Describe Respiration In Human Being.

ANS :
HUMAN RESPIRATORY SYSTEM :



The human respiratory system is well-developed.

It consists of nostrils, nasal cavity, pharynx, larynx, trachea, bronchi and lungs.

Nostrils are the opening of nasal cavity.

The oxygen-rich air enters nasal cavity through the nostrils.

The deoxygenated air (containing CO2) is expelled out through nostrils.

The mucus in nasal cavity keeps it moist so that dust particles and microbes in the air are trapped there and do not enter lungs.

Nasal cavity also warms and moistens the air.

Air enters pharynx through nasal cavity and then into trachea (wind pipe) through a slit called glottis.

Glottis is protected by a cartilaginous flap called epiglottis.

As glottis is covered by epiglottis during the swallowing of food, the food does not enter the wind pipe.

Trachea is a wide tubular structure supported by C-shaped cartilaginous rigs.

Trachea divides into two bronchi which lead into the lungs.

There is a pair of lungs situated in thoracic cavity.

The lungs are covered by two membranes called pleura.

Brochi branch into many bronchioles in the lungs. Each bronchiole terminates in a sac called alveolar sac.

The walls of the alveoli are thin and covered by blood capillaries.



MECHANISM OF BREATHING :



Intake of air into lungs is called inhalation.

When the diaphragm and the muscles attached to the ribs contract, the volume in the thoracic cavity increases, the air pressure decreases and the oxygen-rich air from the atmosphere enters the lungs through nostrils.

Alveolar sacs are filled with oxygen-rich air and exchange of gases occurs.

When the diaphragm relaxes the volume of the thoracic cavity decreases, the pressure increases and the air containing carbon dioxide is expelled out of lungs through nostrils.

This is called exhalation.

The process of inhalation and exhalation is collectively called breathing.



EXCHANGE OF GASES IN TISSUES :


Respiratory gases are exchanged between the blood and the tissues.

Oxygen is utilised in the tissues and carbon dioxide is released.

The blood coming from lungs to the tissues has higher concentration of oxygen and lower concentration of carbon dioxide.

The difference in concentration induces exchange of gases between tissue and blood capillaries.



The end result of respiration process is that the oxidation of simple food molecules like glucose in mitochondria releases energy which is stored in ATP