Respiratory System
Functions of: ** Gas Exchange
O2  CO
Blood  Lungs  Atmosphere
** Gas transport
** Temperature Regulation – warming air (inhaled gases) coming into lungs
** Filters inhaled gases (air)
** Aids cardio and lymphatic systems
** Huge role in pH balance
** Pressure is created by contraction of diaphragm, massaging heart, lymph
nodes and major veins and arteries.
Structure:
Airways:
Nasal Passages: filters, warms and humidifies air. Hair and mucus entrap foreign
particles, dust, etc.
Mouth: alternate rout from nose for air entry. Less protection from foreign particles, less
humidification or warming.
Pharynx: “throat” (area between nose, mouth, esophagus and larynx). Obstruction here
from tongue, foreign body, etc will stop all ventilation. Only area where food and air mix.
Larynx / “voice box”: Contains vocal cords – movement of air causes vibration, which
produces sound. Swallowing: epiglottis covers larynx to prevent aspiration, cartilaginous
rings support structure from collapse.
Trachea / Mainstem Bronchus: single airway leading to right and left Primary Bronchi.
Highly sensitive region at the area of bifurcation known as the CARINA. This area plays
a key role in airway protection from foreign objects (food/water) and cough stimulation
(mucous).
Lungs:
Conducting Airways: made up of cartilage, smooth muscle, elastic connective tissue,
pseudostratified columnar epithelium, serous glands, mucous-secreting goblet cells and
cilia. More for structure and movement of gases, transportation of air. Traps dust,
bacteria, keeps lungs clean. No gas exchange.
Sequence: Left and Right Primary Bronchi -> Secondary Bronchi; one to each lobe: 3 on
the right, 2 on the left (left lingula does not develop fully due to space occupied by heart)
-> Segmental Bronchi -> Terminal Bronchioles (see handout of alveoli) No gas
exchange.
Respiratory Airways: “functional unit” “parenchyma”. Much less smooth muscle,
cartilage, cilia, or goblet cell. Thinner walls and large surface area facilitates diffusion.
Gas exchange.
Sequence: Respiratory Bronchioles -> Alveolar Ducts -> Alveolar Sacs -> Alveoli
(simple squamous epithelium for diffusion) Gas exchange.
Pleura: Double layered serous membrane encapsulating the lungs. Dense connective
tissue. Parietal layer binds to the chest wall, visceral layer binds to the lung.
Pleural fluid between the layers decreases friction and creates a negative pressure (assists
with mechanics of breathing).
Mucociliary Blanket: Protects respiratory system by entrapping dust, bacteria, pollutants
etc. Cilia are in constant motion, sweeping particles up toward the airways (throat,
mouth) to the trachea to be expectorated or swallowed. They line the conducting airways.
It is stimulated by cough and suppressed by dry air, noxious agents, pollution, thick
mucus and cigarette smoking (may paralyze and/or kill cilia).
Thoracic Cage: Contains and protects the lungs and vital organs.
Superior border: neck musculature, scalenes, platysma, etc.
Inferior border: diaphragm
Lateral borders: ribs and intercostal muscles.
Central Division: mediastinum – a midline “space” containing the heart, great vessels,
esophagus, thymus, lymph nodes, vagus, and phrenic nerves.
Function:
Ventilation / Gas transport – movement of gases between internal and external
environments
Respiration / Gas exchange / Diffusion: alveoli to blood to cells and back
Supplies Oxygen to tissues and is primary method of Carbon Dioxide elimination
Strong role in pH regulation – acid/base balance in blood.
Ventilation: movement of gasses into and out of the lung. Controlled by respiratory muscles,
intrapleural pressures (vacuum between pleura), and elastic properties of lung tissue.
Muscles of Respiration:
Primary muscles of Inspiration:
Diaphragm: sole functions respiratory
Attaches to Xiphoid, costal cartilage of lower 6 ribs, lower 4 ribs (interdigitates with
transversus abdominus), upper lumbar vertebrae.
Central tendon rotates downward in all directions.
Concentric contraction pulls tendon inferiorly, muscle descends increasing vertical
diameter of thorax. Increased volume of thorax decreases pressure -> net influx of air into
lungs.
Oscillation of diaphragm ranges from 1.5 – 12.0 cm with varying depths of inspiration.
Downward movement also compresses abdominal contents.
During normal, quiet breathing, diaphragm can produce up to 75% of the effort required
to increase thoracic volumes.
Is innervated by the Phrenic nerve (C3,4,5)
Intercostals: Internal and external layers run at 90 degree angles to each other. Will
function during both inspiration and exhalation. Innervated by intercostal nerves at each
specific spinal level.
Scalenes:
primary muscles of respiration
Anterior: TVP’s C3-6 to 1st rib
Middle: TVP’s C2-7 to 1st rib
Posterior: TVP’s C3-6 to 1st rib
All will elevate the upper ribs with the neck held in a static position, thus increasing
thoracic volumes.
Accessory muscles of Inspiration:
Sternocleidomastoid – helps raise sternum to increase thoracic volume
Pectoralis Minor – will elevate ribs when coracoid is stabilized
Levator Scapulae + Upper/Middle/Lower Trapezius – will stabilize
scapula/coracoid
Action of Exhalation:
Is primarily a passive action during normal, quiet breathing.
