1. Head Primordia

Question 1

Where does Head Mesenchyme come from?

Answer 1

NEURAL CREST!! (Not primitive streak)

Question 2

What are the primordia for each of the cranial nerves?

Answer 2

I - olfactory placode
II - optic cup
III, IV, VI - pre-otic somitomeres
V - arch 1
VII - arch 2
VIII - otic placode
IX - arch 3
X - arch 4
XI - somatic mesoderm (SC)
XII - Postotic somites

Question 3

What are the ectodermal derivatives for each of the: neural tube, surface covering, and placodes?

Answer 3

Neural tube: Brain, SC, optic cup
Surface covering: stomodeum, pharyngeal grooves
Olfactory - CN I/olfactory epithelium
Optic Cup (around lens placode) - retina and CN II
Otic Placode - inner ear (cochlea and semicircular canals) and CN 8

Question 4

Where do the different parts of the ear develop?

Answer 4

Otic placode -> otocyst -> cochlea, semicircular canals, CN8
First pharyngeal groove -> ext auditory meatus
First pharyngeal pouch -> middle ear cavity

Question 5

Where do the different parts of the eye develop?

Answer 5

Optic Cup -> both parts of retina
Lens placode -> lens
Head mesenchyme -> rest of eyeball

Question 6

Name each of the pretrematic nerves and the definition of pretrematic nerve

Answer 6

Provide extra sensory innervation to the territory preceding it
Arch 1: V1 - opthalmic division, sensory to orbit/forehead
Arch 2: chorda tympani (VII) to tongue for taste/parasymps
Arch 3: tympanic nerve (IX) to middle ear cavity

Question 7

What are each of the arch cartilage derivatives?

Answer 7

1: malleus, incus
2: stapes, styloid process of temporal bone, stylohyoid ligament
3: Greater cornu (horn) of hyoid bone
4/6: thyroid/cricoid cartilages

Question 8

What are each of the arch muscle derivatives?

Answer 8

1: Jaw muscles (V3 innervated)
2: SFM
3: 1 tiny, functionally insignificant muscle
4/6: larynx/pharynx muscles to open/close vocal cords

Question 9

What are the endodermal derivatives of the foregut and each of the pharyngeal pouches?

Answer 9

Foregut -> larynx, pharynx, trachea, thyroid gland

Pouch 1: middle ear cavity
Pouch 2: palatine tonsils
thymus and parathyroid glands

Question 10

How do Sympathetic Nerves reach the head? what is its function?

Answer 10

Origin: Thoracolumbar Outflow T1-L2 ventral roots
Synapse: Superior Cervical Ganglion and follow arteries to their targets

Fx: artery smooth muscle, sweat glands, hair muscles, pupil dilator muscles

Question 11

How do Parasympathetic Nerves reach the head?

Answer 11

Craniosacral Outflow = from CNS

CN 3, 7, 9, 10 all carry parasymp fibers, synapse in ganglia to join branches of CN V to their targets