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49 Cards in this Set

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what are the names for the 3 sections of mesoderm that assemble in the embryo?
paraxial mesoder, intermediate mesoderm, lateral plate mesoderm
during development, cavities develop within the lateral plate mesoderm to form which two layers? Give 2 names for each
parietal (somatic) and visceral (splachnic)
what is the name for the original structures formed from the paraxial mesoderm?
somitomeres
how many somitomeres eventually become somites
all but 7
on which day of development does the first somite form?
day 20
by the 5th week of development, how many somites are present in the embryo?
42-44
in which direction do somites form in the developing embryo?
cranial to caudal
following their formation, somites differentiate into two parts. What are the names for these two parts?
sclerotome and dermomyotome
the sclerotome is derived from which part of the somite? What is the name for the sclerotome once it migrates toward the notochord?
the core; mesenchyme
the sclerotome that forms around the notochord becomes what? Around the neural tube?
vertebral body; vertebral arch
the dermomyotome separates into which layers?
dermatome and myotome
None
the dermatome spreads out and accounts form which aspect of the skin?
dermis and hypodermis
of what does the myotome consist? To what do these cells give rise?
myoblasts; muscles of neck and trunk
what is the fate for the myoblasts of the most ventrolateral aspect of the myotome?
skeletal musle of the limbs
into which two layers does the myotome further develop?
epimere and hypomere
to what does the epimere give rise? The hypomere?
intrinsic (true) muscles; anterior and lateral trunk muscles
what is the fate of the interemediate mesoderm?
urogenital structures
which portions of the body are formed from the splanchnic mesoderm (visceral)? The somatic (parietal) mesoderm
structures associated with the respiratory and digestive systems; ventral and lateral portions of the body wall as well as the majority of the limb tissue
limb buds become visible in the embryo at the end of which week?
4th
which appears first in the developing embryo, the upper or lower limb bud?
upper
what are the contents of the limb buds?
ectoderm and mesenchyme
the mesenchyme in the forming lumb buds is derived from where?
the somatic layer of the lateral plate mesoderm
what are the 3 demarcations of a limb bud?
longitudinal axis, postaxial border, preaxial border
at the tip of the ectoderm, the ectoderm thickens to form a ridge. What is the name for this ridge?
apical ectoderm ridge (AER)
what is the role of the AER?
induce underlying mesenchyme to proliferate which causes the limb to grow
what is the fate of the cells closest to the AER? Furthest?
undifferentiated; differentiate into chondrocytes
all the bones of the appendicular skeleton, with the exception of which one, form via endochondral ossification?
clavicle
development of the limb bud proceed in the distal to proximal or proximal to distal direction?
proximal to distal
the terminal portions of the limb buds are flattenen and form which two structures?
hand plates and foot plates
by what are the hand and foot plates separated from the rest of the limb bud?
constrictions (wrist/ankle)
what is the name for the precursors of the fingers and toes in the limb buds?
digital rays
myoblasts originate from which portion of the dermomyotome?
ventrolateral
as the epimere and the hypomere are forming, by what are they innervated?
dorsal and ventral rami, respectively
by what are the ventrolateral cells destined for the limbs innervated?
ventral ramus
the upper limb bud forms near which somites? The lower limb?
C5-T1; L2-S3
once in the limbs, how do the myoblasts organize themselves?
dorsal and ventral condensations on either side of the developing bones
what happens to VPR as it enters into limbs?
separates into dorsal and ventral branches to supply muscles on anterior and posterior of the developing limb bones
in the upper limb, the dorsal branches of the VPR eventually merge to form which two major nerves? The ventral merge to form which three major nerves?
axillary and radial; musculocutaneous, median, and ulnar
during which week of development do the developing limbs undergo horizontal flexion? This brings the limbs from which plane to which other plane?
6th; coronal and sagittal
what additional movement of the limbs occurs at the 7-8th week of development?
rotation 90 degrees on longitudinal axis
when the limbs rotate during the 7-8th week of development, in which direction do the upper limbs rotate? The lower limbs?
laterally; medially
in which direction does the thumb move during rotation of limbs? The big toe?
laterally; medially
what part of development of limbs during development distorts the dematome?
limb rotation
what is amelia? Meromelia? Phocomelia?
absence of one or more limbs; absence of part of a limb; when proximal part of limb is shortened or absent (form of meromelia)
what is a cleft hand or foot?
when there is no middle ray and the first/second digits and fourth/fifth digits fuse
what is polydactyly?
excess digits on hand or foot
what is syndactyly?
fusion of digits due to incomplete cell death in the inter-ray space
what is clubfoot?
when the sole of the foot is turned inward and the foot if plantar flexed
which kind of birth defect is associated with the breech position in the womb?
congenital hip dislocation