Histology and Embryology Lecture Notes - Development of the CNS (2020/2021)

Subject: Histology and embryology Lecture: Development of the CNS First year, Faculty of Medicine, 2020/2021 Department of Histology and Embryology Pomeranian Medical University in Szczecin  DEVELOPMENT OF THE CNS NEURAL PLATE (17th day) NEURAL GROOVE neurulation (18-21day) NEURAL TU...

Subject: Histology and embryology Lecture: Development of the CNS First year, Faculty of Medicine, 2020/2021 Department of Histology and Embryology Pomeranian Medical University in Szczecin  DEVELOPMENT OF THE CNS NEURAL PLATE (17th day) NEURAL GROOVE neurulation (18-21day) NEURAL TUBE & CRESTS (21st day) NEUROPORUS ANTERIOR (25th day) NEUROPORUS POSTERIOR (28th day) 17th day -> 21 21s da O-crests -> Tub An) 25 28  ec to derm cranial wide Neural Plate ectoderm Appears on the 17th day. cranial -> The neural plate is recognizable as the thickening candel -> of the ectoderm opposite to the primitive streak At the cranial end the neural Cut section of the amnion Neural folds plate is wider and consists of the region where the brain Neural plate will arise. At the caudal end it is narrower and gives rise to the spinal cord Neural groove Primitive streak  folds-> fase togebles plate Nervous System Development Develops from Ectoderm Rising of neural folds „Sinking” of neural plate forms neural groove Folds fuse to complete neural tube neural t neural desing  cephatically and candally fold at level othsomite Nervous System Development - fusion of neural groove extends cephalically and caudally - Neural folds begin to fuse at the level of 4th somite - 2 openings at either end- cranial and caudal neuropores Neurulation - includes the transformation of the neural plate into the neural tube - Neural Crest Cells In addition to forming sensory ganglia cells of the neural crest differentiate into: - Schwann cells - Melanocytes - C-cells (in thyroid gland) - Medulla of the adrenal gland - Mesenchyme of the pharyngeal arches  ORIGIN OF NERVOUS SYSTEM CELLS Neural crest  Pseudounipolar neurons of spinal and cranial sensory ganglia  Postganglionic neurons of autonomic nervous system  Glia cells of peripheral nervous system (Schwann cells, satellite cells) Neural tube  Neurons of CNS  Glia cells of CNS (astrocytes, oligodendrocytes, ependymal cells) Mesenchyme ~  Microglia (bone marrow derived) Iligee un NEUROEPITHELIAL LAYER 0 ⑧  DEVELOPMENT OF THE SPINAL CORD lower part of neural cra tube turn into spiral - - (Ventricular zone) Development of the spinal cord Internal limiting membrane  0 ⑳ Expansion of Brain ⑧ Primary brain vesicles Forebrain Midbrain Hindbrain Two flexures: cervical &  Cranial flexure (between hindbrain and the spinal ⑧ cord)  Cephalic flexure (in the midbrain region)  Expansion of Brain Secondary brain vesicles Forebrain Telencephalon Diencephalon Midbrain remains just midbrain Hindbrain Metencephalon (later forms pons and cerebellum) Myelencephalon Neural tube  Development of the Telencephalon The most rostral of the brain vesicles Consists of: - Cerebral hemispheres (two lateral outpocketings) - Lamina terminales (a median portion) Lateral ventricles – the cavities of the hemispheres  Cerebral Hemispheres development Arise at the beginning of the 5th week as bilateral evaginations of the lateral wall of the prosencephalon Corpus striatum – basal part of the hemispheres begins to growth and buldges into the lumen Formation of the hippocampus Hemispheres cover the lateral aspect of the diencephalon, mesencephalon and cephalic portion of the metencephalon Continuous growth of the cerebral hemispheres results in formation of frontal, temporal and occipital lobes DEVELOPMENT OF THE CORTEX  dividesinto Diensephalon:ependymal Hyssulcet I cells thola ↳ Hypothalamey and Development of the Diencephalon Roof plate (single layer of ependymal cells covered by vascular mesenchyme) -> choroid plexus of the third ventricle Caudal part of the roof plate -> pineal body The alar plates form the lateral walls of the diencephalon. A groove, the hypothalamic sulcus, divides the plate into thalamus and hypothalamus The thalamus invaginates into the lumen of the diencephalon The hypothalamus is the lower portion of the alar plate  Development of the Diencephalon Develops from the median portion of the prosencephalon Forms: Mamillary body Pituitary gland Thalamus Hypothalamus Pineal gland Development of the hypophysis - Ectoderm - adenohypophysis Neuroectoderm - neurohypophysis a  Rhombencephalon (Hindbrain) Consists of: Module - Myelencephalon (gives - rise to medulla oblongata) Metencephalon oblongate Pons Cerebellum DEFECTS  NEURAL TUBE DEFECTS Spina bifida&occulta inVicia's - Spina bifida cystica visible Meningocele Meningomyelocele Myeloschisis (rachischisis) Third and fourth week of development SPINA BIFIDA OCCULTA  SPINA BIFIDA CYSTICA arachnoid Neural tissue  MYELOSCHISIS (RACHISCHISIS) Associated with a wide variety of problems: chronic infections, motor and sensory defects, disturbances in bladder function CEPHALUS DEFFECTUS withoutbrain Anencephaly part of cystice -> S neural tube dofrt- Meningocele -> Meningoencephalocele Meningohydroencephalocele Hydrocephalus Internus Externus ANENCEPHALY 23rd-26th day of pregnancy (critical period) 23rd Anencap 23rdl-26)  Cephalus Deffectus Meningocele, Meningoencephalocele, Meningohydroencephalocele Caused by an ossification defect in the bones of the skull. The most frequently affected bone is the squamous part of the occipital bone (it may be partially or totally lacking)  Meningohydroencephalocele Meningocele Meningoencephalocele  Meningohydroencephalocele Meningocele Meningoencephalocele