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The cardiovascular system of the lower torso

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 inferior vena cava

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 aorta

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 heart

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.

The cardiovascular system of the upper torso

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.

Blood vessels of the head and neck

The external carotid artery

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 head and neck

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 sciatic nerve

The sciatic nerve is the largest and longest spinal nerve in the human body. Extending from the lumbar and sacral plexuses in the lower back, the sciatic nerve runs through the buttocks and into the thighs. It delivers nerve signals to and from the muscles and skin of the thighs, lower legs and feet.

The sciatic nerve forms from the merger of the fourth and fifth lumbar nerves with the first, second, and third sacral nerves. From the lower back, the sciatic nerve runs inferiorly into the gluteal region and into the posterior of the femoral region of the leg. Smaller individual nerves branch off from the sciatic nerve to innervate our thigh muscles and skin. At the inferior end of the femoral region, the sciatic nerve branches off into the tibial and common fibular nerves, which continue carrying nerve signals into the lower legs and feet.

The femoral nerve

The femoral nerve is the major nerve that serves the tissues of the thigh and leg, including the muscles and skin. While the much larger sciatic nerve also passes through the thigh on its way to the lower leg and foot, only the femoral nerve innervates the tissues of the thigh. Nerve signals carried by the femoral nerve are crucial to the function of the legs, including standing, walking, and running.

The femoral nerve begins as the largest nerve to extend from the lumbar plexus in the lower back as a combination of fibers from the L2, L3, and L4 spinal nerves. From the lumbar plexus it extends with the fibers of the psoas major muscle inferiorly through the abdomen along the anterior surface of the hip bone. As it passes through the abdomen, a branch of the femoral nerve extends to provide nervous connections to the iliacus muscle, a flexor of the thigh. From the abdomen the femoral nerve next passes deep to the inguinal ligament in the groin and crosses the hip joint to enter the femoral region. In the femoral region, the femoral nerve separates into two nerve trunks - the anterior and posterior divisions - before further dividing into many smaller branches throughout the anterior and medial thigh.

The nerves of the leg and foot

The nerves of the leg and foot serve to propel the body through the actions of the legs, feet, and toes while maintaining balance, both while the body is moving and when it is at rest. Sensory nerves are of course present throughout the lower extremities; however, with the exception of the bottom of the foot, they play a lesser role here than in the upper extremities. Primarily, this section of the peripheral nervous system sends and receives signals regarding locomotion and balance of the body.