Respiratory Anatomy 101 for Parents: Understanding Your Child's Breathing
TL;DR Summary:
The respiratory tract is made up of all the structures that air flows through when we breathe - nose/mouth, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.
The respiratory system basically does two things - bring oxygen into the body and remove carbon dioxide from the body, a process called gas exchange.
The nasal and oral cavities are the entry points for air; infants heavily rely on nasal breathing, which is crucial for feeding and can cause trouble breathing when infants get the cold or other viral infections.
The pharynx (throat) is shorter and narrower in children, and the tonsils and adenoids are more prominent, which can cause breathing difficulties when they become swollen due to infections.
The larynx (voice box) contains the vocal cords and is positioned higher in the neck in children. The epiglottis, which protects the airway during swallowing, is more floppy and U-shaped in infants, making them more prone to breathing issues.
The trachea (windpipe) is narrower and shorter in children, and the cartilage rings supporting it are softer and more pliable, increasing the risk of airway collapse or obstruction.
The bronchi and bronchioles are smaller in diameter and branch off at a more horizontal angle in children, making them more susceptible to obstruction and foreign body aspiration.
Alveoli, the tiny air sacs where gas exchange occurs, are fewer in number and less developed in infants and young children, which can affect their respiratory health and make them more vulnerable to infections and complications.
Introduction:
As a parent, you've probably experienced the worry and frustration of seeing your child struggle with a cough, cold, or trouble breathing. It's natural to feel helpless in these situations, but understanding the basics of your child's respiratory system can help you better navigate these challenges and work with your pediatrician to keep your little one healthy.
In this post, we'll take a deep dive into the anatomy and physiology of the respiratory tract, breaking down the complex concepts into easily digestible information. We'll explore the upper and lower respiratory tracts, learn how the lungs work, and discuss common respiratory issues in children. By the end of this article, you'll have a clearer picture of how your child's body takes in oxygen and removes carbon dioxide, and what happens when things go awry.
We’ll take a spin through the general path of air in and out of the body - Outside air → Nasal/Oral cavity → Pharynx → Larynx → Trachea → Left and right bronchi → Bronchioles → Alveoli
Nasal cavity (nose) / Oral cavity (mouth)
Infants have historically been called 'obligate nasal breathers', which implies that they can only breathe through their noses unless crying
While this isn’t strictly true (babies can breathe through their mouths!), they do rely heavily on breathing through their noses!
Why is nasal breathing so important for infants? Well, when you or I are eating, we usually take breaths in between bites of food or while chewing; in contrast, babies may have their mouths latched to the breast for several minutes at a time, so they need to be excellent at getting air in and out through the nose (and coordinating suck, swallow, breathe synchrony)
Significance for Kids:
When you get sick and have a little nasal congestion it’s probably not a huge deal (though so annoying when you fall asleep on one side and have the whole nostril plugged up!) - for infants though, since they’re so used to breathing through their nose, it can cause significant problems breathing!
Naso/oropharynx (back of the mouth / throat)
In infants and young children, the pharynx (back the mouth/start of the throat) is shorter and more narrow compared to adults; also, adenoids and tonsils are more prominent, especially in school-aged children
Even though many people have heard that we have “tonsils” in the back of our throat, there’s actually more to it! Basically there is a ring of tissue in the back of the throat that has a high concentration of immune cells (white blood cells) to protect the body from infection, called Waldeyer's tonsillar ring. This ring consists of three types of tonsils: the palatine tonsils, the pharyngeal tonsils (adenoids), and the lingual tonsils.
Palatine tonsils (or just “tonsils”): These are the most well-known tonsils, located on either side of the back of the throat. They are visible when you open your mouth and say "ahh." These get swollen and covered in mucus when you have strep throat for example, and are often what the pediatrician is looking at when evaluating a kid with a sore throat.
Pharyngeal tonsils (adenoids): Adenoids are located in the upper part of the throat, behind the nasal cavity and above the soft palate. They are not directly visible when looking into the mouth. Adenoids are made up of lymphatic tissue and help trap and neutralize harmful pathogens that enter the body through the nose.
Lingual tonsils: These tonsils are located at the base of the tongue and are not easily visible without special instruments. Like the other tonsils, lingual tonsils contain lymphatic tissue and help protect against infections.
All three types of tonsils are composed of lymphatic tissue, which contains high concentrations of white blood cells called lymphocytes. These lymphocytes are a part of the body's immune system which recognizes and fights off harmful invaders like bacteria, viruses, and other germs.
Significance for Kids:
When an upper respiratory tract infection (URI) occurs, immune cells in the tonsils and adenoids get activated which makes those tissues get swollen, enlarged, and inflamed
Now you have big / swollen tissue (the tonsils and adenoids) in an already smaller space (the pharynx)
This increases the chance that children will have difficulty breathing, or a hard time getting enough air in and out
Larynx (voice box)
The larynx, also known as the voice box, is a structure in the neck that contains the vocal cords and is basically the entrance to the trachea
The vocal cords are two bands of muscle that stretch across the larynx from front to back; when air passes through them, they vibrate and produce sound, allowing us to speak and sing
They are V-shaped, with the point of the V facing forward, and they attach in the front at the thyroid cartilage (Adam's apple) and in the back to the arytenoid cartilages
The space between the vocal cords is called the glottis, and it varies in size and shape depending on the position of the vocal cords
When we breathe normally, the vocal cords are relaxed and open, allowing air to pass through freely; when we speak or sing, the vocal cords come together and vibrate as air passes through them to make sounds
The length and thickness of the vocal cords also affect the pitch of the voice; longer and thicker vocal cords produce lower pitches, while shorter and thinner vocal cords produce higher pitches - this is why men often have deeper voices than women and children - their larynx is larger and their vocal cords are longer and thicker
Image depicting the major structures of the respiratory tract. Used under the Creative Commons License. Used under the Creative Commons License. Original artwork by OpenStax College. View on Wikimedia Commons.
