IgA is the main immunoglobulin of the respiratory tract.

Acute= severe.

Lower Respiratory Tract= Respiratory system below the larynx.

This refers to a pneumonia or a bronchitis.

Yes, the trachea is the first structure classified as a part of the lower respiratory tract.

The respiratory tract consists of organs and tissues such as the nose, pharynx, bronchi, trachea and alveoli. The respiratory tract starts at the nose.

The residual volume is the portion of air in the respiratory tract that cannot be exhaled.