Respiration and Its Types | HSEB Notes of Biology Class 12

Biology | Zoology
HSEB Notes on Respiration and Its Types
Lesson :  Respiration
Class : 12

Respiration can be defined as a biochemical process in which organic compounds are oxidized to liberate energy. Energy is released in a step wise process. The energy is trapped in a chemical bonds of adenosine triphosphate ATP molecules. ATP is instant sources as universal energy carriers. It is a catabolic process.

Types of Respiration

1. Aerobic 

It occurs in all higher forms (organisms) in this type Oxygen is necessary.

C6H12O6 + 6O2 -------- 6CO2 + 6H2O + 2880 K joule .

2. Anaerobic respiration 

C6H12O6 ----------- C2H5OH(ethyl alcohol) + CO2 + 210 K joule example yeast 

C6H12O6 ----------- C3H6O¬3 (lactic acid)+ energy example intestinal worms 

It occurs in Yeast cells, Bacteria etc. Oxygen is not necessary. Glucose molecules are changed into ethyl alcohol and Carbon dioxide. This process is referred to fermentation.

Pulmonary respiration 

All mammals whether aquatic like Dolphin, Whales etc or terrestrial have lungs as respiratory organ. The respiration by lungs is called pulmonary respiration. In man, respiratory organs are lungs and respiratory tracts which include nostrils, nasal chamber, internal nostril, nasopharynx, larynx, trachea and bronchi etc.

Nostrils are openings of nasal chamber. Nasal chambers are lined with mucous membranes which are ciliated epithelium. Nasal chambers are paired structures separated by nasal septum. Each nasal chamber has 3 parts 

1. Vestibular part - it is the anterior part with hairy skin which acts as filter preventing the entry of dust particles. 
2. Respiratory part - it is the middle part lined by glandular and vascular respiratory epithelium. It acts as air conditioner and brings the inspired air at body temperature.
3. Olfactory part - it is posterior part and lined by highly sensory olfactory epithelium( Schneiderian membrane). It helps in smelling. 

Functions  filtration of air by hairs, prevent dust from entering.

• moisten the dry air by mucous.
• mucous traps dirt.
• air warmed by capillary network.
• detect smell.

Internal nostril open into nasopharynx. Little below this, is the laryngopharynx. There is presence of aperture called glottis. Glottis can be closed by leaf like cartilage epiglottis during the swallowing of food. Epiglottis prevents the entry of food into glottis. Glottis opens into larynx. Larynx is called voice box. It is cartilaginous structure. It is more developed in males than in females. It is also called Adam’s apple. It is supported by four cartilages, one cricoid, one thyroid and two arytenoids. It is lined by stratified columnar ciliated epithelium. The cilia of which beat out ward and eject the unwanted substances. There are presence of 2 pairs of vocal cords. The true pair of vocal cords set into vibrations when air is forced to go out from lungs. The vibrations produce the sound. The pitch of sound is controlled by muscles. The larynx opens into trachea.

Trachea runs through neck in front of oesophagus and extend into the thoracic cavity. It is the wind pipe about 12 cm long. It is provided with 16 to 20 dorsally incomplete c-shaped tracheal rings of cartilage. Cartilagenous rings prevents trachea from collapsing. Trachea divides into 2 primary bronchi. These are also provided with cartilaginous rings. Each primary bronchus enters into lung of its side. The right bronchus divides into 3 branches and left into 2 branches. 

After entering into the lungs, primary bronchioles divide into large no. of bronchial tubes called secondary bronchioles. The secondary bronchioles further subdivides into tertiary bronchioles and then into alveolar ducts. The alveolar duct ends in alveolar sac containing 6 to 8 pocket like outgrowths called air sacs. The air sacs are about 0.1 mm in diameter. These branches make the bronchial tree.

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