Flashcards in Workbook - Eye and ear Deck (92):
Where is the optic nerve and optic disc located?
In the posterior aspect of the eye.
What is the area anterior to the lens called?
The anterior chamber.
What occupies the anterior chamber?
Aqueous humor (fluid).
-enters from the posterior chamber through the pupil
Where is aqueous humor absorbed from the anterior chamber?
Into the scleral venous sinus.
What structures does light pass through before reaching retinal photoreceptors? (6)
>> anterior chamber (aqueous humor)
>> posterior chamber (aqueous humor)
What is the conjunctiva?
Epithelium over exposed sclera and inner eyelids.
What is the function of the conjunctiva?
-produces mucous and tears
What is the function of the sclera (white of the eye)?
-Protective covering (contains collagen and elastin)
-Muscular attachments (extraocular muscles)
What is the function of the iris?
-Controls the size of the pupil (autonomic control)
-Divides ant/post compartments
Which muscles control the size of the pupil? (2)
-Sphincter pupillae (contraction constricts pupil)
-Dilator pupillae (contraction dilates pupil)
What is the circular muscle of the iris?
What is the radial muscle of the iris?
What is the nerve supply to the sphincter pupillae?
Occulomotor (III) nerve.
What is the nerve supply to dilator pupillae?
Superior cervical ganglion (T1).
What is the nerve supply to the ciliary muscle in the ciliary body?
Occulomotor (III) nerve .
What effect does contraction of the ciliary body have upon the lens?
Contraction causes the lens to become more convex.
-improves focus of closer objects
What are cataracts?
Clouding of the lens.
-clumps of protein/pigment
What are the main functions of the ciliary body? (2)
-Muscles control the shape of the lens
-Produces aqueous humor (>> ant compartment)
What is the function of the aqueous humor?
Helps to maintain the shape of the cornea.
>> refractive properties of the eye
What is the route of aqueous humor before being reabsorbed into the blood stream?
>> post chamber
>> ant chamber
>> trabecular meshwork
>> scleral venous canal
>> episcleral veins
What is glaucoma?
Build up of pressure in eyes leading to decreased vision.
-can damage optic nerve
What causes glaucoma?
Problems with drainage of aqueous humor.
What are the main functions of the choroid layer of the eyeball? (4)
-Nourishes outer laters of retina (v. vascular)
-Regulates retinal heat
-Controls intraocular pressure
-Contains dark pigment >> absorbs light
What lines most of the posterior compartment of the eye?
What structures does the retina contain?
-1st and 2nd order neurons
What are the layers of the retina? (2)
-Outer pigment cell layer
-Multi layered neural retina
What is the outer pigment layer of the retina composed of?
Single layer of cuboidal epithelial cells with melanin filled microvilli.
List 4 functional differences between rod and cone cells.
-responds to dim light, insensitive to colour
-20x more numerous
-predominantly in peripheral parts
-multiple served by 1 bipolar neuron
-colour vision (high visual acuity)
-more abundant centrally (fovea)
-each has its own bipolar neuron
What type of visual cell has high visual acuity and is responsible for colour vision; rod cell or cone cell?
Which type of visual cell is more numerous; rod cell or cone cell?
Which type of visual cell is more abundant centrally (fovea); rod cell or cone cell?
Which type of visual cell is located predominantly in the peripheral parts of the eye; rod cell or cone cell?
Which type of visual cell has its own bipolar neuron; rod cell or cone cell?
Where do the axons of the retinal ganglion cells run?
Over the inner surface of the retina.
Where do the axons of retinal ganglion cells converge?
On the optic disc/optic papilla.
>> turn outwards to form the optic nerve
Why is the optic papilla a blind spot on the retina?
It contains no photoreceptors.
What is papilloedema?
Optic disc swelling due to increased ICP.
How does papilloedema arise?
Increased ICP due to tumour/trauma/haemorrhage
>> increased pressure in subarachnoid space surrounding optic nerve
>> swelling and protrusion
What are other causes of optic disc swelling?
UNILATERAL - optic neuritis, ischaemic optic neuropathy
BILATERAL - malignant hypertension, toxic otic neuropathy
What is lateral to the optic disc?
-yellow pigmented zone
What is the specialised region in the centre of the macula lutea called, and what occurs here?
-the point on the retina where the image of the object at the centre of the visual axis falls
How is the fovea specialised for visual acuity?
-Lots of cone cells, few rod cells
-Retinal avascular zone (no dispersion of light)
What are the main blood supplies to the retinal cells? (2)
-Central retinal artery
-Choroidal blood vessels
(Radiate from optic nerve)
What is a detached retina, and why must it be repaired rapidly?
