Respiratory System
- Is the source of air pressure and flows that are the power of speech
- Sounds can be produced either on incoming air (ingressive sounds) or on outgoing air (egressive sounds). The sounds of English are normally egressive, which means that our task in understanding what the respiratory system does in speech is essentially (1) to explain how air is drawn into the lungs to became a potential source of energy for sound production, and (2) to discuss how egressive flow of air is valved to generate sounds
- The task of the respiratory system during speech production is to generate the energy in the form of air pressure needed to produce the vibrations of speech. Speech is though to be an overlaid function, that is, a function that is superimposed on a mechanism that has another original biological purpose
- Breathing to stay alive is the fundamental purpose of respiration. When breathing for life we inhale and exhale in order to move oxygen into the lungs and carbon dioxide from them. Although using the same mechanism, the respiratory patterns for speech production is very different than breathing for life
- To generate and increase air pressure necessary for speech production we need to inflate the lungs. We accomplish this by creating a partial vacuum which requires expansion of the volume of the chest. For speech we capitalize on this inhalatory-exhalatory ability by making the chest function as a pressure pump.
The respiratory pump
- chest wall
- rib cage (respiratory system skeleton)
- diaphragm (most important muscle of inhalation)
- abdominal wall
- contents of abdomen (abdominal viscera)
- muscles of chest and abdomen
- pulmonary system (contained within the rib cage)
Rib Cage
- 12 pairs of ribs and rib cartilages
- 12 thoracic vertebrae
- sternum
- clavicle (collar bone)
- scapula (shoulder bone)
- within the rib cage is the thoracic cavity (thorax) or chest cavity, which contains, in addition to the pulmonary system, the mediastinum and the two thin, air-tight pleural membranes in which lungs are encased
- mediastinum is the space within the thorax, which contains the heart, blood vessels and esophagus
Pulmonary system
- the lungs are the organs that inflate with inhalation and deflates with exhalation
- the lungs are arranged in lobes, 3 on the right and 2 on the left
- the pulmonary system consists of a network of tubes where air travels in and out during respiration
- trachea (windpipe)
- right and left bronchi which continue to branch into smaller tubes leading to the
- alveolar air sacs (outermost reaches of the lungs)
- the alveolar sacs pass oxygen into the blood stream on inhalation and release carbon dioxide on exhalation
- these sacs are like tiny balloons, which are lubricated and resist to inflation
- to inflate the air sacs and consequently increase the volume of the lungs we need to increase the volume of the thorax, that is, the lungs can not inflate by themselves (they are not connected to muscles which can move structures)
- we increase the volume of the lungs by increasing the volume of the rib cage. This is accomplished by action of muscles of the chest wall, more specifically the muscles of inhalation
- inspiration involves raising the rib cage and lowering the diaphragm - unless one stands on one’s head (in which case gravity helps) inhalation is accomplished entirely by muscular contraction
Muscular arrangement for inspiration
Most important muscle of inhalation
- diaphragm
Accessory muscles of inhalation
Second most important muscle of inhalation
- external intercostals
Other accessory muscles of inhalation
- levatores costarum
- serratus posterior superior
- latissimus dorsi
- sternocleidomastoid
- scalenus anterior, medius, posterior
- subclavius
- pectoralis major
- pectoralis minor
- serratus anterior
- Remember this: “When breathing for life, we inhale and exhale in order to move oxygen into the lungs and carbon dioxide from them. For speech, we capitalize on this inhalatory-exhalatory ability by making the chest function as a pressure pump. Before pressure can be increased, the lungs must be inflated. This is accomplished by creating a partial vacuum which requires expansion of the volume of the chest"
- We just reviewed the muscles which helps expanding the chest in three dimensions:
- vertical expansion is achieved by lowering of the diaphragm muscle
- transverse or lateral expansion results from raising the rib cage
- anterior-posterior or front to back expansion also results from raising the rib cage
- As we expand the rib cage the rib cartilages are torqued. That is, due to the existence of rib cartilages (which are flexible and allow for movement) the rib cage can be expanded in the transverse and anterior-posterior dimensions.
Air-tight pleural membranes
- if the lungs were removed from the thorax they would collapse until most completely deflated
- conversely, the thorax would increase in volume because the lungs and the thorax are attached by pleural linkage
- the pleural membranes are 2 airtight membranes within which the lungs are sealed
- the outer pleural membrane adheres to the rib cage
- the inner pleural membrane wrap the lungs
- the 2 membranes are lubricated to prevent the lungs to directly rub against the rib cage
- the pleural membrane stick together like two wet glass surfaces, that is, they are held together by suction
- it is this negative interpleural pressure (similar to a partial vacuum) within the pleural system that sucks the lungs against the rib cage on both sides of the chest
Resistance of lung’s tissue to stretching and elastic recoil
- because the lungs and thorax are attached by the pleural linkage the thorax does not expands excessively nor the lungs collapse until almost completely deflated
- muscular action is required for thoracic expansion resulting in increase of lung volume, that is, as muscles (primarily the diaphragm) expand the dimensions of the rib cage the lungs are also expanded due to the negative pressure within the interpleural space (pleural cavity) which sucks to lungs against the ribs on both sides of the chest
- surface tension between the inner and outer pleural membrane makes to air sac resist to inflation
- the deeper the inspiration the greater the resistance of elastic lung tissue and air sacs against greater stretching and inflation
- at the point in which we stop inhaling and as long as we do not hold our breath, the deflation force from inflated air sacs, gravity and the untorquing of ribs act as the passive expiratory forces
- therefore, expiration is initially passive (depending on the elastic recoil of respiratory muscles)
- if speech demands require exhalation beyond the resting volume level, the muscles of are called in and forced expiration takes place
Passive forces of exhalation
- passive forces of gravity
- untorquing of rib cartilage
- elastic recoil of lungs and abdomen
- controlled relaxation of inspiratory muscles
Muscular arrangement for expiration
Rib cage muscles of exhalation
- internal intercostals
- transversus thoracis
- subcostals
- serratus posterior inferior
- quadratus lumborum
Abdominal muscles of exhalation
- rectus abdominis
- external oblique
- internal oblique
- transversus abdominis
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