Human Anatomy
Neurohistology and Neuroembryology
Neurohistology and neuroembryology for MBBS: microanatomy of cord, cerebellum and cerebrum, neural tube development and neural tube defects, mapped to NMC codes AN64.1 to AN64.3.
MedNext Academy | 3 min read
Neurohistology and Neuroembryology
Neurohistology and neuroembryology for MBBS: microanatomy of cord, cerebellum and cerebrum, neural tube development and neural tube defects, mapped to NMC codes AN64.1 to AN64.3.
This chapter covers the microscopic structure of the spinal cord, cerebellum and cerebrum together with the development of the nervous system from the neural tube. It links neurulation to the neural tube defects seen clinically.
High-yield: Neurohistology and Neuroembryology
- The grey matter of the spinal cord shows large motor neurons in the ventral horn under the microscope.
- The cerebellar cortex shows its three layers with a single row of large flask-shaped Purkinje cells at the interface.
- The cerebral cortex is typically six-layered neocortex, from the outer molecular layer to the inner multiform layer.
- The pyramidal cells of the cerebral cortex are the principal projection neurons and are largest in the fifth layer.
- The neural tube forms in the third week when the neural plate folds and its edges fuse in the process of neurulation.
- The neural crest cells arise at the margins of the neural folds and form sensory ganglia, autonomic ganglia and the adrenal medulla.
- The wall of the neural tube differentiates into ventricular, mantle and marginal zones.
- The mantle zone becomes grey matter and the marginal zone becomes white matter.
- The alar plate is sensory and dorsal, while the basal plate is motor and ventral, separated by the sulcus limitans.
- The cranial end of the neural tube forms three primary brain vesicles: prosencephalon, mesencephalon and rhombencephalon.
- The prosencephalon divides into telencephalon and diencephalon; the rhombencephalon divides into metencephalon and myelencephalon.
- Failure of the cranial neuropore to close causes anencephaly.
- Failure of the caudal neuropore to close causes spina bifida.
- Spina bifida occulta is a bony defect with intact overlying skin, while meningocele and myelomeningocele involve herniation of coverings and cord.
- Folic acid supplementation before and in early pregnancy reduces the risk of neural tube defects.
Neural tube and its derivatives
- **Neurulation:** Neural plate folds and neuropores close in the fourth week. Neural crest gives sensory and autonomic ganglia and adrenal medulla.
- **Alar vs basal plate:** Alar plate dorsal and sensory, basal plate ventral and motor, divided by the sulcus limitans.
- **Brain vesicles:** Prosencephalon, mesencephalon, rhombencephalon; prosencephalon splits into telencephalon and diencephalon.
- **Neural tube defects:** Cranial neuropore failure gives anencephaly; caudal failure gives spina bifida. Folic acid is protective.
NMC competencies in this chapter
- **AN64.1:** Microanatomy of the spinal cord, cerebellum and cerebrum
- **AN64.2:** Development of the neural tube, spinal cord, brainstem, cerebral hemisphere and cerebellum
- **AN64.3:** Open neural tube defects and their embryological basis
Frequently Asked Questions
What distinguishes the alar and basal plates?
The alar plate is the dorsal, sensory part of the neural tube wall and the basal plate is the ventral, motor part. They are separated by a groove called the sulcus limitans.
How do neural tube defects arise?
They result from failure of the neuropores to close. Failure at the cranial end causes anencephaly, while failure at the caudal end causes spina bifida.
What do neural crest cells become?
They form the dorsal root and autonomic ganglia, Schwann cells, melanocytes, parts of the skull and the adrenal medulla, among other structures.
How is the cerebellar cortex recognised under the microscope?
By its three layers and the single row of large, flask-shaped Purkinje cells that lie between the outer molecular layer and the inner granular layer.
Continue reading
MBBSAll Human Anatomy chapters
Continue through the Human Anatomy chapter map.
Continue studying Human Anatomy
Explore clinician-written learning resources, structured revision and practice across the MedNext platform.
Open in the MedNext appSee plans