Special Senses Lecture Notes PDF

Special senses Abeer Gharaibeh © 2015 Pearson Education, Limited.  The Senses  Special senses  Smell  Taste  Sight  Hearing  Equilibrium © 2015 Pearson Ed...

Special senses Abeer Gharaibeh © 2015 Pearson Education, Limited.  The Senses  Special senses  Smell  Taste  Sight  Hearing  Equilibrium © 2015 Pearson Education, Limited.  The Eye and Vision  70 percent of all sensory receptors are in the eyes  Each eye has over 1 million nerve fibers  Protection for the eye  Most of the eye is enclosed in a bony orbit  A cushion of fat surrounds most of the eye © 2015 Pearson Education, Limited.  Accessory Structures of the Eye  Eyelids and eyelashes  Conjunctiva  Lacrimal apparatus  Extrinsic eye muscles © 2015 Pearson Education, Limited. Figure 8.1 Surface anatomy of the eye and accessory structures. Site where Eyebrow conjunctiva Eyelid merges with cornea Eyelashes Palpebral Pupil fissure Lacrimal caruncle Lateral Medial commissure commissure (canthus) (canthus) Iris Sclera (covered by Eyelid conjunctiva) © 2015 Pearson Education, Limited.  Accessory Structures of the Eye  Eyelids  Meet at the medial and lateral commissure (canthus)  Eyelashes  Tarsal glands produce an oily secretion that lubricates the eye  Ciliary glands are located between the eyelashes © 2015 Pearson Education, Limited. Figure 8.1 Surface anatomy of the eye and accessory structures. Site where Eyebrow conjunctiva Eyelid merges with cornea Eyelashes Palpebral Pupil fissure Lacrimal caruncle Lateral Medial commissure commissure (canthus) (canthus) Iris Sclera (covered by Eyelid conjunctiva) © 2015 Pearson Education, Limited.  Accessory Structures of the Eye  Conjunctiva  Membrane that lines the eyelids  Connects to the outer surface of the eye  Secretes mucus to lubricate the eye and keep it moist © 2015 Pearson Education, Limited.  Accessory Structures of the Eye  Lacrimal apparatus  lacrimal gland and ducts  Lacrimal gland—produces lacrimal fluid; situated on lateral aspect of each eye  Lacrimal canaliculi—drain lacrimal fluid from eyes medially  Lacrimal sac—provides passage of lacrimal fluid towards nasal cavity  Nasolacrimal duct—empties lacrimal fluid into the nasal cavity © 2015 Pearson Education, Limited.  Accessory Structures of the Eye  Function of the lacrimal apparatus  Protects, moistens, and lubricates the eye  Empties into the nasal cavity  Lacrimal secretions (tears) contain:  Dilute salt solution  Mucus  Antibodies  Lysozyme (enzyme that destroys bacteria) © 2015 Pearson Education, Limited. Figure 8.2a Accessory structures of the eye. Lacrimal Excretory duct gland of lacrimal gland Conjunctiva Anterior aspect Eyelid Eyelashes Tarsal glands (a) Eyelid © 2015 Pearson Education, Limited. Figure 8.2b Accessory structures of the eye. Lacrimal Lacrimal sac gland Excretory ducts of lacrimal gland Lacrimal canaliculus Nasolacrimal duct Inferior meatus of nasal cavity Nostril (b) © 2015 Pearson Education, Limited.  Accessory Structures of the Eye  Extrinsic eye muscles  Six muscles attach to the outer surface of the eye  Produce eye movements © 2015 Pearson Education, Limited. Figure 8.3a Extrinsic muscles of the eye. Superior oblique muscle Superior oblique tendon Superior rectus muscle Conjunctiva Lateral rectus muscle Optic Inferior Inferior nerve rectus oblique (a) muscle muscle © 2015 Pearson Education, Limited. Figure 8.3b Extrinsic muscles of the eye. Trochlea Superior oblique muscle Superior oblique tendon Axis at Superior center of rectus muscle eye Inferior rectus muscle Medial rectus muscle Lateral rectus muscle (b) © 2015 Pearson Education, Limited. Figure 8.3c Extrinsic muscles of the eye. Controlling Name Action cranial nerve Lateral rectus Moves eye laterally VI (abducens) Medial rectus Moves eye medially III (oculomotor) Superior rectus Elevates eye and turns it medially III (oculomotor) Inferior rectus Depresses eye and turns it medially III (oculomotor) Inferior oblique Elevates eye and turns it laterally III (oculomotor) Superior oblique Depresses eye and turns it laterally IV (trochlear) (c) © 2015 Pearson Education, Limited.  