Ear Flashcards
What does the ear develops from?
The ear develops from the surface ectoderm and component of the first and second pharyngeal arch.
What serves as a primordium for development of the epithelia that line the membranous labyritnth of the internal ear?
The otic vesicle (Otocyst). (Invagination of surface ectoderm that appears on each side of the myelencephalon).
where does the incus, malleus and stapes develop from?
The malleus and incus develops from the 1st pharyngeal arch, and the stapes from the second.
What are the two opening in the medial wall of the middle ear?
The oval window (vestibular).
The round window (cochlear).
What ossicle attaches to the tympanic membrane?
The malleus.
What are the 3 layers of the tympanic membrane?
- The skin of the external acoustic meatus.
- A core of radially and circularly arranged collagen fibers.
- The mucus membrane of the middle ear.
What causes conductive hearing loss?
Diseases that affect tympanic membrane or ossicles.
what bone attaches to the oval window?
The stapes, footplate of which fits into the oval window, acts like a small piston on the cochlear fluid.
Contraction of this muscle increases tension on the tympanic membrane. What muscle is this?
The tensor tympanic muscle.
Contraction of this muscle tend to dampen the movement of the stapes at the oval window.. What is this muscle?
The stapedius muscle.
What is the attenuation reflex?
The stapedus and tensor tympanic muscles of the ear are responsible for the attenuation reflex. Contraction of the muscles make the chain of ossicles more rigid, thus reducing the transmission of the vibrations to the internal ear. This reflex protect the internal ear from the damaging effects of very loud sound.
What connects the middle ear to the nasopharynx?
What is is lined with?
The auditory tube, it is lined with pseudostratified columnar epithelium. 1/5 is composed of goblets cells.
What causes otitis media?
It is common for infections to spread from the pharynx to the middle ear via the auditory tube, common cause of otitis media.
What does the endolymphatic space contain?
Endolymphatic space are contained within the membranous labyrinth. The endolymphis similar in composition to the intracellular fluid (it has a high K+ concentration and a low Na+ concentration).
What does the perilymphatic space contain?
The perylymphatic space lies between the wall of the bony labyrinth and the wall of the membranous labyrinth. The perilymph is similar in composition to the ECF. (Low K+, high Na+).
