Principal Branches of the Aorta

The first portion of the aorta is called the ascending aorta. Located at its base are the three cusps of the aortic valve, and opposite each cusp is a swelling in the aortic wall called an aortic sinus. The right and left coronary arteries arise from two of these sinuses. Blood flow into these arteries is intermittent and is driven by the elastic recoil of the aortic wall following contraction of the left ventricle.

Several small structures called aortic bodies are located within the epithelial lining of the aortic sinuses. These bodies contain chemoreceptors that sense blood concentrations of oxygen and carbon dioxide.

Three major arteries originate from the arch of the aorta (aortic arch). They are the brachiocephalic (innominate) artery, the left common carotid artery, and the left subclavian artery. The aortic arch contains baroreceptors that detect changes in blood pressure.

The brachiocephalic (brak"e-o-se-fal'ik) artery supplies blood to the tissues of the upper limb and head, as its name suggests. It is the first branch from the aortic arch and rises upward through the mediastinum to a point near the junction of the sternum and the right clavicle. There it divides, giving rise to the right common carotid (kah-rot'id) artery, which carries blood to the right side of the neck and head, and the right subclavian (sub-kla've-an) artery, which leads into the right arm. Branches of the subclavian artery also supply blood to parts of the shoulder, neck, and head.

The left common carotid artery and the left subclavian artery are respectively the second and third branches of the aortic arch. They supply blood to regions on the left side of the body corresponding to those supplied by their counterparts on the right (see fig. 15.44 and reference plates 71, 72, and 73).

Although the upper part of the descending aorta is positioned to the left of the midline, it gradually moves medially and finally lies directly in front of the vertebral column at the level of the twelfth thoracic vertebra. The portion of the descending aorta above the diaphragm is the thoracic aorta, and it gives off numerous small branches to the thoracic wall and the thoracic viscera. These branches, the bronchial, pericardial, and esophageal arteries, supply blood to the structures for which they were named. Other branches become medi-astinal arteries, supplying various tissues within the mediastinum, and posterior intercostal arteries, which pass into the thoracic wall.

Below the diaphragm, the descending aorta becomes the abdominal aorta, and it gives off branches to the abdominal wall and various abdominal organs. These branches include the following:

1. Celiac (se'le-ak) artery. This single vessel gives rise to the left gastric, splenic, and hepatic arteries, which supply upper portions of the digestive tract, the spleen, and the liver, respectively. (Note: The hepatic artery supplies the liver with about one-third of its blood flow, and this blood is oxygen-rich. The remaining two-thirds of the liver's blood flow arrives by means of the hepatic portal vein and is oxygen-poor.)

2. Phrenic (fren'ik) arteries. These paired arteries supply blood to the diaphragm.

3. Superior mesenteric (mes"en-ter'ik) artery. The superior mesenteric is a large, unpaired artery that branches to many parts of the intestinal tract, including the jejunum, ileum, cecum, ascending colon, and transverse colon.

4. Suprarenal (soo"prah-re'nal) arteries. This pair of vessels supplies blood to the adrenal glands.

5. Renal (re'nal) arteries. The renal arteries pass laterally from the aorta into the kidneys. Each artery then divides into several lobar branches within the kidney tissues.

Right common carotid a Right internal jugular v Right subclavian a.

Brachiocephalic a. Brachiocephalic v.

Superior vena cava

Right pulmonary a.

Right pulmonary v

Right auricle

Brachiocephalic a. Brachiocephalic v.

Superior vena cava

Right pulmonary a.

Right pulmonary v

Right auricle

Brachiocephalica

Left common carotid a.

Left internal jugular v. Left subclavian a.

Aortic arch

Ligamentum arteriosum

Left pulmonary a.

Left pulmonary v. Left auricle

Pulmonary trunk

Left common carotid a.

Left internal jugular v. Left subclavian a.

Aortic arch

Ligamentum arteriosum

Left pulmonary a.

Left pulmonary v. Left auricle

Pulmonary trunk

Figure 15.44

The major blood vessels associated with the heart.

6. Gonadal (go'nad-al) arteries. In a female, paired ovarian arteries arise from the aorta and pass into the pelvis to supply the ovaries. In a male, spermatic arteries originate in similar locations. They course downward and pass through the body wall by way of the inguinal canal to supply the testes.

7. Inferior mesenteric artery. Branches of this single artery lead to the descending colon, the sigmoid colon, and the rectum.

8. Lumbar arteries. Three or four pairs of lumbar arteries arise from the posterior surface of the aorta in the region of the lumbar vertebrae. These arteries supply muscles of the skin and the posterior abdominal wall.

9. Middle sacral artery. This small, single vessel descends medially from the aorta along the anterior surfaces of the lower lumbar vertebrae. It carries blood to the sacrum and coccyx.

The abdominal aorta terminates near the brim of the pelvis, where it divides into right and left common iliac arteries. These vessels supply blood to lower regions of the abdominal wall, the pelvic organs, and the lower extremities (fig. 15.45). Table 15.4 summarizes the main branches of the aorta.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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