Embryology (Quiz 1/Test 1) Flashcards
What develops first in the spinal column?
trilaminar disc
What does ectoderm develop into?
outer skin/skin of organism
What does mesoderm develop into?
“middle skin” organs, bones, muscle
What does endoderm develop into?
“inner skin” internal linings
Spinal column develops from 3 prior structures. What are they?
1) notochord
2) somites
3) sclerotomes
What is another name for the notochord?
chorda dorsalis
Where is the notochord derived from?
embryonic mesoderm which is a primitive support structure of the axial skeleton
The notochord extends from the _____________ to ___________
sphenoid (base of skull), coccyx
Is the notochord a temporary or permanent structure?
temporary structure (later will be obliterated by the vertebral bodies and part of it persists as nucleus pulposus and apical ligament)
When is the notochord first recognizable?
Think days
day 18
In what direction/axis does the notochord develop?
cranial to caudal axis
What is another name for somites?
mesodermal segments
What are somites?
coronally-paired mesodermal cell masses
When do somites first appear?
week 4 (day 21/22)
Where do somites develop?
on left and right sides of organism and follow the axial gradient
What forms in the first segmentation?
-usually 38-39 pairs form:
>1 occipital pair
>7 cervical pairs
>12 thoracic pairs
>5 lumbar pairs
>5 sacral pairs
>8-9 coccygeal pairs
>3-5 form the coccyx
excess caudal pairs usually get reabsorbed by the embryo
____________________ produce the spinal column. They begin to divide transversely. The lower 1/2 fuses with the top 1/2 of the primary sclerotome below to form the secondary sclerotome. The IVD begins to form between them
primary sclerotomes
The reunited cell masses form the secondary sclerotomes. The secondary sclerotomes proliferate rapidly in 3 directions. What are the 3 directions?
test q
1) medially
2) posteriorly
3) laterally
The reunited cell masses form the secondary sclerotomes. The secondary sclerotomes proliferate rapidly in 3 directions. One of the directions is medially. What does this do and what does it form?
-invades and obliterates the notochord
-the L/R secondary sclerotomes fuse to form centra (centrum) of the vertebral bodies obliterating the notochord
The reunited cell masses form the secondary sclerotomes. The secondary sclerotomes proliferate rapidly in 3 directions. One of the directions is posteriorly. What does this do and what does it form?
-they surround the developing spinal cord
-they form pedicles, laminae, and spinous processes
The reunited cell masses form the secondary sclerotomes. The secondary sclerotomes proliferate rapidly in 3 directions. One of the directions is laterally. What does this do and what does it form?
they project to form the lamina/pedicle junction
The reunited cell masses form the secondary sclerotomes. The secondary sclerotomes proliferate rapidly in 3 directions: medially, posteriorly, laterally. Invading mesenchyme cells forms the annulus fibrosus of IVDs. Encapsulated notochord becomes the….
nucleus pulposus