Key Terms

alveolar ${\text{P}}_{{\text{O}}_{\text{2}}}$

partial pressure of oxygen in the alveoli (usually around 100 mm Hg)

alveolar duct

duct that extends from the terminal bronchiole to the alveolar sac

alveolar sac

structure consisting of two or more alveoli that share a common opening

alveolar ventilation

how much air is in the alveoli

alveolus

(plural: alveoli) (also, air sac) terminal region of the lung where gas exchange occurs

anatomical dead space

(also, anatomical shunt) region of the lung that lacks proper ventilation/perfusion due to an anatomical block

bicarbonate ${\text{(HCO}}_{\text{3}}^{-}\text{)}$ ion

ion created when carbonic acid dissociates into H⁺ and ${\text{(HCO}}_{\text{3}}^{-}\text{)}$

bicarbonate buffer system

system in the blood that absorbs carbon dioxide and regulates pH levels

bronchiole

airway that extends from the main tertiary bronchi to the alveolar sac

bronchus

(plural: bronchi) smaller branch of cartilaginous tissue that stems off of the trachea; air is funneled through the bronchi to the region where gas exchange occurs in alveoli

carbaminohemoglobin

molecule that forms when carbon dioxide binds to hemoglobin

carbonic anhydrase (CA)

enzyme that catalyzes carbon dioxide and water into carbonic acid

chloride shift

exchange of chloride for bicarbonate into or out of the red blood cell

compliance

measurement of the elasticity of the lung

dead space

area in the lung that lacks proper ventilation or perfusion

diaphragm

domed-shaped skeletal muscle located under lungs that separates the thoracic cavity from the abdominal cavity

elastic recoil

property of the lung that drives the lung tissue inward

elastic work

work conducted by the intercostal muscles, chest wall, and diaphragm

expiratory reserve volume (ERV)

amount of additional air that can be exhaled after a normal exhalation

FEV1/FVC ratio

ratio of how much air can be forced out of the lung in one second to the total amount that is forced out of the lung; a measurement of lung function that can be used to detect disease states

flow-resistive

work of breathing performed by the alveoli and tissues in the lung

forced expiratory volume (FEV)

(also, forced vital capacity) measure of how much air can be forced out of the lung from maximal inspiration over a specific amount of time

functional residual capacity (FRC)

expiratory reserve volume plus residual volume

functional vital capacity (FVC)

amount of air that can be forcibly exhaled after taking the deepest breath possible

heme group

centralized iron-containing group that is surrounded by the alpha and beta subunits of hemoglobin

hemoglobin

molecule in red blood cells that can bind oxygen, carbon dioxide, and carbon monoxide

inspiratory capacity (IC)

tidal volume plus inspiratory reserve volume

inspiratory reserve volume (IRV)

amount of additional air that can be inspired after a normal inhalation

intercostal muscle

muscle connected to the rib cage that contracts upon inspiration

intrapleural space

space between the layers of pleura

larynx

voice box, a short passageway connecting the pharynx and the trachea

lung capacity

measurement of two or more lung volumes (how much air can be inhaled from the end of an expiration to maximal capacity)

lung volume

measurement of air for one lung function (normal inhalation or exhalation)

mucin

complex glycoprotein found in mucus

mucus

sticky protein-containing fluid secretion in the lung that traps particulate matter to be expelled from the body

nasal cavity

opening of the respiratory system to the outside environment

obstructive disease

disease (such as emphysema and asthma) that arises from obstruction of the airways; compliance increases in these diseases

oxygen dissociation curve

curve depicting the affinity of oxygen for hemoglobin

oxygen-carrying capacity

amount of oxygen that can be transported in the blood

partial pressure

amount of pressure exerted by one gas within a mixture of gases

particulate matter

small particle such as dust, dirt, viral particles, and bacteria that are in the air

pharynx

throat; a tube that starts in the internal nares and runs partway down the neck, where it opens into the esophagus and the larynx

physiological dead space

(also, physiological shunt) region of the lung that lacks proper ventilation/perfusion due to a physiological change in the lung (like inflammation or edema)

pleura

tissue layer that surrounds the lungs and lines the interior of the thoracic cavity

pleurisy

painful inflammation of the pleural tissue layers

primary bronchus

(also, main bronchus) region of the airway within the lung that attaches to the trachea and bifurcates to each lung where it branches into secondary bronchi

recruitment

process of opening airways that normally remain closed when the cardiac output increases

residual volume (RV)

amount of air remaining in the lung after a maximal expiration

resistance

measurement of lung obstruction

respiratory bronchiole

terminal portion of the bronchiole tree that is attached to the terminal bronchioles and alveoli ducts, alveolar sacs, and alveoli

respiratory distress syndrome

disease that arises from a deficient amount of surfactant

respiratory quotient (RQ)

ratio of carbon dioxide production to each oxygen molecule consumed

respiratory rate

number of breaths per minute

restrictive disease

disease that results from a restriction and decreased compliance of the alveoli; respiratory distress syndrome and pulmonary fibrosis are examples

sickle cell anemia

genetic disorder that affects the shape of red blood cells, and their ability to transport oxygen and move through capillaries

spirometry

method to measure lung volumes and to diagnose lung diseases

surfactant

detergent-like liquid in the airways that lowers the surface tension of the alveoli to allow for expansion

terminal bronchiole

region of bronchiole that attaches to the respiratory bronchioles

thalassemia

rare genetic disorder that results in mutation of the alpha or beta subunits of hemoglobin, creating smaller red blood cells with less hemoglobin

tidal volume (TV)

amount of air that is inspired and expired during normal breathing

total lung capacity (TLC)

sum of the residual volume, expiratory reserve volume, tidal volume, and inspiratory reserve volume

trachea

cartilaginous tube that transports air from the larynx to the primary bronchi

venous ${\text{P}}_{{\text{CO}}_{\text{2}}}$

partial pressure of carbon dioxide in the veins (40 mm Hg in the pulmonary veins)

venous ${\text{P}}_{{\text{O}}_{\text{2}}}$

partial pressure of oxygen in the veins (100 mm Hg in the pulmonary veins)

ventilation/perfusion (V/Q) mismatch

region of the lung that lacks proper alveolar ventilation (V) and/or arterial perfusion (Q)

vital capacity (VC)

sum of the expiratory reserve volume, tidal volume, and inspiratory reserve volume