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Chapter 16 Lecture Outline A. Gustation

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Chapter 16 Lecture Outline A. Gustation Anatomy Lecture Notes Chapter 16 Chapter 16 Lecture Outline A. gustation - gustatory receptor cells are located in organs called taste buds 1. taste buds located in mucosa of mouth and pharynx most are on the sides of fungiform and circumvallate papillae 2. taste buds made of epithelial cells taste pores are openings in the surface of the epithelium gustatory cells - receptor cells supporting cells - separate gustatory cells from each other basal cells - immature cells that replace the other cells 3. gustatory cells have microvilli on apical surface, just inside taste pore membrane covering microvilli contains receptors for sweet, salty, sour, bitter and umami (glutamate) gustatory cells synapse with sensory neurons at base of taste bud Strong/Fall 2008 page 1 Anatomy Lecture Notes Chapter 16 4. gustatory cells activated when molecules dissolved in saliva bind to membrane receptors on microvilli gustatory cell releases neurotransmitter, which initiates action potential in sensory neuron 5. afferent pathways: VII - facial anterior 2/3 of tongue IX - glossopharyngeal posterior 1/3 of tongue X - vagus epiglottis and pharynx sensory neurons terminate in solitary nucleus in medulla oblongata thalamus gustatory cortex B. olfaction - receptors located in olfactory epithelium 1. olfactory epithelium covers superior nasal conchae and superior nasal septum 2. olfactory epithelium contains olfactory cells bipolar neuron receptors supporting cells columnar e. basal cells form new olfactory cells 3. olfactory cells have apical dendrites that project to surface of mucosa olfactory cilia project from surface of olfactory epithelium the membrane of each olfactory cell covering the cilia contains one (out of about a possible 1000) type of olfactory receptor Strong/Fall 2008 page 2 Anatomy Lecture Notes Chapter 16 the axons of the olfactory cells (cranial nerve I) project through the cribriform plate of the ethmoid bone into the olfactory bulb there they synapse with mitral cells in clusters called glomeruli each glomerulus gathers all olfactory cells for the same olfactory receptor convergence amplifies the signal 4. each odorant molecule combines with a unique set of olfactory cell membrane receptors (signature) 5. afferent pathway for olfaction: olfactory cells - axons form cranial nerve I; project to olfactory bulb mitral cells - axons form olfactory tract; project to: limbic system olfactory cortex Strong/Fall 2008 page 3 Anatomy Lecture Notes Chapter 16 C. vision 1. eyelids / palpebrae = skin-covered folds tarsal plates - c.t. attachment for orbicularis oculi levator palpebrae superioris m. - roof of orbit to tarsal plate of upper eyelid tarsal (Meibomian) glands - open onto margin of eyelid; secrete oil ciliary glands - associated with eyelashes; sebaceous and sweat glands palpebral fissure - space between eyelids canthus (canthi) - medial and lateral corners of palpebral fissure lacrimal caruncle - tissue in medial canthus 2. conjunctiva = mucous membrane lining eyelids and covering exposed sclera palpebral conjunctiva - lines eyelids ocular (bulbar) conjunctiva - covers sclera conjunctival sac - space between eyelids and eyeball 3. lacrimal apparatus a. lacrimal gland - in orbit superiorlateral to eyeblal secretes tears (water, mucus, antibodies, lysozyme) excretory ducts open under superior lateral eyelid b. lacrimal puncta - 2 openings in lacrimal caruncle puncta open into lacrimal canals (canaliculi) canals open into lacrimal sac, drains by nasolacrimal duct into nasal cavity under inferior choncha 4. eyeball - spherical sac made of 3 layers and filled with fluid a. fibrous tunic (outermost) made of dense c.t. sclera posterior 5/6; white; opaque anterior 1/6; cornea clear, more curved, avascular corneal epithelium - covers surface of cornea corneal endothelium - lines inside of cornea; removes excess water from cornea Strong/Fall 2008 page 4 Anatomy Lecture Notes Chapter 16 scleral venous sinus - vein at junction of cornea and sclera b. vascular tunic i. choroid - posterior to ciliary body, vascular, pigmented membrane absorbs light ii. ciliary body - posterior to iris, anterior to choroid ciliary muscle – circular fibers, controls lens shape ciliary processes - anchor suspensory ligaments (ciliary zonula) iii. iris - anterior to ciliary body; between cornea and lens opening in center = pupil iris contains muscle fibers that control pupil diameter sphincter inner circular fibers constrict pupil dilator outer radial fibers dilate pupil color caused by brown melanin in pigmented epithelial cells blue or gray - melanin is in posterior epithelial layer of iris only green, hazel and brown - melanin is in the anterior muscular layer and the posterior epithelial