Objective :

• To learn the procedure for collection of lungs from a euthanised rat
• To learn the anatomical structure of the rat lung

Theory :

• The respiratory system is morphologically complex and consists of the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and lungs. Its functions include air conduction, gas exchange, olfaction (reception of odor) and phonation (production of sound). A pair of lungs is enclosed in the thoracic cavity.
• The ventilating system consists of the thoracic cage and intercostals muscles, diaphragm, and elastic connecting tissue of the lung which move air within the respiratory tract. The air from outside passes through the external nostrils and nasal passages into pharynx. From the pharynx, it passes by the glottis into the windpipe or trachea.
• The larynx is found as an enlarged portion at the anterior part of trachea. The lungs are enclosed in a pleural cavity formed by the outer parietal layer that lines the cavity of the thorax and an inner visceral layer investing the lungs. As the thoracic cavity increases in size, the size of the pleural cavity also increases.
• This results in a decrease in its pressure and air being taken into the lungs, called as the process of inspiration. Expiration, is a passive process brought about by the relaxation of the intercostal muscles and the diaphragm, which brings the thoracic cavity to normal size, the air being forced out in consequence.