Aortic Arch Derivatives

Right dorsal aorta

Internal carotid artery Right vagus nerve

Common carotid artery

Right subclavian artery

Right recurrent nerve

7th intersegmental artery

External carotid arteries

External carotid arteries

Common carotid artery

Right subclavian artery

Ascending Aorta And Common Carotid

Pulmonary artery

Arch of aorta

-Left recurrent nerve

Ductus arteriosus

Pulmonary artery

Right external carotid artery

Right vagus

Right subclavian artery

Brachiocephalic artery

Ascending aorta

Right external carotid artery

Right vagus

Right subclavian artery

Brachiocephalic artery

Ascending aorta

Images The Vertebral Arteries

Pulmonary artery

Figure 11.35 A. Aortic arches and dorsal aortae before transformation into the definitive vascular pattern. B. Aortic arches and dorsal aortae after the transformation. Broken lines, obliterated components. Note the patent ductus arteriosus and position of the seventh intersegmental artery on the left. C. The great arteries in the adult. Compare the distance between the place of origin of the left common carotid artery and the left subclavian in B and C. After disappearance of the distal part of the sixth aortic arch (the fifth arches never form completely), the right recurrent laryngeal nerve hooks around the right subclavian artery. On the left the nerve remains in place and hooks around the ligamentum arteriosum.

Pulmonary artery

Left internal carotid artery

Left common carotid artery Left subclavian artery

Ligamentum arteriosum Descending aorta

Figure 11.35 A. Aortic arches and dorsal aortae before transformation into the definitive vascular pattern. B. Aortic arches and dorsal aortae after the transformation. Broken lines, obliterated components. Note the patent ductus arteriosus and position of the seventh intersegmental artery on the left. C. The great arteries in the adult. Compare the distance between the place of origin of the left common carotid artery and the left subclavian in B and C. After disappearance of the distal part of the sixth aortic arch (the fifth arches never form completely), the right recurrent laryngeal nerve hooks around the right subclavian artery. On the left the nerve remains in place and hooks around the ligamentum arteriosum.

nerve

The fifth aortic arch either never forms or forms incompletely and then regresses.

The sixth aortic arch, also known as the pulmonary arch, gives off an important branch that grows toward the developing lung bud (Fig. 11.34B). On the right side the proximal part becomes the proximal segment of the right pulmonary artery. The distal portion of this arch loses its connection

Right And Left Dorsal Aortae
Figure 11.36 Changes from the original aortic arch system.

with the dorsal aorta and disappears. On the left the distal part persists during intrauterine life as the ductus arteriosus.

A number of other changes occur along with alterations in the aortic arch system: (a) The dorsal aorta between the entrance of the third and fourth arches, known as the carotid duct, is obliterated (Fig. 11.36). (b) The right dorsal aorta disappears between the origin of the seventh intersegmental artery and the junction with the left dorsal aorta (Fig. 11.36). (c) Cephalic folding, growth of the forebrain, and elongation of the neck push the heart into the thoracic cavity. Hence the carotid and brachiocephalic arteries elongate considerably (Fig. 11.35C). As a further result of this caudal shift, the left subclavian artery, distally fixed in the arm bud, shifts its point of origin from the aorta at the level of the seventh intersegmental artery (Fig. 11.35B) to an increasingly higher point until it comes close to the origin of the left common carotid artery (Fig. 11.35C). (d) As a result of the caudal shift of the heart and the disappearance of various portions of the aortic arches, the course of the recurrent laryngeal nerves becomes different on the right and left sides. Initially these nerves, branches of the vagus, supply the sixth pharyngeal arches. When the heart descends, they hook around the sixth aortic arches and ascend again to the larynx, which accounts for their recurrent course. On the right, when the distal part of the sixth aortic arch and the fifth aortic arch disappear, the recurrent laryngeal nerve moves up and hooks around the right subclavian artery. On the left the nerve does not move up, since the distal part of the sixth aortic arch persists as the ductus arteriosus, which later forms the ligamentum arteriosum (Fig. 11.35).

Vitelline and Umbilical Arteries

The vitelline arteries, initially a number of paired vessels supplying the yolk sac (Fig. 11.33), gradually fuse and form the arteries in the dorsal mesentery of the gut. In the adult they are represented by the celiac, superior mesenteric, and inferior mesenteric arteries. These vessels supply derivatives of the foregut, midgut, and hindgut, respectively.

