China
Africa
Explore chapters and articles related to this topic
Fertilization and normal embryonic and early fetal development
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Asim Kurjak, Ritsuko K. Pooh, Aida Salihagic-Kadic, Iva Lausin, Lara Spalldi-Barisic
During the latter half of the 3rd week, drastic changes for morphogenesis (development of the body form) begin. The embryonic disc elongates craniocaudally to become pear-shaped and then slipper like. Cranial to the primitive node, a thickening of the ectoderm appears bilaterally and is called the neural plate because it will eventually develop into the neural tissue. Between the bilateral neural plates, a longitudinal neural groove develops in the midline, flanked by the neural folds bilaterally. Around day 20, the bilateral neural folds begin to fuse with each other to form the neural tube, which is the primordium of the central nervous system (CNS; brain and spinal cord). The rostral (anterior) neuropore normally closes on days 24 to 26, and the caudal (posterior) neuropore closes by 28 days. When the neuropores close completely, three brain vesicles (forebrain or prosencephalon, mesencephalon or midbrain, and rhombencephalon) have already appeared. Rarely the neural tube fails to close completely, resulting in a variety of neural tube closure defects such as anencephaly, encephalocele, myeloschisis, and myelomeningocele.
The nervous system
Published in Frank J. Dye, Human Life Before Birth, 2019
The brain has its origins early in human development. It originates as the anterior region of the neural tube, which begins to form during the third week of development. During the fourth week, the brain portion of the neural tube, which is wider than the spinal cord portion, will develop the three primary brain vesicles: forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon) (Figure 13.4).
Measurement of Fetal Mesencephalon and Pons Via Ultrasonographic Cross Sectional Imagining
Published in Fetal and Pediatric Pathology, 2018
Ruiqi Yang, Rui Li, Xuejuan Liu, Limei Fan, Jialing Zhang, Libo Wang, Hong Teng
During the fourth and fifth weeks of gestation, three primary brain vesicles complete their development: forebrain vesicle, midbrain vesicle, and metencephalon vesicle (1). Midbrain vesicle will form mesencephalon or midbrain; metencephalon vesicle will form the pons, medulla oblongata, and cerebellum (2). The mesencephalon, pons, and inferior medulla oblongata compose brainstem, the region of the brain that connects cerebrum with spinal cord. Pons, a major portion of which appears as a broad anterior bulge, participates in the transmission of signals between the cerebrum and the rest of the body and is involved in the regulation of sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture (3).