PNS Final - Special Sense Organs

What structures are derived from neuroectoderm of forebrain?

Retina and pigmented structures

What structures are derived from surface ectoderm?

Lens and cornea

What structures are derived form neural crest mesenchyme?

Sclera

What structures make up the fibrous tunic?

Cornea and sclera

What is the importance of the firmness of the sclera?

increase in pressure does NOT result in bulging

What structure is where extraocular muscles attach?

Sclera

What is the transition between the sclera and the cornea?

Limbus

What is the primary refractor structure?

Cornea

What is the term for an irregularity in the shape of the cornea?

Astigmatism

What is the thickest layer of the cornea?

Substantia propria

What part of the vascular tunic is thin with rich blood supply?

Choroid

What structure produces aqueous fluid that fills the anterior segment of the eye?

Cillary body

What kind of autonomic supply does the ciliary muscle have?

Parasympathetic

What is the result of contraction of the cilliary muscle?

Lens becomes more convex

What kind of autonomic supply does the sphincter pupillae have?

Parasympathetic supply

What kind of autonomic supply does the dilator pupillae have?

Sympathetic supply

The nervous tunic is derived from an outgrowth of what?

Diencephalon

What are the 5 cells involved in the vision pathway?

1. Photoreceptors

2. Bipolar cells

3. Ganglion cells

4. Lateral geniculate body

5. BA 17

What structure of the nervous tunic has NO photoreceptors?

Optic disc

What photoreceptors are found in the macula lutea?

Cones (NO RODS!)

What structure of the retina is the center of the fundus, area of the clearest vision, and only has cones?

Macula lutea

What substance fills the anterior segment of the eye?

Aqueous humor

What is the most important refractory component of the eye?

Cornea

What structure secretes aqueous humor?

Ciliary body

What is the path of aqueous humor in the eye?

Posterior chamber → through pupil → leaves via sclera venous sinus

What clinical condition involves increased fluid in the anterior segment?

Glaucoma

What clinical condition involves loss of resiliency of the lens?

Presbyopia

What clinical condition involves the lens becoming less and less transparent?

Cataracts

What is the vestigial structure that connects the optic nerve and posterior aspect of the lens?

Hyaloid canal

What did the hyaloid canal contain in utero?

Hyaloid artery

What lacrimal structure secretes tears via excretory ducts?

Lacrimal gland

What lacrimal structure drains tears into the lacrimal sac?

Lacrimal ducts

What structure drains tears into the inferior nasal meatus?

Nasolacrimal duct

Where are lacrimal ducts found?

Below and medial to th eyeball

What does the nasolacrimal duct drain into?

Inferior nasal meatus

What glands are modified sebaceous/oil glands that secrete an oily substance to decrease tear evaporation?

Tarsal glands

How many short ciliary arteries are there?

6-12

How many anterior ciliary arteries are found in an eye?

6-8

What artery is the ONLY artery to supply the retina?

Central retinal artery

What nerve provides sensory supply from the ciliary body, iris, and cornea?

Long ciliary nerve

What nerves supply sensory to the eyeball?

Short ciliary nerves

What structure is derived from the ventral mandibular cartilage?

Malleus

What structure is derived from 1st pharyngeal arch?

Incus

What structure is derived from the 2nd pharyngeal arch?

Stapes

What structure is derived from interstitial mesoderm?

Tympanic membrane

What glands are found around the external acoustic meatus?

Ceruminous glands (modified sweat glands)

Where does the external acoustic meatus terminate?

Tympanic membrane

What are the extrinsic ear muscles?

Anterior, superior, and posterior auricular muscles

What are the intrinsic auricular muscles?

Helicus major/minor, tragicus, antitragicus, transverse muscle of auricle, and oblique muscle of auricle 

What nerves provide sensory supply to the external ear?

Auriculotemporal (V3)

Auricular N (CN 10)

Great auricular nerve (cervical plexus)

What is the smallest muscle in the body?

Stapedius

What is the opening that the stapedius tendon passes through?

Pyramidal eminence

Where does the tympanic branch of CN 9 enter the ear?

Floor/jugular wall - carries general sensory and pre para fibers

What is the impression made by the cochlea on the labyrinthine/medial wall?

Promontory

On what middle ear boundary are the promontory, oval window/stapes interface, and round window?

Labyrinthine/medial wall

Where does the stapes attach?

Oval window

Where is there communication with the scala tympani and NO bone?

Round window

T/F: there is NOTHING separating the tympanic cavity from the epitympanic recess?

True

What nerve supplies the stapedius?

Nerve to stapedius - CN 7

What nerve supplies the tensor tympani?

Medial pterygoid nerve - V3

What nerves carry vasomotor and secretomotor fibers from SCG by way of internal carotid plexus?

Caroticotympanic nerves

What are the three parts of the inner ear/labyrinth?

Cochlea, vestibule, semicircular canals

Which diamond is bony?

Solid

Which diamond is membranous?

Open

What semicircular structure makes up the bony labyrinth?

Semicircular canal

What semicircular structure makes up the membranous labyrinth?

Semicircular duct

What part of the vestibular labyrinth connects the utricle and saccule?

Utricosaccular duct

What part of the vestibular labyrinth connects the saccule with the cochlear duct?

Ductus reuniens

What is the bony center of the cochlea?

Modiolus

How many times does the cochlea wrap around the modiolus?

2.5 to 2.75 times

What is the apex of the cochlea?

Cochlear cupula

Where do the scala vestibuli and scala tympani communicate with each other?

Helicotrema

What is above the cochlear duct and filled with perilymph?

Scala vestibuli

What forms the base of the scala vestibuli?

Oval window

What structure is below the cochlear duct and filled with perilymph?

Scala tympani

What structure makes up the base of the scala tympani?

Round window

What structure is located on the floor of the cochlear duct?

Spiral organ

What is the spiral organ attached to?

Basilar/spiral membrane

What is the order of transmission of sound?

External acoustic meatus → tympanic membrane vibrates → middle ear ossicles → oval window → perilymph of scala vestibuli/tympani → round window → vibrations of perilymph cause basilar membrane to vibrate → receptors in spiral organ are stimulated → cochlear nerve

What nerve is made of axons from the spiral organ?

Cochlear nerve

How much do the ossicles of the middle ear amplify fibrations?

1.2 times

How much does the foot of the stapes amplify the vibrations?

17 times

What structure allows the saccule to communicate with the cochlear duct?

Ductus reuniens

What movements does the utricle detect?

Centrifugal and linear accelerations in any plane

What movements does the saccule detect?

Linear accelerations in vertical and A-P planes

T/F: All structures of vestibular labyrinth contain endolymph.

True

What are the sense organs in the utricle and saccule called?

Maculae

What are the sense organs in the semicircular ducts called?

Cristae

Where does the superior branch of the vestibular nerve receive info from?

Anterior/lateral semicircular ducts

utricle

Voit’s nerve from saccule

What branch of the vestibular nerve receives information from Voit’s nerve (from saccule)?

Superior branch

Where does the inferior branch of the vestibular nerve receive information from?

Posterior semicircular ducts, saccule

The internal auditory artery is a branch of what artery?

Basilar artery

What vessels supply the labyrinth?

Internal auditory artery and stylomastoid artery