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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
smoother, and contains numerous muciparous glands and lymph follicles (lingual tonsil). The foramen cecum is the remains of the upper part of the thyroglossal duct or diverticulum from which the thyroid gland is developed; the pyramidal lobe of the thyroid gland indicates the position of the lower part of the duct.
  The Papillæ of the Tongue (Fig. 1014) are projections of the corium. They are thickly distributed over the anterior two-thirds of its dorsum, giving to this surface its characteristic roughness. The varieties of papillæ met with are the papillæ vallatæ, papillæ fungiformes, papillæ filiformes, and papillæ simplices.


FIG. 1013– The mouth cavity. The apex of the tongue is turned upward, and on the right side a superficial dissection of its under surface has been made. (See enlarged image)

  The papillæ vallatæ (circumvallate papillæ) (Fig. 1015) are of large size, and vary from eight to twelve in number. They are situated on the dorsum of the tongue immediately in front of the foramen cecum and sulcus terminalis, forming a row on either side; the two rows run backward and medialward, and meet in the middle line, like the limbs of the letter V inverted. Each papilla consists of a projection of mucous membrane from 1 to 2 mm. wide, attached to the bottom of a circular depression of the mucous membrane; the margin of the depression is elevated to form a wall (vallum), and between this and the papilla is a circular sulcus termed the fossa. The papilla is shaped like a truncated cone, the smaller end being directed downward and attached to the tongue, the broader part or base projecting a little above the surface of the tongue and being studded with numerous small secondary papillæ and covered by stratified squamous epithelium.
  The papillæ fungiformes (fungiform papillæ) (Fig. 1017), more numerous than the preceding, are found chiefly at the sides and apex, but are scattered irregularly and sparingly over the dorsum. They are easily recognized, among the other

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