Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
PowerPoint® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community Ninth Edition College Human Anatomy & Physiology CHAPTER 15 The Special Senses: Part A © Annie Leibovitz/Contact Press Images © 2013 Pearson Education, Inc. Special Senses • Special sensory receptors – Distinct, localized receptor cells in head • • • • • Vision Taste Smell Hearing Equilibrium © 2013 Pearson Education, Inc. The Eye and Vision • 70% of body's sensory receptors in eye • Visual processing by ~ half cerebral cortex • Most of eye protected by cushion of fat and bony orbit Accessory Structures of the Eye • Protect the eye and aid eye function – Eyebrows – Eyelids (palpebrae) – Conjunctiva – Lacrimal apparatus – Extrinsic eye muscles Figure 15.1a The eye and accessory structures. Eyebrow Eyelid Eyelashes Site where conjunctiva merges with cornea Palpebral Fissure (eyelid slit) Lateral commissure Iris Eyelid Pupil *Lacrimal Medial Sclera (covered by caruncle commissure conjunctiva) Surface anatomy of the right eye © 2013 Pearson Education, Inc. *Contains oil and sweat glands Figure 15.1b The eye and accessory structures. Levator palpebrae superioris muscle (raises eyelid to open the eye) Orbicularis oculi muscle (contraction: eye closes) Eyebrow Tarsal plate (connective tissue; supports the eyelids) Cornea Palpebral fissure Eyelashes Orbicularis oculi muscle Lateral view; some structures shown in sagittal section © 2013 Pearson Education, Inc. Conjunctiva • Transparent mucous membrane – Produces a lubricating mucous secretion • Palpebral conjunctiva lines eyelids • Bulbar conjunctiva covers white of eyes • Conjunctival sac between palpebral and bulbar conjunctiva – Where contact lens rests © 2013 Pearson Education, Inc. Lacrimal Apparatus • • • Lacrimal gland and ducts that drain into nasal cavity Lacrimal gland in orbit above lateral end of eye Lacrimal secretion (tears) – Dilute saline solution containing mucus, antibodies, and lysozyme – Blinking spreads tears toward medial commissure – Tears enter paired lacrimal canaliculi via lacrimal puncta – Then drain into lacrimal sac and nasolacrimal duct Lacrimal gland Excretory ducts of lacrimal glands Lacrimal sac Lacrimal punctum Lacrimal canaliculus Nasolacrimal duct Inferior meatus of nasal cavity Nostril Extrinsic Eye Muscles Superior oblique tendon Superior oblique muscle Superior rectus muscle Lateral rectus muscle • Six muscles: • Four rectus muscles; names indicate movements – Superior, inferior, lateral, medial rectus muscles • Inferior rectus muscle Inferior oblique muscle Lateral view of the right eye Two oblique muscles move eye in vertical plane and rotate eyeball – Superior and inferior oblique muscles Figure 15.3b Extrinsic eye muscles. Trochlea Superior oblique muscle Axis of rotation of eye Superior oblique tendon Superior rectus muscle Inferior rectus muscle Medial rectus muscle Lateral rectus muscle Common tendinous ring Superior view of the right eye © 2013 Pearson Education, Inc. Figure 15.3c Extrinsic eye muscles. Muscle Action Controlling cranial nerve Lateral rectus Moves eye laterally VI (abducens) Medial rectus Superior rectus Inferior rectus Moves eye medially III (oculomotor) Elevates eye and turns it medially III (oculomotor) Depresses eye and turns it medially III (oculomotor) Elevates eye and turns it laterally III (oculomotor) Depresses eye and turns it laterally IV (trochlear) Inferior oblique Superior oblique Summary of muscle actions and innervating cranial nerves © 2013 Pearson Education, Inc. Structure of the Eyeball • Wall of eyeball contains three layers – Fibrous – Vascular – Inner • Internal cavity filled with fluids called humors • Lens separates internal cavity into anterior & posterior segments (cavities) © 2013 Pearson Education, Inc. Figure 15.4a Internal structure of the eye (sagittal section). Ciliary body Sclera Ciliary zonule (suspensory ligament) Choroid Cornea Iris Pupil Anterior pole Anterior segment (contains aqueous humor) Lens Retina Macula lutea Fovea centralis Optic nerve Scleral venous sinus Central artery and vein of the retina Posterior segment (contains vitreous humor) Optic disc (blind spot) Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball. © 2013 Pearson Education, Inc. Figure 15.4b Internal structure of the eye (sagittal section). Ciliary body Vitreous humor in posterior segment Iris Margin of pupil Anterior segment Lens Cornea Retina Choroid Sclera Fovea centralis Optic disc Optic nerve Photograph of the human