Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
29 Cards in this Set
- Front
- Back
|
Where are the somites located?
|
On either side of the notochord/ neural tube region
|
|
|
How many pairs of somites are formed? Where do most of them disappear from?
|
44 - a lot disappear from the rostra somites (occipital region) and a large number in the coccygeal region dissapear
|
|
|
When do somites form? It what direction do they form? When do they finish forming?
|
Start forming by day 20 end at day 30 - formed from rostal to caudal
|
|
|
What are the 3 regions of the somite from inner to outer? what do they form?
|
the sclerotome - future axial
myotome- future skeletal muscles dermatome - future dermis of skin in axial regions |
|
|
In what direction does the sclerotome migrate?
|
Cells along its medial side begin to migrate towards the notochord and neural tube
|
|
|
What creates the vertebral arch?
|
the dorsally migrating sclerotome cells that pass posterior to the neural tube
|
|
|
What creates teh vertebral body?
|
The ventrally migrating sclerotome cells
|
|
|
Why does the migrated sclerotome undergo programmed cell death?
|
To shape the sclerotome into a primitive form of the vertebral body and neural arch
|
|
|
Which somites makes up the vertebral body?
|
A rostral and a cadual part of two different numbered somites
|
|
|
Which somites does the spinal nerves go through?
|
the same ones
|
|
|
What does the first cervical somite form?
|
rostal half - fuses with the lower occipital somites -- occipital bone
caudal - helps from the C1 vertebra |
|
|
In what direction does the dermatome migrate?
|
migrates from the lateral part of the somite
|
|
|
What does the dermatome help form?
|
the dermis of the skin everywhere except the head
|
|
|
When does the myotome start migrating? What direction?
|
Week 4 -- Ventraly and dorsally
|
|
|
What does the ventrally migrating myotome form? The dorsal? what do they give rise to?
|
Ventral - hypomere - muscles of body and limbs
Dorsal - Epimere - true back muscles |
|
|
When do limb buds start to form? Where?
|
end of the 4th week
Upper - C4-T1 Lower- L3-S3/4 |
|
|
What are the limb buds mostly made out of at the end of 4th week?
|
mostly somatic lateral plate mesoderm
|
|
|
Why do the limb buds form?
|
Apical ectodermal ridge --the overylying ectoderm a result of inductive influence
|
|
|
What does the hypomere split into?
|
ventral muscle mass -flexors, pronators, and adductors
Dorsal muscle mass - extensors, supinators, and abductors |
|
|
What goes first into a limb bud? What follows
|
the myotome and dermatome go first and the spinal nerves follow
|
|
|
What do bones in the limbs develop from?
|
somatic lateral mesoderm mesenchyme
|
|
|
When does limb development start to occur? end?
|
Day 24 for upper limb adn day 28 for lower
ends by the 8th week |
|
|
When is the most sensitive time for limb development?
|
during week 4-5
|
|
|
How long does limb development last?
|
5 weeks
|
|
|
What is each limb bud composed of?
|
a surface of ectoderm and a core of somatic mesoderm
|
|
|
How is AER induced? what does it do?
|
Apical ectodermal ridge --starts by the somatic mesoderm inducing the ectoderm to get thicker
|
|
|
What does the AER signal to happen?
|
Induces the mesoderm to continue to divide and results in the lengthening of the limbs
|
|
|
What creates the digits?
|
The AER is turned off between the future digits and now undergoes apoptosis
|
|
|
Meromelia-
Amelia- Syndactyly - Phocomelia |
Meromelia- absence of part of a limb
Amelia- absence of 1 or more limbs Syndactyly -- webbing between digits Phocomelia- short, poorly formed limbs |
