Respiratory system includes all the organs and tissues associated with the exchange of gases between an animal and its environment, leading to the release of energy.

The purpose of respiration is to supply oxygen to the cells which oxidise or burn down the food to release energy.

This process is also referred to as fermentation.

The most important organ of respiration in all land animals is the lung, while aquatic animals like fish use the gills to respire. Other organs associated with respiration are the nostrils and diaphragm.

The lung is located in the thoracic cavity of farm animals. The atmospheric oxygen passes through the nostrils, the pharynx, larynx or voice box, bronchi and to the lungs. The movement of oxygen through these organs finally terminates in the alveoli where exchange of gases (oxygen and carbon dioxide) takes place.

Processes of Breathing

Breathing involves two processes:

(1) Inspiration (Inhalation): This involes the breathing in of air into the lungs. During the process, the following take place within and around the lungs.

(i) The diaphragm contracts and flattens out.

(ii) Intercostal muscles contract and ribs are thus raised.

(iii) Sternum moves forward.

(iv) The volume of thoracic cavity therefore increases and the pressure in the lungs is lowered.

(v) This therefore creates a high pressure in the lungs and oxygen is taken into the lungs.

2) Expiration (Exhalation): This involves he breathing out of air from the lungs. During he process, the following take place within and round the lungs.

(i) The diaphragm relaxes and returns to its dome shape

(ii) Intercostal muscles relax and the ribs are lowered.

(iii) The sternum moves backwards.

(iv) The volume of thoracic cavity therefore decreases; pressure in the lungs is increased and carbon dioxide is expelled from the lungs.

The oxygen which diffuse into the blood through the lungs is now transported by the haemoglobin of the blood cells to various cells in the body. This oxygen is used to oxidise food substances in the mitochondria of the cells during tissue respiration to release energy used by farm animals for movement, growth, reproduction and other body metabolic activities.

Importance of the Respiratory System

(i) It supplies oxygen to the body cells.

(ii) It helps to reduce heat load in the body, especially in poultry.

(iii) It removes carbon dioxide from the body.

(iv) It promotes gaseous exchange.

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