Embryology 1.13 Flashcards
Which structure fives rise to the CNS?
neural tube
When does gastrulation occur during development?
Week 3
What do the epiblast cells give rise to?
3 germ layers
Which germ layer is responsible for most of the nervous system?
ectoderm
What is the notocord?
-induce ectoderm to thicken into neural plate and later neural tube
What is neuralation?
folding of neural plate into a closed tube of ectoderm
When does the formation of the neural plate occur?
16-18 days post fertilization
When do the neural folds elevate?
19-20 days post fertilization
When does the fusion of neural folds occur?
21-24 days post fertilization
When does the cranial neuropore close?
25 days post fertilization
When does the caudal neuropore close?
27 days post fertilization
What are the regions of the brain?
forebrain (prosencephalon)
midbrain (mesencephalon)
hindbrain (rhombencephalon)
What occurs at 4 weeks into development?
-segmentation of the CNS
-3 primary brain vesicles formed
prosencephalon
mesencephalon
rhombencephalon
Where is the cephalic flexure during brain development?
midbrain
Where is the cervical flexure during development?
hindbrain and spinal cord
What occurs at 5 weeks into development?
primary vesicles (prosencephalon, mesencephalon, rhombencephalon) form secondary vesicles
telencephalon diencephalon ----- mesencephalon ----- metencephalon mylencephalon myelon
What does the telencephalon give rise to?
cerebral hemispheres
What does the diencephalon give rise to?
thalamus
hypothalamus
What does the mesencephalon give rise to?
midbrain
What does the metencephalon give rise to?
pons
cerebellum
What does the mylencephalon give rise to?
medulla
What does the myelon give rise to?
spinal cord
What is anencephaly?
- result of failure to close anterior (cranial) neuropore
- failure to form brain and cranial vault
What is Spina Bifida?
- results from incomplete closure of embryonic neural tube
- sacrolumbar
- patch of skin
What is meningocele?
- severe form of spina bifida
- protrusion of meninges
What is meningomyelocele?
- severe form of spina bifida
- protrusion of meninges and spinal cord
What is rachischisis?
- severe form of spina bifida
- open neural tube
How can neural tube defects be prevented?
FOLIC ACID
When do sulci and gyri form in the cortex?
30 weeks post fertilization
Which process is responsible for brain growth after birth?
myelination begins in 3rd trimester and continues after birth
When is embryonic CSF formed?
week 5
What occurs when the ventricular system in blocked?
hydrocephalus due to accumulation of CSF
How does eye formation begin?
diverticulae of forebrain and formation of optic groove which becomes optic vesicles
What is the choroid fissure?
- location of lens of the eye
- forms when the optic vesicle and optic stalk invaginate inferiorly
What is the neural retina?
- part of the retina which contains photoreceptors (rods and cones)
- forms from inner layer of optic cup
What is coloboma?
incomplete closure of the choroid fissure; normally fuses during week 7
What does the neural tube form during development?
- ventricular layer, surrounded by
- mantle layer (gray matter)
- marginal layer (white matter after myelination)
What is the sulcus limitans?
- structure in the spinal cord which separates developing gray matter into dorsal alar plate and ventral basal plate
- forms central canal of spinal cord (narrows)
How does the spinal cord change positions during development?
begins by extending all the way to the “sacrum” but ascends as we grow taller/longer during development
What does the peripheral nervous system develop from?
neural crest cells at zone between neural plate and surface ectoderm
What are the nerve fibers categorized as in the DRG?
- sensory
- neural crest-derived
How does referred pain work?
-afferent neurons from the source of pain (organ) and referred pain area (skin) both synapse on same spinal segment
What is the sympathetic innervation of the heart?
T1-T4 (explains referred pain down left arm during heart attack)
Which cranial nerves are derived from neural crest cells?
CN V, VII, VIII, IX, X
sensory ganglia!!!
What is Hirschsprung’s disease?
- congenital aganglionic megacolon
- absence of ganglia in lower colon
- results from failure of neural crest migration due to mutations in several genes
