Key Terms
acclimatization
process of adjustment that the respiratory system makes due to chronic exposure to high altitudes
acute mountain sickness (AMS)
condition that occurs a result of acute exposure to high altitude due to a low partial pressure of oxygen
ala
(plural = alae) small, flaring structure of a nostril that forms the lateral side of the nares
alar cartilage
cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae
alveolar dead space
air space within alveoli that are unable to participate in gas exchange
alveolar duct
small tube that leads from the terminal bronchiole to the respiratory bronchiole and is the point of attachment for alveoli
alveolar macrophage
immune system cell of the alveolus that removes debris and pathogens
alveolar pore
opening that allows airflow between neighboring alveoli
alveolar sac
cluster of alveoli
alveolus
small, grape-like sac that performs gas exchange in the lungs
anatomical dead space
air space present in the airway that never reaches the alveoli and therefore never participates in gas exchange
apex
tip of the external nose
apneustic center
network of neurons within the pons that stimulate the neurons in the dorsal respiratory group; controls the depth of inspiration
atmospheric pressure
amount of force that is exerted by gases in the air surrounding any given surface
Bohr effect
relationship between blood pH and oxygen dissociation from hemoglobin
Boyle’s law
relationship between volume and pressure as described by the formula: P1V1 = P2V2
bridge
portion of the external nose that lies in the area of the nasal bones
bronchial bud
structure in the developing embryo that forms when the laryngotracheal bud extends and branches to form two bulbous structures
bronchial tree
collective name for the multiple branches of the bronchi and bronchioles of the respiratory system
bronchiole
branch of bronchi that are 1 mm or less in diameter and terminate at alveolar sacs
bronchoconstriction
decrease in the size of the bronchiole due to relaxation of the muscular wall
bronchodilation
increase in the size of the bronchiole due to contraction of the muscular wall
bronchus
tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs
carbaminohemoglobin
bound form of hemoglobin and carbon dioxide
carbonic anhydrase (CA)
enzyme that catalyzes the reaction that causes carbon dioxide and water to form carbonic acid
cardiac notch
indentation on the surface of the left lung that allows space for the heart
central chemoreceptor
one of the specialized receptors that are located in the brain that sense changes in hydrogen ion, oxygen, or carbon dioxide concentrations in the brain
chloride shift
facilitated diffusion that exchanges bicarbonate (HCO3–) with chloride (Cl–) ions
conducting zone
region of the respiratory system that includes the organs and structures that provide passageways for air and are not directly involved in gas exchange
cricoid cartilage
portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus
Dalton’s law
statement of the principle that a specific gas type in a mixture exerts its own pressure, as if that specific gas type was not part of a mixture of gases
dorsal respiratory group (DRG)
region of the medulla oblongata that stimulates the contraction of the diaphragm and intercostal muscles to induce inspiration
dorsum nasi
intermediate portion of the external nose that connects the bridge to the apex and is supported by the nasal bone
epiglottis
leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing
expiration
(also, exhalation) process that causes the air to leave the lungs
expiratory reserve volume (ERV)
amount of air that can be forcefully exhaled after a normal tidal exhalation
external nose
region of the nose that is easily visible to others
external respiration
gas exchange that occurs in the alveoli
fauces
portion of the posterior oral cavity that connects the oral cavity to the oropharynx
fibroelastic membrane
specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle fibers
forced breathing
(also, hyperpnea) mode of breathing that occurs during exercise or by active thought that requires muscle contraction for both inspiration and expiration
foregut
endoderm of the embryo towards the head region
functional residual capacity (FRC)
sum of ERV and RV, which is the amount of air that remains in the lungs after a tidal expiration
glottis
opening between the vocal folds through which air passes when producing speech
Haldane effect
relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide
Henry’s law
statement of the principle that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas
hilum
concave structure on the mediastinal surface of the lungs where blood vessels, lymphatic vessels, nerves, and a bronchus enter the lung
hyperpnea
increased rate and depth of ventilation due to an increase in oxygen demand that does not significantly alter blood oxygen or carbon dioxide levels
hyperventilation
increased ventilation rate that leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH
inspiration
(also, inhalation) process that causes air to enter the lungs
inspiratory capacity (IC)
sum of the TV and IRV, which is the amount of air that can maximally be inhaled past a tidal expiration
inspiratory reserve volume (IRV)
amount of air that enters the lungs due to deep inhalation past the tidal volume
internal respiration
gas exchange that occurs at the level of body tissues
intra-alveolar pressure
(intrapulmonary pressure) pressure of the air within the alveoli
intrapleural pressure
pressure of the air within the pleural cavity
laryngeal prominence
