Computer ranking of the sequence of appearance of 40 features of the brain and related structures in staged human embryos during the seventh week of development

Abstract

The sequence of events in the development of the brain in human embryos, already published for stages 8-17, is here continued for stages 18 and 19. With the aid of a computerized bubble-sort algorithm, 58 individual embryos were ranked in ascending order of the features present. The increasing structural complexity provided 40 new features in these two stages. The chief characteristics of stage 18 (approximately 44 postovulatory days) are rapidly growing basal nuclei; appearance of the extraventricular bulge of the cerebellum (flocculus), of the superior cerebellar peduncle, and of follicles in the epiphysis cerebri; and the presence of vomeronasal organ and ganglion, of the bucconasal membrane, and of isolated semicircular ducts. The main features of stage 19 (approximately 48 days) are the cochlear nuclei, the ganglion of the nervus terminalis, nuclei of the prosencephalic septum, the appearance of the subcommissural organ, the presence of villi in the choroid plexuses of the fourth and lateral ventricles, and the stria medullaris thalami.

The human brain at stages 18?20, including the choroid plexuses and the amygdaloid and septal nuclei

“…The dorsal funiculus reaches the area of the gracile and cuneate tubercles. The tracts have already been shown in a reconstruction at stage 19 (O'Rahilly et al 1988, Fig. 4).…”

“…A brief account of the brain was included by O'Rahilly and Mfiller (1987), and the external features of the brain were emphasized by O' Rahilly et al (1986). Characteristic cerebral features for stages 18 and 19 were listed in their sequence of appearance by O'Rahilly et al (1988), who also assessed variations.…”

Midline cystic malformations of the brain: imaging diagnosis and classification based on embryologic analysis

“…12 The cerebellum also begins to develop during stage 14 as two symmetrical thickenings on either side of the midline of the rhombencephalon. 16 These cerebellar bulges, called rhombic lips, arise in the dorsal alar plate just lateral to the rhombencephalic isthmus, where cells contribute to form the cerebellar vermis. 17 Thus, the cerebellar hemispheres unite at the midline by cells derived from the isthmus to form the beginning of the vermis.…”

CaBPs and other immunohistochemical markers of the human vomeronasal system: A comparison with other mammals

“…A human VNO and associated nerve bundle are clearly visible during embryonic-fetal growth in histological sections (Bossy, 1980;Kjaer and Fischer Hansen, 1996;Kreutzer and Jafek, 1980;Labella and Ciges, 1975;Nakashima, et al, 1985c;O'Rahilly et al, 1988;Ortmann, 1989;Pearson, 1942;Smith et al, 1997;Stensaas et al, 1991). Also during this period, an AOB with incoming vomeronasal nerves has been documented (Chuah and Zheng, 1987;Humphrey, 1940).…”