Histology: Ear

Question 1

Thickening of surface ectoderm that will eventually invaginate and form the inner ear.

Answer 1

Otic Placode

Question 2

Portion of the membranous labyrinth that proliferates and forms the semicircular canals.

Answer 2

Utricle

Question 3

Portion of the membranous labyrinth that proliferates and forms the cochlear duct.

Answer 3

Saccule

Question 4

Fluid found inside the membranous labyrinth.

Answer 4

Endolymph

Question 5

Fluid found within the bony labyrinth that is the same composition with CSF.

Answer 5

Perilymph

Question 6

Portions of the bony labyrinth that surround the cochlear duct and are continous with each other.

Answer 6

Scala Vestibuili

Scala Tympani

Question 7

Pharyngeal arches where malleus, incus, and stapes form.

Answer 7

Malleus and Incus –> 1st arch

Stapes –> 2nd arch

Question 8

Name the 3 layers of the tymapnic membrane and the 3 germ layers from which each is derived.

Answer 8

1. Cuticular: ectoderm
2. Fibrous: mesoderm
3. Mucous: endoderm

Question 9

Structure that transmits the mechanical wave signal from the stapes to the scala vestibuli as fluid waves.

Answer 9

Oval Window

Question 10

Name the 3 types of hair cells and where each is located in the inner ear.

Answer 10

1. Cristae Ampularis: semicircular canals
2. Macula: urticle and saccule
3. Organ of Corti: cochlear duct

Question 11

This is the major auditory ganglion that wraps around the modiolus inside the cochlea.

Answer 11

Spiral Organ

Question 12

What are the Spiral ligaments and the Stria Vascularis?

Answer 12

Spiral Ligaments: support the cochlear duct and stabilize it to the bony labyrinth.

Stria Vascularis: component inside the cochlear duct and is actually an extension of the spiral ligament. The main function of these cells is to secrete endolymph.

Question 13

2 types of hair cells that make up the organ of corti and which is more crucial for auditory sensation?

Answer 13

1. Outer Hair cells (rows of three)
2. Inner Hair cells (single row)
   IHC more important for hearing.

Question 14

What is the function of the basilar membrane?

Answer 14

The fluid waves that are transmitted thru the oval window from the stapes travel thru the scala vestibuli and scala tympani and stimulate the basilar membrane.

The basilar membrane transmits the fluid signal to the organ of corti so the information can be analyzed.

Question 15

Describe the tonotopy of the basilar membranes in the cochlear duct.

Answer 15

The basilar membranes that pick up the highest frequency are located at the base of the duct and the ones that pick up the lower frequency are located at the apex.

This is because the basilar membrane increases in length as you progress toward the apex.