. Human embryology and morphology. Embryology, Human; Morphology. DEVELOPMENT OF THE PHARYNX AND NECK. 45 become hypertrophoid. The lymphoid tissue of the naso-pharynx, when hypertrophied, may press on and obstruct the Eustachian tube and respiratory space (see Figure 33). The Lingual Tonsil.—That part of the tongue (pharyngeal) produced between the 2nd and 3rd arches is covered by mucous glands which are surrounded by nodules of lymphoid tissue—the collective glandular mass receiving the name of lingual tonsil. It will thus be seen that from the 2nd cleft is produced a circum-pharyngeal ring
. Human embryology and morphology. Embryology, Human; Morphology. DEVELOPMENT OF THE PHARYNX AND NECK. 45 become hypertrophoid. The lymphoid tissue of the naso-pharynx, when hypertrophied, may press on and obstruct the Eustachian tube and respiratory space (see Figure 33). The Lingual Tonsil.—That part of the tongue (pharyngeal) produced between the 2nd and 3rd arches is covered by mucous glands which are surrounded by nodules of lymphoid tissue—the collective glandular mass receiving the name of lingual tonsil. It will thus be seen that from the 2nd cleft is produced a circum-pharyngeal ring of lymphoid tissue of great physiological and pathological importance. The Thymus.—The thymus arises in the same manner as the tonsil, only from the 3rd instead of the 2nd cleft (Figs 33 and 34). The 3rd cleft is represented in the adult by the tuberculum 1st recess (salivary glands) 2nd recess (tonsil) median thyroid bud. -Jurcula (epiglottis) 3rd recess (thymus) 4th recess (lat. thyroid bud) aryteno. epi. fold coelom (pericardium) pulmonary groove stomach Fig. 34.—Showing the origin of the Tonsil, Thymus, and Thyroid from the Internal Cleft Recesses during the 4th week. (After His.) space in front, and on each side of the epiglottis. The hypoblast in the 3rd cleft recess thickens, becomes pushed out as a minute pouch, shaped like a Florence flask, between the 3rd (internal carotid) and 4th (arch of aorta) vascular arches. The neck of the glandular hypoblastic pocket disappears. By a species of secondary budding it becomes broken up into islands or separated acini. Either by a production of broods of lymphoid cells within the hypoblastic epithelium or by an invasion of lymphoid 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 not perfectly resemble the original Keith, Arthur, Sir, 1866-1955. London : E. Arnold
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