eye. http://www.youtube.com/watch?v= TXFt1Ikl__I&feature=endscreen © 2013 Pearson Education, Inc. Fibrous Layer • Outermost layer; dense avascular connective tissue • Two regions: sclera and cornea 1. Sclera • Opaque posterior region • Protects, shapes eyeball 2. Cornea • Transparent anterior • Bends light as it enters eye Vascular Layer (Uvea) • Middle pigmented layer • Three regions: choroid, ciliary body, and iris 1. Choroid region (posterior portion of uvea) • Supplies blood to all layers of eyeball Brown pigment absorbs light to prevent light scattering and visual confusion 2. Ciliary body • Ring of tissue surrounding lens • Smooth muscle bundles (ciliary muscles) control lens shape • Ciliary zonule (suspensory ligament) holds lens in position 3. Iris (Colored part of eye) • Pupil—central opening that regulates amount of light entering eye – Close vision and bright light—sphincter pupillae (circular muscles) contract; pupils constrict – Distant vision and dim light—dilator pupillae (radial muscles) contract; pupils dilate – sympathetic fibers – Changes in emotional state—pupils dilate when subject matter is appealing or requires problem-solving skills Figure 15.5 Pupil constriction and dilation, anterior view. Sympathetic + Parasympathetic + Sphincter pupillae muscle contracts: Pupil size decreases. © 2013 Pearson Education, Inc. Iris (two muscles) • Sphincter pupillae • Dilator pupillae Dilator pupillae muscle contracts: Pupil size increases. Inner Layer: Retina • Delicate two-layered membrane – Outer Pigmented layer • Single-cell-thick lining • Absorbs light and prevents its scattering • Phagocytize photoreceptor cell fragments • Stores vitamin A – Inner Neural layer • Transparent • Composed of three main types of neurons – Photoreceptors, bipolar cells, ganglion cells • Signals spread from photoreceptors to bipolar cells to ganglion cells • Ganglion cell axons exit eye as optic nerve © 2013 Pearson Education, Inc. The Retina • Optic disc (blind spot) – Site where optic nerve leaves eye – Lacks photoreceptors • Quarter-billion photoreceptors of two types – Rods – Cones http://www.youtube.com/watch?v=1YHghqvGtg&feature=related © 2013 Pearson Education, Inc. Figure 15.6a Microscopic anatomy of the retina. Neural layer of retina Pigmented layer of retina Choroid Pathway of light Sclera Optic disc Central artery and vein of retina Optic nerve Posterior aspect of the eyeball © 2013 Pearson Education, Inc. Figure 15.6b Microscopic anatomy of the retina. Ganglion cells Axons of ganglion cells Bipolar cells Photoreceptors • Rod • Cone Amacrine cell Horizontal cell Pathway of signal output Pathway of light Pigmented layer of retina Cells of the neural layer of the retina © 2013 Pearson Education, Inc. Figure 15.6c Microscopic anatomy of the retina. Nuclei of ganglion cells Outer segments of rods and cones Nuclei of Nuclei of bipolar rods and cells cones Photomicrograph of retina Axons of ganglion cells © 2013 Pearson Education, Inc. Choroid Pigmented layer of retina Photoreceptors • Rods – Dim light, peripheral vision receptors – No color vision or sharp images – Numbers greatest at periphery • Cones – Vision receptors for bright light – High-resolution color vision • Fovea centralis – Tiny pit in center of macula with all cones; best vision Internal Chambers and Fluids • The lens and ciliary zonule separate eye into two segments – Anterior and posterior segments © 2013 Pearson Education, Inc. Internal Chambers and Fluids • Posterior segment contains vitreous humor that – Transmits light – Supports posterior surface of lens – Holds neural layer of retina firmly against pigmented layer – Contributes to intraocular pressure – Forms in embryo; lasts lifetime • Anterior segment composed of two chambers – Anterior chamber—between cornea and iris – Posterior chamber—between iris and lens © 2013 Pearson Education, Inc. Internal Chambers and Fluids • Anterior segment contains aqueous humor – Plasma like fluid continuously formed by capillaries of ciliary processes – Supplies nutrients and oxygen mainly to lens and cornea but also to retina, and removes wastes • Glaucoma: blocked drainage of aqueous humor increases pressure and causes compression of retina and optic nerve blindness Figure 15.4a Internal structure of the eye (sagittal section). Ciliary body Sclera Ciliary zonule (suspensory ligament) Choroid Cornea Iris Pupil Anterior pole Anterior segment (contains aqueous humor) Lens Scleral venous sinus Posterior segment (contains vitreous humor) Retina Macula lutea Fovea centralis Posterior pole Optic nerve Central artery and vein of the retina Optic disc (blind spot) Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball. © 2013 Pearson Education, Inc. Figure 15.8 Circulation of aqueous humor. Cornea Lens Posterior segment (contains vitreous humor) Iris Lens epithelium Lens Cornea 2 Corneal epithelium Corneal endothelium Aqueous humor 1 Aqueous humor forms by filtration from the capillaries in the ciliary processes. 