anatomy of the eye & ear exercise 21, 22. the eye
TRANSCRIPT
ANATOMY OF THE EYE & EAR
Exercise 21, 22
THE EYE
ANATOMY OF THE EYE
■ Sophiticated systems that includes the work of:
■ Retina receptors
■ Pupil dilation and contraction
■ 6 oculomotor muscles
■ 12 cranial nerves
EXTERNAL EYE ■ Only about 17% of the eye is
visible
■ About 2.5 cm in diameter
■ Accessories / external features of the eye:
– Palpebrae - eyelids; evenly distribute tears across the surface of the eye to keep it moist
– Eyelashes
– Palpebral fissure – cleft between upper/lower eyelid
– Lacrimal caruncle – contains sebaceous/sweat glands
– Lateral / medial canthus – 2 points where the upper/lower eyelid meet
– Conjunctiva – thin mucous membrane that covers the eye / lubricates eye and contains vessels
Eye Glands / Ducts
■ Ciliary glands – modified sweat glands to lubricate the eyeball
■ Tarsal glands – secrete an oily lubricant to prevent eyelids from sticking together
■ Lacrimal glands – contains 12 excretory larcrimal ducts that secrete tears and lacrimal fluid
■ Lacrimal Apparatus
– Lacrimal fluid contains lysozyme fluid moves across eyeball surface and enters two openings in medial canthus superior / inferior lacrimal puncta lacrimal canals lacrimal sac nasolacrimal tract drains the tears into the nasal cavity
Eye Muscles – come back to haunt us
INTERNAL EYE ■ Fibrous tunic – dense connective outer layer tissue – Sclera – white part of the tunic that covers the eye – Corneal lambus – the border between sclera and cornea; contain canal of
Schlemm, – Cornea – NOT covered by sclera, transparent tissue where light enters the eye
■ Vascular tunic (uvea)– Iris (anterior)– Lens (posterior to iris) – focuses light – Ciliary body – where iris attaches – Pupil– Choroid (posterior) – melanin that absorbs light and prevents against reflection
■ Neural tunic (aka retina)– Pigemented part (outer layer)– Neural part – contains light-sensitive photoreceptors – Aqueous humor – maintains intraocular eyepressue and supplies nutritents to
lens/ cornea– Vitreous body – holds retina against choroid and prevents collapse
How does the pupil change size?
■ Pupillary sphincter muscles / pupillary dilator muscles
■ Parasympathetic vs Sympathetic innervation
Cellular Organization of the Retina ■ Neural part of the retina contains the photoreceptors
■ And 2 types of sensory neurons bipolar cells and ganglion cells
■ Photoreceptors – Rods – motion detection – Cones – visual acuity
■ Light pigemented area neural part photoreceptors bipolar cells ganglion cells axons converge at optic disc
■ Amacrine cells – communication between bipolar and ganglion cells
■ Horizontal cells – inhibit or facilitate communication b/w photoreceptors and bipolar cells
■ Macula lutea – contains many cones – Fovea (center of ML) – sharpest vision at this point / no rods here
Diseases of the Eye
■ Glaucoma
■ Diabetic Retinopathy
■ Conjunctivitis
■ Macular Degeneration
■ Sty
Marijuana and Glaucoma
■ THC causes the blood vessels in the eye to decrease
■ Therefore, reduced IOP levels
THE EAR
Anatomy of the Ear
■ External – direct sound waves
■ Middle – direct sound waves
■ Outer – balance and hearing
External Ear ■ Pinna, auricle – funnels sound waves into external acoustic
meatus tympanic membrane (eardrum)
■ Ceruminous glands – prevent dust and debris from entering the middle ear
Middle Ear
■ AKA tympanic cavity
■ Connected to the back of the upper throat by the auditory tube
■ Sound vibrations malleus incus and stapes pushes on the oval window (inner ear) stimulate auditory receptors
■ Tiny muscles – tensor typani and stapedius – Smallest skeletal muscles on the human body
Inner Ear – Regions ■ Cochlea – receptors
for hearing
■ Vestibule – receptive to static equilibrium
■ Semicircular canals – receptors for “dynamic equilibrium” (when body moves)
– Contain semicircular ducts that have a swollen ampulla that houses the balance receptors called cristae
Inner Ear – Regions ■ Vestibule
■ Contain utricle and saccule
■ Maintain maculae
■ Receptors that maintain static EQ
■ Suspended in a gel matrix which also contains statoconia (calcium carbonate crystals)
■ Gel + Statoconia = otolith
Inner Ear – Regions ■ Cochlea
■ 3 ducts in a spiral formation – chochlear duct
– Contains hair cells that are sensitive to vibrations
– Contains sensory receptor, organ of Corti
■ Inner hair cells / outter hair cells
■ Vestibular duct and tympanic duct - filled with perilymph
■ Basilar membrane – where hair cells occur