The umbilical arteries, initially paired ventral branches of the dorsal aorta, course to the placenta in close association with the allantois (Fig. 11.33). During the fourth week, however, each artery acquires a secondary connection with the dorsal branch of the aorta, the common iliac artery, and loses its earliest origin. After birth the proximal portions of the umbilical arteries persist as the internal iliac and superior vesical arteries, and the distal parts are obliterated to form the medial umbilical ligaments.

CLINICAL CORRELATES Arterial System Defects

Under normal conditions the ductus arteriosus is functionally closed through contraction of its muscular wall shortly after birth to form the ligamentum arteriosum. Anatomical closure by means of intima proliferation takes 1 to 3 months. A patent ductus arteriosus, one of the most frequently occurring abnormalities of the great vessels (8/10,000 births), especially in premature infants, either may be an isolated abnormality or may accompany other heart defects (Figs. 11.29A and 11.31). In particular, defects that cause large differences between aortic and pulmonary pressures may cause increased blood flow through the ductus, preventing its normal closure.

In coarctation of the aorta (Fig. 11.37, A and B), which occurs in 3.2/10,000 births, the aortic lumen below the origin of the left subclavian artery is significantly narrowed. Since the constriction may be above or below the entrance of the ductus arteriosus, two types, preductal and postductal, may be distinguished. The cause of aortic narrowing is primarily an abnormality in the media of the aorta, followed by intima proliferations. In the preductal type the ductus arteriosus persists, whereas in the postductal type, which is more common, this channel is usually obliterated. In the latter case collateral circulation between the proximal and distal parts of the aorta is established by way of large intercostal and internal thoracic arteries. In this manner the lower part of the body is supplied with blood.

Coarctation The Aorta Preductal
Figure 11.37 Coarctation of the aorta. A. Preductal type. B. Postductal type. The caudal part of the body is supplied by large hypertrophied intercostal and internal thoracic arteries.
Aortic Arches Derivatives

Figure 11.38 Abnormal origin of the right subclavian artery. A. Obliteration of the right fourth aortic arch and the proximal portion of the right dorsal aorta with persistence of the distal portion of the right dorsal aorta. B. The abnormal right subclavian artery crosses the midline behind the esophagus and may compress it.

Figure 11.38 Abnormal origin of the right subclavian artery. A. Obliteration of the right fourth aortic arch and the proximal portion of the right dorsal aorta with persistence of the distal portion of the right dorsal aorta. B. The abnormal right subclavian artery crosses the midline behind the esophagus and may compress it.

Abnormal origin of the right subclavian artery (Fig. 11.38, A and B) occurs when the artery is formed by the distal portion of the right dorsal aorta and the seventh intersegmental artery. The right fourth aortic arch and the proximal part of the right dorsal aorta are obliterated. With shortening of the aorta between the left common carotid and left subclavian arteries, the origin of the abnormal right subclavian artery finally settles just below that of the left subclavian artery. Since its stem is derived from the right dorsal aorta,

Trachea

Esophagus

Persis' portior right do aort

Trachea

Esophagus

Persis' portior right do aort

Distal Aorta
Figure 11.39 Double aortic arch. A. Persistence of the distal portion of the right dorsal aorta. B. The double aortic arch forms avascular ring around the trachea and esophagus.

it must cross the midline behind the esophagus to reach the right arm. This location does not usually cause problems with swallowing or breathing, since neither the esophagus nor the trachea is severely compressed.

With a double aortic arch the right dorsal aorta persists between the origin of the seventh intersegmental artery and its junction with the left dorsal aorta (Fig. 11.39) A vascular ring surrounds the trachea and esophagus and commonly compresses these structures, causing difficulties in breathing and swallowing.

In a right aortic arch, the left fourth arch and left dorsal aorta are obliterated and replaced by the corresponding vessels on the right side. Occasionally, when the ligamentum arteriosum lies on the left side and passes behind the esophagus, it causes complaints with swallowing.

An interrupted aortic arch is caused by obliteration of the fourth aortic arch on the left side (Fig. 11.40, A and B). It is frequently combined with an abnormal origin of the right subclavian artery. The ductus arteriosus remains open, and the descending aorta and subclavian arteries are supplied with blood of low oxygen content. The aortic trunk supplies the two common carotid arteries.

Was this article helpful?

0 0
Healthy Weight Loss For Teens

Healthy Weight Loss For Teens

Help your Teen Lose Weight Easily And In A Healthy Way. You Are About to Discover What psychological issues overweight teens are facing and how do you go about parenting an overweight teen without creating more problems?

Get My Free Ebook


Responses

  • fraser davidson
    Why left recurrent nerve hooks around arch of aorta?
    2 years ago

Post a comment