1. ANATOMY OF THE EYE & EAR Exercise 21, 22

2. THE EYE

3. ANATOMY OF THE EYE ■Sophiticated systems that includes the work of: ■Retina receptors ■Pupil dilation and contraction ■6 oculomotor muscles ■12 cranial nerves

4. 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

5. 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

6. Eye Muscles – come back to haunt us

7. 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

9. How does the pupil change size? ■Pupillary sphincter muscles / pupillary dilator muscles ■Parasympathetic vs Sympathetic innervation

10. 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

11. Diseases of the Eye ■Glaucoma ■Diabetic Retinopathy ■Conjunctivitis ■Macular Degeneration ■Sty

12. Marijuana and Glaucoma ■THC causes the blood vessels in the eye to decrease ■Therefore, reduced IOP levels

13. THE EAR

14. Anatomy of the Ear ■External – direct sound waves ■Middle – direct sound waves ■Outer – balance and hearing

16. 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

17. 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

18. 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

19. 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

20. 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