Labeled Human Lung Anatomy: Key Parts and Their Roles
The human respiratory system enables breathing by drawing in oxygen and removing carbon dioxide. It consists of multiple parts, including the nose, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli. All these parts work together to keep our cells well supplied with oxygen and to expel waste gases.
Location and Gross Structure of the Lungs
Our lungs occupy most of the space in the chest (thoracic) cavity. They are covered by a thin membrane called the pleura and are situated on either side of the heart.
Right Lung: Divided into three lobes (superior, middle, and inferior). It is slightly larger than the left lung to accommodate the heart’s position.
Left Lung: Divided into two lobes (superior and inferior), separated by an oblique fissure.
Each lung has a pointed top region, known as the apex, that extends just above the first rib, while the broad base rests on the diaphragm.
Respiratory Pathway and Air Flow
Air enters the body primarily through the nose, where it is warmed, filtered, and moistened. It then moves through the pharynx and the larynx (voice box) into the trachea.
Nose/Mouth → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
In the pharynx, air from the nose and mouth converges, then passes to the larynx.
The larynx leads air into the trachea (windpipe), which is supported by rings of cartilage to prevent collapsing.
The trachea branches into two main bronchi (one for each lung), which further subdivide into smaller bronchi and then into bronchioles.
Eventually, air reaches tiny air sacs called alveoli, where oxygen is transferred into the blood, and carbon dioxide is released from the blood into the alveolar air to be exhaled.
Functions of the Lungs
Gas Exchange: The primary function is to add oxygen to the bloodstream and remove carbon dioxide.
Regulation of Blood pH: By controlling carbon dioxide levels, the lungs help regulate acidity in the blood.
Protection: Fine hairs, mucus, and immune cells in the airways trap and eliminate foreign particles.
Pulmonary Segments and Bronchioles
Each lung is further divided into smaller regions called pulmonary segments. The right lung has 10 pulmonary segments, while the left lung typically has 8 to 10 segments.
Bronchi: The main bronchi branch repeatedly, gradually becoming narrower to form bronchioles.
Bronchioles: These are small tubes without cartilage in their walls. They eventually lead to clusters of alveoli.
Alveoli: The Site of Gaseous Exchange
Each bronchiole ends in tiny, spongy sacs called alveoli. A single air sac is called an alveolus. Millions of alveoli in each lung create a large surface area for gas exchange. Oxygen from inhaled air diffuses into the surrounding capillaries, while carbon dioxide diffuses from the blood into the alveoli to be exhaled.
Role of the Diaphragm in Breathing
The diaphragm is a sheet of muscle located beneath the lungs, separating the chest cavity from the abdominal cavity. During inhalation, the diaphragm contracts and moves downward, increasing space in the chest cavity and pulling air into the lungs. During exhalation, it relaxes, moving upwards and forcing air out of the lungs. One full cycle of inhalation and exhalation is one complete breath.
Diagram of Lungs with Labelling
A simple lung diagram typically shows the trachea branching into the bronchi, which then divide into smaller bronchioles and end in alveolar sacs. A human lungs diagram with parts highlighted helps learners understand each component’s placement. Make sure to note important features like the lobes, fissures, and the structure of the lungs diagram to see how the air passageway connects to the alveoli.
Additional Points about the Lungs
Protective Mucus: The lining of the airways produces mucus, which traps dust and microorganisms.
Cilia: Tiny hair-like structures (cilia) push mucus upwards towards the throat, where it can be swallowed or coughed out.
Number of Alveoli: A newborn baby’s lungs have 20–50 million alveoli, while adults have around 300 million alveoli in each lung.
Short Quiz (With Answers)
1. Which lung is larger in humans?
Answer: The right lung is larger because of the heart’s position slightly to the left.
2. What is the function of the alveoli?
Answer: Alveoli are tiny air sacs where oxygen and carbon dioxide are exchanged between the air and blood.
3. Where does air travel immediately after it passes through the nose?
Answer: The air moves into the pharynx.
4. Which structure prevents food from entering the windpipe?
Answer: The epiglottis in the larynx helps prevent food from going into the windpipe.
