NCERT Class 10 Physics Assignments for Life Processes (Respiration) Board Sample Problems Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 18

Describe inspiration and expiration in fish?


Water moves through the gills by the coordinated action of mouth and the operculum. Taking in water and thereby oxygen is called inspiration and exit of water is called expiration.


When the mouth is open, the space inside buccal cavity increases which reduces the pressure inside. This makes the water enter the buccal cavity.

At the same time, the water pressure outside presses the posterior end of the operculum against the body preventing the entry of water into the gills from this end. The opercular cavity is enlarged by the contraction of the pressure in the opercular cavity and draws water from the buccal cavity into the opercular cavity. This water flows over the gill filaments during which the exchange of gases between the capillaries and the water take place.


The mouth and the entrance to the esophagus close and the floor of the buccal cavity rises. This pushes the water out into the opercular cavity. This water which is under high pressure forces open the operculum at the posterior end and moves out into surrounding.

Question 19

Which are the respiratory organs in man?


The respiratory organs in man are the lungs.

Question 20

Where are the lungs in man situated?


In man, there are a pair of lungs present in the thoracic cavity.

They are found next to the heart. Towards the front they are protected by the chest wall that is formed by the rib cage and the muscles associated with the ribs.

There are 12 pairs of ribs and two sets of muscles called the outer and inner intercostal muscles in the chest wall.

Posteriorly, lungs are bound by a muscular diaphragm that separates the thoracic cavity Lungs are spongy, lobed and elastic organs that are broad at the bottom and tapering towards the top.

They consist of air sacs, the alveolar ducts, bronchioles (which connect them to the respiratory tract) and the blood vessels.

Each lung in enclosed by two membranes called the outer and the inner pleural membrane.

The membranes enclosed a space called the pleural cavity that contains a fluid.

The lungs are capable of expanding and contracting as they are elastic organs. Lubrication for their free movement is provided by the fluid in the pleural cavity.

Question 22

Name the various parts of the respiratory tract.


The various parts of the respiratory tract are nose, pharynx, glottis, larynx, trachea, bronchus, bronchioles, alveolar ducts and alveoli.

Question 23

Write a brief note about the nasal cavity?


The nasal cavity opens to the outside through the opening called the nostrils. The nasal cavity is lined by fine hairs that filter the dust particles from the air.

It is separated from the mouth by hard and soft palate that form its floor. It opens into the region called the pharynx.

Question 24

What are the functions of the pharynx?


Pharynx is the region of the respiratory tract that connects the nasal cavity to the larynx. It is a region which is common to the passage of food and air.

It has two functions:

Taking in of extra air when required. For example, during heavy exercise.

Allowing passage of air when the nose is blocked.

Question 25

What is the significance of respiration?


Respiration is an important process in nature. It is the process by which the organic compounds are broken down to release energy in the form of ATP molecules.

Respiration makes use of oxygen and releases carbon dioxide, which is then used by plants during photosynthesis that releases oxygen.

Thus, respiration has an important role to play in maintaining the delicate oxygen- carbon dioxide balance in nature.

Question 26

Write short notes on trachea.


Trachea is also called the windpipe. The trachea are held open with the help of C-shaped cartilaginous rings.

The open ends of the rings are towards esophagus- the food pipe. Trachea is situated in front of the esophagus.

The cartilages keep the larynx and trachea from collapsing even when there is no air in them. The trachea then into two main branches called bronchi.

Question 27

How do the trachea and bronchi keep the respiratory tract healthy?


The trachea and the bronchi and lined with ciliated epithelial cells and secretory cells (goblet cells) .

The secretory cells secrete mucus which moistens the air as it passes through the respiratory tract and also traps any fine particles of dust or bacteria that have escaped the hairs of the nasal cavity.

The cilia beat with an upward motion so that the foreign particles along with the mucus is sent to the base of the buccal cavity from where it may be either swallowed or coughed out.


How does exchange of gases take place in the alveoli?


The capillaries lining the alveoli have impure blood which has low concentration of oxygen.

So, the oxygen from the air easily diffuses into the blood through the thin barriers of the alveolus wall.

Similarly when the concentration of carbon dioxide is quite high in the blood, the gas easily diffuses out into the alveolar space.

From here, the air which has comparatively more concentration or carbon dioxide than the air that entered it, leaves the lungs.

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