The senses Flashcards
what does the Ears do
Ears provide hearing and maintain body balance
Ear structure has 3 parts
- Outer ear
- Middle ear
- Inner ear
The outer ear functions
- The visible part of the ear
- Protects the inner structures from damage
- The passage for sound waves
functions of External auditory meatus - the
auditory canal
- Lined with ceruminous glands and hairs
- Filter out dust and foreign particles
functions of The tympanic membrane
(eardrum)
separates the auditory canal from the middle ear
The middle ear
1-Found within a cavity in the temporal bone
2-Has minute bones known as auditory ossicles
3-Auditory ossicles transmit sounds from
the tympanic membrane to the inner ear
The inner ear structure
1- ampulla
2- oval window
3- round window
The inner ear functions
- Responsible for hearing and balance
- Within the inner ear structures the vibrations of sound waves are translated into nerve impulses
- Semi-circular canals and vestibule help to maintain posture and balance
function of The eustachian tube
Connects the middle ear to the throat Maintains the atmospheric pressure of air within the ear Enables eardrum to vibrate as the soundwaves reach it
how does the inner ear work
The cochlea receives sound in the form of vibrations
* Vibrations cause the stereocilia to move.
* Stereocilia then convert these vibrations into nerve impulses which are taken up to the brain to be interpreted.
Eye structures
Eyelids
* Layers of tissue above and below the
front of the eye
* Protect the eyes through blinking
Eyelashes
* Line the edges of the eyelids
* Filter and trap substances e.g. dust
Sebaceous and mucous secretions
lubricate the eyelids
Lacrimal glands
secretes what
lacrimal fluid
what is lacrimal fluid function
- keeps the surface of the
eye moist - Prevents the cornea from
drying out
Parasympathetic stimulation of the lacrimal
glands causes
crying
what is The sclera
- A fibrous outer layer
- At the front of the eye it is continuous with the cornea
what is Conjunctiva
- A mucous membrane covering he front of the eye
- Also lines the inside of the eyelids
- Helps prevent damage and drying of the eye
- The eye is divided into 2 structures/chambers
1-Anterior chamber
* Between the cornea and the lens
* Contains the aqueous humour
2-Vitreous chamber
* Cavity behind the lens
* Filled with vitreous humour
* Both filled with fluids that maintain the pressure and shape of the eyeball
what is Pathway of light through the eye
1-Light enters through the cornea
2-Passes through the pupil
3-Iris controls the amount of light entering the eye
4-Lens refracts light rays
5-Light rays are focused on to the retina at the back of the eye
the lens Thickness controlled by
ciliary muscle
Thick =
nearby objects
Thin =
far away objects
what is The retina
- Forms the inner layer of the eye wall
- Contains photoreceptors
what is Macula lutea
- Near the centre of the retina
- Highly sensitive
- Contains millions of rods and cones
- Cones predominate in the fovea centralis
- Responsible for sharp, detailed central vision
The retina layers
1-Photoreceptor layer - rods and cones
2-Bipolar cell layer: Neurons that receive neurotransmitter from the photoreceptors & Synapse with ganglion cells
3-Ganglion cell layer: axons of neurons here form optic nerve that exits eye at optic disc (“blind spot” - no rods/cones)
what is Labyrnthitis
- An inflammation of the inner ear which can cause balance disorders
Symptoms of blepharitis include:
- sore eyelids
- itchy eyes
- a gritty feeling in the eyes
- flakes or crusts around the roots of the eyelashes
- red eyes or eyelids
- eyelids sticking together in the morning when you wake up
types of Blepharitis
1-Anterior blepharitis affects the outside front of the eyelid, where the eyelashes are attached. Common causes are bacteria (Staphylococcus) and scalp dandruff.
2-Posterior blepharitis affects the inner eyelid and is caused by problems with the oil glands in this part of the eyelid.
what is Cataracts
Clouding of the lens of the eye which leads to a decrease in vision
what is Glaucoma
A condition that damages the eye’s optic nerve
Can cause permanent vision loss or even total blindness
what is Myopia
Myopia (nearsightedness): can see near but not far
objects
- Eyeball is too long so lens cannot accommodate enough to focus images of distant objects onto retina
what is Hyperopia - farsightedness
- Distant images are brought to a point of focus behind the retina.
- Often due to a short eyeball
- Corrected by lenses that are convex
what is Astigmatism
- Asymmetry of the cornea and/or lens curvatures
- Get several points of focus on the retina
- Corrected by cylindrical lenses
what Diabetic retinopathy
- When high blood sugar levels cause damage to blood vessels in the retina.
- These blood vessels can swell and leak. Or they can close, stopping blood from passing through.
- Sometimes abnormal new blood vessels grow on the retina.
