The eye, ear, nose and mouth Flashcards
light reflects off an object and first strikes the eye at
cornea (thin, protective layer, corneal epithelium)
- non vascular and made from collagen
where does light go from the cornea?
it enters the anterior cavity : which is filled with aqueous humour.
where does it go from the anterior cavity?
it enters the lens, the ciliary muscle circles the lens.
the light is then focused through the gel like vitreous humour and onto the retina
what does the retina cover?
it covers the inside of the back of the eye. it has light sensitive cells called rods and cones.
the tips of these cells contain light sensitive photochemical called pigments that go through a chemical change when one of their electrons is struck by a single photon.
what do rods do?
they cannot distinguish color
what about the cones?
they can distinguish color , but there are 3 types of cones each with a different pigment that is stimulated by a slightly different spectrum of wavelengths.
what part of the eye has mostly cones in it ?
fovea!
what is the iris?
coloured portion of the eye that creates an opening called the pupil. the iris is made from circular and radial muscles.
The ear is divided into what three parts?
the outer ear
the middle ear
the inner ear
what is the auricle or the pinna?
skin and cartilage flap that is called the ear. The auricle functions to direct the sound wave into the external auditory canal.
where does the external auditory canal do?
it carries the wave to the tympanic membrane or eardrum . the tympanic membrane begins the middle ear.
what 3 small bones does the middle ear contain?
malleus
incus
stapes
these 3 act as a lever system translating the wave to the oval window where pressure is increased
wave is then transferred to what resistant fluid within the inner ear?
perilymph
what is the wave moving through in the inner ear?
through the cochlea - where the alternating inc and dec in pressure moves the vestibular membrane in and out.
this movement is detected by the hair cells of the organ of cortisones and tranduced into neural signals, which are sent to the brain.
what else is in the inner ear and what’s the function?
semicircular canals. - responsable for balance. each canal has hair cells and fluid. when the body moves and position changes with respect to gravity , the momentum of the fluid is changes impacting on the hair cells and the body senses motion.