1) Diaphragm raises to return to it’s natural resting position, decreasing thoracic volume, causing
a net efflux of air from the lungs.
2) The lung’s natural elastic properties cause recoil, increasing intrapleural pressures aiding
recoil of the chest wall (negative pressure between pleural layers “pull” the ribs back in) as
3) the costal cartilages return to their normal resting position.
Accessory muscles of “forced” Exhalation:
All abdominal muscles:
Rectus Abdominus
Internal/External Oblique
Transversus Abdominus
Contraction increases abdominal pressures, forcing the diaphragm to rise. This decreases
the thoracic volume and increases the pressure facilitating a net efflux of gases from the
lungs.
Intercostal Muscles : bring the ribs closer together, decreasing volume while increasing
pressure within the thorax.
Serratus Posterior Inferior
Early Signs and Symptoms of Possible Respiratory Distress:
Dyspnea:
“difficulty breathing” “Shortness of Breath”
Always subjective, depends on the person:
BORG SCALE OF PERCEIVED EXERTION, 0-10 restful to out of breath,
similar to pain scale.
Results from impaired gas exchange due to changes affecting:
Lungs: obstruction in airways (foreign bodies, tumors, thick mucus or plugging, something
physically blocks airway), bronchoconstriction (narrows), edema/swelling of airways, lung tissue
pathology (fibrosis, scarring – loss of single cell layer), loss of functional units (disease, surgery,
cancer)
Vascular system: impaired perfusion (shunting, atherosclerosis, pulmonary embolism), low
hemoglobin/anemia etc
Musculoskeletal system: fatigue or restriction to respiratory muscles (barrel chest with advanced
lung disease limits ROM of chest wall, neuromuscular disease, musculoskeletal trauma, exercise,
prolonged cough etc), pain from trauma, pleuritic pain etc.
An obese abdomen (overweight or pregnant) will compromise diaphragmatic excursion, limiting
depth of inspiration (especially in a supine or prone position).
“Breathlessness positions” – sitting forward with elbows propped on knees or a table will allow
the abdomen to drop forward and gravity can assist in diaphragmatic movement.
Also occurs during exercise when cellular respiration needs exceed alveolar respiration capacity
(oxygen debt). Runners bending over to catch their breath.
Cough: Coughing and sneezing help to expel material from the respiratory tract. Coughing
clears the lower tracts, sneezing from the pharynx up. Coughing requires co-ordination and
adequate strength of respiratory and throat muscles in order to be effective.
3 stages of coughing:
1) deep inspiration to fill the lungs with air
2) compressive phase: glottis must close, activation of accessory muscles of forced exhalation
contract, thus increasing intrathoracic pressures
3) expulsive phase: sudden opening of the glottis allows forced outflow of air.
Productive cough: produces expectorant (mucous)
Effective cough: adequate strength and co-ordination but may or may not be productive (ie:
strong but dry cough – still effective in loosening secretions to eventually be expelled.
Conditions Associated with Pulmonary Disease:
Pneumothorax: (air in your thoracic cage)
Accumulation of air within the pleural cavity resulting in collapse of a lobe or entire lung.
Normally, a negative pressure is present between pleural layers which acts to fight the natural
elastic recoil of the lungs. When air enters the pleural space, this vacuum is lost, the lung recoil
and collapse in whole or in part. May be a rapid or slow process depending on mechanism of air
entry. May be painful due to involvement of pleural layers.
Causes:
Trauma -external leak (fractured leak, stab wound, bullet, etc)
Pathology - internal hole in lung (instead of alveoli have burst or ruptured, leaks into
pleural layers, tumors
Idiopathic- w/tall thin athletic teen boys with a thorax that grows too fast. lungs have to
catch up and grow
Atelectasis:
Derived from the Greek roots: “Ateles” = imperfect and “Ektasis” = expansion. Atelectasis
occurs when one of more segments or lobes of the lung collapse. Atelectasis results in reduced
ventilation and oxygenation of lung tissue and impairs secretion clearance. This increases the
risk for infection and decreases oxygen delivery to tissues. You can have this w/o pneumothorax.
(look up in Tabers).
1.Atelectasis Neonatorum / Primary Atelectasis:
Implies that the lung has never been inflated or hasn’t inflated properly
May be complete or partial
Lungs should inflate immediately after birth
Most commonly seen in premature or other high risk births
MEDICAL EMERGENCY – may be fatal to infant (no expansion – no oxygenation of blood!)
2. Acquired Atelectasis:
3 main types:
1) Compressive: lung tissue is compressed by adjacent structures such as fluid (pleural
effusion), air (pneumothorax), or blood in the pleural cavity, tumors, or an
elevated/paralyzed diaphragm (compresses lung upward) (from physical trauma, CN
damage, surgery).
2) Obstructive / Resorptive: occurs secondary to internal airway obstruction such as mucus
plugging, tumors, or inhaled foreign bodies. Trapped air distal to obstruction is absorbed
--> airway collapses.
3) Contraction: a lung that doest not fully expand. Local or generalized fibrotic changes in
the lung tissues preventing full lung expansion. Can also occur secondary to anesthetics,
narcotic use or musculoskeletal pain. Anesthetics and narcotics can depress central
respiratory drive. Pain will inhibit voluntary inspiratory effort.
As MT’s we can help them with the pain. Using ribcage properly instead of upper thoracic
muscles.