Ear anotomy

• Anatomy and physiology of the peripheral auditory system: I
• The Outer and middle ear learning goals include knowledge of basic outer and middle ear anatomy, understanding of the outer ear function, understanding of middle ear function (especially impedance matching), knowledge of basic anatomy of the middle ear muscles and their function, understanding of the middle ear ventilation, understanding of air conduction and bone conduction.
• The pinna and ear canal increase the sound pressure at the tympanic membrane.
• Anatomy is the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
• The horizontal location of a sound source causes small variations in pressure gain, but they are not of much use for horizontal sound localisation.
• The pinna consists of cartilage (brusk), fatty tissue (fettvev), skin and a rich blood supply (blodtilførsel).
• Pressure increase in the pinna and ear canal is referred to as forsterkning.
• The muscles of the pinna are mostly controlled by the autonomic nervous system and are considered vestigial (rudiment).
• Physiology is the branch of biology that deals with the normal functions of living organisms and their parts.
• Anatomical terms are defined as back, foran, lavere høyere, nærmere kroppens sentrum, lenger bort fra kroppens sentrum, handen ligger distalt i forhold til skulderen, albuen ligger proksimalt i relasjon til hånden, men distalt i relasjon til skulderen.
• The temporal bone (tinningbein), frontal bone (frontalben), parietal bone (Parietalben), and mastoid bone (Mastoidben) are parts of the blank bone.
• The temporal bone contains the porus acusticus, processus mastoideus, and processus zygomaticus.
• The middle ear reflex can be acoustically activated and decreases the ability of the middle ear to transmit sound to the oval window by stiffening the ossicular chain.
• The Processus mastoideus is part of middle ear ventilation.
• The Eustachian tube (Tuba auditive, øretrompete) is a connection between the middle ear cavity and the nasopharyngeal cavity lined by two muscles, the levator and tensor veli palatini.
• Opening the Eustachian tube allows for pressure equilibration between the middle ear and the nasopharyngeal cavity, i.e. the outside world.
• The Eustachian tube is closed most of the time, swallowing or yawning opens it.
• Bone conduction is much less efficient than air conduction because the middle ear is bypassed.
• The Eustachian tubes (Tuba auditiva) are part of middle ear ventilation.
• A reflex is a relatively quick and uniform response to a stimulus.
• Malfunction of the Eustachian tubes can result in hearing impairment because the tympanic membrane cannot move properly due to the pressure differences.
• The middle ear reflex can be simultaneously evoked in both ears, meaning presenting sound to just one ear will cause muscle contractions in both ears.
• The function of the middle ear reflex is to protect the inner ear from loud sounds, including your own voice.
• The outer ear functions include sound transfer, which depends heavily on elevation for localisation.
• The outer ear consists of the pinna, ear canal, middle ear, inner ear, cochlea, vestibular system, and tympanic membrane.
• The first third of the ear canal is cartilaginous (brusk) and has hair follicles and cerumen (ear wax) glands, the inner two thirds have a bony wall covered with skin only.
• Cerumen (ear wax) can be either wet or dry, which depends on a single gene.
• Interference patterns caused by the pinna change frequency content at the ear drum as a function of elevation.
• The human ear canal is about 25 mm long and about 8 mm wide, and is predominantly S-shaped as it proceeds to the tympanic membrane, but the shape can be highly individual.
• The notch frequencies depend heavily on the vertical localisation of the sound source.
• Increasing the sound pressure level at the tympanic membrane improves the hearing thresholds by up to about 20 dB, which is 10 times more sound pressure, depending on frequency and therefore wavelength.
• Cerumen (ear wax) is a mixture of dead skin cells (keratinocytes) and waxy oils discharged from glands in and around the ear canal.
• Increasing the sound pressure level at the tympanic membrane is important for vertical sound source localisation, which works if you have at least one functioning ear.
• The petrous bone (pars petrosa), part of the temporal bone, is included in the macro-anatomy of the ear.
• The external ear (ytre øret), middle ear (mellomøret), and inner ear (indre øret) are parts of the macro-anatomy of the ear.
• The pressure increase is proportional to the area ratio of the tympanic membrane and the oval window (60 mm2/3.2 mm2).
• Without middle ear bones, most acoustic energy would be reflected at the boundary between liquid and air.
• As the area of the tympanic membrane becomes smaller, the pressure must increase.
• The mechanical force is constant in the middle ear.
• Without impedance matching, most acoustic energy would be reflected at the tympanic membrane, and would not reach the inner ear.