NEET Biology Breathing and Exchange of Gases Respiration
Respiration
It is an oxidative process involving the oxidation of food substances such as carbohydrates, fats and proteins within the tissues to form C02, water and consequent release of energy. The released energy is temporarily stored as ATP.
The respiratory system provides the route by which the oxygen present in our environment gains entry into the body and the carbon dioxide produced is excreted. This whole process of exchange of gases is called breathing. This process is carried out through specialised structures called respiratory organs, which differ among organisms.
Types of Respiration
Respiration may be of two types, i.e. anaerobic respiration (the respiration without oxygen) and aerobic respiration (respiration that requires oxygen).
Anaerobic Respiration
When food is oxidised without using molecular oxygen, the respiration is called anaerobic respiration, e.g. anaerobic bacteria, yeast, parasitic worms like Ascaris, Taenia, Fasciola, etc.
In microorganisms, the term ‘fermentation’ is more commonly used in place of anaerobic respiration, which is defined as the anaerobic break down of carbohydrates and other organic compounds into alcohols, organic acids, gases, etc., with the help of microorganisms or their enzymes.
Aerobic Respiration
When oxygen is used for respiratibn, it is called aerobic respiration, e.g. most plants and animals. In higher animals, whole process of respiration includes external respiration, internal respiration and cellular respiration.
Human Respiratory System
Structurally and functionally the conducting part of human respiratory system is highly complicated. The respiratory system is derived from embryonic endoderm.
The mammalian respiratory system consists of two groups
- Respiratory TractsDifferent types of respiratory tracts are as follows :
- Nostrils
A nostril (or nares) is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation.
- Nasal Cavity
It is divided into two nasal chambers by the nasal septum. Each nasal chamber consists of three regions, i.e. vestibular, respiratory and olfactory regions.
- Larynx
- Larynx contains vocal cords the sound producing elastic fibres called voice box.
- There is a little difference in the size of the larynx in man and woman, it grows larger and becomes prominent in man, therefore, it is called Adam’s apple in man.
- Human larynx consists of glottis, cartilages, hyoid bone, thyro-hyoid membrane, vocal cords, laryngeal ligaments and muscles.
- Glottis is an opening in the floor of pharynx leading to larynx.
- There are nine pieces of cartilages (3 are single and 3 are paired).
- Epiglottis is a leaf-like structure that prevents the entry of food into respiratory tract during swallowing.
- Trachea
The trachea or windpipe is a continuation of the larynx. Trachea is supported by incomplete (C-shaped) rings of hyaline cartilages. The mucosa of trachea is lined with a ciliated pseudostratified epithelium containing mucous secreting Goblet cells, which helps in pushing mucus out.
- Bronchi
These are one pair of small, thin walled tubular structures formed by the division of trachea at the level of 5th thoracic vertebra.
- Bronchiole
The tertiary bronchi sub-divided into smaller branches, the bronchioles. After repeated branching one of the smaller bronchiole enter a lung lobule called
lobular bronchiole.
- Respiratory Organs
The different types of respirations organs are as follows:
- Lungs
Each lung is covered by double membrane called pleurae. The outer covering membrane of lung is called parietal pleura. The inner covering membrane of lung is called visceral pleura. In human, the right lung has three lobes and left lung has two lobes.
- Alveoli
The alveoli are the ultimate structural and physiological units of lung. These provide great surface area for gaseous exchange by diffusion.
Gaseous exchange occurs across the respiratory membrane of the alveoli.
- Diaphragm
The diaphragm is a dome-shaped muscular structure separating the thoracic and abdominal cavities. The diaphragm is characteristic of mammals. The diaphragm is supplied by the phrenic nerves. Puncturing of diaphragm results in stoppage of breathing and is fatal.
