Anatomy of the Voice

The information in this section is summarised with permission from Scott McCoy’s wonderful book “Your Voice: An inside View – Multimedia Voice Science and Pedagogy”. (1)

There are approximately 33 muscles used in respiration, posture and phonation that need to be functioning at optimal levels for good breathing and phonation.

 

See images below

Source: Henry Gray, Anatomy of the Human Body, 1918
Primary muscles of ‘Inspiration’

 

 

Primary Muscles of ‘Inspiration’

External intercostal muscles

  • Place your right hand on the right side of your chest with your fingers pointing towards your naval. This is the direction of the external intercostals in-between the ribs.
  • The lungs in the rib cavity or thorax are organs and cannot move by themselves.
  • The intercostal muscles are attached to the walls of the ribs and are strongly voluntary. This means they can easily be controlled to enlarge or decrease the size of the rib cage.
  • For inspiration the external intercostal muscles pull the ribs apart causing a decrease in air pressure and pulling the lungs open. The diaphragm also contracts and because the lower part of each lung is attached to the diaphragm they are expanded downwards. This causes a vacuum and air is pulled in to equalise the pressure inside and outside the lungs.

Diaphragm

  • This is the second largest muscle in the body. When contracted it descends 3-5cms.
  • It is shaped like a dome and completely bisects the body (bar a few important vessels!) at the base of the lungs separating them from the organs and contents of the abdomen.
  • When the diaphragm is contracted (the only movement any muscle can make) it flattens and increases the lung’s volume capacity.
  • Signals to the diaphragm are sent by two phrenic nerves which originate at the 3rd, 4th and 5th cervical (neck) vertebrae. Compression of the nerves through muscular tightness or misplacement of the vertebrae can inhibit the way the breathing muscles are recruited, reducing lung capacity and breath management.
  • Although the diaphragm is termed a voluntary muscle most people cannot control it (including most singers).
  • It is primarily a muscle of inspiration and cannot physiologically push air out for expiration. Expiration is controlled by the lower abdominal muscles.

 

Primary muscles of ‘Expiration’

Internal intercostal muscles

Place your right hand on the left side of your rib cage and point it towards your hip. This is the direction of the muscle fibres of these muscles.

  • The internal intercostals originate from a lower rib and insert into the rib above it. When the muscle contracts it pulls the ribs downwards and inwards, depressing the rib cage and decreasing the volume of air inside it.
  • In singing, these muscles are usually employed only at the very end of a phrase as a strong initial contraction in these muscles will cause a strident, forced sound.

Abdominal muscles

  • External and internal obliques, rectus and transverse abdominis are all found in the front of the abdomen and the quadratus lumborum lies at the back.
  • These muscles depress the rib cage and compress the contents of the abdomen pushing them up into the base of the diaphragm and deflating the lungs (like a hand pushing on the bottom of a balloon).

 

Secondary muscles of ‘Inspiration’

Secondary muscles affect localised parts of the breath mechanism but can still affect breath capacity. Postural muscles are very important – efficient breathing cannot occur if posture is compromised in any way.

Sternocleidomastoids
(on the neck)
These muscles elevate the top of the rib cage aiding inhalation and help to turn the head.

Scalenes
(on the neck)
The scalenes stabilise and move the head but as they are attached to the top ribs they are also activated on inhalation to elevate the top of the rib.

Intercostals (Interchondral portion), pectoral muscles, subclavian and serratus anterior (on front of rib cage)
These muscles expand the top of the rib cage.

Trapezius/ levator scapulae
(upper back of the body)
Together these muscles raise the top of the rib cage increasing breath capacity.

Rhomboids
(between the side border of the scapula and spine)
These are important muscles as they help maintain the ‘noble’ posture of singing (a non-collapsed sternum).

Serratus posterior/ erector spinae
(muscles which run up the spine)
These maintain a correct upright posture for singing.

Levator costarum
(found in the deepest layer of the back)
These muscles help expand the upper back for breathing.

 

Secondary muscles of ‘Expiration’

Innermost intercostals/ Transverse thoracis
These are small muscles that depress the front portion of the lower ribs for expiration.

Latissimus dorsi
(mainly a muscle that raises the arm)
These are large muscles on both sides of the body that aids compression of the back of the rib cage. Singers who rely on expansion in the middle and lower back must consciously relax these muscles during inhalation.

Serratus posterior inferior
These muscles help to depresses ribs 7-12.

 

Postural muscles (secondary)

Psoas major/minor muscles
(top of the leg)
These are important postural muscles that lift the leg and also tilt the pelvis. An incorrect pelvis position can compromise the ability of the abdominal muscles to function well in respiration.