Structure of the Eye  Layers forming the wall of the eyeball  Fibrous layer: outside layer  Vascular layer: middle layer  Sensory layer: inside layer  Humors are fluids that fill the interior of the eyeball © 2015 Pearson Education, Limited. Figure 8.4a Internal anatomy of the eye (sagittal section). Sclera Ciliary body Choroid Ciliary zonule Retina Cornea Iris Fovea centralis Pupil Optic nerve Aqueous humor (in anterior segment) Lens Scleral venous sinus (canal of Schlemm) Central artery and vein of the retina Vitreous humor (in posterior segment) Optic disc (blind spot) (a) © 2015 Pearson Education, Limited. Figure 8.4b Internal anatomy of the eye (sagittal section). Ciliary body Vitreous humor in posterior segment Iris Retina Margin of pupil Choroid Aqueous humor Sclera (in anterior segment) Fovea centralis Optic disc Lens Optic nerve Cornea Ciliary zonule (b) © 2015 Pearson Education, Limited.  Structure of the Eye: The Fibrous Layer  Sclera  White connective tissue layer  Seen anteriorly as the “white of the eye”  Cornea  Transparent, central anterior portion  Allows for light to pass through  Repairs itself easily  The only human tissue that can be transplanted without fear of rejection © 2015 Pearson Education, Limited.  Structure of the Eye: Vascular Layer  Choroid is a blood-rich nutritive layer in the posterior of the eye  Pigment prevents light from scattering  Modified anteriorly into two structures: 1.Ciliary body—smooth muscle attached to lens by ciliary zonule (suspensory ligament) 2.Iris—regulates amount of light entering eye  Pigmented layer that gives eye color  Pupil—rounded opening in the iris © 2015 Pearson Education, Limited.  Structure of the Eye: Sensory Layer  Retina contains two layers 1. Outer pigmented layer absorbs light and prevents it from scattering 2. Inner neural layer  Contains receptor cells (photoreceptors)  Rods  Cones © 2015 Pearson Education, Limited. Figure 8.5a The three major types of neurons composing the retina. Pigmented layer of retina Rod Cone Bipolar cells Ganglion Pathway cells of light (a) © 2015 Pearson Education, Limited. Figure 8.5b The three major types of neurons composing the retina. Pigmented layer of Neural layer retina of retina Central artery and vein of retina Optic disc Sclera Optic (b) nerve Choroid © 2015 Pearson Education, Limited.  Structure of the Eye: Sensory Layer  Neurons of the retina and vision  Rods  Most are found toward the edges of the retina  Allow vision in dim light and peripheral vision  All perception is in gray tones © 2015 Pearson Education, Limited.  Structure of the Eye: Sensory Layer  Neurons of the retina and vision  Cones  Allow for detailed color vision  Densest in the center of the retina  Fovea centralis–lateral to blind spot  Area of the retina with only cones  Visual acuity (sharpest vision) is here  No photoreceptor cells are at the optic disc, or blind spot © 2015 Pearson Education, Limited.  Lens  Biconvex crystal-like structure  Held in place by a suspensory ligament attached to the ciliary body © 2015 Pearson Education, Limited. Figure 8.4a Internal anatomy of the eye (sagittal section). Sclera Ciliary body Choroid Ciliary zonule Retina Cornea Iris Fovea centralis Pupil Optic nerve Aqueous humor (in anterior segment) Lens Scleral venous sinus (canal of Schlemm) Central artery and vein of the retina Vitreous humor (in posterior segment) Optic disc (blind spot) (a) © 2015 Pearson Education, Limited.  