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The Aorta and Its Major Branches The aorta is the biggest artery in the body, with a diameter of approximately 3 cm (1 in.). All systemic arteries branch off the aorta. The aorta has four major segments: ascending aorta, arch of the aorta (or aortic arch), thoracic aorta, and abdominal aorta. Arteries that branch off each section of the aorta divide into smaller arteries that supply different organs. These arteries then divide into arterioles within the organs, and finally into capillaries that supply all systemic tissues accept the alveoli of the lungs. The Ascending Aorta The ascending aorta, which is approximately 5 cm (2 in.) long, is the first section of the aorta. It begins at the aortic valve, at the upper part of the base of the left ventricle. It has three dilations called aortic sinuses. The right and left coronary arteries originate from the right and left aortic sinuses. The posterior interventricular branch of the right coronary artery supplies the right and left ventricles. The right ventricle also receives blood from the second branch of the right coronary artery, the marginal branch. The left coronary artery has two branches: the anterior interventricular branch (left anterior descending branch), which supplies both ventricles, and the circumflex branch, which supplies the left ventricle and left atrium. The Arch of the Aorta The ascending aorta curves to the left and becomes the arch of the aorta, which is about 4–5 cm (2 in.) long. It runs downward and ends in front of the border between the fourth and fifth thoracic vertebrae. The arch of the aorta gives rise to three major branches: the brachiocephalic trunk, left common carotid artery, and left subclavian artery. Branches of the Arch of the Aorta Branch Area Supplied Description Brachiocephalic trunk Right upper limb, head, neck Brachiocephalic trunk (brachiocephalic artery) is the largest branch of the aortic arch; Gives rise to the right subclavian arteryand right common carotid artery Right subclavian Right upper limb, artery brain, spinal cord, neck, shoulder, thoracic viscera and wall, scapular muscles Runs from the brachiocephalic trunk and to the first rib before passing into the armpit (axilla) Internal thoracic Anterior thoracic artery wall, mediastinum structures The internal thoracic artery branches from the first part of the subclavian artery; Ends at the sixth intercostal space; Used to create the bypass for single coronary artery bypass grafting Vertebral artery The right vertebral artery branches off from the right subclavian artery and passes through the foramen magnum to reach the inferior surface of the brain; Joins with the left vertebral artery to form the basilar artery, branches of which Posterior part of brain Branch Area Supplied Description supply the cerebellum and pons of the brain, and the inner ear Axillary artery Shoulder, thoracic and scapular muscles, humerus The axillary artery is the part of the subclavian artery that passes into the armpit; The same vessel has different names as it passes through different areas of the body Brachial artery Upper limb The axillary artery becomes the brachial artery in the arm, where it is easy measure BP; To control bleeding, the brachial artery should be compressed near the middle of the arm Radial artery Radial (lateral) aspect of forearm, wrist, hand The radial artery is a direct continuation of the brachial artery very near the skin surface at the wrist, where the radial pulse is typically measured Ulnar artery Ulnar (medial) aspect of forearm, wrist, hand The ulnar artery is the larger of the two brachial artery branches; Reconnects with the smaller branch (the radial artery), in the palm, creating the superficial palmar arch and the deep palmar arch Superficial palmar arch Branches supply palm and fingers Lies over the flexor tendons of the fingers and extends to the palm; Gives rise to the common palmar digital arteries that perfuse the palm, each of which divides into a pair of proper palmar digital arteries that perfuse the fingers palmar Branches supply the palm and fingers Lies below the flexor tendons of the fingers and extends to the palm; Gives rise to palmar metacarpal arteries that perfuse the palm and join with the common palmar digital arteries Deep arch Right common Head and carotid artery (right side) neck External carotid Face, scalp, neck artery Begins where the brachiocephalic trunk divides into its two branches; Divides into the right external and right internal carotid arteries; Often used to measure the pulse (at the side of the neck), for example, when exercising or administering cardiopulmonary resuscitation Near the temporomandibular joint, the external carotid artery divides into the superficial Branch Area Supplied Description temporal and maxillary arteries; Used to detect the carotid pulse Internal artery carotid Orbital structures (including the eyeball), ear, cerebrum, pituitary gland, external nose Left common Head and carotid artery (left side) neck Left subclavian Left upper limb artery Branches of the internal carotid artery: the anterior cerebral arteries supply parts of the frontal and parietal lobes; Branches merge with branches of the basilar artery— the posterior cerebral arteries(that supply the occipital lobes)—to form the cerebral arterial circle(circle of Willis) at the base of the brain; Posterior communicating arteries connect the posterior cerebral arteries with the internal carotid arteries; Anterior communicating arteriesconnect the anterior cerebral arteries; Cerebral arterial circle (which also