Railway Science (Biology – Respiratory System)

Breathing in fishes: It begins when a fish gulps water through its mouth; The water enters the mouth and passes through the fish's gills, which are rich in blood; These gill filaments absorb oxygen from the water and move it into the bloodstream.

Alveoli are tiny air sacs in the lungs at the end of the bronchioles, with an average diameter of 5×10⁻⁵ meters, where oxygen diffuses into the blood and carbon dioxide diffuses out of the blood. The alveoli increase the overall internal surface area of the lungs, so that more oxygen and carbon dioxide can diffuse in and out.

In males, the front of the thyroid cartilage that surrounds the larynx tends to protrude outward, creating a feature known as the “Adam's apple”. The function of Adam's Apple is to protect the vocal cords.
Lung - An organ involved in the respiratory system. It is responsible for the exchange of oxygen and carbon dioxide in the body. Palate - It is the roof of the mouth which separates the oral cavity from the nasal cavity.
Tongue - A muscular organ in the mouth that helps with functions like tasting, swallowing, and speaking.

Halitosis - Condition of having persistent, unpleasant breath odor. It can be caused by poor oral hygiene, dental problems, dry mouth, certain foods, smoking and underlying medical conditions. Proper oral hygiene practices, regular dental check-ups, and addressing any underlying causes can help manage and prevent bad breath.

Aerobic respiration is the process by which organisms use oxygen to turn fats and sugars into chemical energy. Anaerobic respiration is respiration using electron acceptors other than molecular oxygen. Some examples include alcohol fermentation in yeast.

Sinus are air-filled spaces and a connected system of hollow cavities inside the skull. Types - Frontal Sinus, Maxillary Sinus, Sphenoid Sinus, Ethmoid Sinus. Sinusitis is the inflammation or swelling of the tissue lining the sinus.

Vital capacity: The capacity of lungs to expire the maximum volume of air after a deep inspiration. The largest quantity of air that can be expired after a maximum inspiratory effort. Residual volume: The volume of air that remains in the lungs after the most forceful expiration. Residual air mostly occurs in alveoli. Minute Volume: The amount of air moved in and out of the lungs during one minute. It is equal to the tidal volume against the number of breaths per minute.

It is an invertebrate animal that is a member of the phylum ‘Annelida’ and the order ‘Opisthopora’. It is usually a ‘hermaphrodite’, which means it has both male and female organs.
Cutaneous respiration : Gas exchange that occurs through the skin or body surface of animals. Examples - Earthworms, frogs, leeches.
Pulmonary respiration : The gas exchange occurs through the alveoli in the lungs. Examples - Reptiles, birds and mammals.
Branchial respiration : The breathing through the gills. Examples - Fishes, aquatic arthropods and molluscs.

Its examples are Peptostreptococcus, Treponema, Fusiform, Porphyromonas, Veillonella and Actinomyces. Aerobe - The organism which survives in the presence of oxygen. Parasite - An organism that lives on or in a host and gets its food from or at the expense of its host.
Symbiotic - Relationship or interaction between two different organisms that share similar habitat. There are three types of behaviours observed in symbiotic relationships, namely – Mutualism, Commensalism and Parasitism.

The volume in the lung can be divided into four units: Tidal volume - It is the normal volume of air displaced during the respiratory cycle without extra effort. Expiratory reserve volume - It is the additional amount of air that can be exhaled after a normal exhalation.
Inspiratory reserve volume - It is the additional amount of air that can be inhaled after a normal inhalation. Residual volume - It is the amount of air that remains in a person's lungs after fully exhaling.