You take roughly 22,000 breaths every single day. That adds up to about 8 million breaths a year, and most of them happen without you giving it a second thought. Every one of those breaths is powered by an intricate system of airways, tissues, muscles, and membranes working together inside your chest.
Your lungs are, pound for pound, some of the most remarkable organs in your body. If you could spread out all the tiny air sacs packed inside them, they’d cover an area roughly the size of a tennis court. That massive surface area exists for one reason: to keep every cell in your body supplied with oxygen and free of carbon dioxide.
Despite how hard they work, most people know surprisingly little about what’s actually going on inside their lungs. The good news is that understanding the basic anatomy doesn’t require a medical degree. Once you see how the pieces fit together, you’ll have a much clearer picture of how your body breathes — and why each part matters so much.
Lungs Parts Diagram & Details
The diagram above provides a front-facing, cross-sectional view of the human respiratory system, with both the left and right lungs displayed inside the rib cage. Starting from the top, you can trace the airway from the larynx down through several rings of cartilage into the trachea, which then splits into two primary bronchi — one feeding each lung. Inside each lung, the bronchi branch further into smaller and smaller passages, eventually ending in clusters of tiny air sacs. Surrounding the lungs, the diagram highlights the protective membranes, the bony ribs, the muscles between them, and the large dome-shaped diaphragm sitting at the base.
In total, the diagram labels 25 distinct structures. Each one plays a specific role in getting air into your lungs, exchanging gases, or protecting the delicate tissue that makes breathing possible. Let’s walk through every single one of them.
1. Larynx
Sitting right at the top of the diagram, the larynx is the short, hollow tube that connects your throat to the rest of your airway. You probably know it better as the voice box, because it houses your vocal cords. When air passes over those cords, they vibrate, and that vibration is what produces your voice.
But the larynx does far more than help you talk. It acts as a kind of gatekeeper, directing air down into the trachea while routing food and liquids into the esophagus behind it. Without this traffic control, every sip of water could end up in your lungs.
The larynx is built from several pieces of cartilage stacked together, which you can feel if you press gently on the front of your neck. That firm but slightly flexible structure keeps the airway open at all times, even when you swallow or move your head.
2. Epiglottis Cartilage
Just above the larynx sits a small, leaf-shaped flap called the epiglottis. Its job is deceptively simple but absolutely critical: every time you swallow, the epiglottis folds down like a trapdoor to cover the opening of the larynx. This prevents food, saliva, and drinks from slipping into your airway.
Once you finish swallowing, the epiglottis springs back up and the airway opens again. The whole process takes a fraction of a second, and you rarely notice it happening. It only becomes obvious when something goes wrong — like that sharp, choking sensation when a crumb “goes down the wrong pipe.”
3. Hyoid Bone
The hyoid bone is a small, horseshoe-shaped bone located just above the thyroid cartilage. What makes it unique is that it doesn’t directly attach to any other bone in the body. Instead, it’s suspended by muscles and ligaments, almost like a floating anchor point in your neck.
Its primary role is to support the base of the tongue and help with swallowing and speech. When you speak, the muscles attached to the hyoid bone shift and adjust the position of the larynx, which changes the pitch and tone of your voice. Think of it as the behind-the-scenes stagehand that keeps everything running smoothly every time you talk or eat.
4. Thyroid Cartilage
That noticeable bump on the front of your neck — sometimes called the Adam’s apple — is the thyroid cartilage. It’s the largest piece of cartilage in the larynx and forms a protective shield around the vocal cords and the inner structures of the voice box.
Beyond protection, the thyroid cartilage serves as an attachment point for several small muscles that control vocal cord tension. When those muscles pull on the cartilage, they stretch or relax the cords, which is how you shift between high and low notes when you speak or sing. Men typically have a larger, more angled thyroid cartilage than women, which is why the Adam’s apple tends to be more visible on male necks.
