. The chordates. Chordata. 612 Comparative Morphology of Chordates consists of a fold of the skinlike investing layer of the "hard" palate. It prolongs the nasal passages backward, but as a single or undivided passage, separating the original pharynx into an upper nasopharynx and a lower buccal division (Fig. 469). Trachea The anterior region of the trachea is enlarged to form the larynx, containing the vocal apparatus (Figs. 470, 471). The walls of the larynx are supported by cartilages. The most anterior and largest of them is the thyroid, which encloses the larynx ventrally and la
. The chordates. Chordata. 612 Comparative Morphology of Chordates consists of a fold of the skinlike investing layer of the "hard" palate. It prolongs the nasal passages backward, but as a single or undivided passage, separating the original pharynx into an upper nasopharynx and a lower buccal division (Fig. 469). Trachea The anterior region of the trachea is enlarged to form the larynx, containing the vocal apparatus (Figs. 470, 471). The walls of the larynx are supported by cartilages. The most anterior and largest of them is the thyroid, which encloses the larynx ventrally and laterally but not dorsally. Attached to its mid ventral anterior edge and freely projecting forward is a flap of tissue consisting internally of elastic fibrocartilage and covered externally by a continuation of the mucous membrane which invests all neighboring surfaces. This flap, the epi- glottis, is usually rounded or oval in outline, its form being such that,. Fig. 470. {Left) Front view of the human laryngeal cartilages and ligaments. (Sappey.) (1) Hyoid bone; (2) its large cornua; (3) its small cornua; (4) thyroid cartilage; (5) thyrohyoid membrane; (6) lateral thyrohyoid ligament, containing the cartilago triticea (7); (8) cricoid cartilage; (9) cricothyroid membrane; (10) lateral ceratocricoid ligaments; (11) uppermost ring of trachea. {Center) Back view of the laryngeal cartilages and ligaments. (Sappey.) (1) Thyroid cartilage; (2) cricoid cartilage; (3) arytenoid cartilages; (4) their muscular processes; (5) ligament connecting lower cornu of thyroid with back of cricoid cartilage; (6) upper ring of trachea; (7) epiglottis; (8) ligament connecting it to the angle of the thyroid cartilage. {Right) Muscles of the larynx, as seen from the right side. (Sappey.) (1) Hyoid bone; (2, 3) its cornua; (4) right lamina of thyroid cartilage; (5) posterior part of same, separated by oblique line from anterior part; (6, 7) superior and inferior tubercles, at ends of oblique line; (8)
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