Ear Anatomy PDF

30 Noor Hamadneh Nadine Dababseh Ghada Abu el Ghanam  Ear Ear is responsible for equilibrium & hearing Has 3 parts: - External - hearing - Middle - hearing - Internal – equilibrium & hearing The external ear: Function: Collects sounds and dir...

30 Noor Hamadneh Nadine Dababseh Ghada Abu el Ghanam  Ear Ear is responsible for equilibrium & hearing Has 3 parts: - External - hearing - Middle - hearing - Internal – equilibrium & hearing The external ear: Function: Collects sounds and directs them to the middle ear Auricle (pinna): irregular funnel shaped elastic cartilage covered by skin (directs waves) External acoustic meatus (within the skull): canal lined with keratinized stratified squamous epithelium, hair, sebaceous & ceruminous glands (modified apocrine glands) which produces cxerumen (ear wax). External part of it is supported by elastic cartilage while the internal is supposed by temporal bone At the deep end there is the tympanic membrane (between the middle and external ear) The middle ear: Function: collects the sounds and vibrates the tympanic membrane which are then collected by the ossicles, they vibrate and move the vibrations to the inner ear Tiny, constricted region within the temporal bone, lies between tympanic membrane & inner ear Lined with simple cuboidal epithelium Communicates with nasopharynx via auditory/eustachian tube Connected to the inner ear via auditory ossicles (3 tiny bones covered with periosteum and simple squamous epithelium, joined by synovial joints) Malleus Distally articulates with tympanic membrane Stapes articulates with inner ear  When you get sick with the flu the eustachian tube gets filled with fluid and you feel pain in your ears, it could lead to infections (more common in kids), it depends on the direction of the tympanic membrane, it should have a slight inclination, some people have it more vertical so the drainage of it will be harder and fluids from the respiratory tract gets accumulated in the middle ear causing infections, having enlarged pharyngeal tonsils (adenoids) makes it worse by closing the opening of this tube. This affects the function of the tympanic membrane, it could be helped by putting ear tubes in the ear to connect the external ear to the middle ear to drain the fluid, the pharyngeal tonsils could also be removed Adenoids result in constant stretching of the facial muscles which limits the growth of the maxilla and mandible and causes complications in occlusion so it should be fixed as soon as possible The internal ear (most complex and important): Function: sensation because it has nerve endings (from CN VIII), however it will not function without the ossicles, hearing (cochlea) & equilibrium (vestibule) Interconnected space Has a bony labyrinth and a membrane labyrinth Bony labyrinth (tiny bones covered with periosteum): - Vestibule: irregular central cavity, houses saccule and utricle (connected) - Semicircular canals: houses semicircular ducts - Cochlea: houses cochlear ducts - Perilymph: protection, support, has fluids similar to ECF Membranous labyrinth (lines the bone from inside): - Two connected sacs: utricle & saccule (vestibule nerve) - Semicircular ducts - Cochlear duct: connected to saccule in the vestibule - Endolymph: similar to ICF (high K+, low Na+) Hair cells: they are a specialized type of epithelial cells that are columnar mechanoelectrical transducers among epithelium (similar to merkel cells)  Utricle & saccule: Thin CT lined with simple squamous epithelium Has hair cells Maculae: small areas of columnar neuroepithelial cells (hair cells) innervated by branches of the vestibular nerve, Has Kinocilium (rigid long cilium) & stereocilia (rigid and unbranched) Embedded in otolithic membrane (gelatinous proteoglycan & otoliths) and is covered by endolymph Basal synapses with afferent nerve endings Efferent fibers: modulates the sensitivity of the receptors Static position & linear acceleration of the head (along with that provided visually and by musculoskeletal proprioceptors -sensation from muscles and joints-) is important for maintaining equilibrium and allowing the eyes to remain fixed on the same point while moving the head Semicircular ducts Three in number Connected to utricle Has hair cells covered by endolymph - 3 crista ampularis (in ampullary region) - Afferent nerve endings in the distal end - Important for the Rotational movement of the head Sensation (not required): There is a gelatinous membrane and fluid covering the hair cells so when the fluid goes over the membrane it will bend slightly, when it bends it bends the stereocilia, so mechanical movement happens and that leads to the opening of the K+ channels, so influx will happen meaning depolarization (if the stereocilia moved towards the kinocilium), so these cells are excited which means calcium is involved and neurotransmitters are released, Ca+2 allows fusion of vesicles and releasing the transmitters into the axon, When the fluid moves in the direction opposite of the kinocilium, hyperpolarization occurs. Cochlear duct: Spiral tube Auditory function Supplied by cochlear nerve hair cells are supported by support cells, excited and are translated into hearing through cochlear fibers - Spiral organ of corti - Outer hair columnar cells (V shaped stereocilia) - Inner shorter cells (shorter stereocilia) Outer hair cells Inner hair cells ‫تمت كتابة هذا الشيت صدقة جارية عن روح والدة زميلنا عمرو رائد من دفعة تيجان‬ ‫دعواتكم لها بالرحمة والمغفرة‬ Thank you