alveoliThe clusters of tiny sacs where the bronchioles end. Oxygen passes into the blood here. One of them is an alveolus.
breathOne drawing in of air and one letting out. A person can hold a breath for a short time, but breathing mostly runs without thought.
bronchiThe two large air tubes, one entering each lung. One of the two is called a bronchus.
bronchiolesThe thinnest air tubes, deep inside the lungs. Thousands of bronchioles branch off the bronchi.
chest cavityThe space inside the ribs that holds the heart and lungs. Another name for it is the thoracic cavity.
diaphragmThe dome of muscle that pulls downward to fill the lungs. It lies below the lungs, at the bottom of the chest cavity.
exhaleTo let air flow back out of the lungs. The diaphragm relaxes when you exhale.
inhaleTo take in a breath, by the nose or by the mouth. The diaphragm tightens and moves down when you inhale.
lungsThe pair of spongy organs where air and blood meet. One lung lies on each side of the heart.
noseThe organ on the face where air usually enters the body. The nose warms and moistens the air on its way in.
respiratory systemThe organs that take in oxygen and send out carbon dioxide. The lungs are its main organs.
tracheaThe windpipe: the main airway, which splits into two bronchi. Cartilage in its wall keeps the trachea from closing.
Show all 36 terms (24 more)
Gas exchange 12
capillaryThe narrowest type of blood vessel, with thin walls. A mesh of capillaries surrounds the alveoli.
carbon dioxideThe gas that cells make as waste and the lungs breathe out. Cells give off carbon dioxide when they make energy.
cellular respirationHow a cell uses oxygen to get energy from food. It gives off carbon dioxide as a waste product.
gas exchangeOxygen moving into the blood while carbon dioxide moves out. Gas exchange takes place in the alveoli.
lung capacityThe total amount of air that full lungs can contain. The lungs are at their greatest capacity in early adulthood.
oxygenThe gas in the air that body cells need to make energy. Red blood cells carry oxygen around the body.
oxygen-poor bloodBlood that has given its oxygen to the body's cells. It carries carbon dioxide back toward the lungs.
oxygen-rich bloodBlood fresh from the lungs, loaded with oxygen. The heart pumps it on to every part of the body.
pulmonary arteryThe vessel taking blood out of the heart toward the lungs. The blood in it is low in oxygen.
pulmonary veinA vessel bringing blood back from a lung to the heart. The blood in it is rich in oxygen.
red blood cellA blood cell that picks up oxygen and carries it. The protein in it that holds the oxygen is called hemoglobin.
respiratory rateHow many breaths a person takes each minute. At rest, an adult breathes 12 to 15 times a minute. The rate goes up during exercise.
Airways and lungs 12
intercostal musclesThe rib muscles that lift the chest for a breath in. They pull the rib cage up and out when you inhale.
larynxThe voice box: the part of the airway where sound is made. A flap called the epiglottis keeps food out of the larynx.
left lungThe lung with two lobes and a notch for the heart. It is slightly smaller than the right lung.
lower respiratory tractThe windpipe, the air tubes and the lungs, taken together. It begins where the larynx ends.
mucusThe wet coating of the air passages, which catches dust. Tiny hairs called cilia sweep the mucus upward.
nasal cavityThe hollow space inside the head behind the nose. A wall called the septum divides it in two.
nostrilsThe pair of holes at the outer end of the nose. Air goes in and out through them, and hairs just inside trap large particles.
pharynxThe passage that links the nose and mouth to the larynx. Its everyday name is the throat, and both air and food pass through it.
right lungThe lung with three lobes. It is shorter and broader than the left lung.
sinusesAir-filled hollows in the bones around the nose. There are four pairs of them, and they open into the nasal cavity.
upper respiratory tractThe nose, throat and voice box, taken together. Air is warmed and moistened here before it goes deeper.
vocal cordsThe paired bands in the larynx that give you a voice. They vibrate as air passes between them, and they stay open during breathing.
How this list was compiled: Term list chosen for this site on 2026-10-11. Each meaning is written in our own words and was checked that day against the English Wikipedia article on the term (https://en.wikipedia.org/), whose text is under the Creative Commons Attribution-ShareAlike license: Respiratory system, Lung, Trachea, Bronchus, Bronchiole, Pulmonary alveolus, Thoracic diaphragm, Inhalation, Exhalation, Human nose, Breathing, Thoracic cavity, Gas exchange, Oxygen, Carbon dioxide, Capillary, Red blood cell, Cellular respiration, Pulmonary artery, Pulmonary vein, Respiratory rate, Lung volumes and capacities, Nostril, Nasal cavity, Paranasal sinuses, Mucus, Pharynx, Larynx, Vocal cords, Respiratory tract and Intercostal muscles. Each was checked a second time against pages of the U.S. National Institutes of Health: How the Lungs Work, of the National Heart, Lung, and Blood Institute (https://www.nhlbi.nih.gov/health/lungs, with its pages The Respiratory System, How Your Body Controls Breathing and What Breathing Does for the Body), for the lungs, the airways, the breathing muscles, gas exchange and the blood that enters and leaves the lungs; and the Respiratory System pages of the SEER Training Modules of the National Cancer Institute (https://training.seer.cancer.gov/anatomy/respiratory/) for the upper and lower respiratory tract, the nose and sinuses, the pharynx, the larynx, the breath and breathing rate. The fact after each meaning is from the same pages. Licence: own work
How it works
This respiratory system worksheet for 5th grade prints twelve terms, among them lungs, trachea, bronchi, alveoli and diaphragm, to match to their meanings, with an answer key. It has words and meanings only, no diagram to label.
Read the full guide
Gas exchange
Set opens on The respiratory system. Gas exchange follows oxygen into the blood: gas exchange, oxygen, carbon dioxide, capillary, red blood cell, cellular respiration, pulmonary artery, pulmonary vein, oxygen-rich blood, oxygen-poor blood, respiratory rate and lung capacity.
Airways and lungs
The third set names what air passes on its way in: nostrils, nasal cavity, sinuses, mucus, pharynx, larynx and vocal cords, then the upper and lower respiratory tract, the right lung, the left lung and the intercostal muscles.
The everyday names windpipe and voice box are printed in the meanings of trachea and larynx.
Questions and answers
What are the parts of the respiratory system?
The nose and mouth, the pharynx, the larynx, the trachea, the two bronchi and their branches, and the lungs, where the bronchioles end in air sacs called alveoli. The diaphragm and the muscles between the ribs move the air.
What happens when you breathe in?
The diaphragm tightens and moves down, and the muscles between the ribs lift the rib cage. The chest cavity gets bigger, the lungs expand into it, and air is drawn in through the nose or the mouth.
What is gas exchange?
In the alveoli, oxygen from the air passes through thin walls into the capillaries, where red blood cells pick it up. Carbon dioxide moves the other way, out of the blood, and leaves the body when you breathe out.
Is there a respiratory system worksheet for 3rd grade or 4th grade?
This is the page for those grades too: the sheet itself prints no grade. The first set has lungs, trachea, bronchi, alveoli and diaphragm. The other two sets go further, into gas exchange and the parts of the airways.