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1. Anatomy
1.1 Immune system, blood and lymphoreticular system
1.2 Nervous system and special senses
1.3 Skin and subcutaneous tissue
1.4 Musculoskeletal system
1.5 Anatomy of the cardiovascular system
1.6 Respiratory system
1.7 Respiratory system additional information
1.8 Renal and urinary system
1.9 Renal system additional information
1.10 Gastrointestinal system
1.11 Gastrointestinal system additional information
1.12 Duodenum
1.13 Liver
1.14 Female reproductive system and breast
1.15 Female reproductive system additional information
1.16 Fallopian tubes
1.17 Male reproductive system
1.18 Male reproductive system additional information
1.19 Prostate
1.20 Endocrine system
1.21 Embryology
1.21.1 Gastrointestinal system
1.21.2 Gastrointestinal developmental disorders
1.21.3 Genitourinary system
1.21.4 Nervous system
1.21.5 Respiratory and cardiovascular systems
1.21.6 Pharyngeal arches
1.21.7 Placenta
1.21.8 Umbilical cord and fetal circulation
1.21.9 Additional information
1.22 Additional information
2. Microbiology
3. Physiology
4. Pathology
5. Pharmacology
6. Immunology
7. Biochemistry
8. Cell and molecular biology
9. Biostatistics and epidemiology
10. Genetics
11. Behavioral science
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1.21.4 Nervous system
Achievable USMLE/1
1. Anatomy
1.21. Embryology

Nervous system

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The notochord is formed from mesoderm. It induces the overlying ectoderm to form the neural plate. The ectoderm that forms the neural plate is called neuroectoderm. The neural plate undergoes folding to eventually form a neural tube. The cavity of the neural tube is called the neural canal, it gives rise to the ventricles of the brain, the cerebral aqueduct and the spinal canal. The cranial and caudal openings of the neural tube , called neural pores close by days 24-27. Folic acid supplementation prevents open neural tube defects, which happen when the above process is hampered.

The neural tube develops three primary vesicles which give rise to five secondary vesicles as follows:

Primary Vesicles Secondary Vesicles Derivatives
Prosencephalon (forebrain) Telencephalon Cerebral hemispheres, preoptic area, basal ganglia
Diencephalon Thalamus, hypothalamus, epithalamus and subthalamus, optic nerve cranial nerve II, retina, neurohypophysis
Mesencephalon (midbrain) Remains the same Midbrain
Rhombencephalon (hindbrain) Metencephalon Pons, cerebellum
Myelencephalon Medulla
Holoprosencephaly
Holoprosencephaly

The spinal cord develops from the neural tube. A few specialized cells from the neural plate form the neural crest. The neural crest gives rise to primary sensory neurons, postganglionic autonomic neurons, sensory and autonomic ganglia, melanocytes, aorticopulmonary septum, endocardial cushions, adrenal chromaffin cells in the adrenal medulla, cranial nerves, Schwann cells, pia and arachnoid mater, skull bones, pericytes, myenteric and Auerbach plexuses, odontoblasts as well as bones and cartilages derived from the pharyngeal arches.

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