Question

Draw a neat labelled diagram of human respiratory system. Describe briefly the mechanism of respiration in mammals.

Answer 1

Human respiratory system:

1. The human respiratory system consists of a group of organs and tissues that help us to breathe.
2. There are muscles and a vast network of blood vessels that facilitate the process of respiration.
3. The respiratory system is important for the generation of the energy by the breakdown of glucose molecules in all living cells of the human body.
4. Oxygen is inhaled and is transported to various parts and is used in the process of breaking down glucose at the cellular level in a series of chemical reactions.

Parts of the respiratory tract:

1. External nostrils

Nostrils function for the inspiration of air.

2. Nasal chamber

It is lined with hair and mucus to filter the air from dust and dirt.

3. Pharynx

It is a passage present behind the nasal chamber and it serves as the common passage for both air and food.

4. Larynx

Larynx is known as the voice box as it houses the vocal chords.

5. Epiglottis

It is a flap-like structure that covers the glottis and prevents the entry of food into the windpipe.

6. Trachea

It is a long tube passing through the mid-thoracic cavity.

7. Bronchi

The trachea divides into left and right bronchi.

8. Bronchioles

Each bronchus is further divided into finer channels known as bronchioles.

9. Alveoli

The bronchioles terminate in balloon-like structures known as the alveoli.

10. Lungs

Humans have a pair of lungs, which are sac-like structures and covered by a double-layered membrane known as pleura.

Mechanism of respiration:

1. Air is inhaled with the help of nostrils, and in the nasal cavity, the air is cleansed by the fine hair follicles present within them.
2. The cavity also has a group of blood vessels that warm the air.
3. This air then passes to the pharynx, then to the larynx and into the trachea.
4. Once the air reaches the bronchus, it moves into the bronchioles, and then into the alveoli.
5. The respiratory system helps in breathing, also known as pulmonary ventilation.
6. The air is exhaled back through the same pathway.
7. Changes in the volume and pressure in the lungs aid in pulmonary ventilation.

Gas exchange:

1. Gas exchange at the alveolar–capillary interface is influenced by the time it takes a red blood cell to pass from one end of a capillary to the other end, called the transit time.
2. The time it takes for complete saturation of hemoglobin with oxygen in the pulmonary capillary, called the equilibrium time.
3. Gas exchange occurs in alveoli when freshly-inspired air comes in contact with capillary blood.
4. Gas exchange begins at the respiratory bronchioles.
5. The gaseous exchange continues in the lungs even during expiration because expiration is the result of reverse movements of the ribs and diaphragm.
6. As a consequence of the movements of the ribs and the diaphragm, the thoracic cavity is diminished and the lungs are compressed, forcing the air out into the atmosphere.

Site of gaseous exchange in lungs:

1. Lungs are the respiratory organs of the human body.
2. Lungs comprises the trachea, bronchus, bronchioles and air sacs.
3. The ends of bronchioles contain the air sacs which are known as the alveoli.
4. Gas exchange occurs at the alveoli.
5. Oxygen moves from the lungs to the bloodstream and carbon dioxide passes from the blood to the lungs simultaneously.
6. This is because of the fact that alveoli is surrounded by a network of tiny blood vessels called capillaries.