5. Cricoid Cartilage
Directly below the thyroid cartilage, the cricoid cartilage forms a complete ring around the airway. While most other cartilages in the larynx are open at the back, the cricoid is the only one that wraps all the way around. That full ring gives the lower larynx extra structural support.
This ring also serves as the foundation on which the other laryngeal cartilages sit. Doctors pay close attention to the cricoid during procedures like intubation because it marks a key landmark in the airway. If you’ve ever had someone press gently on the front of your neck during an emergency airway procedure, they were likely applying pressure to the cricoid cartilage.
6. Trachea
The trachea, or windpipe, is the main highway for air flowing between your larynx and your lungs. It runs about 10 to 12 centimeters down the center of your chest and is reinforced by 15 to 20 C-shaped rings of cartilage. Those rings keep the trachea from collapsing every time you inhale.
Lining the inside of the trachea is a layer of mucus-producing cells topped with tiny hair-like projections called cilia. Together, the mucus and cilia trap dust, bacteria, and other particles, then sweep them upward like a slow-moving conveyor belt so you can cough or swallow them out of your airway. It’s an elegant self-cleaning system that works around the clock.
7. Apex of Lung
The apex is the very top of each lung, and it sits surprisingly high in your chest — actually rising above the collarbone and tucking up into the base of the neck. Many people assume the lungs start somewhere around the shoulders, but the apex extends a few centimeters higher than that.
Because of its position, the apex is close to several important blood vessels and nerves that run through the upper chest. This is clinically significant because tumors at the top of the lung, known as Pancoast tumors, can press on those nearby structures and cause shoulder pain or nerve-related symptoms long before any breathing problems show up.
8. Bronchi (Left & Right Primary Bronchus)
Where the trachea ends, it splits into two branches — the left and right primary bronchi. Each one angles off and enters its respective lung through an area called the hilum. If you look at the diagram, you’ll notice that the right bronchus is slightly wider and steeper than the left. This small anatomical difference means that inhaled objects, like a stray peanut, are more likely to end up in the right lung.
The walls of the primary bronchi are reinforced with cartilage rings, much like the trachea, so they stay open under varying pressures. Once inside the lung, each bronchus continues to branch into smaller and smaller airways, forming a tree-like network that delivers air to every corner of the lung tissue.
9. Right Secondary Bronchus
After the right primary bronchus enters the lung, it divides into three secondary bronchi — one for each lobe of the right lung. These are sometimes called lobar bronchi because each one is responsible for supplying air to an entire lobe.
The secondary bronchi still contain cartilage in their walls, though less than the primary bronchus. They continue the job of channeling air deeper into the lung, and each one branches further into even narrower passages. If a blockage or infection affects one secondary bronchus, it can cut off airflow to an entire lobe while leaving the others unaffected.
10. Bronchioles
As the bronchial tree keeps dividing, the airways eventually become too small to need cartilage support. These tiny tubes are called bronchioles, and they’re roughly a millimeter or less in diameter. Their walls are made mostly of smooth muscle, which means they can widen or narrow in response to signals from your nervous system.
This ability to constrict and relax is both useful and, in some cases, problematic. During exercise, your bronchioles open up to let more air through. But in conditions like asthma, those same muscles can spasm and tighten, dramatically reducing airflow and making it hard to breathe. That tight, wheezy feeling during an asthma attack is essentially your bronchioles squeezing shut when they shouldn’t be.
11. Right Upper Lobe
The right lung is divided into three lobes, and the right upper lobe occupies the top portion. It sits beneath the apex and extends down to a deep groove called the horizontal fissure. This lobe receives air from one of the three secondary bronchi and handles a significant share of the gas exchange that happens in the right lung.
Because of its position near the top of the chest, the right upper lobe is a common site for certain types of infections, particularly tuberculosis, which historically has shown a preference for the upper regions of the lungs. Doctors often check this area carefully on chest X-rays when upper-lobe disease is suspected.
