Weekly Development Flashcards
1-6 EL
Conception- zygote- blastomere
6-8 EL
Blastomere adheres to uterine wall
9-12 days EL
Gastrulation occurs
What happens at 12 days of EL?
Maternal blood supply, gastrolation, and 3 germ layers
After 12 days of EL what do we have?
3 germ cell layers
What are the 3 germ cell layers
Endoderm, mesoderm, ectoderm.
After gastrulation why does the embryo become fragile?
- Specialized cells have specific duties
- Very few specific types
- Subtypes appear quickly
- One specialized cell cannot substitute for another damaged specialized cell.
3rd week of Embryo life
Somites begin to develop and ectoderm forms.
What happens during the 4th week of embryo life?
30 somites and head, heart beat, and tail.
What happens during week 3 of ear development.
Inner: Otic pit forms
Mid: tubotympanic recess begins.
What happens during the 4th week of ear development.
Inner: otic cyst forms
Mid and outer: branchial grooves/ arches appear.
What happens during the 5th week of ear development?
Outer: external ear canal begins to form.
What happens during week 6 of ear development.
Inner: Vestibular organs begin to form 3 semicircular canals.
Outer: 6 hillocks appear on mandibular and hyoid arches. Cartilage begins to form.
What happens during week 7 of ear development.
Inner: cochlea elongates to one coil. Sensory cells in vestibular organ begins to form.
What happens during week 8 of ear development
Mid: lower half of tympanic cavity is formed by extended tubotympanic recess. Migrating cells from branchial arches form malleus and incus.
Outer: lateral cartilaginous 1/3 of ear canal formed.
What happens during week 9 of ear development
Mid: 3 layers of tympanic membrane form. Each layer has a specific germ cell layer.
What happens during week 11 of ear development
Inner: cochlea lengthens to 35mm and 2 5/8 turns. This is adult shape and size.
What happens during week 12 of ear development?
Inner: sensory cells appear in cochlea and membranous labryinth. The Otic capsule begins to ossify.
What happens during week 15 of ear development.
Mid: stapes forms from migrating cells from 2nd branchial arch.
What happens during week 16 of ear development.
Mid: malleus and incus begin to ossify
What happens during week 18 of ear development
Mid: stakes begins to ossify
What happens during week 20 of ear development.
Inner: sensory and supporting cells are fully formed. Inner ear hearing is now fully functional
Outer: pins completes mature Shape
What happens during week 21 of ear development
Mid: neatly plug dissolves exposing the TM.
What happens during week 32 of ear development.
Mid: malleus and incus complete ossification
What happens during week 34 of ear development
Mid: mastoid air cells develop. These are the last things to develop.