Two Segments, or Chambers, of the Eye  Lens divides the eye into two chambers: 1. Anterior (aqueous) segment  Anterior to the lens  Contains aqueous humor 2. Posterior (vitreous) segment  Posterior to the lens  Contains vitreous humor © 2015 Pearson Education, Limited. Figure 8.4a Internal anatomy of the eye (sagittal section). Sclera Ciliary body Choroid Ciliary zonule Retina Cornea Iris Fovea centralis Pupil Optic nerve Aqueous humor (in anterior segment) Lens Scleral venous sinus (canal of Schlemm) Central artery and vein of the retina Vitreous humor (in posterior segment) Optic disc (blind spot) (a) © 2015 Pearson Education, Limited. Figure 8.4b Internal anatomy of the eye (sagittal section). Ciliary body Vitreous humor in posterior segment Iris Retina Margin of pupil Choroid Aqueous humor Sclera (in anterior segment) Fovea centralis Optic disc Lens Optic nerve Cornea Ciliary zonule (b) © 2015 Pearson Education, Limited.  Anterior Segment  Aqueous humor  Watery fluid found between lens and cornea  Similar to blood plasma  Helps maintain intraocular pressure  Provides nutrients for the lens and cornea  Reabsorbed into venous blood through the scleral venous sinus, or canal of Schlemm © 2015 Pearson Education, Limited.  Posterior Segment  Vitreous humor  Gel-like substance posterior to the lens  Prevents the eye from collapsing  Helps maintain intraocular pressure © 2015 Pearson Education, Limited.  The Ear  Houses two senses: 1. Hearing 2. Equilibrium (balance)  Receptors are mechanoreceptors  Different organs house receptors for each sense © 2015 Pearson Education, Limited.  Anatomy of the Ear  The ear is divided into three areas: 1. External (outer) ear 2. Middle ear (tympanic cavity) 3. Inner ear (bony labyrinth) © 2015 Pearson Education, Limited. Figure 8.12 Anatomy of the ear. External (outer) ear Middle ear Internal (inner) ear Vestibulocochlear nerve Auricle (pinna) Semicircular canals Oval window Cochlea Vestibule Round window Pharyngotympanic (auditory) tube Tympanic membrane (eardrum) Hammer Anvil Stirrup External acoustic (malleus) (incus) (stapes) meatus Auditory ossicles (auditory canal) © 2015 Pearson Education, Limited.  The External Ear  Involved in hearing only  Structures of the external ear  Auricle (pinna)  External acoustic meatus (auditory canal)  Narrow chamber in the temporal bone  Lined with skin and ceruminous (wax) glands  Ends at the tympanic membrane (eardrum) © 2015 Pearson Education, Limited.  The Middle Ear (Tympanic Cavity)  Air-filled cavity within the temporal bone  Involved only in the sense of hearing  Located between tympanic membrane and oval window and round window © 2015 Pearson Education, Limited.  The Middle Ear (Tympanic Cavity)  Two tubes are associated with the inner ear: 1. The opening from the auditory canal is covered by the tympanic membrane 2. The pharyngotympanic, or auditory, tube connects the middle ear with the throat  Allows for equalizing pressure during yawning or swallowing  This tube is otherwise collapsed © 2015 Pearson Education, Limited.  Bones of the Middle Ear (Tympanic Cavity)  Three bones (ossicles) span the cavity: 1. Malleus (hammer) 2. Incus (anvil) 3. Stapes (stirrup)  Function  Vibrations from tympanic membrane move the hammer anvil stirrup oval window of inner ear © 2015 Pearson Education, Limited. Figure 8.12 Anatomy of the ear. External (outer) ear Middle ear Internal (inner) ear Vestibulocochlear nerve Auricle (pinna) Semicircular canals Oval window Cochlea Vestibule Round window Pharyngotympanic (auditory) tube Tympanic membrane (eardrum) Hammer Anvil Stirrup External acoustic (malleus) (incus) (stapes) meatus Auditory ossicles (auditory canal) © 2015 Pearson Education, Limited.  