Neurulation. The structure of the neural tube. Development of the spinal cord

what is neurulation?

process which the neural tube and the neural crest form

what is the notochord developed from?

mesoderm

how does the notochord help form the neural plate?

the notochord induces the overlying ectoderm to form the neural plate

which signalling molecules do the notochord release?

noggin

chordin

goosecoid

follistatin

what do the signalling molecules from the notochord do? what is the consequence?

inhibit BMP4

prevents ectoderm from differentiating into epidermis → causing the ectoderm to differentiate into neural tissue

what is the function of WNT3a and FGF?

induce development of the hindbrain and spinal cord

what is the function of retinoic acid?

regulates expression of homeobox genes important for nervous system development

what happens after the notochord has induced the overlying ectoderm to form the neural plate?

the neural plate will lengthen

a depression will form → neural groove

lateral edges elevate → neural folds

where do the fusion of the neural folds begin?

at the level of the 5th somite

what is the two openings of the neural tube called?

anterior and posterior neuropore

when do the anterior neuropore close?

ca day 25

when do the posterior neuropore close?

ca day 28

what marks the end of neurulation?

when the posterior neuropore close

how are the neural crest formed?

cells that dissociate from the neural folds deposit between the neural tube and the surface ectoderm

where does the CNS develop from?

neural tube

what are the three primary brain vesicles

prosencephalon

mesencephalon

rhombencephalon

when do the primary brain vesicles differentiate into five secondary brain vesicles?

by week 5

what do the prosencephalon develop into?

telencephalon

diencephalon

what do the rhombencephalon differentiate into?

metencephalon

myelencephalon

what do the mesencephalon differentiate into?

stays as the mesencephalon

what are the three flexures between the brain vesicles?

cephalic, pontine and cervical flexures

where does the cephalic flexure form?

in the region of the mesencephalon

where do the pontine flexure form?

boundary between metencephalon and myelencephalon

where do the cervical flexure form?

boundary between the myelenecephalon and the mesencephalon

what lies between the metencephalon and the mesencephalon?

rhombencephalic isthmus

what do the telencephalon develop into?

cerebral hemispheres

basal ganglia

what does the diencephalon develop into?

thalamus

hypothalamus

subthalamus

pineal gland

optic nerve

retina

what do the mesencephalon develop into?

midbrain

what do the metencephalon develop into?

cerebellum and pons

what do the myelencephalon develop into?

medulla oblongata

what do the wall of the neural tube initially consist of?

neuroepithelium

what do the neuroepithelium peripheral to the lumen differentiate into? and which layer does it form

neuroblasts

mantle layer

what will the axons of the neuroblasts form?

marginal layer

what will the mantle layer give rise to?

grey matter

what will the marginal layer give rise to?

white matter

what do the neuroblast form as they continue to proliferate?

dorsal and ventral thickenings

what are the ventral thickenings formed by the neuroblast? what do they contain?

basal plates

motor neurons

what are the dorsal thickenings formed by the neuroblast?

what do they contain?

alar plates

sensory neurons

what marks the boundary between the basal and alar plates in the neural tube?

sulcus limitans

what forms in the roof and the floor of the neural plate?

roof and floor plate

what do the roof and floor plate do?

secrete factors which regulate the organization of the neural tube

what doesn’t the roof and floor plate contain?

neuroblasts

what forms at the thoracic and upper lumbar levels of the spinal cord?

intermediate horn

which system do the neurons in the intermediate horn belong to?

sympathetic nervous system

what do the alar plates give rise to in the spinal cord?

dorsal horns

where do the bodies of the sensory nerve cells of the peripheral nerves lie?

in the dorsal root ganglia outside the spinal cord

what do the basal plates give rise to in the spinal cord?

ventral horns

what do the neuroepithelial cells lining the central canal differentiate into?

ependymal cells