Embryology

Question 1

notochord

Answer 1

forms on the midline of the trilaminar embryo from mesoderm
induces overlying ectoderm to thicken and grow into neural plate
becomes future nucleus pulposus

Question 2

neurulation

Answer 2

16-18 days neural plate formed
19-20 days neural folds elevate, beginning at first 5 somites
21-24 days neural folds begin to fuse, leaving neuropores where neural tube communicates with amniotic sac
25 days - cranial neuropore closes
27 days - caudal neuropore closes

Question 3

segmentation of neural tube

Answer 3

prosencephalon (becomes diencephalon and telencephalon)
mesencephalon
rhombencephalon (becomes metencephalon and myelencephalon)
myelon

Question 4

prosencephalon

Answer 4

diencephalon - thalamus, hypothalamus

telencephalon - cerebral hemispheres

Question 5

mesencephalon

Answer 5

midbrain

Question 6

rhombencephalon

Answer 6

myelencephalon - medulla

metencephalon - pons, cerebellum

Question 7

myelon

Answer 7

spinal cord

Question 8

anencephaly

Answer 8

failure of cranial / anterior neuropore closure

failure to develop brain in cranial vault

Question 9

spina bifida

Answer 9

failure to close caudal neuropore
occulta - benign, asymptomatic
meningocele - protrusion of meninges
myelomeningocele - protrusion of spinal cord and meninges
rachischisis - open neural tube due to no neural tube elevation

Question 10

brain volume growth

Answer 10

sulci and gyri form mostly between 20-30 weeks

brain grows mostly from myelination that beings in third trimester and continues after birth

Question 11

CSF formation

Answer 11

CSF formed in week 5

Question 12

eyes

Answer 12

begin as ‘optic grooves’ - diverticulae of diencephalon around 24 days
grooves become pouches (vesicles) by day 27
vesicle and stalk invaginate to form the choroid fissure (future iris)
choroid fissure fuses at week 7
neural retina forms from inner layer of optic cup
coloboma (incomplete iris) due to incomplete choroid fissue closure

Question 13

layers of neural tube (inner to outer)

Answer 13

ventricular - gives rise to neuroblasts
mantle - derived from neuroblasts; becomes gray matter
marginal - fibers of neuroblasts; becomes white matter

Question 14

spinal cord plates

Answer 14

sulcus limitans divides gray matter into the alar (dorsal) and basal (ventral) plates

Question 15

DiGeorge Syndrome

Answer 15

deletion on chromosome 22 that causes a neurocristopathy - defect in development of tissues containing cells derived from neural crest
thymic hypoplasia, cleft palate, kidney abnormalities, heart defects, facial abnormalities, no parathyroid

Question 16

tissues derived from neural crest

Answer 16

pigment, teeth, bones and cartilage of face / neck, parts of glands, adrenal medulla, dorsal root afferent neurons, cranial nerve afferents, schwann cells, parts of the heart

Question 17

PNS development

Answer 17

neural crest (ectodermal) cells migrate from neural fold through somites to form dorsal root ganglia, sympathetic and parasympathetic postganglionics, cranial nerve sensory ganglia

Question 18

sympathetic innervation of heart

Answer 18

T1-4

Question 19

nerves derived from neural crest

Answer 19

afferent dorsal root ganglia
CN sensory
ANS postganglionic

Question 20

nerves derived from CNS

Answer 20

CN efferent ventral root

CN motor