Respiratory system of man includes the following:
I. External nostrils (External Nares)
A pair of external nostrils opens out above the upper lip. They lead into nasal chambers through the nasal passages.
II. Nasal Chambers
They lie above the palate and are separated from each other by a nasal septum. Each nasal chamber can be differentiated into three parts namely; i. vestibular part (which has hair and sebaceous glands to prevent the entry of dust particles),ii. respiratory part (which is involved in the conditioning the temperature of inhaled air ,it has three thin, twisted bony plates called turbinate /conchae) and iii. olfactory part (which is lined by an olfactory epithelium).
HI. Naso-pharynx
Nasal chambers lead into nasopharynx through a pair of internal nostrils, located above the soft palate. Nasopharynx is a portion of the pharynx, the common chamber for the passage of food and air. Nasopharynx leads into oropharynx and opens through glottis of larynx into the trachea.
IV. Larynx
Larynx is a cartilaginous box which helps in sound production, hence called the voice box. Wall of larynx is supported by nine cartilages. Thyroid, cricoid and epiglottis are the unpaired cartilages, whereas corniculate cartilages (cartilages of Santorini - two small conical nodules of elastic cartilage articulating with the arytenoid cartilages), arytenoids, and cuneiform cartilages are the paired cartilages. Epiglottis is a thin leaf like elastic :-artilaginous flap attached to the thyroid cartilage to prevent the entry of food nto the larynx through the glottis. The yellow elastic fibres which connect ".he thyroid and arytenoid cartilages are called vocal cords/vocal folds. The ?pace between the true vocal cords and the arytenoids cartilages is called rima glottidis.
Respiration in humans involves the following steps:
i. Breathing or pulmonary ventilation by which atmospheric air with 21% of Oais drawn in and alveolar air rich in COa is sent out.
ii. Diffusion of gases (and) across the alveolar membrane
iii. Transport of gases by blood, between the lungs and tissue cells.
iv. Diffusion of and between the blood in the systemic capillaries and the tissues.
v. Utilization of by the cells for catabolic reactions and resultant production of H2o, and ATP(Cellular respiration).
