Ventilation Mechanics
The dome-shaped muscle located below the lungs that contracts and flattens during inhalation to increase thoracic volume.
Diaphragm
The microscopic, sac-like structures in human lungs where gas exchange occurs between air and surrounding capillaries.
Alveoli
Blood vessels with thick, muscular, and elastic walls that carry blood under high pressure away from the ventricles.
Arteries
The maximum total volume of air that a person can expel from their lungs after taking a maximal inhalation.
Vital Capacity
The main central airway tube lined with cartilage that carries air down from the throat before splitting into two bronchi.
Trachea
The specific group of intercostal muscles that contract during forced exhalation to pull the ribcage downward and inward.
Internal Intercostal Muscles
The passive physical process driven by concentration differences through which oxygen enters the bloodstream and carbon dioxide leaves it across alveolar walls.
Simple Diffusion
Low-pressure blood vessels equipped with internal pocket valves to prevent the backflow of blood returning to the heart.
Veins
The maximum volume of extra air that can be forcibly breathed into the lungs beyond a normal resting inhalation.
Inspiratory reserve volume
Narrow, branching airway tubes containing smooth muscle that connect the bronchi directly to the alveoli.
Bronchioles
The volume of air moved into or out of the human lungs during a single quiet, relaxed breath.
Tidal Volume
The essential feature of the inner alveolar lining that allows atmospheric oxygen to dissolve prior to diffusing across the respiratory membrane.
Moist Surface
Microscopic blood vessels featuring walls made of a single layer of endothelial cells with tiny pores to enable exchange of nutrients and gases.
Capillaries
The maximum volume of extra air that can be forcefully exhaled from the lungs after completing a normal, relaxed exhalation.
expiratory reserve volume
Specialized respiratory organs in aquatic animals where oxygen diffuses from water flowing past the mouth directly into capillary blood.
Gills
Explain how the pressure inside the thoracic cavity changes relative to atmospheric pressure during inspiration.
thoracic pressure decreases below atmospheric pressure (allowing air to flow into the lungs down a pressure gradient)
List three essential structural features of the alveolar network that maximize the rate of gas diffusion.
large total surface area, extremely thin diffusion barrier (one cell thick), and a dense capillary network (or moist lining)
The middle layer of an artery or vein wall, composed primarily of smooth muscle and elastic fibers, which controls vessel diameter and withstands blood pressure.
Tunica Media
The number of times a person inhales and exhales in one minute.
Ventilation rate (breathing rate)
The primary physiological purpose of continuous blood flow in capillaries combined with continuous ventilation of the lungs.
maintaining steep concentration gradients for oxygen and carbon dioxide
Name the antagonistic muscle pairings involved during normal inspiration, specifying which muscle group contracts and which relaxes.
external intercostals contract while internal intercostals relax (and/or diaphragm contracts while abdominal muscles relax)
The physical property of water inside alveoli that pulmonary surfactant reduces to prevent alveolar collapse during exhalation.
surface tension
The structural mechanism in major arterial walls that maintains continuous blood flow and blood pressure during ventricular diastole.
Elastic recoil
The waste gas produced by body cells that diffuses from capillaries into the alveoli to be exhaled from the lungs.
Carbon Dioxide
List four structural properties required by all animal gas exchange surfaces to maximize diffusion efficiency.
large surface area, thin tissue layer (short diffusion distance), moist surface, and permeability to gases (or dense capillary network)