Note on Respiration System

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Respiration system

respiration is a process of exchange of-of gases.In which oxygen is taken in and carbon dioxide is liberated and release of energy . the former is extentrenal and later is internal or conducts air to and from the lungs. All mammals have ribs cae that are lifted up and out abdominal muscular diaphragm that is the thoracic cavity .Where they are protected from drying out . Cells lining the nose filter moisten and worm incoming air. These lining epithelium cells are long and fringed with cilia . this surface covered by mucous membrane containing may blood supplies along with filtering out impurities ,the nose also protects the lungs . By the time the reach the lungs, it is at body temperature and humidity of the incoming air.They maintain the temperature and is saturated with water in the trachea and the bronchi, cilia beat upward carrying mucus dust and occasional bit food that went down the wrong way into the throat ,where the accumulation may be swallowed or expectorated . the back of nose leads into pharynx air passes from the pharynx through the glottis an opening into the larynx, the larynx, and the trachea are permanently held open to receive air , the larynx s held open by the complex of cartilages the from the Adam's apple.

the trachea is held open by a series of the horseshoe.

– shaped , cartilaginous rings that do not completely meet in the rear ,when food is swallowed the larynx rises and the glottis is closed by the flap of tissue called epiglottis . the trachea divides into two bronchi, which enter the right and left – lungs each the branches into a great number of smaller passages called "bronchioles".The two bronchi resemble the trachea in structure but as the bronchial tubes divide and subdivide their walls become thinner and the ring of cartilages are no longer present .Each bronchiole terminates in an elongated space enclosed by a multiple of air pockets called alveoli which make up the lungs the bronchial tree and the alveoli are housed within the paired lungs.Each lung weight about 454 gms and is spontaneously in consistency due to numerous alveoli. The lung tissue of newborn are characteristically pink but tissue darkens with age as the person breathing environment effect due to their environments , smoking habits.
the right lungs have 3 lobes and left have 2 lobes.

Breathing mechanism

Air moves between the atmosphere and the lungs in response to pressure graidients. Air moves in when the air pressure in the lungs is lower than the pressure in the lungs are greater that the atmosphere pressure.The anatomy of the thoracic cavity explains the generation of the pressure changes responsible for the pulmonary ventilation. An abroad sheet of muscle the diaphragm separates it from the abdominal cavity membrane coat all the surface in the thoracic cavity ,which the lung essentially fill changing the size of thoracic cavity creates pressure change,that moves air in and out of the lungs .When the muscles of ribs cage and diaphragm contact the size of the thoracic cavity incearas and air draws into the lungs this process is called "inspiration or inhalation" .when the muscled of the rib cage and diaphragm relax, the thoracic cavity decreases in size causing expiration or exhalation . Not all of respiratory tract actively participates in gas exchange . the part not used in gas exchanges the pharynx trachea and the upper third of lung called dead space . the air in the bottom third of lungs is not exchanged in every breath because most of this air remains in the lungs it is called residual air .

Respiratory Organs

it includes respiratory tract from the pair of nasal opening up to the pair of the lung including thoracic cavity.

1 respiratory tract

it is the path for fresh and foul air and is comprised of following parts:-
a Nostrils or external nares
b nasal chambers

1 vestibular part
2 respiratory part
3 olfactory part

nasal chamber helps in worming filtration of air conditensation , moistening, and sterilize by lysozyme of-of the inspiratory air it also help in swelling.

c internal nares
d laryngopharynx
e larynx
1 thyroid cartilage
2 Arytenoids
3 Cricoid cartilage
4 Vocal cords


check the entrance of food particles and produces various sound frequencies by vibration.


Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.

  1. respiration is a process o exchange of of gases in which oxygen is taken in and carbonidoxide is liberated and release of energy
  2.  cartilagesinous rings that do not completely meet in the rear ,when food is swallowed the larynxa rises and the glottis is closed by flap of tissue called epiglottis 
  3. Air moves between the atsophere and the lungs in response to pressure graidients
  4. Air moves in when the air preseeure in the lungs is lower than the pressure in the lungs is greater that the atmosphere pressure
  5. cheack the netrance of food particles and produces various sound frequenieces by vibration

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