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Anatomy NEET MDS Synopsis - Lecture Notes
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📖 Anatomy

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Skeletal System Formation
Anatomy
  • Bones begin to form during the eighth week of embryomic life in the fibrous membranes (intramembranous ossification) and hyaline cartilage (endochondral ossification)
Nerves of the Face
Anatomy

Nerves of the Face

Innervation of the Muscles of Facial Expression

The Facial Nerve (CN VII)

 

  • The seventh cranial nerve supplies the superficial muscle of the neck (platysma), the muscles of facial expression, the auricular muscles and the scalp muscles.
  • CN VII is the sole motor supply to the muscles of facial expression.
  • The facial nerve emerges from the skull though the stylomastoid foramen.
  • Almost immediately, it enters the parotid gland. It runs superficially in this gland before giving rise to its five terminal branches: temporal, zygomatic, buccal, marginal mandibular, and cervical.
  • These nerve emerge from the superior, anterior and inferior margins of the gland and spread out like the abducted digits of the hand to supply the muscles of facial expression.
  • The temporal branches of CN VII cross the zygomatic arch to supply all the superficial facial muscles superior to it, including the orbital and forehead muscles.
  • The zygomatic branch of CN VII passes transversely over the zygomatic bone to supply the muscles in the zygomatic, orbital and infraorbital regions.
  • The buccal branches of CN VII pass horizontally, external to the masseter muscle, to supply the buccinator and the muscles of the upper lip.
  • The marginal mandibular branch of CN VII supplies the muscles of the lower lip and chin.
  • The cervical branch of CN VII supplies the platysma and the superficial muscles of the neck.
Ossification
Anatomy

  • Ossification

  • Intramembranous-found in the flat bones of the face
    • Mesenchymal cells cluster and form strands
    • Strands are cemented in a uniform network. Which is known as osteoid
    • Calcium salts are deposited; osteoid is converted to bone
    • Trabeculae are formed and make cancellous bone with open spaces known as marrow cavities
    • Periosteum forms on the inner and outer surfaces of the ossification centers
    • Surface bone becomes compact bone
  • Endochondral-primary type of ossification In the human
Speech
Anatomy

o    English: all speech sounds produced by making exhaled air audible

o    Two ways of producing sound
    at larynx
    further up in vocal tract (tongue, lips)
    
o    How to produce sound at larynx
    changes in breathing: regulate airstream from lungs to atmosphere by changing movements of vocal folds, pharynx, soft-palate, tongue, lips and jaws
    
•    inhalation: take in greater volume more quickly, abduct folds

•    expiration: variable force; use muscles of inhalation to control rate of expiration, adduct

    How to vibrate vocal cords
    
•    NOT rhythmic contraction of laryngeal muscles: would be impossible b/c frequenceies of virbration
•    Changes in air pressure cause vibrations


    o    Adduct folds increase in subglottal pressure force folds apart folds sucked back together (Bernouilli effect)
•    The vibration of vocal cords disturbs airareas of low pressure (rarefaction) alternating with areas of high pressure (compression)
•    Changes in pressure sound at ears
•    Sine waves

    o    Changes in amplitudes: loudness

    o    Changes in frequency: pitch

    o    Normal sounds have fundamental frequency, overtones or harmonics

    o    Mass of folds: critical in voice
    Low pitch of lion’s roar: due to massive fibrous pad that forms part of vocal cords
    Men: more massive vocal cords
    Larger foldsslow vibrationdeeper voice

    o    Producing vowels and constants
    Most vowels are “voiced”: vocal folds produce sounds
    Consonants: can be “voiced” (Z) or “non-voiced” (S)
•    Use higher regions of vocal tract to control by stopping, restricting airflow from vocal folds; use lips, teethaperiodic sound

o    Vocal folds and resonators emphasize and deemphasize certain frequencies
    Never hear sounds produced at vocal foldsevery sound changed by passage thru vocal tract: sinuses/resonating chambers
    Howling monkeys: large hyoid bonepowerful resonator

    o    Age-related changes in voice
    
    Infant larynx is smaller, different proportions
•    Arytenoids are proportionately larger
•    Smaller vocal apparatushigher pitch
•    Larynx sits higher easier to breathe thru nose
    Abrupt change in larynx at pubertycan’t control voice
    Older adult: normal degenerative changes in lamina propria, ossification of thyroid cartilagechanges in fundamental frequency
    Lose your voice vocal fold are irritated
•    Can’t adduct foldsair escapes

o    Singing v. speaking
    Singing: greater thoracic pressure and uneven breathing with changes in resonators

    o    Whispering
    Intercartilaginous portions of vocal folds: open to allow air to escapelesser subglottal pressureslittle vibration of foldslittle tonal quality, low volume

    o    Falsetto
    Allowing only part of vocal folds to vibrate
    Increase range by training which part of vocal folds to vibrate

    o    Colds
    Mucus secretions add mass to folds—decrease in pitch, can’t adduct folds as well

    o    Surgeryscars, fibrotic changes can interfere with voice