Overview of the Human Respiratory System
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 and Structure: Complete Explanation
1. Why does the left lung have fewer lobes than the right lung?
The left lung has two lobes because the heart tilts slightly towards the left side of the chest, leaving less space. The right lung, having more space, is divided into three lobes.
2. What happens if the diaphragm is not functioning properly?
If the diaphragm cannot contract or relax effectively, breathing becomes difficult. This can lead to reduced oxygen intake and accumulation of carbon dioxide in the blood.
3. How does smoking affect the lungs?
Smoking damages the alveoli and airways, reduces lung capacity, and increases the risk of chronic diseases such as lung cancer, emphysema, and bronchitis.
4. What is the pleura?
The pleura is a double-layered membrane surrounding each lung. It produces a lubricating fluid that helps the lungs expand and contract smoothly.
5. How can we keep our lungs healthy?
Avoid smoking, breathe clean air, exercise regularly, and follow a balanced diet. Regular check-ups also help monitor lung health and detect any issues early.