Inner Ear or Bony Labyrinth  Includes sense organs for hearing and balance  Filled with perilymph  Contains a maze of bony chambers within the temporal bone:  Cochlea  Vestibule  Semicircular canals  Membranous labyrinth is suspended in perilymph and contains endolymph © 2015 Pearson Education, Limited. Figure 8.12 Anatomy of the ear. External (outer) ear Middle ear Internal (inner) ear Vestibulocochlear nerve Auricle (pinna) Semicircular canals Oval window Cochlea Vestibule Round window Pharyngotympanic (auditory) tube Tympanic membrane (eardrum) Hammer Anvil Stirrup External acoustic (malleus) (incus) (stapes) meatus Auditory ossicles (auditory canal) © 2015 Pearson Education, Limited.  Organs of Equilibrium  Equilibrium receptors of the inner ear are called the vestibular apparatus  Vestibular apparatus has two functional parts: 1. Static equilibrium 2. Dynamic equilibrium © 2015 Pearson Education, Limited. Figure 8.14a Structure and function of the crista ampullaris (dynamic equilibrium receptor region). Semicircular canals Ampulla Vestibular nerve Vestibule (a) © 2015 Pearson Education, Limited.  Organs of Hearing  Spiral organ of Corti  Located within the cochlear duct  Receptors  hair cells on the basilar membrane  Gel-like tectorial membrane is capable of bending hair cells  Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe © 2015 Pearson Education, Limited. Figure 8.15a Anatomy of the cochlea. Temporal Perilymph in scala vestibuli bone Spiral Vestibular organ of membrane Corti Afferent fibers of the cochlear nerve Temporal bone Cochlea duct (contains Perilymph in endolymph) scala tympani (a) © 2015 Pearson Education, Limited. Figure 8.15b Anatomy of the cochlea. Vestibular Hair (receptor) Tectorial membrane cells of spiral membrane organ of Corti Fibers of Basilar Supporting the cochlear membrane cells nerve (b) © 2015 Pearson Education, Limited.  Chemical Senses: Taste and Smell  Both senses use chemoreceptors  Stimulated by chemicals in solution  Taste has four types of receptors  Smell can differentiate a large range of chemicals  Both senses complement each other and respond to many of the same stimuli © 2015 Pearson Education, Limited.  Olfaction—The Sense of Smell  Olfactory receptors are in roof of nasal cavity  Olfactory receptors cells (neurons) with long cilia known as olfactory hairs detect chemicals  Chemicals must be dissolved in mucus for detection by chemoreceptors called olfactory receptors  Impulses are transmitted via the olfactory filaments to the olfactory nerve  Interpretation of smells is made in the cortex © 2015 Pearson Education, Limited. Figure 8.18 Location and cellular makeup of the olfactory epithelium. Olfactory bulb Cribriform plate of ethmoid bone Olfactory tract Olfactory filaments of the olfactory nerve Supporting cell Olfactory Olfactory mucosa receptor cell Olfactory hairs Mucus layer (cilia) (a) Route of inhaled air containing odor molecules (b) © 2015 Pearson Education, Limited.  Taste Buds and the Sense of Taste  Taste buds house the receptor organs  Locations of taste buds  Most are on the tongue  Soft palate  Cheeks © 2015 Pearson Education, Limited.  Taste Buds and the Sense of Taste  The tongue is covered with projections called papillae  Filiform papillae—sharp with no taste buds  Fungiform papillae—rounded with taste buds  Circumvallate papillae—large papillae with taste buds  Taste buds are found on the sides of papillae © 2015 Pearson Education, Limited. Figure 8.19a Location and structure of taste buds. Epiglottis Palatine tonsil Lingual tonsil Fungiform papillae (a) © 2015 Pearson Education, Limited.