layer Strong/Fall 2008 page 5 Anatomy Lecture Notes Chapter 16 c. sensory tunic = retina i. pigmented layer next to choroid. made of a single layer of melanocytes extends forward to cover the back of the ciliary body and the iris absorbs excess light; helps photoreceptors maintain photopigments ii. nervous layer inside consists of 3 cell layers: photoreceptor cells (rods and cones) - tips embedded in pigmented layer, sensitive to light bipolar cells - superficial to photoreceptors, connect photoreceptors to ganglion cells ganglion cells - surface of nervous layer; axons form cranial nerve II (optic nerve) anterior margin of nervous layer = ora serrata macula lutea - spot in exact center of back of eyeball fovea centralis - indentation in the macula lutea; contains only cones; maximal visual acuity optic disc = where II leaves eyeball; medial to macula lutea; lack of photoreceptors causes blind spot central artery and vein - enter/leave with optic nerve Strong/Fall 2008 page 6 Anatomy Lecture Notes Chapter 16 d. lens = biconvex transparent elastic disc changes shape to focus images on retina outside is an elastic capsule inside the capsule on the front of the lens is a layer of lens epithelium behind the lens epithelium are lens fibers, which are made by the peripheral cells of the lens epithelium the lens is avascular its density increases with age and its elasticity decreases with age, preventing focusing on near objects (presbyopia) cataracts are clouding of the lens and are correlated with smoking, exposure to UV radiation, and diarrhead. cavities and fluids e. cavities and fluids i. posterior segment posterior to lens filled with vitreous body (humor) made mostly of collagen and water holds retina in place helps maintain intraocular pressure ii. anterior segment anterior to lens subdivided into: o anterior chamber - anterior to iris o posterior chamber - posterior to iris contains aqueous humor o formed at ciliary processes in posterior chamber o circulates through pupil to anterior chamber o drains into scleral venous sinus o maintains intraocular pressure glaucoma - caused by increased intraocular pressure Strong/Fall 2008 page 7 Anatomy Lecture Notes Chapter 16 5. photoreceptors (rods and cones) = specialized neurons outer segment = receptor region of cell embedded in pigmented layer plasma membrane contains visual pigment molecules that are sensitive to light plasma membrane folded inwards increases surface area folds form membrane-covered discs rods cones 1 type 3 types: red, blue, green sensitive to entire visual spectrum each sensitive to part of the visual spectrum shades of gray color work in dim light only work in bright light only low acuity (convergence of rods onto high acuity (no convergence) bipolar cells) concentrated around periphery of concentrated in center of retina retina 6. afferent pathway rods and cones bipolar cells ganglion cells optic nerve optic chiasma optic tract superior colliculus of midbrain thalamus primary visual cortex Strong/Fall 2008 page 8 Anatomy Lecture Notes Chapter 16 D. hearing and equilibrium 1. outer ear a. auricle/pinna - funnels sound into ear canal b. external auditory canal goes through external acoustic meatus 2.5 cm long, angled anteriorly skin contains ceruminous glands, hair follicles, hair, sebaceous glands c. tympanic membrane made of 2 layers of collagen and elastin fibers external surface covered by skin internal surface covered by simple squamous or cuboidal e. 2. middle ear - inside petrous temporal bone a. ossicles amplify sound vibrations (they form a "bridge" between the tympanic membrane and the inner ear) malleus attached to tympanic membrane incus stapes fits into oval window of inner ear b. muscles adjust sensitivity of middle ear: tensor tympani (O) pharyngotympanic tube (I) tympanic membrane increases tension of tympanic membrane, decreases vibration stapedius (O) posterior wall of middle ear cavity (I) stapes limits movement of stapes c. openings into inner ear: oval window - where sound waves enter cochlea round window - where sound waves leave cochlea d. pharyngotympanic (auditory or Eustachian) tube connects middle ear to nasopharynx equalizes air pressure across eardrum Strong/Fall 2008 page 9 Anatomy Lecture Notes Chapter 16 3. inner ear a. bony labyrinth = cavity inside temporal bone filled with perilymph 3 subdivisions: semicircular canals (posterior) vestibule cochlea (anterior) b. membranous labyrinth = set of interconnected membrane tubes that are suspended in the perilymph filled with endolymph 3 subdivisions: semicircular ducts utricle and saccule cochlear duct Strong/Fall 2008 page 10 Anatomy Lecture Notes Chapter 16 4. cochlea - hearing a. overall structure modiolus - pillar of bone in center of cochlea spiral lamina - shelf of bone coiling around modiolus scala vestibuli - filled with
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