Notes on the functions, structure and mechanism of our Respiratory system

The air we breathe passes through the Nasal cavities. Three changes take place here:

(1) The dust particles and bacteria become caught up in the nasal mucus;

(2) The air is cooled down and is made moist

(3) The odour of the inspired air can be easily taken by the sense organ of smell.

Thus purified, the air passes down the trachea, enters the lungs and reaches the alveoli, where gaseous exchange takes place.

Functions of Respiration:

(1) By the gaseous exchange it supplies oxygen and elimi­nates carbon di-oxide;

(2) It excretes volatile substances like ammonia, alcohol, water vapor etc.;

(3) Through lungs various gases and volatile drugs may be absorbed into blood;

(4) By eliminating water vapor it maintains water balance;

(5) The upper respiratory tract secrete mucus in which the foreign particles are Caught up and washed outside;

(6) Coughing and sneezing are protecting expiratory reflexes by which irritant particles are forced out;

(7) Voice is a respiratory function. It is usually produced during expiration;

Structure of the Respiratory Organs:

The trachea or the wind pipes is about 4.7 inches long and extends from the Larynx up to the fifth thoracic vertebra. It is there divided into two branches known as Bronchi. The trachea is composed of a series of cartilaginous rings, about 16′ to 20 in number. These ‘rings are connected together by fibrous tissues but to complete the circumference at the back of the trachea where there are certain muscular tissues. This arrangement provides for flexibility as well, as rigidity.

The two main bronchi, one for the right and the other for the left lung pass downward and outward towards the root of the lungs. The right bronchus is shorter and wider as compared to the left. The main bronchi repeatedly divided into primary, secondary, and tertiary bronchi and ultimately into the terminal respiratory bronchioles. The wall of these bronchioles contains patches of thin cells through which gaseous interchange can take place.

Each bronchiole opens into an expansion known as vestibule, from which several air passages arise which ultimately open into numerous air sacs or alveoli. Outside the alve­oli, there are numerous elastic fibers and thin walled blood capillaries. In the bronchioles, instead of cartilage there is a well developed muscular layer. Due to the presence of muscles the bronchioles rhythmically contract and dilate, during inspiration and expiration respectively.

The lungs are the two principal organs of respiration. They are situated on either side of the heart and almost fill the chest cavity. The lungs are cone-shaped organs. There is an apex which rises a little highest than the clavicle into the root of the neck.

The base of the lungs lies on the floor of the thoracic cavity, supported by the diaphragm, which separates it from the abdominal cavity. The outer surface of the lungs is in contact with the ribs and the inner surface with the vertebral column.

The lungs are covered with a membrane called the pleura which has got two layers. The lungs are divided into lobes by fissures the right lung has three lobes and the left two. These lobes are composed of lobules. A small bronchial tube enters into each lobule. This divides its walls into various portions. The lungs are like spongy rubber balls burstable in, character.

Mechanism of Respiration:

Respiration includes two movements such as Inspiration and Expiration. Inspiration is the active movement, while expiration is passive, Inspiration involves the co-ordinate contraction of a large number of muscles and expiration is due to the relaxation of the same muscles.

Only in forced expiration the abdominal muscles may contract. Due to the contraction of the intercostal muscles, the ribs are lifted upwards and outwards as well as diaphragm descends.

Consequently, during inspiration the thoracic 4 cavity increase on all sides. This tends to reduce the intra-pleural pressure, as a result of which the lungs are pulled away in this way the lungs expand. As the lungs expand, the intrapulmonary pressure falls and the atmos­pheric air rushes in this way inspiration takes place.

A lay man generally thinks that chest expands because air enters in it but the fact is that, air enters because the chest expands. At the end of inspiration all the muscles of inspiration suddenly relax and the whole chest wall collapses upon the expanded lungs, consequently the intrapulmonary pressure goes above that of the atmosphere and air rushes out this is how normal expiration takes place. But respira­tion is regulated and controlled by the chemical and nervous elements of the body or the nerves are stimulated, there are certain changes in the rate of respiration.

Though there is difference in the rate of respiration between men and women, yet the respiration goes on at the rate of 14 to 18 per minute in an adult.

The increase in the percentage of Nitrogen in the expired air is not real but relative. This is because the volume of the expired air is slightly less than that of inspi­red air. Which is caused by the fact that the amount of carbon dioxide evolved is less than the amount of oxygen absorbed, consequently, in the percentage composition Nitrogen show a relative rise.

Infection of Respiratory System:

The air that is exhaled Tout of the respiratory organ is unhealthy and it is quite possible that the person who has some infection may throw out certain germs into atmosphere at the time of sneezing and coughing. So it is necessary that the students should be trained in the school to sneeze and cough properly. As far as practicable at the time of sneezing and coughing, hand or handkerchief should be placed against nose and mouth.

Healthy breathing habit should be developed in children and they should be asked to breathe through no sell because breathing through mouth has certain grave consequences, as it lowers the, vitality and slackens activity checks growth and development prevents the growth of I the nasal region and leads to certain ailments of the repertory system. Certain ailments such as Adenoiditis, Tonsillitis, Bronchitis, Sore throat, Pleurisy, Pneumonia. Inflammation in Larynx, Common cold etc., may be caused to the respiratory system on account of infection or unhealthy breathing habits.