Tsui, B.C.H. Physiological considerations related to the pediatric airway. Can J Anesth/J Can Anesth 58, 476–477 (2011). https://doi.org/10.1007/s12630-011-9464-z
Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014"
Used under Creative Commons License. Original Source Eleonoreo. File location Wikimedia.
Used under Creative Commons License. Original Source Olek Remesz. File location Wikipedia.
Used under Creative Commons License. Original Source Lumen Learning.
Used under Creative Commons License. Original Source Dr. James P Thomas MD.
The epiglottis is a small flap of cartilage that sits above the larynx with the main purpose of protecting the lungs from inhaling saliva and food
When we are not swallowing, the epiglottis is upright, allowing air to pass through the larynx and into the trachea and lungs
When we swallow, the epiglottis moves downward and backwards, covering the glottis and directing food and liquid into the esophagus and stomach instead of the trachea and lungs
Used under Creative Commons License. Original Source pharmacampus.
Significance for kids:
In infants and young children, the larynx is positioned higher in the neck compared to adults, and the epiglottis is more floppy and U-shaped, making it less efficient at protecting the airway; this can make it less efficient at protecting the airway during swallowing
When the epiglottis is super floppy and actually collapses on the airway while breathing, it’s called “laryngomalacia” - it’s the most common cause of noisy breathing in infants and often presents in the first few weeks of life
This usually gets better on its own as the airway muscles strengthen, by 12-18 months of age
Croup is a common infection in infants that causes inflammation and swelling of the larynx and trachea, leading to a barking cough and stridor (noisy breathing) - it’s usually caused by a virus so doesn’t need antibiotics, but if the child has a really hard time breathing they’ll often get steroids or a racemic epinephrine to reduce the swelling
Laryngitis is an inflammation of the larynx, often caused by viral infections or overuse of the voice; it can cause hoarseness, loss of voice, and throat pain in both children and adults
Trachea (wind pipe), Bronchi, and Bronchioles
Trachea
The trachea, also known as the windpipe, is a tube that connects the larynx to the bronchi and allows air to pass through to the lungs.
In infants and young children, the trachea is narrower, shorter, and made up of more flimsy cartilage compared to adults, making the airway more susceptible to collapse or obstruction.
Bronchi
At the lower end of the trachea, it divides into two smaller tubes called bronchi, one leading to each lung.
The angle at which the bronchi branch off from the trachea is more horizontal in children compared to the more vertical angle in adults, which increases the risk of causing deep aspiration (inhalation of liquids and solids) into the lungs.
Bronchioles
As the bronchi enter the lungs, they divide over and over again into smaller and smaller tubes called bronchioles.
Bronchioles are smaller in diameter in children, making them more prone to obstruction by mucus and inflammation.
Significance for Kids: Due to the anatomical differences in the trachea, bronchi, and bronchioles, children are more susceptible to certain respiratory conditions:
Foreign body aspiration / choking: Children are more likely to inhale small objects like toys, food, or coins due to their curious nature, less developed oral motor control, and the horizontal angle of their bronchi.
Bronchiolitis: This is a common viral infection that causes inflammation and obstruction of the bronchioles, leading to wheezing, coughing, and difficulty breathing. It is most often caused by the respiratory syncytial virus (RSV) and primarily affects infants and young children (read more about bronchiolitis and RSV in our latest post).
Asthma: The smaller diameter of bronchioles in children can make them more prone to asthma symptoms, such as wheezing, coughing, and shortness of breath, when exposed to triggers like allergens, viral infections, or exercise.
Used under Creative Commons License. Original work by Sumaiya, Wikimedia.
Alveoli
Alveoli are tiny, balloon-like air sacs surrounded by blood vessels that are located at the end of the bronchioles in the lungs. They are the primary site of gas exchange, where oxygen from the inhaled air is absorbed into the blood, and carbon dioxide is removed from the blood and exhaled.
At birth, infants have fewer alveoli than adults, and these alveoli are not fully developed.
The number of alveoli continues to increase throughout childhood and into adolescence, increasing from about 20-50 million at birth to 300-500 million by adulthood.
Significance for Kids:
The immaturity and lower number of alveoli in infants and young children can have several implications for their respiratory health:
Vulnerability to respiratory infections: The smaller size and lower number of alveoli make it easier for infections to spread and cause more severe symptoms in children.
Reduced gas exchange efficiency: With fewer and less developed alveoli, infants and young children may have a harder time getting enough oxygen into their bloodstream and removing carbon dioxide effectively.
Increased risk of complications from premature birth: Premature infants are born with even fewer and less developed alveoli, putting them at higher risk for respiratory distress syndrome (RDS) and other breathing difficulties.