Development

Question 1

How is CN 1 (Olfactory) formed?

Answer 1

Invagination and delamination

Question 2

How is the lens formed?

Answer 2

Invagination - optic cup invaginates and lens forms within

Question 3

What forms the sensory/nervous elements of the eye?

Answer 3

Neural crest

Question 4

How is the otic formed?

Answer 4

Invagination and delamination (otic pit is invagination, placode cells migrate out/delaminate to form statoacoustic ganglion)
Also formed by ectoderm of pharyngeal arch 1

Question 5

How are CN V, VII, IX, and X formed?

Answer 5

Delamination
Neural crest (not placode) cells make up proximal ganglia of these nerves; placodes make up distal ganglia

Question 6

When does the primary palate and face form?

Answer 6

4-6 weeks

Question 7

When does the secondary palate form?

Answer 7

6-12 weeks

Question 8

Define: merging

Answer 8

Mesenchyme proliferates to eliminate a groove

If the epithelium is included, then facial cleft or cyst will occur

Question 9

Define: fusion

Answer 9

Contact of epithelium-covered surfaces across a gap, removing the epithelium (either by apoptosis, stretch, or EMT)

Question 10

What does the periprosencephalon form?

Answer 10

Frontonasal processes (lateral nasal; medial nasal)
Forehead
Nose
Philtrum

(can be affected by cell proliferation issues)

Question 11

What is formed by Pharyngeal Arch 1?

Answer 11

Mandibular Process
Maxillary Process
Oropharyngeal Membrane
Cheek
Chin
Lips

Affected by cell migration issues.

Question 12

What is the oropharyngeal membrane made out of?

Answer 12

Communication between foregut and amniotic cavity - formed by ectoderm-endoderm

Question 13

What is the oronasal membrane made out of?

Answer 13

Ectoderm-ectoderm

Pulled apart at 6 weeks (eat b4 6mell)

Question 14

What is a “typical” cleft? An “atypical”?

Answer 14

Typical = MNP+Lateral Maxillary P fusion issue
Atypical = merging issue

Question 15

When do the pharyngeal arches form and disappear?

Answer 15

20-35 days (between forebrain and heart developmeent)

Question 16

What are pharyngeal arches made out of?

Answer 16

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)

Question 17

Define: Pharyngeal Arch I

Answer 17

Rhombomeres 1,2
No Hoxx gene
Artery disappears
Creates CN V, muscles of mastication, malleus, incus, Merckel’s cartilage

Question 18

What does Pharyngeal Pouch I make?

Answer 18

Auditory tube
Primitive tympanic cavity
Middle ear

Question 19

What is the pharyngeal groove I derivative?

Answer 19

External auditory meatus

Question 20

Define: Pharyngeal Arch II

Answer 20

Rhomb 3,4
Hox gene
Artery disappears
Creates CN VII, muscles of facial expression, stapes, styloid process, lesser horn of hyoid

Question 21

What does Pharyngeal Pouch II make?

Answer 21

Palatine Tonsil

Question 22

Define: Pharyngeal Arch III

Answer 22

Rhom 6
Hox gene
Common carotid
CN IX - stylopharyngeus, body of hyoid

Question 23

What does Pharyngeal Pouch III form?

Answer 23

Thymus

Inferior Paraythyroid

Question 24

Define: Pharyngeal Arch IV

Answer 24

Rhom 7
Hox gene
R subclavian, L aortic arch
CN X and XI, laryngeal muscle, thyroid cartilage

Question 25

What are the derivatives of Pharyngeal Pouch IV?

Answer 25

Superior paraythroid gland | ultimbobranchial body

Question 26

How does the thyroid form?

Answer 26

NOT from the pharyngeal arches, but instead from endoderm | Derives from the foramen cecum (pit in tongue), migrates inferiorly to mid-neck

Question 27

Define: placode

Answer 27

Thickened ectoderm between epidermis and neural plate, which leads to the development of organs of special sense, the Trigeminal nerve, and the branchomeric nerves.

Question 28

What are the layers of the skin, and what would you find there?

Answer 28

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

Question 29

What holds the layers of the skin together?

Answer 29

Integrins

Question 30

When does the skin form?

Answer 30

Week 4: ectoderm can become CNS or skin Week 7-21: skin can become hairy or non-hairy (glabrous)

Question 31

What does the notochord create?

Answer 31

Nucleus pulposus of the intervertebral disks

Question 32

What does the neural tube create and what is it composed of?

Answer 32

It is thickened central ectoderm and creates the CNS (brain, spinal cord)

Question 33

What do neural crest cells create?

Answer 33

PNS (Schwann cells, sensory neurons, ANS ganglia) head structures melanocytes They are ectodermal cells lateral to the neural plate

Question 34

What forms the axial skeleton? Appendicular skeleton and sternum? Craniofacial skeleton?

Answer 34

Axial: somitic Append + Sternum: lateral mesoderm Craniofacial: neural crest

Question 35

When do the limbs form?

Answer 35

Limbs form in week 4 and rotate in weeks 6-8

Question 36

Define: stylopod

Answer 36

Most proximal element (humerus or femur)

Question 37

Define: zeugopod

Answer 37

2 elements (ulna/radius or tibia/fibula)

Question 38

Define: autopod

Answer 38

Phalanges/carpals/tarsals

Question 39

When does implantation occur? Gastrulation?

Answer 39

Implantation: week 2 Gastrulation: week 3

Question 40

Define: Morphogen

Answer 40

Signal that is long range with a dose-dependent response and feedback loop (ex - Nodal)

Question 41

Define: forward genetics

Answer 41

Phenotype to genotype

Question 42

Define: reverse genetics

Answer 42

Genotype to phenotype