In deep abdominal breathing the singer should aim to feel expansion right down at the level of the psoas (just above the hip), not just in the belly area.

 

Laryngeal anatomy and physiology

Breath support and breath control

The amount of air taken in during inhalation and its pressure during exhalation is support; the rate at which air escapes the glottis [the area between the vocal folds], and therefore the maximum phrase duration can be sung, is control (McKinney, 1994).

A few interesting facts about the larynx

The length of vocal folds (strips of tissue running transversely on the horizontal plane from front to back in the neck): 18-23mm.

  • The portion of vocal fold responsible for sound phonation is only 12-15mm long (only the front section vibrates to make sound). At rest they form a letter V, the bottom of which forms at the front of your neck and comes together for phonation. The space between the folds is called the glottis. The vocal folds are closed by the intrinsic muscles within the larynx.
  • The epiglottis is a leaf-shaped flap of skin that covers the airway during swallowing.
  • The size of a male larynx is typically the size of a walnut and a woman’s is about 40% smaller – the size of a pecan.
  • The larynx is suspended from the hyoid bone by extrinsic muscles in the neck.
  • The hyoid bone is one of two bones in the body not connected to another bone (the other is the knee cap). It is suspended in the neck by ligaments and if it moves, the larynx moves. For singers this means that if the jaw, tongue or upper neck muscles are tense this affects the position of the larynx in the neck.
  • Two nerves innervate the larynx. They are both portions of the Vagus or 10th cranial nerve. Damage to these nerves can lead to a persistent dry cough, paralysis and vocal problems.

Intrinsic (internal) laryngeal muscles

These are activated by the nervous system i.e., if we think of what we want to sing, the muscles respond accordingly. We cannot voluntarily control these muscles. We can control the amount of breath that oscillates the folds, however, and this can affect the pitch. For example, if too much air is forced through the glottis the pitch will be sharp.

External laryngeal muscles
(muscles of the neck)
Many of the extrinsic muscles used in singing also have a function in swallowing. When we swallow, the larynx and hyoid bones ascend which helps fold the epiglottis over the airway so we don’t choke and send food down the airway.

Three extrinsic muscles are constrictors that wrap around the vocal tract and exert a downward squeeze when we swallow.

  • No muscles exist that hold the throat open – you can only achieve this sensation by relaxing the constrictors.
  • The two upper constrictors narrow the pharynx, the lower also lifts the larynx.
  • Opera singing requires a high soft palate and normal or slightly lowered laryngeal position.
  • When we swallow the natural mechanism is that the larynx lifts and soft palate lowers so singers have to fight this reflex.

 

Laryngeal elevation

This is achieved by:

  • Being lifted by the thyroid or cricoid cartilage.
  • Being lifted as it is attached to the hyoid bone which is elevated by the larynx, tongue or jaw.

Thyrohyoid muscle

This muscle lifts the larynx towards the hyoid bone. Excessive tension in this muscle can lead to Muscular Tension Dysphonia and a chronic breathy sound.

Digastric muscles
These muscles raise the larynx and hyoid (posterior portion) and/or lower the jaw (anterior portion). If you have a tight over-extended jaw the anterior portion then becomes a laryngeal elevator leading to many problems for a singer.

Stylohyoid Muscle
This draws the larynx and hyoid bone up and back for swallowing.

Mylohyoid/ Geniohyoid Muscles
These form the musculature of the floor of the mouth: like the digastrics they drop the jaw and/or elevate the larynx.

Hyoglossus
The hyoglossus connects from the hyoid bone to the base of the tongue. Its function is to depress the tongue when swallowing but with certain tensions it too can elevate the larynx.

Laryngeal depression

Sternothyroid muscles
These are connected from the sternum to the base of the thyroid cartilage: contraction lowers the larynx. In singing, depressing this can lead to tension in the intrinsic muscles of the larynx so most teachers advocate just keeping these muscles free of tension so the larynx is anchored gently without actively pulling it down.

Sternohyoid muscles
These connect the sternum to the hyoid bone and lower the larynx as do the Omohyoid muscles which also attach to the scapular. Shoulder tension can therefore affect the ability of the body to anchor the larynx.

The tongue
For optimum singing the tongue must be free of tension in order to articulate vowels and consonants well and to produce the best possible resonance in the singing voice. The tongue attaches to the jaw, hyoid bone and soft palate. If there is tension or the jaw or hyoid bone are pulled out of alignment singing will be compromised.

More information

There are many sites on the internet and wonderful anatomy books to increase your knowledge of how the body works for you as a singer. Please ask me for some recommendations.

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