Le développement du corps humain; un manuel d'embryologie humaine . e itétant extrêmement fin et soyeux et constituant ce qui a istered la lanugo. Cette croissance est bientôt coupée après la naissance, sauf au-dessus du visage, où elle est à peine remarquée en raison de son extrême finesse et de son manque de coloration.Les poils plus grossiers qui le remplacent dans certaines régions des GLANDES SUDORIPAROUS. 169 le corps provient probablement de nouveaux follicules, puisque la formationdes follicules a lieu pendant les périodes ultérieures de la fetalvie et éventuellement après la naissance. Mais même ces poils plus tard ne persistent pas individuellement f

• Contributeur: The Reading Room / Alamy Banque D'Images
• ID de l’image: 2AWFF3P
• Taille du fichier: 7,1 MB (302,4 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 1618 x 1544 px | 27,4 x 26,1 cm | 10,8 x 10,3 inches | 150dpi

Informations supplémentaires

Cette image appartient au domaine public, ce qui signifie que le droit d’auteur a expiré ou que le titulaire du droit d’auteur a renoncé à ses droits. Les frais facturés par Alamy couvrent l’accès à la copie haute résolution de l’image.

Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.

The development of the human body; a manual of human embryology . e itbeing exceedingly fine and silky and constituting what istermed the lanugo. This growth is cast off soon afterbirth, except over the face, where it is hardly noticeableon account of its extreme fineness and lack of coloration.The coarser hairs which replace it in certain regions of the THE SUDORIPAROUS GLANDS. 169 body probably arise from new follicles, since the formationof follicles takes place throughout the later periods of fetallife and possibly after birth. But even these later formedhairs do not individually persist for any great length oftime, but are continually being shed, new or secondaryhairs normally developing in their places. The sheddingof a hair is preceded by a cessation of the proliferation ofthe cells covering the dermal papilla and by a shrinkage ofthe papilla whereby itbecomes detached fromthe hair, and the replac-ing hair arises from a pa-pilla which is probablybudded off from the olderone before its degenera-tion and carries with it acap of epidermal cells.. —h Fig. 83.—Lower Surface op a De-tached Portion of Epidermis fromthe Dorsum of the Hand. h, Hair follicle; s, sudoriparous gland.—(Blasckko.) It is uncertain whetherthe cases of excessive de-velopment of hair over theface and upper part of thebody which occasionallyoccur are due to an ex-cessive development of the later hair follicles (hypertrichosis) or to a persistence and con-tinued growth of the lanugo. The Development of the Sudoriparous Glands.—The sudoriparous glands arise during the fifth month as solidcylindrical outgrowths from the primary ridges of the epi-dermis (Fig. 83), and at first project vertically downwardinto the subjacent dermis. Later, however, the lowerend of each downgrowth is thrown into coils, and at thesame time a lumen appears in the center. Since, how-ever, the cylinders are formed from the deeper layers ofthe epidermis, their lumina do not at first open upon the 170 THE DEVELOPMENT

Recherche dans la banque de photos par tags

• bookcentury1900
• bookdecade1900
• booksubjectembryol
• bookyear1902