What is the partial pressure of oxygen in  oxygenated blood ?

95 mm Hg

Write a note on rate of respiration.

Rate of respiration : The rate of respiration is slightly quicker in women than in men. In normal breathing, expiration succeeds inspiration and is followed by a slight pause of Inspiration-expiration-pause. In sick babies, this order is sometimes reversed and the sequence

becomes : inspiration-pause-expiration. This is described as inverse breathing.

Normal rate per minute

In newly born → 40

At twelve months → 30

From two to five years → 24

In adults → 10-20


List the causes of pneumothorax, haemothorax and pleural effusion.

Pneumothorax : It is the presence of air in the pleural cavity.

Causes : It may be caused by :

1. Penetrating injury, e.g. compound fracture of rib. 

2. Rupture of the lung over a diseased area, e.g. emphysema.

3. Therapeutic introduction of air to rest the lung.

Haemothorax : It is the presence of blood in the pleural cavity.

It may be caused by :

1. Penetrating chest injury involving blood vessels.


Pleural effusion (excess fluid in the pleural cavity) : It may be caused by :

1. Inflammation, usually due to infection.

2. Malignant tumour involving the pleura.


Discuss the various ways in which animals obtain oxygen.

Animals obtain oxygen in the following five ways :

1. From water or air through moist body surface directly into the body as in Amoeba.

2. From air or water through the thin body wall in blood vessels e.g. Earthworm.

3. From air through spiracles to a system of air tubes-tracheae to tissues and tissue cells or from water through tracheal gills e.g. insects.

4. From water through gill surface to blood vessels and then to tissue cell e.g. fishes and amphibians.

5. From air through moist lung surfaces to blood vessels and from there to tissue cells e.g. animals.


Write notes on the following :

Hypoxia, pneumonia, emphysema and cough.

i. Hypoxia is the condition produced due to the lack of oxygen.

ii. Pneumonia :is th inflammation of lungs caused by bacteria Diplococcus pneumoniae,  in which the air sacs fill with pus and may become solid

iii. Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. In this disease, walls present in between the alveoli break, as a result gas exchange area of the lungs is reduced. It may be caused due to oedema, inflammation or mucus deposition in the bronchi.

iv. Cough : It is the expelling of air from the lungs with a sudden sharp sound.



Explain the respiratory tract of man.

Respiratory tract of man consists of :

1. External nostrils : The external nares are two slits at the lower end of the nose. These open into the nasal chambers.

2. Nasal chambers : Two nasal chambers are separated from each other by nasal septum. Each chamber has the following three regions :

3. Internal nares (conchae) : The nasal chambers open into the nasopharynx by internal nares.

Explain the respiratory tract of man.

Fig. Respiratory Organs of man

4. Pharynx : Its upper part is called nasopharynx. The internal nares open into it. Its middle part is called oropharynx and lower part is called laryngopharynx.

5. Larynx : The larynx is called the Adam’s apple and is more prominent in men than in women. 

6. Trachea : It is a long thin-walled tube. It extends downward through the neck. In the middle of thorax, it divides into two primary bronchi, one major bronchus enters the right lung and subdivides to form secondary and tertiary bronchi which divide into smaller bronchioles which further divide into alveolar ducts. The latter enter the infundibulum which is made up of central duct and alveoli. All infundibula which get alveolar ducts from one bronchiole is called lobule. The cartilagenous rings are incomplete behind, support the wall of the trachea and bronchi and finally disappear over the bronchioles.