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2010 EAR Complete +lab - THE EAR Diane L M Bick PhD Reading...

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THE EAR Diane L. M. Bick, PhD Reading: Gartner & Hiatt, Chapter 19; Klein and McKenzie, pp319-325 Learning Objectives: Describe the structural and histological components of the outer, middle, and inner ear. Know the components of the membranous and bony labyrinths. Describe the structures found in the 3 scala of the inner ear. Key Words: Tympanic cavity, external auditory meatus, Eustachian tube, tympanic membrane, cupula, organ of Corti, perilymph, endolymph, ampulla, utricle, saccule, otoconia, crista ampullaris, macula, stria vascularis, vestibular membrane, basilar membrane, scalas. I. BASIC EAR INFORMATION Paired sensory organs that consist of the auditory system and the vestibular system. Composed of external, middle, and inner ear. THE THREE DIVISIONS OF THE EAR II. EXTERNAL EAR A. Auricle (or pinna) consists of elastic cartilage. Covered by keratinized stratified squamous epithelium with hairs, sebaceous glands, and sweat glands. B. External auditory meatus extends from the auricle to the tympanic membrane of the middle ear. Outer one-third of wall composed of elastic cartilage that is continuous with auricle. Inner two- thirds of wall is formed by the temporal bone. Lined by stratified squamous epithelium with hairs, sebaceous glands, and ceruminous glands . Secretions of sebaceous and ceruminous glands combine to form cerumen . III. MIDDLE EAR Consists of tympanic cavity and its components - tympanic membrane (eardrum), 3 ossicles, and auditory or eustachian tube. Tympanic cavity is an air-filled space. Lined by simple squamous to low cuboidal epithelium. Cells become ciliated and cuboidal near the opening of the auditory tube. Lateral wall is composed of the tympanic membrane; medial wall is shared by the inner ear. Medial wall contains the oval window and the round window.
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Auditory ossicles = malleus (hammer), incus (anvil), and stapes (stirrup). 1. Composed of compact bone joined by synovial joints 2. Malleus is attached to inner aspect of tympanic membrane. Stapes is attached to the oval window of the inner ear by a fibrous ligament. Incus joins the malleus and the stapes. 3. Associated with 2 skeletal muscles, the Tensor Tympani (attached to the malleus), and the Stapedius (attached to the stapes). Tympanic membrane is a thin, rigid, semitransparent membrane between the external and middle ears. 1. Consists of a central core of connective tissue containing fibrous tissue and elastic fibers. 2. External surface covered by stratified squamous epithelium; inner surface covered by simple low cuboidal epithelium. 3. Divided into 2 parts. Lower four-fifths is the pars tensa and contains an organized core of connective tissue. Upper one-fifth is the pars flaccida (lacks a middle fibrous layer). Auditory Tube (eustachian tube) extends from tympanic cavity to nasopharynx.
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  • Spring '10
  • RogerJ.Bick
  • Inner Ear Labyrinths Bony Labyrinth Vestibule Semicircular canals Cochlea Membranous Labyrinth Saccule Utricle Semicircular

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