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Respiratory System
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One of the largest organ systems in the body
 1,500 miles of airways and almost 1,000 miles of
capillaries in the lungs
 Surface area of lungs is 80x greater than surface
area of skin
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Exchange of oxygen and carbon dioxide
through respiration
 External, internal and cellular respiration
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Production of sound
 Larynx contains vocal cords
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External respiration/breathing
 Exchange of oxygen and carbon dioxide between the
lungs, the body, and the outside environment
 Consists of inspiration (inhalation) and expiration
(exhalation)
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Internal respiration
 Exchange of carbon dioxide and oxygen between the
cells and the lymph surrounding them
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Cellular respiration/oxidation
 Use of oxygen to release energy stored in nutrient
molecules such as glucose
 This chemical reaction occurs within the cells
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Nasal cavity
 Air enters nostrils or anterior nares, then the nasal cavity
(separated by the nasal septum) lined with mucous membrane
 Three nasal conchae bones (turbinates) that increase the
surface area of the nasal cavity
 Air moistened by mucous and warmed by blood vessels
 Cilia entrap particles and filter air
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Pharynx
 Commonly known as throat; passageway for food and air
 5 inches long and subdivided into nasopharynx (connected to
eustachian tubes), oropharynx, and laryngopharynx
 Epiglottis is flap of cartilage lying behind the tongue and in
front of entrance to larynx
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Larynx
 Aka voice box, a triangular chamber found below the pharynx
 Composed of 9 fibrocartilaginous plates, largest known as the Adam’s
apple
 Characteristic vocal cords with space known as glottis
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Trachea
 Aka windpipe, tubelike passageway extending from larynx and continues
to form the two bronchi
 Composed of 15 to 20 C-shaped virtually non-collapsible rings of hyaline
cartilage
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Bronchi and Bronchioles
 Lower end of trachea separates into right and left bronchus (right
bronchus is shorter, wider, and more vertical in position)
 As they enter the lung, they subdivide into smaller bronchioles (Y shaped
in form)
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Alveoli
 Alveolar sacs consist of many alveoli
 Adult lung has about 500 million alveoli (3x the amount
necessary to sustain life)
 Inner surfaces covered with surfactant which helps stabilize
the alveoli
 Through the moist walls of alveoli and capillaries is where
rapid exchange of carbon dioxide and oxygen occurs
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Lungs
 Separated by the mediastinum
 The apex is the top of each lung; broad lower part is the base
which rests over the diaphragm
 Right lung has three lobes, left lung has two lobes
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Pleura
 A thin, moist, slippery membrane of tough endothelial cells
that covers the lungs
 Each lung encased in double-walled sac (visceral and parietal
pleura)
 Pleural fluid is located between the two membranes and
prevents friction during each breath
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Mediastinum
 AKA the interpleural space, located between the lungs
 Contains the thoracic viscera (thymus gland, heart, aorta,
esophagus, trachea, thoracic duct, lymph nodes, and vessels)
Due to changes in pressure that occur within the chest cavity
caused by cellular respiration and mechanical breathing
movements
 Inhalation/inspiration
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 Diaphragm contracts and pulls downward, causing the thoracic cavity to
expand
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Exhalation/expiration
 Diaphragm relaxes and moves upwards, causing the thoracic cavity to
become narrower
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Respiratory movements and frequency of respiration
 Normal rate in quiet breathing for an adult male is about 14 to 20 breaths
per minute (females are 16 to 20 breaths)
 Can be increased by muscular activity, increased body temperatures,
emotions, and certain pathological disorders
 Can be decreased by sleeping and emotions
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Neural factors
 Two neuronal pathways involved in breathing: phrenic
nerves lead to diaphragm and intercostal muscle; the
vagus nerve carries impulses to nose, larynx, lungs,
skin, and abdominal organs
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Chemical factors
 Level of carbon dioxide in the blood: as blood
circulates through respiratory center, it senses
increased carbon dioxide levels in blood and increases
respiratory rate
 Chemoreceptors found in carotid arteries and aorta: if
oxygen levels decline to low levels, impulses are sent
which will stimulate the rate and depth of respiration
Spirometer: device that measures the volume and
flow of air during inspiration and expiration
 Tidal volume: amount of air that moves in and
out of lungs with each breath (~500 mL)
 Inspiratory reserve volume (IRV): amount of air
you can force a person to take in above the tidal
volume (~2100-3000 mL)
 Expiratory reserve volume (ERV): amount of air
you can force a person to exhale above the tidal
volume (~1000 mL)
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Apnea: temporary stoppage of breathing
movements
Dyspnea: difficult, labored, or painful
breathing
Eupnea: normal or easy breathing
Hyperpnea: increase in depth and rate of
breathing accompanied by abnormal
exaggeration of respiratory movements
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Orthopnea: difficult or labored breathing when
in a horizontal position
Tachypnea: abnormally rapid and shallow rate
of breathing
Hyperventilation: condition that can be caused
by disease or stress; rapid breathing causing
the body to lose carbon dioxide too quickly
leading to dizziness and possible fainting
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Lung tissue loses elasticity
Rib cage becomes less flexible
Muscle strength decreases
Functioning alveoli decrease
Common cold: hundreds of strains of the virus;
runny nose, watery eyes, sneezing, stuffy head,
and sore throat
 Pharyngitis: bacterial or viral; painful swallowing
and extreme dryness of throat
 Laryngitis: secondary to other infections;
hoarseness or loss of voice
 Sinusitis: viral or bacterial; sinus pain and nasal
discharge
 Bronchitis: viral or bacterial; cough, fever,
substernal pain, and rales/raspy sound
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Influenza (flu): viral infection; fever, mucous
discharge, muscular pain, and extreme
exhaustion
Pneumonia: viral or bacterial; chest pain,
fever, chills, and dyspnea
Tuberculosis (TB): bacterial infection; cough,
low-grade fever, weight loss, night sweats
Pertussis (whooping cough): bacterial
infection; severe coughing attacks and
dyspnea
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Rhinitis: inflammation of nasal mucous
membranes causing swelling and increased
secretions
Asthma: airways become obstructed due to an
inflammatory response to a stimuli
Atelectasis: lungs fail to expand normally due
to blockage of air passages
Pneumothorax: buildup of air within the
pleural cavity on one side of the chest causing
the lung to collapse
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Chronic obstructive pulmonary disease
(COPD): group of lung diseases that limit air
flow as a person exhales due to lung irritants and
smoking
Cancer of the lung: most common cause of
cancer death in the US
Pulmonary embolism: blood clot travels to the
lungs after surgery or bed rest
Sudden infant death syndrome (SIDS): occurs in
infants between 2 weeks to 1 year who stop
breathing; exact causes unknown