12. Right Middle Lobe
Tucked between the horizontal fissure above and the oblique fissure below, the right middle lobe is the smallest of the three right-lung lobes. It’s a wedge-shaped section that sits along the front of the chest, close to the heart.
Its relatively small size and the angle of the bronchus that feeds it make this lobe slightly more prone to blockage and infection. A condition sometimes referred to as “right middle lobe syndrome” occurs when this lobe collapses or becomes chronically inflamed, often because the narrow bronchus is easily compressed by nearby lymph nodes.
13. Left Upper Lobe
The left lung has only two lobes instead of three, and the left upper lobe is the larger of the two. It occupies the upper and front portion of the left lung and includes a small tongue-shaped projection called the lingula, which is roughly equivalent to the right middle lobe.
The left upper lobe shares its space with the heart, which pushes into the left side of the chest and creates a concave indentation on the lung’s inner surface called the cardiac notch. This is why the left lung is slightly smaller than the right — it literally makes room for your heart.
14. Left Lower Lobe
Separated from the upper lobe by the oblique fissure, the left lower lobe fills the base of the left lung. It sits on top of the diaphragm and extends toward the back of the chest cavity.
This lobe is a common location for aspiration pneumonia — the type of lung infection that occurs when food, liquid, or stomach contents are accidentally inhaled. Gravity plays a role here: when a person is lying on their back, aspirated material tends to settle into the lower lobes, making this area particularly vulnerable.
15. Fissures
Fissures are the deep grooves that separate the lobes of each lung. The right lung has two fissures — the horizontal fissure and the oblique fissure — while the left lung has one oblique fissure. You can clearly see these dividing lines on the diagram, running diagonally and horizontally across each lung.
These separations are lined with visceral pleura, the same slippery membrane that coats the outer surface of the lungs. The fissures allow each lobe to move somewhat independently during breathing, which means one lobe can expand or shift without dragging the others along. This independent movement helps the lungs fill with air more evenly, even when your body is in an awkward position.
16. Visceral Pleura
The visceral pleura is a thin, moist membrane that wraps tightly around the outer surface of each lung, dipping into every fissure and following every contour. If you’ve ever peeled the thin skin off a hard-boiled egg, you have a rough idea of how closely this membrane clings to the lung tissue beneath it.
Its surface produces a small amount of lubricating fluid that reduces friction as the lungs expand and contract. Without this membrane and its fluid, every breath would involve your lung tissue grinding directly against the chest wall — a painful and damaging scenario.
17. Parietal Pleura
While the visceral pleura hugs the lungs, the parietal pleura lines the inside of the chest wall, the top of the diaphragm, and the sides of the mediastinum. Together, these two membranes form a double-layered envelope around each lung.
The parietal pleura is packed with nerve endings, which is why conditions that irritate it — like pleurisy — can be extremely painful. Each breath stretches the inflamed membrane, producing a sharp, stabbing chest pain that often gets worse when you cough or take a deep breath. The visceral pleura, in contrast, has very few pain fibers, so problems originating on the lung surface itself may go unnoticed longer.
18. Pleural Cavity
The pleural cavity is the narrow space sandwiched between the visceral and parietal pleurae. Under normal conditions, it contains only a thin film of fluid — roughly a teaspoon’s worth — that allows the two membranes to glide over each other with almost no friction.
That tiny amount of fluid also creates a slight vacuum-like effect through surface tension, keeping the lungs pulled up against the chest wall. This negative pressure is essential for breathing. If air leaks into the pleural cavity — a condition called pneumothorax — that suction is broken, and the affected lung can partially or fully collapse.
19. Right Tertiary Bronchus
The tertiary bronchi, also called segmental bronchi, branch off from the secondary bronchi and supply air to specific segments within each lobe. In the right lung, there are ten of these segments, each served by its own tertiary bronchus.
