The Respiratory System

Respiratory system.

The respiratory system, which consists of the airway, the lungs and the muscles of respiration, works with the cardiovascular system to oxygenate blood and eliminate carbon dioxide. The two primary processes involved in respiration are ventilation and gas exchange. Ventilation is to the movement of gas through the airway to and from the lungs. Gas exchange refers to the passive exchange by diffusion of oxygen and carbon dioxide between pulmonary alveoli and blood in the pulmonary capillaries. Ventilation occurs under the control of the autonomic nervous system in coordination with the medulla oblongata and the pons in the brainstem, the areas of the brain constituting the respiration regulatory center.

WikiPremed Resources

The Respiratory System Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for The Respiratory System
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Understand the anatomical structure of the human respiratory system.

Be able to describe the functional unit of the lung comprised of bronchiole, alveoli and capillaries.

Be able to describe the underlying physical science principles governing gas exchange across capillary and alveolar walls.

Understand the mechanics of ventilation.

Be familiar with the terminology for describing lung volumes and capacities.

Be able to describe how alveolar surface tension affects compliance and pulmonary ventilation.

Be able to describe the components of the innate and adaptive immune systems that protect the respiratory tract from inhaled microorganisms.

Be prepared to describe why hypoventilation or hyperventilation may effect blood pH.

Understand the roles played by central and peripheral chemoreceptors as well as mechanoreceptors in the regulation of the ventilation rate.

Suggested Assignments

Review the terminology for the respiratory system using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Complete the advanced crossword puzzle for the respiratory system. Here is the solution to the puzzle.

Read pp. 105-113 in ExamKrackers Biology II. Perform practice items 73-80 on pg. 114.

Review the web resources for the respiratory system.

Conceptual Vocabulary for The Respiratory System

Respiratory system
The respiratory system consists of the airways, the lungs, and the muscles that mediate the movement of air into and out of the body.
Respiratory tract
In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration.
The larynx, colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production.
Vertebrate trachea
The trachea, or windpipe, is a tube that extends from the larynx to the primary bronchi.
Thoracic diaphragm
The diaphragm is a sheet of muscle extending across the bottom of the ribcage which separates the thoracic cavity from the abdominal cavity and performs an important function in respiration.
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening.
A bronchus is a caliber of airway in the respiratory tract that conducts air into the lungs.
Right main bronchus
The right main bronchus is wider, shorter, and more vertical in direction than the left, entering the right lung nearly opposite the fifth thoracic vertebra.
Left main bronchus
The left main bronchus is smaller in caliber but longer than the right, entering the root of the left lung opposite the sixth thoracic vertebra.
Tertiary bronchus
The tertiary bronchi arise from the secondary bronchi.
Primary bronchiole
The primary bronchioles arise from the tertiary bronchi.
Inhalation, also known as inspiration, is the movement of air from the external environment, through the airways, into the alveoli during breathing.
Exhalation, or expiration, is the movement of air out of the bronchial tubes, through the airways, to the external environment during breathing.
Pulmonary circulation
Pulmonary circulation is the portion of the cardiovascular system which carries oxygen-depleted blood away from the heart, to the lungs, and returns oxygenated blood back to the heart.
Terminal bronchiole
A terminal bronchiole is a bronchiole at the end of the conducting zone.
Alveolar duct
Alveolar ducts are the tiny end tubules of the branching airways that fill the lungs.
Vital capacity
Vital capacity is the maximum volume of air that a person can exhale after maximum inhalation.
Functional residual capacity
Functional residual capacity is the volume of air present in the lungs at the end of passive expiration.
Dead space
Dead space is air that is inhaled by the body in breathing, but does not partake in gas exchange.
Pulmonary surfactant
Pulmonary surfactant is a surface-active lipoprotein complex formed by type II alveolar cells which reduces surface tension in the air water interface within alveoli.
Nasal cavity
The nasal cavity, or nasal fossa, is a large air-filled space above and behind the nose in the middle of the face.
Bronchopulmonary segment
Each of the tertiary bronchi serves a specific bronchopulmonary segment, and each of these segments have their own artery.
Respiratory bronchiole
A respiratory bronchiole is an airway at the beginning of the respiratory zone.
Ventilation rate is the rate at which gas enters or leaves the lung.
Pulmonary stretch receptors
Pulmonary stretch receptors are mechanoreceptors found in the lungs, which when the lung expands, initate the Hering-Breuer reflex, reducing the respiratory rate.
Hering-Breuer reflex
The Hering-Breuer reflex is a reflex triggered to prevent overinflation of the lungs by pulmonary stretch receptors present in the smooth muscle of the airways which respond to excessive stretching of the lung.
Clara cell
Clara cells are non-mucous and non-ciliated secretory cells found in the primary bronchioles of the lungs.
Alveolar-capillary barrier
The alveolar-capillary barrier exists in the gas exchanging region of the lungs, preventing air bubbles from forming in the blood and preventing blood from entering the alveoli.
Advanced terms that may appear in context in MCAT passages
Respiratory minute volume
Respiratory minute volume is the volume of air which can be inhaled or exhaled from a person's lungs in sixty seconds.
Lamellar bodies
Lamellar bodies, or keratinosomes, are secretory organelles found in type II pneumocytes which deliver pulmonary surfactant after being released from the cell.
Spirometry is the most common of the Pulmonary Function Tests (PFTs), measuring lung function, specifically the measurement of the amount and/or speed of air that can be inhaled and exhaled.
A respirometer is a device used to measure the rate of respiration of a living organism by measuring its rate of exchange of oxygen and carbon dioxide.
Dipalmitoylphosphatidylcholine (DPPC) is a phospholipid and the major constituent of pulmonary surfactant.
Pulmonary compliance
Compliance is the ability of the lungs to stretch in a change in volume relative to an applied change in pressure.
Respiratory quotient
The respiratory quotient is a unitless number used in calculations of basal metabolic rate when estimated from carbon dioxide production.
Diffusion capacity
Diffusion capacity is a measurement of the lung's ability to transfer gases.