Ear 1 Flashcards
Name the 3 regions the ear is divided into
external (outer) ear
middle ear
internal (inner) ear
Describe the function of the external/outer ear
to collect sound waves and direct them inwards
Name the 3 parts the external ear consists of
Pinna/Auricle
External Auditory Canal/Meatus (EAM)
Tympanic Membrane
Describe the pinna/auricle
flap of elastic cartilage covered in thick skin
Describe the EAM - external auditory meatus
2.5cm curved tube in the temporal bone that leads to the tympanic membrane, hairs and sebaceous glands which secrete cerumen (ear wax) near the exterior opening prevent objects from entering the ear
Describe the tympanic membrane (eardrum)
thin, semi-transparent partition between the EAM and middle ear, concave external surface covered with skin, convex internal surface covered with mucous membrane
Describe the middle ear
an air filled cavity within the petrous portion of the temporal bone, separated from the external ear by the tympanic membrane, separated from the internal ear by a thin body partition containing 2 openings = oval window and round window
Describe how the Auditory/Eustachian tube fits in
the anterior wall of the middle ear contains an opening that leads directly to the Eustachian tube, connects the middle ear with the nasopharynx
Describe the function of the Auditory/Eustachian tube
to equalise air pressure on both sides of the tympanic membrane, otherwise rupture of this membrane can occur, also a route for pathogens to travel from the nose and throat to the middle ear - can lead to infection such as otitis media
Name where the auditory ossicles lie and their names and shape
lie within the middle ear, 3 smallest bones in the body The malleus (hammer) The incus (anvil) The stapes (stirrup)
Describe how the auditory ossicles are connected, attached and their roles
connected to each other by synovial joints, the ossicles are attached to the cavity by ligaments and muscles, they reduced the amplitude and range of oscillations within the ear to protect it from damage due to loud noise
Describe how each auditory ossicle is attached
the handle of the malleus is attached to the internal surface of the tympanic membrane, the head of the malleus articulates with the body of the incus, the incus articulates with the head of the stapes, the base of the stapes fits into the oval window which sits between the middle and inner ear, below the oval window is the round window
Describe the inner ear
also known as the labyrinth, a complex series of canals that form the bony and membranous labyrinth, located in the petrous portion of the temporal bone
Name the 3 series of cavities the bony labyrinth is divided into
vestibule
cochlea
semicircular canals
What are all 3 cavities filled with
fluid called perilymph
Describe the membranous labyrinth
the perilymph of the bony labyrinth surrounds the membranous labyrinth, its a series of sacs and tubes lying insde and following the same form as the bony labyrinth
What does the membranous labyrinth contain
endolymph
Describe the semicircular canals
3 bony canals that project upward and posteriorly from the vestibule , each lie at approx right angles to each other, due to their positions = called anterior, posterior and lateral semicircular canals, the ends of each enlarge into a swelling called the ampulla
the membranous labyrinth within the canals are the semicircular ducts
Describe the cochlea
lies anterior to the vestibule, shell-like appearance, 2 & 3/4 turns, contains hair cells that act as receptors for auditory sensation, the free ends of the hair cells extend into the endolymph of the membranous labyrinth, the basal ends of these cells are in contact with the fibres of the cochlear branch of vestibulocochlear nerve (CNVIII)
