The larynx develops from fourth and sixth branchial arches. The anlage of the respiratory system appears in human embryo about 3.2 mm in size. A hollow linear evagination of the lung groove develops on the ventral side of the oesophageal portion of the primitive gut. The lung groove soon becomes separated from the gut by a constriction which appears at the caudal end and gradually progresses forward. Thus, there is formed a tube which lies ventral to gut and which open upon the floor of the later at the boundary line between oesophagus and pharynx.
From this simple tube entire respiratory system develops. The cephalic end gives rise to the larynx. The middle portion gives rise to the trachea. Two outgrowths from the caudal end of the tube, which appear about the time of separation from the oesophagus, develop bronchi and their continuation of the lung. Prenatal development can be…
