Development Flashcards
How is CN 1 (Olfactory) formed?
Invagination and delamination
How is the lens formed?
Invagination - optic cup invaginates and lens forms within
What forms the sensory/nervous elements of the eye?
Neural crest
How is the otic formed?
Invagination and delamination (otic pit is invagination, placode cells migrate out/delaminate to form statoacoustic ganglion)
Also formed by ectoderm of pharyngeal arch 1
How are CN V, VII, IX, and X formed?
Delamination Neural crest (not placode) cells make up proximal ganglia of these nerves; placodes make up distal ganglia
When does the primary palate and face form?
4-6 weeks
When does the secondary palate form?
6-12 weeks
Define: merging
Mesenchyme proliferates to eliminate a groove
If the epithelium is included, then facial cleft or cyst will occur
Define: fusion
Contact of epithelium-covered surfaces across a gap, removing the epithelium (either by apoptosis, stretch, or EMT)
What does the periprosencephalon form?
Frontonasal processes (lateral nasal; medial nasal)
Forehead
Nose
Philtrum
(can be affected by cell proliferation issues)
What is formed by Pharyngeal Arch 1?
Mandibular Process Maxillary Process Oropharyngeal Membrane Cheek Chin Lips
Affected by cell migration issues.
What is the oropharyngeal membrane made out of?
Communication between foregut and amniotic cavity - formed by ectoderm-endoderm
What is the oronasal membrane made out of?
Ectoderm-ectoderm
Pulled apart at 6 weeks (eat b4 6mell)
What is a “typical” cleft? An “atypical”?
Typical = MNP+Lateral Maxillary P fusion issue Atypical = merging issue
When do the pharyngeal arches form and disappear?
20-35 days (between forebrain and heart developmeent)
What are pharyngeal arches made out of?
Cephalic somitomeres
Neural crest cells
Patterned by unique Hox gene combo
Made out of: outer/lateral ectoderm, inner/medial endoderm, core NCC and mesoderm (mesenchyme)
Define: Pharyngeal Arch I
Rhombomeres 1,2
No Hoxx gene
Artery disappears
Creates CN V, muscles of mastication, malleus, incus, Merckel’s cartilage
What does Pharyngeal Pouch I make?
Auditory tube
Primitive tympanic cavity
Middle ear
What is the pharyngeal groove I derivative?
External auditory meatus
Define: Pharyngeal Arch II
Rhomb 3,4
Hox gene
Artery disappears
Creates CN VII, muscles of facial expression, stapes, styloid process, lesser horn of hyoid
What does Pharyngeal Pouch II make?
Palatine Tonsil
Define: Pharyngeal Arch III
Rhom 6
Hox gene
Common carotid
CN IX - stylopharyngeus, body of hyoid
What does Pharyngeal Pouch III form?
Thymus
Inferior Paraythyroid
Define: Pharyngeal Arch IV
Rhom 7
Hox gene
R subclavian, L aortic arch
CN X and XI, laryngeal muscle, thyroid cartilage
What are the derivatives of Pharyngeal Pouch IV?
Superior paraythroid gland
ultimbobranchial body
How does the thyroid form?
NOT from the pharyngeal arches, but instead from endoderm
Derives from the foramen cecum (pit in tongue), migrates inferiorly to mid-neck
Define: placode
Thickened ectoderm between epidermis and neural plate, which leads to the development of organs of special sense, the Trigeminal nerve, and the branchomeric nerves.
What are the layers of the skin, and what would you find there?
Epidermis - made from ectoderm; includes keratinocytes, melanocytes, Merkel, Langerhans, dendritic; hair shafts, sweat and sebaceous glands
Dermis - mesoderm; fibroblasts; nerves and vessels
Hyodermis - mesoderm; fibroblasts, adipocytes, muscles
What holds the layers of the skin together?
Integrins
When does the skin form?
Week 4: ectoderm can become CNS or skin
Week 7-21: skin can become hairy or non-hairy (glabrous)
What does the notochord create?
Nucleus pulposus of the intervertebral disks
What does the neural tube create and what is it composed of?
It is thickened central ectoderm and creates the CNS (brain, spinal cord)
What do neural crest cells create?
PNS (Schwann cells, sensory neurons, ANS ganglia)
head structures
melanocytes
They are ectodermal cells lateral to the neural plate
What forms the axial skeleton? Appendicular skeleton and sternum? Craniofacial skeleton?
Axial: somitic
Append + Sternum: lateral mesoderm
Craniofacial: neural crest
When do the limbs form?
Limbs form in week 4 and rotate in weeks 6-8
Define: stylopod
Most proximal element (humerus or femur)
Define: zeugopod
2 elements (ulna/radius or tibia/fibula)
Define: autopod
Phalanges/carpals/tarsals
When does implantation occur? Gastrulation?
Implantation: week 2
Gastrulation: week 3
Define: Morphogen
Signal that is long range with a dose-dependent response and feedback loop (ex - Nodal)
Define: forward genetics
Phenotype to genotype
Define: reverse genetics
Genotype to phenotype
