Special Senses Flashcards
What are the four types of tongue papillae?
Filiform
Fungiform
Foliate
Circumvallate
Which papillae has no taste buds?
Filiform
Structure of taste bud
Approx 50 microns in diameter
Contain about 50 specialised cells in a barrel shaped structure
Small apical taste pore at surface
What are the 3 cell types present in a taste bud?
Sensory cells
Support cells
Basal cells
Structure of sensory cells in taste bud
Apical microvilli with chemical receptors at the apical pore
Role of basal cells in taste bud
Act as stem cells for sensory and supporting cells which have a lifespan of 10-14 days
How do taste buds work?
An appropriate chemical enters the taste pore and binds its receptor
Neurotransmitter is released from the sensory cell
Sensory nerve endings stimulated within taste bud
What are the 5 principal tastes?
Sweet Sour Bitter Salty Umami
What is olfactory epithelium?
Pseudostratified columnar with receptor cells, support cells and basal cells
Role of support cells in olfactory epithelium?
Provide mechanical and metabolic support to the neurons
Role of basal cells in olfactory epithelium?
Stem cells
Structure and role of receptor cells in olfactory epithelium?
Have an olfactory vesicle that extends above epithelium with 10-20 motile cilia attached
Receptors located on cilia respond to odorants that we can detect and depolarise the cell, producing action potentials
Structure of support cells in olfactory epithelium?
Numerous apical microvilli
Secrete odorant binding proteins
What does the olfactory mucosa consist of?
Olfactory epithelium and underlying lamina propria
What does the olfactory mucosa lamina propria contain?
Connective tissue
Blood vessels for warming the air
Bowman’s glands which produce secretion that dissolves odorants
Bundles of axons from receptor cells
What covers the ear canal?
Hairy skin with sebaceous glands and modified apocrine sweat glands (ceruminous glands) which produce cerumin, a yellowish waxy substance
What are the three layers of the tympanic membrane?
Outer - thin epidermis
Middle - collagenous connective tissue
Inner - simple cuboidal
Properties of the cochlea
2.5 turn spiral
Central core - modiolus
Ganglion of bipolar nerve cell bodies - spiral ganglion
3 compartments - scala vestibuli, cochlear duct, scala tympani
Helicotrema - where SV and ST communicate with eachother at very tip of cochlea
Sounds tranduced by hair cells in organ of corti
Where is the organ of corti?
Sits on basilar membrane which gets longer and more flexible as you move toward the tip of the cochlea
Why do different areas of cochlea respond to different sounds?
The lengthing of the organ of corti
Organ of corti near tip of cochlea - reponds to lower frequencies
Organ of corti near base of cochlea - higher frequencies
Structure of the organ of corti
Two sets of hair cells:
- row of 3-5 outer hair cells
- single row of inner hair cells
each with phalangeal support cells
How is sound transferred through the organ of corti?
Vibrations in basement membrane cause stereocilia on apical ends of hair cells to move against tectorial membrane
Deformation of stereocilia opens ion channels that depolarise hair cell
Cells then release neurotransmitters that cause action potentials in the terminals of the spiral ganglion neurons
What do hair cells in the utricle and saccule detect?
Head position
What do hair cells in the semicircular canals detect?
Movement
Structure of semicircular ducts?
Each duct contains a swelling called the ampulla within which is a sensory organ called the crista ampullaris
How does the cupola detect movement?
When the head turns the fluid bows the cupola which bends the stereocilia
This changes the amount of transmitter released by these cells
They have a resting output, so bending one way increases and the other decreases
What are the utricle and saccule?
Two swellings in the vestibule
Fluid filled spaces lined by simple cuboidal epithelium everywhere except a small patch of sensory epithelium (the macula)
What is otoconia?
Crystals of calcium carbonate and protein embedded in a gelatinous layer in the utricle and saccule
