the circulatory system. These vital structures are critical to the process of pumping deoxygenated blood to the lungs for gas exchange as well as pumping oxygenated blood to the body’s tissues to support their metabolic functions.

The heart is a muscular organ about the size of a closed fist that functions as the body’s circulatory pump. It takes in deoxygenated blood through the veins and delivers it to the lungs for oxygenation before pumping it into the various arteries (which provide oxygen and nutrients to body tissues by transporting the blood throughout the body). The heart is located in the thoracic cavity medial to the lungs and posterior to the sternum.

On its superior end, the base of the heart is attached to the aorta, pulmonary arteries and veins, and the vena cava. The inferior tip of the heart, known as the apex, rests just superior to the diaphragm. The base of the heart is located along the body’s midline with the apex pointing toward the left side. Because the heart points to the left, about 2/3 of the heart’s mass is found on the left side of the body and the other 1/3 is on the right.

At about one inch in diameter and traveling almost the entire length of the trunk, the aorta is the largest artery in the human body. The aorta also has the thickest walls of any blood vessel in the body. This artery ascends superiorly from the left ventricle of the heart, arches over the heart and to the back and to the left, and descends inferiorly behind the heart just anterior to the spinal column.

Following the aorta from its origin at the left ventricle of the heart, the first section of the aorta is known as the ascending aorta. The ascending aorta branches into the left and right coronary arteries. The coronary arteries carry blood to the surface of the heart so that it has oxygen and nutrients to keep beating.

The inferior vena cava is the largest vein in the human body. It collects blood from veins serving the tissues inferior to the heart and returns this blood to the right atrium of the heart. Although the vena cava is very large in diameter, its walls are incredibly thin due to the low pressure exerted by venous blood.

The cardiovascular system of the lower torso, including the abdomen and pelvis, features many vital blood vessels that supply blood to the many organs of this region. A vast network of blood vessels supplies essential blood to the diverse organs of the digestive, reproductive, urinary, lymphatic and endocrine system in the abdomen and pelvis. Many muscles, nerves, and bones surrounding the vital organs depend on this blood supply as well.

Oxygenated blood from the heart enters the lower torso through the descending aorta, a huge elastic artery that passes anterior to vertebral column. As the descending aorta passes through the diaphragm and enters the abdomen, it becomes known as the abdominal aorta. From the abdominal aorta, many visceral branches separate to perfuse the vital organs of the abdomen, while several parietal branches perfuse the bones, muscles, skin and tissues of the abdominal body wall. The abdominal aorta bifurcates at the pelvis to form the left and right common iliac arteries, which provide blood to the pelvis and hips before continuing into the legs as the femoral arteries.

The kidneys filter about one-quarter (750-1000 pints) of the blood that is output by the heart daily. This blood is sent to the body\'s filter treatment plant, where it is purified by the kidneys and circulated on to the rest of the body. Some of the blood flow becomes fluid waste (1/1000th to 2/1000th) and is sent into the bladder for storage until it can be conveniently expelled. This toxic waste is called urine.

The cardiovascular system of the upper limbs plays the vital role of ensuring the adequate flow of blood to and from the shoulders, arms, hands and fingers. Adequate flow of oxygenated blood to the tissues of the upper limbs is critical to their health through the delivery of oxygen, water, and nutrients. Blood flow also helps to regulate body temperature in this region and reduces the risk of frostbite of the fingers in extreme weather conditions.