This segmental organization is extremely useful in medicine. If a tumor or severe infection is confined to a single segment, surgeons can remove just that segment without having to take out an entire lobe. Each tertiary bronchus acts like a dedicated supply line to its own self-contained section of lung tissue, making targeted treatment possible.
20. Left Terminal Bronchiole
Terminal bronchioles are the very last airways that carry air purely for conduction — meaning they don’t participate in gas exchange themselves. They mark the transition point between the conducting zone and the respiratory zone of the lungs.
Each terminal bronchiole is only about half a millimeter wide, and the human lungs contain roughly 30,000 of them. Beyond each terminal bronchiole, the airway branches into respiratory bronchioles, which have a few scattered alveoli on their walls and represent the very beginning of the gas-exchange region.
21. Alveoli
Alveoli are the tiny, balloon-like sacs clustered at the ends of the smallest airways. Your lungs contain approximately 480 million of them, and their combined surface area is enormous — estimated at around 70 square meters. This is where the actual magic of breathing happens: oxygen passes from the air inside the alveoli into the blood, while carbon dioxide moves in the opposite direction.
The walls of each alveolus are incredibly thin — just one cell thick — and they’re wrapped in a dense mesh of capillaries. The distance between the air in the alveolus and the blood in the capillary is less than a micrometer, which makes gas exchange almost instantaneous. A special substance called surfactant coats the inner surface of each alveolus, lowering surface tension and preventing these delicate sacs from collapsing every time you exhale.
22. Rib
Your ribs form a bony cage around the lungs and heart, providing protection from external impact. Most people have 12 pairs of ribs, and you can see their curved outlines on both sides of the diagram. The upper seven pairs attach directly to the sternum at the front, while the remaining five have increasingly loose or indirect connections.
Beyond protection, the ribs are active participants in breathing. As you inhale, the ribs swing upward and outward, expanding the chest cavity and creating more room for the lungs to fill. When you exhale, they settle back down. This rhythmic swinging motion happens thousands of times a day, driven by the intercostal muscles attached between them.
23. Intercostal Muscles
Filling the spaces between adjacent ribs, the intercostal muscles are thin sheets of muscle fibers arranged in two main layers: the external intercostals and the internal intercostals. The external layer lifts the ribs during inhalation, while the internal layer helps pull them down during forceful exhalation.
During quiet, relaxed breathing, the external intercostals do most of the work alongside the diaphragm. However, when you’re exercising hard or deliberately forcing air out — like blowing up a balloon — the internal intercostals kick in to speed up the process. You can actually feel these muscles working if you place your hands on the sides of your rib cage and take a few deep breaths.
24. Diaphragm
The diaphragm is a large, dome-shaped muscle that stretches across the bottom of the chest cavity, separating your lungs from the abdominal organs below. It’s the primary muscle of respiration, responsible for about 70 to 80 percent of the work involved in normal, quiet breathing.
When you inhale, the diaphragm contracts and flattens downward, pulling the lungs with it and creating a drop in air pressure inside the chest. Air rushes in through your nose or mouth to equalize that pressure — and that’s an inhalation. When the diaphragm relaxes, it domes back up, pushing air out of the lungs. Hiccups, by the way, are caused by sudden, involuntary spasms of this very muscle, followed by the snap-shut of the vocal cords that produces the characteristic “hic” sound.
25. Mediastinum
The mediastinum isn’t a part of the lungs themselves but rather the central compartment of the chest that sits between the two lungs. It houses the heart, the great blood vessels, the trachea, the esophagus, and a collection of nerves and lymph nodes.
Shown at the bottom-center of the diagram, the mediastinum acts as the body’s central corridor, keeping the lungs separated while bundling together all the vital structures that need to pass through the chest. If disease or swelling affects the mediastinum — such as enlarged lymph nodes from an infection or a tumor — it can compress the airways, blood vessels, or nerves nearby and produce a wide range of symptoms, from difficulty breathing to swelling of the face and arms.
