In trachea 16-20 ?C? shaped cartilagenous rings are present which prevent trachea from collapsing. These rings are c shaped in order to allow easy passage of food through oesophagus.

Bronchitis is a disorder of bronchi in which re is regular swelling and itching of bronchi and is characterized by regular coughing. It may be both acute disorder or chronic disorder.

In industries, produced dust can?t be cope up by defense system of human body. Long and continuous exposure gives rise to inflammation leading to fibrosis and thus leading to severe lung damage.

Gaseous exchange occurs in respiratory tree, while it is absent in bronchial tree. Respiratory tree is also known as exchange zone which which includes respiratory bronchiole, alveolar duct, atria, alveolar sac and alveoli.

Epiglottis prevents food from entering into glottis during swallowing. It is a thin elastic cartilaginous flap. And if food enters into glottis, n it can lead to severe coughing or choking.

Chloride shift occurs in response to HCO3-. In response of bicarbonate ion, chloride ions diffuse from plasma into erythrocyte to maintain ionic balance. Thus, electrochemical neutrality is maintained. This is called chloride shift or Hamburger phenomenon.

Residual air is volume of air remaining in lungs even after most forceful expiration. It cannot be expelled out of lungs. Its value on an average in adult man is approximately 1200 ml.

Alveoli is made up of simple squamous epilium. Diffusion membrane is made up of three major layers: Thin squamous epilium of alveoli, endolium of blood capillaries, basement substances in between m.

Radial muscles are present in diaphgram. By contraction in se muscles, diaphragm becomes flattened in shape, so, volume of thoracic cavity increases in anterior posterior axis.

Pleura is doubled layered. It protects lungs. Also, re is a fluid called pleural fluid present between pleura. It reduces friction between surfaces of lungs.