Anatomy and Cell Biology 3309 Lecture Notes - Lecture 36: Semicircular Canals, Membranous Labyrinth, Vestibular Nerve
22 May 2018
School
Department
Professor
Histology 3309
Ear II
Objectives
1. Describe the organization of the membranous labyrinth
2. Describe how the vestibular apparatus functions
3. Describe the difference between the crista and the maculae in terms of structure and function
4. Describe the importance of the vestibular system for vision
The Inner Ear
- Collectively called the membranous labyrinth
o The structure formed by membranes suspending within the inner ear
o The membranous labyrinth is one continuous system filled with endolymph
- Vestibular System: 2 sacs (utricle and saccule) + 3 semi circular canals
o This is filled with endolymph
- There is innervation to different parts of the inner ear
o Innervation to the organ of corti→innervated by the auditory nerve part of the 8th nerve
o Innervation to the saccule and utricle →innervated by the 8th cranial nerve
▪ Sot he 8th cranial nerve is made of the vestibular nerve and the auditory nerve
but the saccule and utricle are innervated by the vestibular nerve part of the 8th
nerve
▪ There are 2 sensory structures in the saccule and utricle called macula utriculi
and macula sacculi
o Innervation to the semicircular ducts
▪ Semicircular ducts have thickenings called ampulla
▪ In the ampulla, there are hair cells (sensory organs) which are also innervated
by the vestibular nerve
- Auditory System: Cochlea containing the Organ of Corti
The Membranous Labyrinth
- The membranous labyrinth is the purple structure in the bottom left image
- The blue structure would be the osseous labyrinth (opening within the bone filled with
perilymph)
- So anything that is blue is filled with perilymph and everything that is purple is filled with
endolymph
find more resources at oneclass.com
find more resources at oneclass.com
- So the inner ear contains the auditory and the vestibular system
- It is continuous with the other portions of the inner ear that make up the vestibular system
The Vestibular System
- 3 Semicircular canals (ducts)
o every time you rotate in an axis, the canal moves
▪ as it rotates, the endolymph lags behind due to inertia so it starts to flow
through the semicircular duct
▪ this flow is picked up by hair cells
o respond to rotational movement of the head and body
o all connect to the utricle
o dilations of the semicircular canals are ampullae
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Objectives: describe the organization of the membranous labyrinth, describe how the vestibular apparatus functions, describe the difference between the crista and the maculae in terms of structure and function, describe the importance of the vestibular system for vision. Collectively called the membranous labyrinth: the structure formed by membranes suspending within the inner ear, the membranous labyrinth is one continuous system filled with endolymph. Vestibular system: 2 sacs (utricle and saccule) + 3 semi circular canals: this is filled with endolymph. There is innervation to different parts of the inner ear. Innervation to the organ of corti innervated by the auditory nerve part of the 8th nerve. Innervation to the semicircular ducts: semicircular ducts have thickenings called ampulla. In the ampulla, there are hair cells (sensory organs) which are also innervated by the vestibular nerve. The membranous labyrinth is the purple structure in the bottom left image.
