Respiratory System - Notes, Biology Notes | Study General Science(Prelims) by IRS Divey Sethi - UPSC

RESPIRATORY SYSTEM

• All physical and chemical reactions in which atmospheric air oxidizes food in the body cells resulting in production of energy and liberation of CO₂ are included in respiration.
• Types of Respiration

1.  Anaerobic Respiration
2. II. Aerobic Respiration

1. Anaerobic Respiration

• When nutrients are oxidized without using O₂ (also called fermentation).
• In yeast, glucose forms ethyl alcohol and CO₂.
• In bacteria and muscles, glucose is converted into lactic acid.
• Endoparasites like Ascaris, Fasciola, Taenia also respire anaerobically.
• It is a low energy yielding process.

2. Aerobic Respiration

• Cells utilize O₂ for oxidizing nutrients.
• O₂ is used either from atmospheric air or from water.
• It is found in most plants and animals.
• It provides much more energy than the anaerobic one.

It involves:

• External Respiration: Gaseous exchange of O₂ and CO₂ between blood and air (or water).
• Transport of gases to the tissues.
• Internal Respiration: Gaseous exchange between blood and tissues.
• Cellular Respiration: Oxidation of nutrients in the cells and liberation of energy.

Respiratory Organs in Human Body

I. Nasal Cavity

• It opens to the exterior through nostrils.
• The small hair present in the cavity help to filter particles of dust and other foreign matter.
• The air in the nasal cavity gets warmed (because nasal cavity has a very good blood supply) and moistened before it enters lungs.

II. Pharynx 

• From the nasal cavity the air enters the pharynx.
• It serves as a common passage for both air and food.
• The opening into the wind pipe or trachea is a narrow slit, the glottis.
• The glottis is protected against the entrance of food by a triangular flap of tissue, the epiglottis.

III. Larynx (Voice Box)

• Called Adam’s apple in man. It is the first part of trachea present in the neck.
• When air is forced into the larynx, the vocal cords present in it vibrates and sound is produced.
• The pitch of a sound is determined by the tension on the vocal cords – the greater the tension, the higher the pitch.

IV. Trachea

• It is four and a half inch long tube with C – shaped ring of cartilages in its walls.
• These tings of cartilage make the wall non – collapsable.
• The trachea branches into two bronchi on to each lung and these branches within the lung into many smaller bronchioles.

V. Lungs

• Surrounding each lung is a double walled sac, the pleural cavity. Hence, the covering of lungs are called pleural membrane.
• The right lung is divided into three lobes and left into two.
• The left lung is smaller than the right and has a concavity, the cardiac notch, where the heart lies.
• Inside the lung, each bronchi divides into numerous bronchioles, each of which terminates into an elongated saccule, the alveolar duct, which bears on its surface air sac or alveoli.
• The latter provide a large surface for gaseous exchange.

Respiratory Disorders in Human Body

• Asphyxia : It is a condition caused by increase in CO₂ concentration in tissue.
• Hypoxia : Shortage of oxygen supply to body.
• Hypopnoea : Slow breathing.
• Hyperpnoea : Rapid breathing.
• Apnoea : No breathing.
• Dyspnoea : Painful breathing except in upright position.
• Orthopnoea : Difficult breathing. 
• Tachypnoea : Rapid shallow breathing.
• COPD : Chronic Obstructive Pulmonary Disease which includes Emphysema, Chronic bronchitis and Asthma.
• Emphysema : A situation of ‘short breath’ due to die break down of alveolar walls and reduction of respiratory area as it happens due to smoking.
• Tuberculosis : A bacterial disease caused by Mycobacterium tuberculosis.
• Pneumonia : Infection of lungs by Diplococcus pneumonia and leads to accumulation of mucous and lymph in alveoli, impairing gaseous exchange.
• Whooping cough or Pertussis : An infectious disease caused by bacterium Bordetella pertussis.
• Asthma : Difficult breathing due to spasm in bronchial muscles and narrowing of bronchi.
• Sleep Apnoea Syndrome (SAS) : Persons with snoring habit suffer with sleep apnoea syndrome because their upper respiratory tract closes on inhalation leading to apnoea and sleep breaks.
• Hypercapnia : Excess of CO₂ in the body.
• Cyanosis : Means blueness of skin because of excessive amount of deoxygenated haemoglobin.
• Pleurisy : Inflammation of pleural membrane causing severe chest pain.

Respiratory Pigments