. Human embryology and morphology. Embryology, Human; Morphology. DEVELOPMENT OF THE PHARYNX AND NECK. 37 and entrance of the ductus arteriosus. The fifth arch on the left side is represented in its entirety by the pulmonary artery and ductus arteriosus. The fifth arch on the right side disappears, in the greater part of its extent at least. Probably the right pulmonary artery is formed from the inner part of this arch. All the aortic arches are not present at the same time; some have only a brief period of existence. One of these transient arches is said to appear between what are usually des
. Human embryology and morphology. Embryology, Human; Morphology. DEVELOPMENT OF THE PHARYNX AND NECK. 37 and entrance of the ductus arteriosus. The fifth arch on the left side is represented in its entirety by the pulmonary artery and ductus arteriosus. The fifth arch on the right side disappears, in the greater part of its extent at least. Probably the right pulmonary artery is formed from the inner part of this arch. All the aortic arches are not present at the same time; some have only a brief period of existence. One of these transient arches is said to appear between what are usually described as the 4th and 5th arches. If this is always the case then the pulmonary arteries should be described as derived not from the 5th but from the 6th aortic arches. Subclavian Arteries.—The visceral arches with their arteries are well developed before the limb buds appear. When, at the end of the third week, the buds grow out to form the upper extremities, the artery which supplies each bud grows out from innominate carotid vert.— subclau. constriction right put. art 5th right arch •— right dorsal aorta. vert, vbclav. constriction arch, left side left pulmonary art. 'eft dorsal aorta Fig 29 —The condition of the Eight and Left Dorsal Aortae in a 6th week human foetus (After His.) The right arch disappears beyond the origin of the right subclavian; a constriction may appear at the corresponding point on the left side. the dorsal aortae opposite the 4th arches (Fig. 29). This artery forms the entire subclavian on the left side, but only its third stage on the right. The Arch of the Aorta on the Right Side.—In birds it is the 4th right arch which forms the aortic arch, and this occasionally happens in man. In amphibians both the right and left 4th arches persist as aortic arches. The two. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may n
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