5. What is the role of the diaphragm during inhalation?
Answer: It contracts and moves downwards, creating more space in the chest cavity and pulling air into the lungs.
Related Topics
FAQs on Human Lungs Diagram: Structure, Parts, and Function
1. What are the main parts of the human lungs and the respiratory tract leading to them?
The human respiratory system is a complex network designed for efficient gas exchange. Air enters through the trachea (windpipe), which then splits into two primary bronchi, one for each lung. Inside the lungs, these bronchi branch out into smaller tubes called bronchioles, which terminate in tiny, clustered air sacs known as alveoli. The lungs themselves are divided into sections called lobes; the right lung has three lobes, while the left has two.
2. What are the essential parts to label in a diagram of the human lungs for a Class 10 or 11 exam?
For a clear and complete diagram of the human lungs, you should label the following key structures:
- Trachea (Windpipe)
- Bronchus (plural: Bronchi)
- Bronchioles (finer branches)
- Alveoli (air sacs, usually shown in a magnified view)
- Right Lung (with its three lobes: superior, middle, and inferior)
- Left Lung (with its two lobes: superior and inferior)
- Pleural Membrane (the covering of the lungs)
- Diaphragm (the muscle below the lungs)
3. How do the lungs and diaphragm work together to enable breathing?
Breathing is a mechanical process driven by the diaphragm and intercostal muscles. During inhalation, the diaphragm contracts and flattens, while the rib cage moves upwards and outwards. This increases the volume of the chest cavity, reducing the pressure inside the lungs and causing air to rush in. During exhalation, the diaphragm relaxes and domes upwards, the rib cage moves down and in, decreasing the chest cavity volume, which increases the pressure and forces air out.
4. What are alveoli, and why are they considered the functional units of the lungs?
Alveoli are the tiny, balloon-like air sacs at the end of the bronchioles. They are considered the primary functional units of the lungs because this is where the crucial process of gaseous exchange occurs. Their importance stems from three key features:
- Vast Surface Area: Millions of alveoli create a surface area roughly the size of a tennis court for maximum gas absorption.
- Thin Walls: Each alveolus has a wall that is only one cell thick, allowing for rapid diffusion of gases.
- Rich Blood Supply: They are surrounded by a dense network of capillaries, ensuring efficient transport of oxygen and carbon dioxide.
5. Why does the left lung have only two lobes while the right lung has three?
The asymmetry between the lungs is due to the position of the heart. The heart is located in the middle of the chest but is tilted slightly to the left. To accommodate the heart, the left lung has a depression called the cardiac notch and is consequently smaller, containing only two lobes (superior and inferior). The right lung, having more space, is larger and divided into three lobes (superior, middle, and inferior).
6. What is the importance of the pleural membrane and the fluid it contains?
The pleura is a double-layered membrane that surrounds each lung. Its importance is twofold. Firstly, the space between the two layers is filled with pleural fluid, which acts as a lubricant, allowing the lungs to expand and contract smoothly against the chest wall without friction. Secondly, the surface tension of this fluid helps keep the lungs' surface in close contact with the chest wall, aiding in the mechanics of breathing.
7. How does the exchange of oxygen and carbon dioxide actually happen in the alveoli?
The exchange of gases in the alveoli happens through a physical process called diffusion, driven by differences in partial pressures. When you inhale, the air in the alveoli is rich in oxygen, creating a high oxygen pressure. The blood arriving in the capillaries around the alveoli is low in oxygen but high in carbon dioxide. This pressure gradient causes oxygen to naturally diffuse from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled.
8. As a real-world example, how does smoking structurally damage the lungs?
Smoking causes severe structural damage to the lungs. The tar in cigarette smoke paralyses and eventually destroys the cilia, the tiny hairs that clear mucus and debris from the airways. This leads to mucus buildup, causing a 'smoker's cough'. More critically, toxic chemicals in smoke damage the delicate, elastic walls of the alveoli, causing them to break down and merge. This condition, called emphysema, permanently reduces the surface area available for gas exchange, leading to severe shortness of breath.