includes the internal carotid arteries) equalizes BP in the brain and keeps blood flowing to the brain if other arteries are damaged The left common carotid artery branches from the arch of the aorta and divides into branches with the same names as branches of the right common carotid artery The left subclavian artery branches from the arch of the aorta; Its branches and their names are similar to those of the right subclavian artery The Thoracic Aorta As the aorta continues its descent, it passes through the aortic hiatus, an opening in the diaphragm. The part of the aorta between the arch of the aorta and the diaphragm is called the thoracic aorta. It is approximately 20 cm (8 in.) long and starts at the border between the fourth and fifth thoracic vertebrae. The thoracic aorta gives rise to a number of small arteries. The visceral branches supply the viscera, and the parietal branches supply the body wall structures of the thorax. Branches of the Thoracic Aorta: Visceral Branch Area Supplied Description Pericardial arteries Pericardium Two or three of these tiny pericardial arteries perfuse the pericardium Bronchial arteries Pleurae, bronchial tubes, bronchial lymph nodes, esophagus Right bronchial artery branches from the third posterior intercostal artery; Two left bronchial arteries branch from the thoracic aorta Esophageal arteries Esophagus Four or five esophageal arteries perfuse the esophagus Mediastinal arteries Mediastinum structures Numerous small mediastinal arteries Branches of the Thoracic Aorta: Parietal Branch Area Supplied Description Branch Area Supplied Description Posterior intercostal arteries Intercostal, pectoralis major and minor, Nine pairs of and serratus anterior muscles; overlying intercostal arteries subcutaneous tissue and skin; mammary glands; vertebrae, meninges, spinal cord Subcostal arteries Same as the posterior intercostal arteries Superior phrenic arteries Superior and diaphragm posterior aspects posterior The subcostal arteries derive their name from their location below the rib cage (costal, rib area) of The small superior phrenic arteries arise from the lower part of the thoracic aorta The Abdominal Aorta The abdominal aorta is the part of the aorta between the diaphragm and its bifurcation (division into two branches) into the two common iliac arteries at the level of the fourth lumbar vertebra. The abdominal aorta is about 13 cm (5.1 in.) long. Like the thoracic aorta, the abdominal aorta gives off visceral and parietal branches. Branches Branches of the Abdominal Aorta: Unpaired Visceral Branch Area Supplied Celiac trunk Description After emerging from the abdominal aorta, the celiac trunk divides into the left gastric artery, splenic artery, and common hepatic artery Left gastric artery Stomach, esophagus Smallest of the three branches of the celiac trunk Splenic artery Branches supply pancreas, stomach, greater omentum Largest branch of the celiac trunk; Three branches: pancreatic artery(supplies the pancreas), left gastroepiploic artery (stomach and greater omentum), short gastric artery (stomach) Common hepatic artery Branches supply liver, gall bladder, stomach, duodenum, pancreas, greater omentum Intermediate-sized branch of the celiac trunk; Three branches: proper hepatic artery (supplies the liver, stomach, and gall bladder), right gastric artery (stomach), gastroduodenal artery (stomach, greater omentum, duodenum, and pancreas) Superior Branches supply The superior mesenteric artery runs between the layers Branch Area Supplied Description mesenteric artery duodenum, pancreas, parts of small and large intestines of mesentery; Five branches: inferior pancreaticoduodenal artery (supplies the duodenum and pancreas), jejunal artery (jejunum of small intestine),ileal artery (ileum of small intestine), ileocolic artery (ascending colon of large intestine), middle colic artery (transverse colon of large intestine) Inferior mesenteric artery Branches supply The inferior mesenteric artery has three branches: left parts of large colic artery(supplies transverse and descending colons intestine of large intestine), sigmoid arteries (sigmoid and descending colons of large intestine), superior rectal artery (rectum) Branches of the Abdominal Aorta: Paired Visceral Branches Branch Area Supplied Description Suprarenal arteries Adrenal glands Only the middle pair of suprarenal arteries arises from the abdominal aorta; Superior pair arises from the inferior phrenic artery; Inferior pair arises from the renal arteries Renal arteries Kidneys, adrenal glands, ureters Right renal artery is longer than the left Gonadal arteries Ureters, ovaries, fallopian tubes (females); testes, epididymis (males) In males, the gonadal arteries are called the testicular arteries; In females, they are called the ovarian arteries(which are much shorter than the testicular arteries) Branches of the Abdominal Aorta: Unpaired Parietal Branch Branch Median sacral artery Area Supplied Sacrum, coccyx Description The median sacral artery originates in the posterior part of the abdominal aorta, about 1cm above the bifurcation into the right and left common iliac arteries Branches of the Abdominal Aorta: Paired Parietal Branches Branch Area Supplied Description Inferior phrenic arteries Diaphragm (inferior aspect), adrenal glands The inferior phrenic arteries are the first paired branches of the abdominal aorta; Arise from just above the origin of the celiac trunk and, occasionally, from the renal arteries Lumbar arteries Lumbar vertebrae, spinal cord and it meninges, back muscles and skin in the lumbar region Four pairs of lumbar arteries