embryology Flashcards
define embryology
the study of embryos and their development
pre embryonic stage
first 2 weeks
when is the developing human referred to as en embryo
weeks 3-8
the pre embryonic and embryonic stage are characterized by
cell division, migration , and differentiation
when is a human referred to as a fetus
from the 9th week of gestation until birth
when are all organ systems structure ?
by week 9
define gastrulation
cellular rearrangement which involved migration, invagination, and differentiation of the epiblast
during gastrulation the 2 cell layers become
3 germ cell layers and the bodily axes in the mature adult are created
mesoderm
notochord
musculoskeletal system
muscular layer of stomach
circulatory system
ectoderm
epidermis of skin
cornea and lens of eye
nervous system
when do dermatomyotomes originate
3rd week of embryogenesis
after day 20 the mesoderm differentiates into
44 pairs of semite’s and then change into 31 sets of spinal nerves
dorsal portion of somites
comes from dermis , as limbs grow the dermis i stretched and moved down the limb
ventral portion of somites
consists of sclerotome, the precursor to the ribs and vertabrae
during the 4th week of development , the upper limbs buds appear as elevations of
C5-T1 segments if the anterolateral body wall
the lower limb buds grow
laterally from the broader bases formed by the L2-S2 segments
flex urges occur where
gaps develop between the precursors of the long bones
by the end of the 7th week the proximal parts of the upper and lower limbs
undergo a 90 degree torsion around their long axes but in opposite directions
elbows go caudally and knee cranially
what is the precursor structures of the limbs
limb buds
syndactyly
represents fusion of two or more digits
polydactyly
extra digits , typically occurs bilaterally
macrodactyly
enlarged digits
adactyly
absence of digits
ectrodactyly
“lobster-claw deformity” typically missing middle digit and occurs unilaterally
amelia
complete a sense of one or more extremities
meromelia
partial absence of one or more extremities
phocomelia
shortened lower extremities
following gastrulation , rudiments of the CNS develop from the ectoderm in the process of
neurulation
what vitamin is important to the healthy development of the neural tube and preventing neural tube defects?
folate one of the vitamin b
the neural plate border separates thh
ectoderm from the neural plate
What is a disorder which two sides of the vertebral arches fail to fuse during development, resulting in an open vertebral canal
spina bifida
Spina bifida occulta
occurs when there is a defect in the vertebral arch of L5 or S1
10% of ppl
pt is asymptomatic with a tuft of hair
meningocele
large outpouching of the meninges that contains cerebrospinal fluid
myelomeningocele
large outpuching of the meninges that is a portion of the spinal cord
anencephaly
absence of a major portion of the brain, skull, and scalp
fetal neural tube defect
folic acid
failure of neural tube to close at the base of the skull