2 Aqueous humor flows from the posterior chamber through the pupil into the anterior chamber. Some also flows through the vitreous humor (not shown). 3 Aqueous humor is reabsorbed into the venous blood by the scleral venous sinus. © 2013 Pearson Education, Inc. Anterior segment (contains aqueous humor) Anterior chamber Ciliary zonule (suspensory ligament) Posterior chamber Scleral venous sinus Corneoscleral junction 3 1 Ciliary processes Ciliary muscle Bulbar conjunctiva Sclera Ciliary body Lens • Biconvex, transparent, flexible, and avascular • Changes shape to precisely focus light on retina • Two regions – Lens becomes more dense, convex, less elastic with age • cataracts (clouding of lens) consequence of aging, diabetes mellitus, heavy smoking, frequent exposure to intense sunlight © 2013 Pearson Education, Inc. Figure 15.9 Photograph of a cataract. © 2013 Pearson Education, Inc. Visual Pathways Visual Pathways • Ganglion cells of the retina make up optic nerves • Left and right optic nerves (II) into brain via optic foraminae • Optic chiasma (nasal side fibers cross to contralateral brain) • Optic tracts (carry fibers back to the thalamsus) • Ganlion cell axons terminate in lateral geniculate n. of thalamus • Optic radiations carry fibers back to occipital cortex The Chemical Senses: Smell And Taste • Smell (olfaction) and taste (gustation) • Chemoreceptors respond to chemicals in aqueous solution Taste – to substances dissolved in saliva Smell – to substances dissolved in fluids of the nasal membranes Sense of Smell Taste Buds • Most of the 10,000 or so taste buds are found on the tongue • Taste buds are found in papillae of the tongue mucosa • Papillae come in three types: filiform, fungiform, and circumvallate • Fungiform and circumvallate papillae contain taste buds Taste Buds Basic Taste Sensations • There are five basic taste sensations 1. Sweet—sugars, saccharin, alcohol, some amino acids, some lead salts 2. Sour—hydrogen ions in solution 3. Salty—metal ions (inorganic salts) 4. Bitter—alkaloids such as quinine and nicotine; aspirin 5. Umami—amino acids glutamate and aspartate © 2013 Pearson Education, Inc. Gustatory Pathway The Ear: Hearing and Balance • Three major areas of ear 1. External (outer) ear – hearing only 2. Middle ear (tympanic cavity) – hearing only 3. Internal (inner) ear – hearing and equilibrium • Receptors for hearing and balance respond to separate stimuli • Are activated independently © 2013 Pearson Education, Inc. External Ear • Auricle (pinna)Composed of – Helix (rim); Lobule (earlobe) – Funnels sound waves into auditory canal • External acoustic meatus (auditory canal) – Short, curved tube lined with skin bearing hairs, sebaceous glands, and ceruminous glands – Transmits sound waves to eardrum • Tympanic membrane (eardrum) – Boundary between external and middle ears – Connective tissue membrane that vibrates in response to sound – Transfers sound energy to bones of middle ear © 2013 Pearson Education, Inc. Figure 15.24a Structure of the ear. Middle Internal ear External ear (labyrinth) ear Auricle (pinna) Helix Lobule External acoustic Tympanic Pharyngotympanic meatus membrane (auditory) tube The three regions of the ear © 2013 Pearson Education, Inc. Middle Ear (Tympanic Cavity) • A small, air-filled, mucosa-lined cavity in temporal bone – Connected laterally by eardrum – Connected medially by bony wall containing oval (vestibular) and round (cochlear) windows • Epitympanic recess—superior portion of middle ear • Mastoid antrum – Canal for communication with mastoid air cells • Pharyngotympanic (auditory) tube—connects middle ear to nasopharynx – Equalizes pressure in middle ear cavity with external air pressure Figure 15.24b Structure of the ear. Oval window (deep to stapes) Entrance to mastoid antrum in the epitympanic recess Malleus (hammer) Incus Auditory (anvil) ossicles Stapes (stirrup) Tympanic membrane Semicircular canals Vestibule Vestibular nerve Cochlear nerve Cochlea Round window Middle and internal ear © 2013 Pearson Education, Inc. Pharyngotympanic (auditory) tube Otitis Media • Middle ear inflammation – Especially in children • Shorter, more horizontal