Müller F, O'Rahilly R
Carnegie Laboratories of Embryology, California Primate Research Center, Davis 95616.
Anat Embryol (Berl). 1988;179(1):55-71. doi: 10.1007/BF00305100.
Twenty-six embryos (6-11 mm) of stage 15 (approximately 33 days) were studied in detail and graphic reconstructions of three of them were prepared. Characteristic features of this stage include closed lens vesicles, presence of nasal pits, and retinal pigment. The neuromeric pattern is still visible. Each cerebral hemisphere is limited by the torus hemisphericus internally and by the di-telencephalic sulcus externally. The medial (diencephalic) eminence of the basal nuclei (previously misinterpreted by others as the lateral) had appeared in stage 14, and the lateral eminence, which is telencephalic, is now distinguishable. The amygdaloid body in stages 14 and 15 is derived from the medial eminence. The hippocampal thickening is identifiable in the dorsomedial part of the cerebral hemisphere. Medial and basal forebrain bundles are developing. The olfactory eminence is visible. Future olfactory bulb and tubercle possess an intermediate layer. The wall of the diencephalon presents five longitudinal zones: epithalamus, dorsal thalamus, ventral thalamus, subthalamus, and hypothalamus. The primordium of the epiphysis cerebri is beginning in the more advanced embryos. The sulcus limitans ends rostrally at the midbrain (M1) and is not continuous with the hypothalamic sulcus. Hence the alar/basal distinction does not arise in the forebrain. In the roof of the midbrain (M2) the mesencephalic evagination already noticed at stage 14 is characteristic. It is suggested that it may function as a temporary circumventricular organ. The precursors of some new tracts are identifiable: habenulo-interpeduncular, medial tectobulbar, and mamillotegmental fibres. Commissures include the supramamillary, that of the superior colliculi, and (in some embryos) the first fibres of the posterior commissure. Nuclei include the habenular, mamillary, and probably subthalamic. The cerebellum, the beginning of which was already noted at stages 13 and 14, consists of (1) a rostral part that arises from the alar plate of the isthmic segment and will form the superior medullary velum and part of the corpus cerebelli; and (2) a caudal part that develops from rhombomere 1. The involvement of the isthmic segment, first elucidated with stage 14, has not been observed in previous reports. All cranial nerves except the olfactory and optic are present in the more advanced embryos.
对26个处于第15阶段（约33天）、胚胎长度为6 - 11毫米的胚胎进行了详细研究，并对其中3个胚胎进行了图形重建。该阶段的特征包括闭合的晶状体泡、鼻凹的存在以及视网膜色素。神经节模式仍然可见。每个大脑半球内部由半球隆凸限制，外部由间脑沟限制。基底核的内侧（间脑）隆起（之前被其他人错误地解释为外侧隆起）在第14阶段就已出现，现在可以区分出属于端脑的外侧隆起。第14和15阶段的杏仁体源自内侧隆起。海马增厚在大脑半球的背内侧部分可以识别。内侧和基底前脑束正在发育。嗅隆起可见。未来的嗅球和嗅结节有一个中间层。间脑壁呈现五个纵向区域：松果体、背侧丘脑、腹侧丘脑、下丘脑和底丘脑。在更成熟的胚胎中，松果体原基开始出现。界沟在中脑（M1）的前方终止，不与下丘脑沟连续。因此，前脑不存在翼板/基板的区分。在中脑顶部（M2），在第14阶段就已注意到的中脑外翻是其特征。有人认为它可能作为一个临时的室周器官发挥作用。一些新束的前体可以识别：缰核 - 脚间核纤维、内侧顶盖 - 延髓纤维和乳头体 - 被盖纤维。连合包括乳头体上连合、上丘连合以及（在一些胚胎中）后连合的第一批纤维。核团包括缰核、乳头体核，可能还有底丘脑核。小脑在第13和14阶段就已开始出现，它由两部分组成：（1）一个来自峡部节段翼板的前部，将形成上髓帆和小脑体的一部分；（2）一个从菱脑节1发育而来的后部。峡部节段的参与情况在第14阶段首次阐明，之前的报告中未观察到。除嗅觉和视神经外，所有颅神经在更成熟的胚胎中均已存在。
