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Special Senses

Special Senses. Equilibrium, Hearing, Vision. Ear. Three regions External ear Auricle External auditory meatus Tympanic membrane Middle ear Auditory ossicles Malleus, incus, stapes Inner ear Equilibrium and hearing. Auditory ossicles.

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Special Senses

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  1. Special Senses Equilibrium, Hearing, Vision

  2. Ear • Three regions • External ear • Auricle • External auditory meatus • Tympanic membrane • Middle ear • Auditory ossicles • Malleus, incus, stapes • Inner ear • Equilibrium and hearing

  3. Auditory ossicles • Malleus attaches to the inner surface of the tympanic membrane • Incus attaches between the malleus and the inner stapes • Stapes attaches to the oval window • Auditory ossicles conduct and amplify sound waves reaching the inner ear

  4. Auditory ossicles

  5. Inner Ear • Equilibrium and hearing • Receptors found inside fluid filled tubes and chambers called the MEMBRANOUS LABYRINTH • The membranous labyrinth is filled with a fluid called endolymph – necessary for receptor function • The membranous labyrinth is surrounded by a bony shell called the BONY LABYRINTH • The bony labyrinth is filled with perilymph

  6. Bony Labyrinth • Divided into the: • 1. vestibule • Contains the • Utricle – gravity and linear acceleration • Saccule – gravity and linear acceleration • 2. semicircular canals – rotation of head • 3. cochlea – hearing • 4. Vestibule and semicircular canals together are called the vestibular complex

  7. Equilibrium (Balance) • Semicircular canals surround the semicircular ducts • Anterior, lateral, posterior semicircular ducts • The ducts respond to rotational movement of the head • Each duct contains an area called the ampulla which contains the sensory receptors • Sensory receptors are called HAIR CELLS. • Hair cells contain sterocilia and kinocilium which are embedded in a structure called the cupula • Simple answer for rotation: movement of the endolymph causes distortion on the hair cells and release neurotransmitter

  8. Equilibrium • Semicircular ducts respond to one of three rotational planes • Lateral duct - horizontal rotation (NO) • Anterior duct - nodding (YES) • Posterior duct - tilting the head side to side

  9. Ampulla

  10. Hair cell movement

  11. Movement in the ampulla

  12. Semicircular ducts

  13. Utricle and Saccule • Gravity and linear acceleration • Hair cells of the utricle and saccule are clustered in the maculae • Bottom line on gravity and acceleration: • When the hair cells are distorted by the movement of the head the change in these receptors “tells” the CNS the head is no longer level!

  14. Maculae

  15. Head and otolith movement

  16. Hearing • Cochlea • Divided into three chambers • Vestibular duct - perilymph • Cochlear duct- endolymph • Organ of Corti (spiral organ) • Tympanic duct – perilymph

  17. CochleaChambers and movement of pressure waves

  18. Organ of Corti(Spiral organ) • Found in the cochlear duct • Contains hair cells for sound detection • Organ of Corti rest on the basilar membrane • Hair cells are in contact with overlying tectorial membrane • Pressure waves in the perilymph move the hair cells, and neurotransmitter is released

  19. Cochlear chambers

  20. Organ of Corti

  21. Production of auditory sensation • 1. Sound waves hit the ear drum • 2. Auditory ossicles move, stapes on the oval window causes pressure waves in the perilymph of the vestibular duct • 3. Pressure waves distort the basiliar membrane • 4. Movement of basiliar membrane cause distortion of hair cells in the Organ of Corti against the tectorial membrane • 5. Neurotransmitter release • 6. Information concerning the sound goes to the brain via the cochlear branch of cranial nerve VIII

  22. Vision Structure of the Eye

  23. Accessory Structures • 1. Eyelids – palpebrae • Inner surface of eyelid is the palpebral conjunctiva • 2. Eyelashes • 3. Tarsal glands • Inner margin of the eyelid • Lipid secretion, prevent eyelid sticking! • 4. Lacrimal apparatus • Produces tears – keeps eye surface clean and moist • Lysozyme

  24. Eye • Two large chambers • Posterior cavity – vitreous humor • Anterior cavity – aqueous humor • Three layers or tunics • Fibrous tunic • Vascular tunic • Neural tunic

  25. Anatomy of the Eye

  26. Fibrous tunic • Outermost layer • Consists of the sclera and the cornea • Sclera is the “white of the eye” • Fibrous connective tissue • Cornea is continuous with the sclera but is composed of stratified squamous epithelium • Cornea is avascular and transparent

  27. Vascular tunic • Blood vessels for the eye • Regulation of the amount of light entering the eye • Secretion of aqueous humor • Controls shape of lens • Consists of • Iris • Ciliary body • Choroid

  28. Iris • Seen through the cornea • Contains muscles that change the shape of the opening of the iris the pupil • May also contain pigment cells that give color to the eyes

  29. Ciliary Body • Begins at the junction of the sclera and the cornea • Attachment of the iris • Most of the structure is the ciliary muscle • Suspensory ligament of the lens attach to the ciliary muscle at the ciliary processes • Hold the lens centered on the pupil

  30. Choroid • Layer of blood vessels that delivers oxygen and nutrients to the retina

  31. Neural tunic • Also called the retina • Consists of several layers • Pigment layer • Neural layer • Photoreceptors – rods and cones • Bipolar cells • Ganglion cells

  32. Layers of the neural tunic

  33. Photoreceptors • Found in the outermost layer next to the pigment layer • Rods • Very light sensitive • Allow us to see in dim rooms or at night • 125 million rods in the retina • Cones • Color vision • Sharp vision but need more light • 6 million cones in the retina

  34. Rods and Cones

  35. Distribution of rods and cones • 125 million rods spread around the retina • 6 million cones on the posterior retina surface • Most cones are concentrated in an area called the macula lutea • Center of the macula lutea is the fovea centralis • Sight of the sharpest vision • When you look directly at an object this is where the image falls on the retina

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