pharyngotympanic tubes • Most frequent cause of hearing loss in children – Most treated with antibiotics – Myringotomy to relieve pressure if severe Myringotomy (myringa: eardrum):A surgical procedure; a tiny incision is created in the eardrum to relieve pressure caused by excessive build-up of fluid or to drain pus from the middle ear. © 2013 Pearson Education, Inc. Ear Ossicles • Three small bones in tympanic cavity: the malleus, incus, and stapes – Suspended by ligaments and joined by synovial joints – Transmit vibratory motion of eardrum to oval window – Tensor tympani and stapedius muscles contract reflexively in response to loud sounds to prevent damage to hearing receptors © 2013 Pearson Education, Inc. Figure 15.25 The three auditory ossicles and associated skeletal muscles. View Superior Malleus Incus Epitympanic recess Lateral Anterior © 2013 Pearson Education, Inc. Pharyngotym- Tensor tympani panic tube muscle Tympanic Stapes Stapedius membrane muscle (medial view) Internal Ear • Bony labyrinth – Tortuous channels in temporal bone – Three regions: 1) vestibule, 2) semicircular canals, and 3) cochlea – Filled with perilymph – similar to CSF • Membranous labyrinth – Series of membranous sacs and ducts – Filled with potassium-rich endolymph © 2013 Pearson Education, Inc. Figure 15.26 Membranous labyrinth of the internal ear. Temporal bone Semicircular ducts in semicircular canals Anterior Posterior Lateral Facial nerve Vestibular nerve Cristae ampullares in the membranous ampullae Superior vestibular ganglion Inferior vestibular ganglion Cochlear nerve Maculae Spiral organ Utricle in vestibule Cochlear duct in cochlea Saccule in vestibule © 2013 Pearson Education, Inc. Stapes in oval window Round window Vestibule • Central egg-shaped cavity of bony labyrinth • Contains two membranous sacs 1. Saccule is continuous with cochlear duct 2. Utricle is continuous with semicircular canals • These sacs – House equilibrium receptor regions (maculae) – Respond to gravity and changes in position of head © 2013 Pearson Education, Inc. Semicircular Canals • Three canals (anterior, lateral, and posterior) • Membranous semicircular ducts line each canal and communicate with utricle • Ampulla of each canal houses equilibrium receptor region called the crista ampullaris – Receptors respond to angular (rotational) movements of the head © 2013 Pearson Education, Inc. Figure 15.26 Membranous labyrinth of the internal ear. Temporal bone Semicircular ducts in semicircular canals Anterior Posterior Lateral Facial nerve Vestibular nerve Cristae ampullares in the membranous ampullae Superior vestibular ganglion Inferior vestibular ganglion Cochlear nerve Maculae Spiral organ Utricle in vestibule Cochlear duct in cochlea Saccule in vestibule © 2013 Pearson Education, Inc. Stapes in oval window Round window The Cochlea • A spiral, conical, bony chamber – Size of split pea – Extends from vestibule – Contains cochlear duct, which houses spiral organ (organ of Corti) and ends at cochlear apex © 2013 Pearson Education, Inc. The Cochlea • Cavity of cochlea divided into three chambers – Scala vestibuli—joins oval window, contains perilymph – Scala media (cochlear duct)—contains endolymph – Scala tympani—terminates at round window; contains perilymph • Scalae tympani and vestibuli are continuous with each other at helicotrema (apex) © 2013 Pearson Education, Inc. Figure 15.27b Anatomy of the cochlea. Vestibular membrane Tectorial membrane Cochlear duct (scala media; contains endolymph) Stria vascularis Spiral organ Basilar membrane © 2013 Pearson Education, Inc. Osseous spiral lamina Scala vestibuli (contains perilymph) Scala tympani (contains perilymph) Spiral ganglion Figure 15.27a Anatomy of the cochlea. • The "roof" of cochlear duct: Vestibular membrane • External wall is stria vascularis – secretes endolymph • "Floor" of cochlear duct composed of – Bony spiral lamina – Basilar membrane, which supports spiral organ • The cochlear branch of nerve VIII runs from spiral organ to brain Helicotrema at apex Modiolus: Coils around bony pillar Cochlear nerve, division of the vestibulocochlear nerve (VIII) Spiral ganglion Osseous spiral lamina Vestibular membrane Cochlear duct (scala media) Figure 15.27c Anatomy of the cochlea. Tectorial membrane Inner hair cell Hairs (stereocilia) Afferent nerve fibers Outer hair cells Supporting cells Fibers of cochlear nerve Basilar membrane © 2013 Pearson Education, Inc. Figure 15.27d Anatomy of the cochlea. Inner hair cell Outer hair cell © 2013 Pearson Education, Inc. Simplified Auditory Pathways