region where the two lamine of the thyroid cartilage join, forming a protrusion known as “Adam’s apple”
laryngopharynx
portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food
laryngotracheal
bud forms from the lung bud, has a tracheal end and bulbous bronchial buds at the distal end
larynx
cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs
lingual tonsil
lymphoid tissue located at the base of the tongue
lung
organ of the respiratory system that performs gas exchange
meatus
one of three recesses (superior, middle, and inferior) in the nasal cavity attached to the conchae that increase the surface area of the nasal cavity
naris
(plural = nares) opening of the nostrils
nasal bone
bone of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones
nasal septum
wall composed of bone and cartilage that separates the left and right nasal cavities
nasopharynx
portion of the pharynx flanked by the conchae and oropharynx that serves as an airway
oropharynx
portion of the pharynx flanked by the nasopharynx, oral cavity, and laryngopharynx that is a passageway for both air and food
oxygen–hemoglobin dissociation curve
graph that describes the relationship of partial pressure to the binding and disassociation of oxygen to and from heme
oxyhemoglobin
(Hb–O2) bound form of hemoglobin and oxygen
palatine tonsil
one of the paired structures composed of lymphoid tissue located anterior to the uvula at the roof of isthmus of the fauces
paranasal sinus
one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses
parietal pleura
outermost layer of the pleura that connects to the thoracic wall, mediastinum, and diaphragm
partial pressure
force exerted by each gas in a mixture of gases
peripheral chemoreceptor
one of the specialized receptors located in the aortic arch and carotid arteries that sense changes in pH, carbon dioxide, or oxygen blood levels
pharyngeal tonsil
structure composed of lymphoid tissue located in the nasopharynx
pharynx
region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea
philtrum
concave surface of the face that connects the apex of the nose to the top lip
pleural cavity
space between the visceral and parietal pleurae
pleural fluid
substance that acts as a lubricant for the visceral and parietal layers of the pleura during the movement of breathing
pneumotaxic center
network of neurons within the pons that inhibit the activity of the neurons in the dorsal respiratory group; controls rate of breathing
pulmonary artery
artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli
pulmonary plexus
network of autonomic nervous system fibers found near the hilum of the lung
pulmonary surfactant
substance composed of phospholipids and proteins that reduces the surface tension of the alveoli; made by type II alveolar cells
pulmonary ventilation
exchange of gases between the lungs and the atmosphere; breathing
quiet breathing
(also, eupnea) mode of breathing that occurs at rest and does not require the cognitive thought of the individual
residual volume (RV)
amount of air that remains in the lungs after maximum exhalation
respiratory bronchiole
specific type of bronchiole that leads to alveolar sacs
respiratory cycle
one sequence of inspiration and expiration
respiratory epithelium
ciliated lining of much of the conducting zone that is specialized to remove debris and pathogens, and produce mucus
respiratory membrane
alveolar and capillary wall together, which form an air-blood barrier that facilitates the simple diffusion of gases
respiratory rate
total number of breaths taken each minute
respiratory volume
varying amounts of air within the lung at a given time
respiratory zone
includes structures of the respiratory system that are directly involved in gas exchange
root
region of the external nose between the eyebrows
thoracic wall compliance
ability of the thoracic wall to stretch while under pressure
thyroid cartilage
largest piece of cartilage that makes up the larynx and consists of two lamine
tidal volume (TV)
amount of air that normally enters the lungs during quiet breathing
total dead space
sum of the anatomical dead space and alveolar dead space
total lung capacity (TLC)
total amount of air that can be held in the lungs; sum of TV, ERV, IRV, and RV
total pressure
sum of all the partial pressures of a gaseous mixture
trachea
tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a route for air to enter and exit the lung
trachealis muscle
smooth muscle located in the fibroelastic membrane of the trachea
transpulmonary pressure
pressure difference between the intrapleural and intra-alveolar pressures
true vocal cord
one of the pair of folded, white membranes that have a free inner edge that oscillates as air passes through to produce sound
type I alveolar cell
squamous epithelial cells that are the major cell type in the alveolar wall; highly permeable to gases
type II alveolar cell
cuboidal epithelial cells that are the minor cell type in the alveolar wall; secrete pulmonary surfactant
ventilation
movement of air into and out of the lungs; consists of inspiration and expiration
ventral respiratory group (VRG)
region of the medulla oblongata that stimulates the contraction of the accessory muscles involved in respiration to induce forced inspiration and expiration
vestibular fold
part of the folded region of the glottis composed of mucous membrane; supports the epiglottis during swallowing
visceral pleura
innermost layer of the pleura that is superficial to the lungs and extends into the lung fissures
vital capacity (VC)
sum of TV, ERV, and IRV, which is all the volumes that participate in gas exchange