Книги по МРТ КТ на английском языке / The Embryonic Human Brain An Atlas of Developmental Stages. Third Edition. 2006. By Ronan O'Rahilly

Figure 24–23. 46 mm. A nearly median section. The dorsal thalamus, which appears dark because it is cut at the level of the ventricular layer, is well shown. It is separated from the ventral thalamus by a band of gray material, which is probably the tract of the zona intrathalamica. When the individual thalamic nuclei are said to appear depends on the criteria selected, and these are mainly the establishment of cell-poor boundaries and the presence of nerve fibers, followed by differentiation into nuclear groups. Further information: Dekaban (1954), Fabiani and Barontini (1956), Yamadori (1965). The lateral geniculate body shows lamination during trimester 2. The pulvinar, which begins to develop at the commencement of trimester 2, is derived mainly from the medial ventricular eminence and grows greatly during the second half of prenatal life. Migrating cells from the medial ventricular eminence cover the fetal corpus striatum adjacent to the sulcus terminalis (constituting the “corpus gangliothalamicum” of Rakic and Sidman, 1969) and are said to participate in the formation of other thalamic nuclei (Letinic,´ and Kostovic,´ 1997). See Figure 24–9.

The epiphysis cerebri, the posterior commissure, and the commissure of the superior colliculi are all recognizable. The three subdivisions of the axis (termed X, Y, and Z by O’Rahilly, Muller,¨ and Meyer, 1983, in their account of the occipitocervical region) are evident. A key drawing is provided with Figure 23-6.

Inf. cerebellar peduncle

Figure 24–24. An ultrasonic image at 35 mm. The mesencephalon and the diencephalon can be identified, and the choroid plexus of the lateral ventricle (cf. Fig. 24–26) is evident. Courtesy of Dr. Harm-Gerd Blaas, Trondheim, Norway.

Figure 24–25. (A) dorsal and (B) lateral views of the brain at 42 mm, with parts of the hemisphere removed. In A the external capsule, not clearly distinguishable in stage 23, is now visible. In B the basal nuclei, choroid fissure, and internal and external capsules are exposed. The part of the cerebral hemisphere removed here is indicated in Figure 24–28 by a dotted line. These instructive views are (with a few corrections) based on Kollmann’s Handatlas der Entwicklungsgeschichte des Menschen (1907).

Fig. 24 – 26

Figure 24–26. A sagittal section at 40 mm. The relatively great size of the choroid plexus is noticeable. The key shows the hippocampal thickening. (The cortical plate is present in most of the hemispheres.) The dorsal thalamus is closely related to the ventricular eminences. Thalamocortical fibers are already numerous, although the thalamic nuclei have yet to form. The habenulo-interpeduncular and mamillotegmental tracts can be followed to the mesencephalic tegmentum. The decussation of the trochlear nerves is identifiable in the isthmus. The internal cerebellar swelling is large. The rhombic lip can be seen here and again further caudally at the end of the medulla oblongata.

Figure 24–27. 50 mm. A coronal section showing the anterior commissure, the caudate nucleus, the internal capsule, and the putamen. Based on a photomicrograph in Feess-Higgins and Larroche (1987).

Figure 24–28. 37 mm. A coronal section showing the interventricular foramina and a number of important relationships. Based on an excellent photo-micrograph in Richter (1965). The dotted line indicates the part of the cerebral hemisphere removed in Figure 24–25B.

Cholinesterase-reactive fibers from the nucleus basalis complex are distributed widely to the neocortex and limbic cortex by the end of trimester 2 (Kostovic,´ 1986).

Fig.

24 – 25