Neural Development (Quiz 4) Flashcards
Human development is divisible into 2 primary periods. What are they?
1) pre-natal (before birth)
2) postnatal (after birth)
Development of the NS begins in the embryonic period (at the time of fertilization when the union of a spermatozoon and an oocyte form a zygote) and extends into the….
post-natal period
A zygote is unicellular with 2 sets of chromosomes- paternal 46 ___ and maternal 46 ____
XX, XY
By 36 hours, the zygote divides into 2 cells, then has rounds of cleavage divisions forming an embryo- ______ then blastocyst over 6 days
morula
What are blastomeres?
identical cells
What are blastocysts?
its the cell/embryo that implants into uterus
Secondary oocytes have not completed meiosis 2 due to a protective mechanism. The secondary oocyte will only complete meiosis 2 when it penetrates sperm. Where was sperm made?
seminiferous tubules of the testes
define morula
solid ball of cells
define blastocyst
hollow ball of cells with an inner cell mass that becomes embryo and everything else becomes extra-embryonic tissue
there is a blastocele cavity and trophoblast cells (outer layer)
ICM becomes….
bilaminar disc
What does gastrulation start with?
primitive streak
What does gastrulation end with?
trilaminar disc
What are the primary germ layers and when were they formed?
formed during gastrulation
-endoderm
-mesoderm
-ectoderm
What is the internal germ layer?
endoderm
What does endoderm form?
lining of gut and other internal organs (basically anything visceral)
What is the external germ layer?
ectoderm
What does ectoderm form?
-skin
-brain
-NS
What does the mesoderm form?
-muscle
-skeletal system
-circulatory system
The NS begins to form in the 3rd week of development. The first evidence of the developing NS is a thickening of the ectoderm of the trilaminar embryo, the _____________. Its a thickening of a longitudinal band of ectoderm in response to chemicals from the underlying midline mesoderm
neural plate
The neural plate begins to fold medially forming a….
neural groove
Either side of the neural groove are the _______________. As the neural groove deepens, the folds start to fuse, the initial join is at the location of the future cervical spinal cord
neural folds
Put structures in order from 1st to appear to last:
-neural tube
-neural groove
-neural fold
-neural plate
-cranial neuropore
-caudal neuropore
1) neural plate
2) neural groove
3) neural fold
4) neural tube
5) cranial neuropore
6) caudal neuropore
Which structure is this?
-thickening of ectoderm between primitive node and oropharyngeal membrane
neural plate
Which structure is this?
-neural folds join in the midline to form this structure and fusion of the folds proceeds cranially and caudally, eventually leaving a cranial and caudal neuropore (open ends)
-it separates from surface ectoderm to lie between it and the notochord
-the cranial part forms the brain and the caudal portion forms the spinal cord
-the lumen forms the central canal of spinal cord and ventricular system of the brain
neural tube
Which structure forms the lamina terminalis?
cranial neuropore (its also the first structure to close!)
Neurulation is the process of formation of the hollow neural tube by folding the epithelial neural plate. Neurulation in humans occurs in 2 distinct phases. What are they?
1) primary neurulation during weeks 3/4 of gestation leading to the development of the brain and spinal cord
2) secondary neurulation during weeks 5/6, with formation of the lower sacral and coccygeal cord with the help of the neural crest cells
defects of either of these can lead to abnormalities and usually miscarriages
Fusion of the neural folds forms the….
neural tube
Fusion proceeds cranially and caudally. By the end of the 4th week the tube is closed, a process called __________________. The close neural tube pulls away from the overlying ectoderm. A cluster of cells forms from the crest of each neural fold and fills the gap between the neural tube and ectoderm. This is the __________.
primary neurulation, neural crest
Neural crest cells will develop into the….
PNS
The formed neural tube develops into the..
CNS