Respiration:-
Air enters body through nose or mouth. Nose and mouth are seperated by palate.
From the mouth or nose the air passes into the trachea. At the top of trachea
there is a ring of cartilage called epiglottis. This closes the trachea when bolus
touches the soft palate. Breathing through nose is better because structure of nose allows the air to become warm, moist and filter. That is because there are some thin bones (turbinal bones) which are covered with a thin layer of cells, some of these cells make a liquid containing water and mucus which evaporates into the air in the nose and moistens it.
There are other cells in the nose. They have thin hair like structures known as cilia. Cilia are also found in the trachea and bronchi. they waft mucus containing dust or bacteria up to the back of the throat. So that it does not block the lungs. The cilia in the nose also waft mucus into the oesophagus where it is swallowed.
The trachea goes down through the neck and into the thorax. The thorax is the upper part of the body from neck to the end of the ribs and diaphragm. In the thorax the trachea divides into 2 branches. Collectively they are known
as bronchi. Each bronchus goes into the each lung and divides into many tiny air sacs known as alveoli. This is where gaseous exchange takes place.
The walls of alveoli are the respiratory surface. Capillaries are closlty wrapped around the alveoli. So that oxygen diffuses in the blood and CO2 other way.
The walls of alveoli have several features which enable them to carry out there function efficiently.
(1) They are very thin, only one cell thick and the wall of capillaries is also one cell thick so the oxygen molecule only have to pass the small thickness to get in blood.
(2) They have an exellent transport system. The blood is pumped to the lungs through pulmonary artery, which divides into thousands of capillaries. Which take blood to all parts of the lungs. CO2 in the blood can diffuses out into the alveoli
and O2 diffuses into the blood. The blood is taken back to the heart in pulmonary vein and then the blood is ready to be pumped to the rest of the body.
(3) They have larger surface area.
(4) They have a good supply of Oxygen. The breathing movements keep lungs well supplied with O2.
Breathing:- is muscular movements which keep the respiratory surface supplied with oxygen.
[(to make air in and out of the lungs is breathing. For this it is necessary that the volume of thorax is made larger to suck in the air and vice versa.)]
There are 2 sets of muscles which help in breathing.
(1) Internalcostal muscles.
(2) Diaphragm.
Diaphragm is a large sheet of muscle and elastic tissue which streches across the body . It is underneath the lungs and heart.
Breathing in is called inspiration:-
When breathing in, the muscles of diaphragm contracts which pulls it down
and incerase the volume of chest cavity. At the same time, the external
internal costal muscles contract. This pulls the ribcage upwards and outwards.
Together these movements increase the volume of the thorax or chest cavity.
As the volume of thorax increase the pressure inside the thorax decrease below
the chest cavity. Extra space has been made now, So something must come in to
fill the space. So air rushes to the lungs through traches and bronchi.
Breathing out is called expiration :- When breathing out the muscles of diaphragm relaxes which springs it to iis original (domed) shape and position. This is due to the diaphragm is made of elastic tissues. At the same time the muscles of external internal Costal muscles relaxes which decrease the volume of thorax. Hence the Volume of thorax decreases so, the pressure inside the lungs increase which squeezes air out of the lungs to the mouth and nose and finally out of the body. Function of internal internalcostal muscles. These muscles forces air out. Normally a person breath out by the relaxation of external internalcostal muscles and diaphragm.
But sometimes during coughing air is forced out more forcefully. This is due to the contraction of internalcostal muscles. The muscles of abdomen wall also contract to squeeze the extra air out of the thorax.
Pleural membranes help with breathing:-
Each lung is covered with a thin, smooth membrane. Another similar membrane lines the inside of the ribcage. These are called Pleural membranes. These membranes make pleural fluid. As the lungs inflate and deflate this helps to lubricate them so that they do not rub against the ribcage too much.
Exercise create an Oxygen debt:-
Sometimes cells need a lot of oxygen very quickly. During exercise muscles use a lot of energy.
To produce this energy the mitochondria in the cells will be combining glucose with oxygen as fast as it can. And the heart and the lungs provides oxygen as fast as they ca. A person breath deeper and faster to get more oxygen to the blood. Eventually a limit is reached when heart and lungs
cannot supply oxygen to the muscles any faster. But energy is still needed. So, the glucose breaks down, without combining with oxygen, to lactic acid and energy.
After the exercise a person still continues to breathe deeper and fasterto use up all the lactic acid by combining it with oxygen. This is known as oxygen debt.
Glucose ------> lactic acid + energy.
Smoking:- Cigarette smoking is very harmful to a person's lungs. Heavy smoking also damages and heart . Non smokers can also get cough s and brochists by spending lot of their time with smokers. Cigarette smoke contains 3 main ingreients:- Tar,Nicotine and carbondioxide.
Nicotine:- It is an addictive. It makes a person feel more active and alert. It also increases heart beat rate and blood pressure. that's why smokers suffer more from heart diseases than non-smokers.
Tar:- This is absorbed by some cells especially those lining the lungs. Normally, these cells form a thin protective layer. But the tar makes them divide again and agin. Some of these groups of dividing cells go on dividing, developing into cancer.
Tar aslo damages the cilia lining the respiratory passages, and causes extra mucus to be made by the goblet cells. So it makes cilia paralysed and make it nable to perform its functions properly. This mucus trickles down into the lungs. Bacteria breed in mucus and causes infections.
Carbon monoxide cuts down oxygen supply:-
Carbon monoxide is absorbed in the blood and combines more rapidly with haemoglobin than oxygen.
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