NB8-2 - Special Senses - Ear Flashcards
What is the significance of this area
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The inner ear structures are located within this structure
Describe the structure, composition, and function of the tympanic membrane.
External side is thin skin. Inner side is simple cuboidal epithelium. Middle is collagen fibers. Functions in transmitting vibrations of sound pressure waves to the malleus.
List and describe the composition of the different fluids within the bony labyrinth.
Endolymph - fluid within the membranous labyrinth with similar composition to intracellular fluid
Perilymph - fluid outside of the membranous labyrinth with similar composition to ECF and CSF
Differentiate semicircular canals from semicircular ducts.
Semicircular canals are part of the bony labyrinth while the ducts are part of the membranous labyrinth.
What is the vestibule of the inner ear? What does it consist of and what does it contain?
The vestibule is the large irregular central cavity of the bony labyrinth from which the cochlear duct and ampullae of the semicircular canals arise. It also where the oval and round windows are located.
The membranous labyrinth components within are the utricle and saccule
List the structures and cells found within the membranous labyrinth. Mention where within the labyrinth they are found and their general functions.
There are 2 primary types of cells - sensory hair cells and supporting cells. Supporting cells are found throughout the membranous labyrinth while sensory hair cells are concentrated to form sensory organs in 6 places:
- One crista ampullaris in the ampullae of each of the three semicircular ducts. These are used to detect angular acceleration of the head. Horizontal detects rotation around a vertical axis (looking left and right). Superior (anterior) detects rotation in the sagittal plane (nodding head up and down). Posterior detects rotation in the coronal plane (touching ears to shoulders)
- One macula in the utricle and one in the saccule. These organs detect linear acceleration (not rotational) of the head and its orientation when it is not moving.
- One organ of corti in the cochlear duct for detecting sound
Describe the structure and composition of a crista ampullaris.
A crista ampullaris consists of mostly a layer of supporting cells on a basement membrane with hair cells nestled between the supporting cells. A nerve fiber penetrates the basment membrane and surrounds the basal part of the hair cell. The apical suface of the hair cell has rows of stereocilia projecting out past the supporting cell layer. Each row of sterocilia increases in height in a particular direction (polarity) with a single motile cilium, kinocilium, behind the tallest row. All of the stereocilia and kinocilia from all of the hair cells in a crista ampullaris are embedded within this gelatinous protein-polysaccharide mass called a cupula which projects into the lumen and is surrounded by endolymph.
Describe the structure and composition of macula.
The structure and composition is almost identical to that of the cristae ampullaris with a few key exceptions.
- Instead of a cupula, the stereocilia and kinocilia are covered in a more viscous polysaccharide material called the otolithic membrane
- The outer aspect of the otolithic membrane also contains crystalline bodies of calcium carbonate and protein called otoconia
Describe the structure and composition of the organ of corti.
The organ of corti consists of a single row of inner hair cells (closer to the modiolus), three rows of outer hair cells sitting on phalangeal cells, a row of inner and outer pillar cells in between, a tectorial membrane which the stereocilia is embedded in, the spiral limbus which the tectorial membrane is attached to, and the cells of Henson and Claudius at the periphery (function unknown). Refer to image
SC - stereocilia
Cu - cupula
Ep - epithelium
CT - connective tissue
Other arrow head is the tectorial membrane
SG - spiral ganglia
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