Eye and Ear B Flashcards
What does control of shape of lens do>
Vissual accomodation
From what does the upper eylid develop from?
Lower Eyelid?
Upper: Frontonasal Process
Lower: Maxillary process
What occurs to eyelids during gestation, and late gestatin or postnatally?
Gestation: grow together and fuse
Late Gestaion or postnatally: reopen
3 distinct subdivisions of ear
External ear
Middle Ear
Inner Ear
What part of the ear derives from firsth pharyngeal cleft and surrounding mesenchyme?
External Ear- Auricle
External Auditory Meatus
Outer lining of Tympanic Membrane
What produces the exteranl Auditory meatus or Ear canal?
Inward expansion of First Pharyngeal Cleft
What produces the meatal plug?
Eptihelial cells at blind end of cleft can grow and produce this plug
What does the outer portion of tympanic membrane form from?
Outer ectodermal lining at bottom of Ext. Aud. Meatus
What comprises eardrum?
Inner Endodermal Lining from pouch
Mesenchyme between outer membrane and inner one
What do auricles develop from?
Mesenchymal tissue in the First and Second pharyngeal arches that surround the first pharyngeal cleft
Explain auricle development
Observed as nodules or “auricular hillocks” that enlarge, change shape and fuse in a very species specific manner
Move from base of neck to more definitive location
What is the middle ear made up of?
Tympanic Cavity
Auditory Tube
Middle Ear Ossicles
Middle Ear muscels
What is the partition between the external and middle ear?
Tympanic membrane (eardrum)
What does the dorsal blind end of First Pharyngeal Pouch give rise to?
Auditory of Eustachian Tube and primitive Tympanic cavity
What are ossicles derived from?
Mesenchyme of First and Second Pharyngeal Arches
Ossicles and their derivation
Malleus (Hammer) : 1 Pharyngeal Arch
Incus (Anvil): 1 Pharyngeal Arch
Stapes (Stirrup): 2nd pharyngeal arch
Muscles related to Ossicles
Tensor tympani - from 1st arch innvervated by Cranial Nerve V
Stapedius - From 2nd arch and innervated by Cranial Nerve VII
What does the inner ear consist of?
Membranous labyrinth
Vestibular and Acoustic Ganglia associated with Vestibulocochlear nerve VIII
What does the membranous labyrinth consist of?
Vestibulocochlear Organ
What is the Vestibulocochlear Organ involved in?
Hearing
Balance
What does the inner ear arise from?
Paired thickenings of ectoderm (octic placodes)
What occurs to oticc placodes?
Invaginated placodes pinch off into otic vesicles that separate from ectoderm
Vessicles fill with endolymph fluid
Cells bud off the otic vesicle epithelium forming ganglia
What does the first elongation of inner ear form?
Endolymphatic duct
What two regions form in otic vesicle?
Utricle (dorsally)
Saccule (Ventrally)
What develops from Utricle portion of otic vessicle?
Semicircular ducts
What form at the ends of each semicircular duct?
Ampullae
What are ampullae
Sensory organs of balance
What forms from the ventral part of the otic vessicle?
Conchlear duct
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