Lecture 15 – Articulation, Hearing.docx

Lecture 16 – Articulation, Hearing

14.03.24

• Mandible muscles (restricted to elevation and depression)
  • Mandibular elevators
    • Masseter – elevates mandible
    • Temporalis – elevates mandible (and retracts)
    • Medial pterygoid – elevates mandible
  • Mandibular depressors
    • Digastricus (anterior and posterior) – depress mandible
    • Mylohyoid – depresses mandible if hyoid fixed
    • Geniohyoid – depresses mandible if hyoid fixed
    • Platysma
• Q: how can I identify the two big mandibular muscles masseter and temporalis?
  • By touching your face and side of the head while at the same time elevating and depressing the jaw
• Velum
  • Referred to as the soft palate
    • Performs wide range of movements
    • Production of most speech sounds
      • Must remain in a moderately elevated position (for non-nasal sounds)
    • Non-nasal speech: velum generally remains closed (velum raised) (=most of the time)
    • Nasality
      • Hypernasality – excessive nasal resonance due to inadequately closing velum
      • Hyponasality – absence absence of nasalized speech in nasal sounds such as /m/ and /n/ due to inadequate velopharyngeal (VP) opening
    • Raised= closed=active/contracted muscles, lowered=open=relaxed
  • Velum is closed for non-nasalized speech
    • Muscle function for closing: Levator veli palatini (most important one)
    • Assimilation – some nasal quality to adjacent phonemes
    • High pressure consonants (fricatives and stops) require greater velo[haryngeal closure
  • Hard and soft palate are endowed with sensors
  • Uvula is part of the velar structure (hangs from the end of the soft palate)
• Can one actively move the uvula?
  • You can actively move the velum which moves the uvula but you can’t move the uvula itself?
  • = yes. We don’t entirely know why we have a muscle but probably to help push uvula backwards/sideways out of the way of food if you are swallowing food that is hard, large, spiky so you don’t damage it
  • Uvula muscularis
  • Don’t use it for speech though
• Nasal tract and velum
  • Upper part of the nasopharynx merges into the nasal tract and ends at the nose
  • Biological functions
    • Warming of the inhaled air while breathing
  • All surfaces are covered by mucous membranes
  • 
• Coupling to the oral tract
  • Connection to oropharynx is achieved by lowering the velum 🡪 this process opens the velopharyngeal port (VPP)
• Sound propagation
  • The nasal tract cannot produce speech sounds by itself 🡪 but in connection to the rest of the vocal tract (connected or not connected) it can alter acoustic properties of speech sounds considerably 🡪 coupling nasal tract is achieved by lowered or raised velum (lowered velum = nasal cavity coupled; raised velum = nasal cavity not coupled 🡪 not active in speech production)
  • Nearly no sound energy leaves the nasal tract 🡪 due to small openings plus high damping (reason: the mucous walls)
  • Rather the nasal cavity “draws” energy away from the sounds that are produced and modified in the oral tract
• Velum muscles
  • Muscles of velum compress to elevate the velar structure to completely separate oral and nasal areas 🡪 this preventing the nasal cavity to be coupled to the oral cavity
  • Muscles are compressed during most speaking time and when swallowing
  • Muscles not compressed only when using a few speech sounds in English – nasals
    • In other languages velum is opened for both nasal phonemes and nasalized vowels
• The pharynx
  • The top of the larynx joins with the esophagus at the laryngopharynx (area above the larynx)
  • The most superior part of the epiglottis marks the beginning of the oropharynx
  • The area above the velum is the nasopharynx
  • The pharynx is a four-way crossing: nasal tract, oral tract, larynx and esophagus
    • Esophagus is used during swallowing and eating (epiglottis closed)
  • 

Anatomy and physiology of Hearing

• The ear
  • The hearing organ “ear”) is composed of a series of structures:
    • The external ear
    • The middle ear
    • The internal ear
  • The neural impulses registered by the sensory cells are then analyzed by the brain
  • 
  • 
  • Two balance systems: visual and semicircular canals. You get dizzy when they are disturbed / not agreeing
• 1. The external ear
  • Everyday use of the word “ear” means technically the external ear
  • External ear consists of
    • Auricle (pinna)
    • Meatus (ear canal)
    • Tympanic membrane (ear drum)
  • task of the auricle: localize the sound source (important: evolution)
  • tympanic membrane works like a loudspeaker or microphone membrane
  • Hardly relevant for hearing – just used to sensing directionality of sounds, otherwise you can hear perfectly fine if it is cut off
• External audiotry meatus
  • External ear canal
  • 7mm in diameter and 2.5 cm long
  • This generates resonance frequencies at 3400 Hz
  • From an acoustic point of view: ear canal is a filter that amplifies frequencies between 2kHz and 5 kHz
  • Terminates at the tympanic membrane
    • Two-thirds of ear canal houses in bone (osseus portion)
    • One-third of ear canal composed of cartilaginous parts
  • Resonating cavity that contributes to hearing
    • Determine resonant frequency
  • Outer third-line with hair cells and cerum (ear wax) – protects by trapping dirt and insects
• Tympanic membrane
  • Also known as the ear drum
  • Separates the middle ear from the outer ear
  • Oval shaped, 10 mm in diameter
  • Thin three layered sheets of tissue
  • Landmarks
    • Umbo – point of attachment for malleus, middle ear bone – location is cone of light (reflects light from otoscope)
  • Responsible for initiating mechanical impedance-matching process of middle ear
    • first layer: outer (cuticular) layer
    • second layer: intermitted (fibrous) layer
    • third layer: inner (mucous) layer
• 2. The middle ear
  • The middle ear consists of the tympanic cavity
    • This cavity contains the smallest moving bones of the human body – the ossicles:
      • Malleus (hammer): touches the tympanic membrane and transmits to
      • The incus (anvil) which transmits to
      • Stapes (stirrup) which transmits to internal ear (oval window)
    • Malleus and stapes are attached to muscles (may attenuate to transmission of sound by these bones
  • The stapes connect directly to the internal ear through the oval window 🡪 transmission of stapes movement to the lymphatic fluid inside the internal ear
• Ossicles
  • Malleus
    • Largest of the ossicles
    • 9mm long and weighs only 25 mg
    • Provides point of attachment with tympanic membrane
    • Bulk of bone is the head of caput
  • Incus
    • Shaped like an anvil
    • Weighs 20 gm and is around 7mm long
    • Provides intermediate link of ossicular chain
    • Incus and malleus articulate by means of a saddle joint
  • Stapes (stirrup)
    • Third bone of the ossicular chain
    • Weights 4 mg with an area of 3.5 mm^2
    • Helps to transmit sound vibrations from eardrum to oval window
    • Articulation of the incus and stapes of ball and socket type
  • Ossicular chain is held in place by ligaments
• Tympanic muscles
  • Muscles of middle ear attached to ossicles
  • Smallest muscles of human body
    • Stapedius muscle
      • Imbedded in posterior wall of middle ear
      • Pulls stapes posteriorly
    • Tensor tympani
      • Pulls malleus anterior and medial