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module 5: CRANIOFACIAL DEVELOPMENT AND GROWTH - Coggle Diagram

- - - - STRUCTURE
        
        EXTERNAL
        
        The visible portion of the ear
        
        Auricle or pinna
        
        formed by elastic tissue, cartilage and muscles.
        
        Function : facilitating the passage of sound into the external auditory canal
        
        EXTERNAL UDITORY CANAL
        
        Length : 24mm
        
        Bent canal
        
        Narrowest part  isthmus is ± 5mm from the eardrum
        
        Ceruminous glands present  cerumen
        
        Functions :
        
        as a passageway for sound that ends at the eardrum
        
        : the narrow part provides protection from accidental injuries
        
        : cerumen helps deny access to foreign objects or insects, and slows the growth of microorganisms
        
        EXAMINATION
        
        OTOSTOPIC
        
        ADULT
        
        Pull the ear UPWARDS, OUTWARDS & BACKWARDS (due to the bent course of the external acoustic meatus)
        
        CHILD
        
        Pull the ear DOWNWARDS & BACKWARDS ( the external acoustic meatus is shorter and straighter)
        
        TYMPANIC MEMBRAN [eardrum]
        
        Oval shaped, greyish colour
        
        Thin and semitransparent sheet
        
        Separates the external ear from the middle ear
        
        Functions :
        
        provides surface for sound collection
        
        responds to sound waves and generates sound VIBRATION
        
        INTERNAL
        
        BONE LABYRINTH
        
        Protects the membranous labyrinth
        
        Contains perilymph
        
        Subdivided into
        
        vestibule : round window
        
        semicircular canals
        
        cochlea- oval window [makes 21⁄2 turns around the modiolus]
        
        MEMBRANOUS LABYRINTH
        
        Lies within the bony labyrinth
        
        Filled with endolymph
        
        Subdivided into :
        
        VESTIBULE
        [housing the receptors that provide sensations of gravity and linear acceleration]
        
        SACCULE
        
        UTRICLE
        
        semicircular canals - housing the receptors that provide sensations of rotation of the head
        
        cochlear duct – housing the spiral organ of Corti for auditory sensation
        
        RECEPTOR FOR BALANCING
        
        Maculae of utricle and saccule. & Crista ampullaris
        
        SEMICIRCULAR CANALS
        
        Anterior, posterior, lateral.
        
        Hair cells - at the swollen region (ampulla).
        
        Sensory receptor region - the crista ampullaris.
        
        ROTATIONAL MOVEMENTS
        
        Horizontal (“no”).
        
        Vertical (“yes”).
        
        Tilting the head from side to side
        
        LOCATION STIMULATED CELL
        
        Lateral semicircular canal
        
        Anterior semicircular canal
        
        Posterior semicircular canal
        
        HAIR CELL
        
        spiral organ of Corti
        
        located above the basilar membrane
        
        the stereocilia of hair cells are in contact with the tectorial membrane
        
        MIDDLE
        
        TYMPANIC CAVITY
        
        Narrow space in the petrous part of the temporal bone
        
        Biconcave shape
        
        Filled with air
        
        Connected to the :
        
        nasopharynx via the auditory tube (eustachian tube)
        
        mastoid sinuses and mastoid air cells via aditus
        
        Function : to equalize the pressure inside and outside the
        eardrum (eustachian tube)
        
        CONTENT
        
        ossicles (3) : malleus, incus, stapes
        
        muscles (2) : tensor tympani, stapedius
        
        ossicle ligaments
        
        blood vessels
        
        nerves : chorda tympani (branch of CN VII), tympanic plexus (CN IX)
        
        WALLS
        
        • roof (tegmental wall)
        
        • floor (jugular wall)
        
        • anterior (carotid wall)
        
        • posterior (mastoid wall)
        
        • lateral (membranous wall)
        
        • medial (labyrinthine wall)
      - FORMATION
      - NEURAL PATHWAY [equilibrium]
        
        hair cell stimulation.
        
        activation of sensory neurons located at vestibular ganglia
        
        vestibular branch of the vestibulocochlear nerve (CN VIII)
        
        synapse at vestibular nuclei
        
        to cerebellum
        
        to cerebral cortex- (conscious sense of position and movement)
        
        to motor nuclei
        
        in brain stem- for cranial nerves involved in the eye, head and neck movements (CN III, IV, VI & XI)
        
        in spinal cord- via vestibulospinal tracts
      - AUDITORY PATHWAY
        
        hair cell stimulation.
        
        activation of sensory neurons located at spiral ganglia
        
        cochlear branch of the vestibulocochlear nerve (CN VIII)
        
        synapse at cochlear nuclei
        
        synapse at inferior colliculi
        
        to medial geniculate (thalamus)- to the auditory cortex at temporal lobe (conscious awareness)
        
        motor output to cranial nerve- via tectobulbar tracts
        
        to sinal cord- via the tectospinal tracts