Exam 1: Neurogenesis

Dr. Ghosh - Fall 2023

pre-embryonic stage

conception to day 14

embryonic stage

day 15-8th week

nervous system development is necessary

fetal stage

end of 8th week until birth

neurogenesis

development of nervous system from ectoderm

when does fertilization of the ovum occur?

in the pre-embryonic stage in the fallopian tube

pre-embryonic stage: cell division

starts and continue while zygote moves down the tube

movement of zygote down the tube

stage of morula to blastula

morula requirements

< 8 cells for division

blastula requirements

> 8 cells for division

pre-embryonic stage: blastocyst

solid sphere of cells is formed in the cavity and implants into the endometrium, thus, creating the blastocyst

pre-embryonic stage: embryonic disc

during implantation, the inner cell mass develops into the embryonic disc, and three layers are formed (ectoderm, mesoderm, and endoderm)

pre-embryonic stage: ectoderm

outer layer of the sphere and becomes the fetal contribution of the placenta

embryonic stage developments

organs

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embryonic stage ectoderm developments

CNS, PNS, skin, nails, sensory epithelia of eyes, ears, and nose

embryonic stage mesoderm developments

muscles, skeleton, cardiovascular system, kidneys, spleen, gonads, and adrenal glands

embryonic stage endoderm developments

gut, liver, pancreas, thyroid, and respiratory system

fetal stage developments

all organs and systems develops more fully

nervous system develops nad myelination begins

CNS development

18th day: thickened part of ectoderm (neural plate)

20th day: edges fold to create the neural groove

22nd day: edges of neural tube come together and fuse at the center

neural tube location

on 22nd day, the tube is located in the cervical area of the embryo

how does the neural tube grow?

rostral and caudal

rostral and caudal neuropores

persists until the 24th and 26th days

rostral neuropore closure

24th day

caudal neuropore closure

26th day

anencephaly

failure to close rostral neuropore, resulting in deficient development of the rostral brain structures (cerebrum)

myelomeningocele

failure to close caudal neuropore, resulting in spina bifida (incomplete development of caudal nervous system - lumbar and sacral spinal cord)

completion of rostral neural tube

formation of brain and structures

completion of caudal neural tube

forms spinal cord

neural crest

ectoderm cells that remain outside the neural tube

dorsal clumps form sensory ganglia (DRG) while ventral clumps form sympathetic trunk ganglia

neural vesicle formation

formed by the 28th day and expanded in 3 points with vesicles

rostral vesicle

prosencephalon (forebrain)

middle vesicle

mesencephalon (middle brain)

caudal vesicle

rhombencephalon (hindbrain)

cervical flexure

bending between the hindbrain and spinal cord in the area od the cervical cord

cephalic flexure

bending between the mesencephalon and hindbrain

telencephalon

subdivision of the prosencephalon at the 5th week and leads to the formation of cerebral hemisphere and basal ganglia

diencephalon

subdivision of the prosencephalon at the 5th week and develops into the thalamus, hypothalamus, optic nerves, and tracts