Gills are positioned in such a way so that it is regularly bathed with water currents.

The maxillary sinus is lined with schneiderian membrane. This membrane is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal side and periosteum on the osseous side.

All the enzymes required for aerobic respiration are present in mitochondria. Therefore, the process of aerobic respiration takes place in mitochondria.

Nasal hair acts as a filter because large-sized bacteria, spores, dust particles, etc. which are inhaled with air get entangled between the nasal hair and removed.

Larynx is made up of thyroid, circoid, paired arytenoid and epiglottis cartilages.

It is the voice-box or sound producing organ located in the neck region.

Trachea is a tube connecting pharynx with the lungs. It has no role in articulated speech characteristic of human beings.

Larynx or sound box in males is called Adam's apple.

Alveolus is the tiny air sac (only 1 cell thick) in the lungs at the end of the smallest airways, where the exchange of oxygen and carbon dioxide takes place. This is the functional unit of lungs.

The branches of trachea entering into the lungs are called bronchi. They are further branched into secondary and tertiary bronchi, which further branch in bronchioles.

The gaseous exchange in fishes takes through gills. Gills also known as branchiae, are small portions of richly vascularised tissues, internal or external to the body and in direct contact with the surrounding water.

Increase in the volume of thoracic cavity is both due to contraction of intercostal/rib muscles and diaphragm.

Paramecium obtains O₂ from air or water through general body surface.

In cutaneous respiration molecular oxygen penetrates through the skin and it is collected by the blood circulation that then distributes the gas to the tissues. Carbon dioxide is also collected from the tissues by the blood and taken to the skin to be eliminated to the environment. So, there is important participation of blood in cutaneous respiration.

Ethmoturbinal region or schneiderian membrane detects the smell.