ABSTRACT
Investigations were made on serial sections of human embryos at developmental stages from 13 to 23 (32-56 postovulatory days). The trochlear nucleus appears in the posterior region of the basal plate of the midbrain at stage 13. It is composed of large neurons, the processes of which are sharply defined. Since stage 15 the trochlear fibers can be followed through the alar region to their decussation in the mid-dorsal part of the midbrain. The trochlear nerve emerges from the dorsal surface of the lowest part of the midbrain.
Subject(s)
Embryonic and Fetal Development , Trochlear Nerve/embryology , Embryo, Mammalian , Gestational Age , Humans , Trochlear Nerve/anatomy & histologyABSTRACT
Investigations were made on serial sections of human embryos at developmental stage 23 (56 days). The oculomotor complex in embryos at this stage consists of lateral, median, and accessory nuclei. The lateral (chief) nucleus forms the greatest part of the oculomotor complex and it is subdivided into ventromedial and dorsolateral groups. Between the posterior portions of lateral nuclear groups is the median nucleus. Dorsally and medially to the lateral nucleus is the accessory (parasympathetic) nucleus.
Subject(s)
Mesencephalon/anatomy & histology , Mesencephalon/embryology , Oculomotor Nerve/anatomy & histology , Oculomotor Nerve/embryology , Fetus/anatomy & histology , Gestational Age , HumansABSTRACT
Investigations were made on serial sections of human embryos at developmental stages 16 and 17 (37-41 days). The oculomotor nucleus in embryos at these stages is located at the cephalic flexure of the neural tube. It consists of paired lateral nucleus which is formed by well defined group of large neurons in the basal plate of the midbrain. Within the lateral nucleus two groups of cells (medial and lateral) can be distinguished. Posteriorly these groups unite and form a single nucleus.
Subject(s)
Oculomotor Nerve/embryology , Embryonic and Fetal Development/physiology , Female , Humans , Pregnancy , Pregnancy Trimester, FirstABSTRACT
Studies of serial sections and reconstructions of embryos at stage 13 (32) postovulatory days) revealed that the cranial neural tube in the investigated embryos possesses 15 neuromers: 1 telencephalic, 3 diencephalic, 3 mesencephalic, and 8 rhombencephalic. Within the primary efferent column all nuclei of the cranial nerves may be distinguished. Also fibers entering brain from cranial nerve ganglia form the common afferent tract. The relation of neuromers to the motor nuclei of the cranial nerves is following: M1-oculomotor, M2-trochlear, Rh2-trigeminal, Rh4-facial, Rh6-glossopharyngeal, Rh7-vagal, Rh8-hypoglossal.