Retina detaches from underlying choroid tissue.
-faster repair >> less likely to lose vision
What structures do sound waves pass through before reaching the auditory receptors?
External acoustic meatus
>> tympanic membrane
>> oval window vibrates
>> moves fluid in cochlea
>> moves cochlea duct fluid
>> basilar membrane vibrates
>> stimulates receptor cells
>> cochlear part of vestibulocochlear nerve
What is the function of the tympanic membrane?
Sound waves cause the membrane to vibrate >> transmits vibrations to the ossicles and middle ear.
What bones make up the ossicles? (3)
What is the function of the ossicles?
Transmit vibrations of the tympanic membrane to the oval window >> cochlea.
What is the function of the Eustachian tube?
Connects the middle ear to the nasopharynx.
-maintains pressure in the middle ear and clears mucus
What is the oval window?
Membrane at start of cochlea. Contacted by stapes >> sound to inner ear.
What is the round window?
Membrane at the end of the cochlea.
-allows movement of perilymph in cochlea when the stapes hits the oval window
Where is ear wax produced?
By skin in the external auditory canal.
What is wax composed of?
Dead skin cells, hair and sebaceous gland secretions.
How does wax travel along the ear canal?
Epithelial migration aided by jaw movements.
How is the tympanic membrane viewed clinically?
Using an otoscope.
What is the chorda tympani a branch of?
What is the function of the chorda tympani?
Taste from ant 2/3 of tongue and PS to salivary glands.
What type of epithelium lines the middle ear?
What opening connects the middle ear to the mastoid air cells posteriorly?
Why is facial nerve damage a potential complication of middle ear infection?
Chorda tympani passes through temporal bone.
-infection can >> compression
What is the function of tensor tympani?
Contraction pulls the handle of malleus medially >> dampens down sound.
What is the nerve supply to tensor tympani?
Mandibular branch of the trigeminal nerve (V3).
What is the function of stapedius?
Contraction pulls stapes posteriorly >> prevents excessive vibrations.
What is the nerve supply to stapedius?
Branch of the facial (VII) nerve.
What is another name for the inner ear?
Where is the inner ear located?
In the petrous part of the temporal bone.
What fluid does the cochlea contain?
What fluid does the cochlear duct contain?
What are the types of receptor in the walls of the membranous labyrinth? (3)
-Spiral organ (of Corti)
What type of receptor are maculae and christae ampullaris?
What type of receptor is the spiral organ of Corti?
In which regions of the membranous labyrinth are the maculae located?
In the vestibule - utricle and saccule.
What type of sensory information are the maculae concerned with?
Static position of the head and balance.
In which regions of the membranous labyrinth are the christae ampullaris located?
Ampulla (semicircular ducts).
What type of sensory information are the christae ampullaris concerned with?
Changes in direction and rate of movement of the head.
-balance, position, equilibrium
What are the structural similarities between the maculae and christae ampullaris? (3)
-Hair cells of same morphological type (I & II)
-Hair cells have numerous seterocilia
-Hair cells are supported by a single layer of columnar cells
In which nerve do the 1* sensory axons associated with the maculae and christae ampullaris run?
Vestibular part of the vestibulocochlear (VIII) nerve.
What can damage to the peripheral vestibular system lead to?
What is nyastagmus?
Rapid involuntary eye movements.
What is vertigo?
Dizziness and perception of motion.
What is the cochlear duct?
The part of the membranous labyrinth in the bony cochlea (part of the bony labyrinth).
Where is the spiral organ of Corti located?
In the wall of the cochlear duct.
How many times does the cochlea duct spiral round?
What does the central region of the cochlea enclose?
The spiral ganglion.
-composed of cell bodies of 1* auditory neurons
What does vibration of the basilar membrane cause?
Causes hair cells to be deformed against the tectorial membrane >> depolarisation of sensory hair cells and generates an action potential in sensory nerve fibres.
Which region of the basilar membrane vibrates maximally in response to high frequency sound?
Base (proximal, near oval window).
Which region of the basilar membrane vibrates maximally in response to low frequency sound?
Apex (near helicotrema).
Where are the cell bodies of the sensory fibres that contact the hair cells?
Which cranial nerve do 1* sensory fibres stimulated by the basilar membrane join?
Cochlear part of the vestibulocochlear nerve.
Where does the vestibulocochlear nerve enter the brainstem?
Internal acoustic meatus.
What is conduction deafness?
Sound cannot pass freely to the inner ear.