Respiratory System: Definition, Organs and Functions

Introduction to the Respiratory System

The respiratory system in the human body is highly significant in its ability to enable us to breathe, and through that, the biological exchange of atmospheric oxygen and carbon dioxide between an organism and its surroundings. This system is involved in taking in oxygen through the human body into the circulatory system's blood and getting rid of the metabolic product carbon dioxide.

Organs of the Human Respiratory System

The respiratory system in humans is made up of specialised organs that work together to enable breathing and gas exchange. These organs filter air, transport oxygen, and remove carbon dioxide to maintain life processes. Its efficiency also depends on the regulation of respiration, which ensures proper control of breathing rate and rhythm. The respiratory system of humans is discussed below:

• Nasal cavity

• Pharynx

• Larynx

• Vocal Cord – The Source of Human Voice

• Trachea

• Bronchi & Bronchioles

• Lungs

• Alveoli

• Diaphragm

Human Respiratory Tract: Upper & Lower Divisions

Further elaboration can be done in the form of the upper and lower respiratory tracts, which have individual structures in them.

Upper Respiratory Tract

• Nasal cavity: Filters, warms, and humidifies air.

• Pharynx: Air and food passageway.

• Larynx: Where the vocal cords are located, and also provides protection.

Lower Respiratory Tract

• Trachea: The tube for air to pass in the direction of the bronchi.

• Bronchi and Bronchioles: Airways carrying the air to the lungs.

• Lungs: Major organ of breathing.

Functions of the Respiratory System

There are several extremely critical functions of the respiratory system in the human body, which are:

• Oxygen Delivery: Supplies oxygen inhaled by the body for cellular respiration.

• Carbon Dioxide Excretion: Removes carbon dioxide, which is the gas waste product of metabolism.

• Acid-Control of pH: It maintains the balance among the acid-base constituents in the blood, thus regulating the pH.

• Voice Production: The larynx is the organ of voice production.

Mechanism of Breathing (Pulmonary Ventilation)

The mechanism of breathing takes place via two main processes, inhalation and exhalation.

1. Inhalation Process

When the diaphragm contracts, it becomes flat, and it moves down into the chest cavity space below, creating more space in the chest cavity and air rushes into the lungs.

2. Exhalation Process

The diaphragm relaxes and moves upward, reducing the chest cavity size and forcing air out of the lungs.

Diaphragm & Intercostal Muscles: Major Breathing Muscles

The diaphragm and intercostal muscles are the major muscles of respiration.

Diaphragm

• Main muscle of respiration

• Dome-shaped, which flattens during inhalation

Intercostal Muscles

• The intercostal muscles expand and contract the rib cage.

• Assist inspiration & expiration

Gas Exchange in the Lungs

The respiratory system enables efficient gas exchange in the lungs, where oxygen enters the blood and carbon dioxide is expelled. This process occurs in the alveoli, tiny sac‑like structures surrounded by capillaries, providing survival and energy production are the sites of gas exchange in the lungs.

Alveoli And Capillaries

• Tiny sac-like structures within the lungs

• Moist, thin walls for diffusion of gases in a body.

Capillaries

• Minute blood vessels that exchange oxygen and carbon dioxide.

• Capillaries surround alveoli.

Mechanism Of Gaseous Exchange

• Inhalation of oxygen through the lungs.

• The oxygen is then diffused from the alveoli into the blood.

• On exhalation, the carbon dioxide extinguishes the blood to be exhaled.

Respiratory System Diseases

The respiratory system is prone to several common diseases that affect breathing and gas exchange. These conditions can range from mild inflammation to severe infections and cancers. Several common disorders of the respiratory system are:

• Asthma: Inflammation in the airways leads to a tight chest.

• COPD (Chronic Obstructive Pulmonary Disease): A grouping of progressive lung diseases that gets in the way of airflow.

• Pneumonia: It is an infection that can bring inflammation to the air sacs of a lung.

• Tuberculosis: An infectious and severe disease in the lungs.

• Lung Cancer: A disease of the lungs characterised by uncontrolled growth of malignant tumours.

Respiratory System NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Mechanism of breathing

• Diseases of the respiratory system

Practice Questions for NEET

Q1. The trachea divides into the right and left bronchi at the level of

1. L5

2. C5

3. T5

4. L7

Correct answer: 3) T5

Explanation:

The trachea splits into the right and left bronchi at the level of the fifth thoracic vertebra, or T5, which is also referred to as the sternal angle. This is called the carina and signifies the start of the bronchial tree, from which each bronchus leads to its particular lung. The right main bronchus is generally more vertical and larger in diameter, while the left is smaller in diameter and horizontally oriented because it is located below other anatomical structures. Such branching of bronchi will provide proper air entry to the lungs to facilitate gas exchange.

Hence, the correct answer is option (3) T5.

Q2. Regarding the functions of our respiratory system, mark the wrong entry.

1. Humidifier the air

2. Warms up the air

3. Exchange of gases

4. Cleans up the air

Correct answer: 4) Cleans up the air

Explanation:

The respiratory system removes undesirable carbon dioxide from the air we breathe and absorbs oxygen from it. The lungs are the respiratory system's primary organ. The trachea, the nose, and the breathing muscles (the diaphragm and the intercostal muscles) are further respiratory organs.

Hence, the correct answer is option 4) Cleans up the air.

Q3. The respiratory process is regulated by certain specialised centres in the brain. One of the following listed centres can reduce the inspiratory duration upon stimulation

1. Medullary inspiratory centre

2. Pneumotaxic centre

3. Apneustic centre

4. Chemosensitive centre

Correct answer: 2) Pneumotaxic centre

Explanation:

Inspiration is the process of breathing in oxygen-rich air. The lungs' volume increases during inspiration as a result of the diaphragm being flat and the ribs being drawn higher and outward. To control inspiratory volume and respiratory rate, the pneumatic centre, which is situated in the upper pons, sends inhibitory impulses to the inspiratory centre, stopping inspiration. The fine-tuning of respiration most certainly involves this region.

Hence, the correct answer is option 2) Pneumotaxic centre.

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