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Respiratory System

Respiratory system

Respiratory system: This is related with the process of respiration between the living body and the atmosphere.

Respiration: This is the process in which the air is taken into the lungs and given out of the air in the atmosphere. The respiration takes place in two parts.

  1. Inspiration: The taking of air (O2) in the lungs is called as the inspiration.
  2. Expiration: The giving out of the air (Co2) out of the lungs in the atmosphere is called as the expiration.

Tissue respiration: The exchange of O2 and CO2 between the blood and the tissue of the body is called as the tissue of the respiration.

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Respiratory systems image

Organs involved in respiratory system:

  1. Nostrils
  2. Nasal cavity
  3. Nasopharynx
  4. Larynx
  5. Trachea
  6. Bronchus
  7. Bronchiole’s
  8. Lungs

Nostril: The opening of the respiratory system starts from nostrils. These are also called the nasal opening. The nostrils are two in numbers and it leads to the next part nasal cavity.

Nasal cavity:

  • The nasal cavity is the next part to the nasal openings. It starts from the nasal opening to the nasopharynx the length of the nasal cavity is about few.
  • The nasal cavity is divided by a common wall septum. The septum divided it into two equal parts each half is about 5cm in height, 7cm in length and 1.5cm in width. The top of the nasal cavity contains the olfactory cells.
  • The olfactory nerve is supplied in olfactory cells.
  • The position is responsible for the sense of small. The nasal cavity is present above the buccal cavity this nasal cavity is formed by two bones. Vomer and ethmoid bone. The nasal cavity has following important function.

It makes the hot air slightly cool and cool air slightly hot. It makes the dry air moist.

The nasal cavity contains the three turbinate’s (folds) which are superior middle and inferior turbinate’s. There are present the four small openings of the Para nasal sinuses (pocket) which are called as meatuses. These are present as following:

  1. Inferior meatus: This is present above the inferior turbinate
  2. Middle meatus: This is present under the middle turbinate
  3. Superior meatus: This is present below the superior turbinate
  4. Sphenoethmoidal recurs: This is present above the superior turbinate.

Nasopharynx : The nasal cavity opens into the next part nasopharynx. This is the upper part of pharynx the air passes through the nasopharynx into the next part larynx.

Larynx: It starts from the epiglottis to the lower border of the cricoid cartilage. The larynx is present opposite to the C3-C6 vertebral in the adults. The wall of the larynx is made up of cartilage muscles membranes and ligaments the cartilages are nine in no. the vocal chord are present in larynx. The muscles and mucus membrane of the larynx are supplied by Vagus nerve.

Trachea: This is also called as wind pipe, the length of trachea is about 10-11cm. Trachea contains incomplete C shaped rings of cartilage the number of rings is about 16-20.

Bronchus: There are present two bronchi each bronchus enters to the right and left lung the branches also contain the rings of cartilage and after entering the lung it divides into many small branches which are called as bronchioles.

Bronchioles: The branches divide and divide in the lungs just like the branches of a tree. The maximum branches are present in the complete lings and supply the air in the lungs, at the end of the lungs these are present the bunch of air cells. The air cells are richly supplied by the blood capillaries. The exchange of O2 and CO2 takes place on the surface of air cells.



Bronchiole’s Image

Lungs: The lungs are the main respiratory organs. These are two in numbers. The lungs are highly elastic, porous, spongy it the newly born baby. The color is rosy pink and in adults the color is dark salty grey each lung contains the upper pointed part apex and the lower broader part base. The base is concave in shape. The lung contains the three surface (costal, medial and inferior) and 3 three borders (anterior, posterior and inferior). The apex is present 25cm above the medial end of clavicle bone. The base is concave and is present on the upper surface of diaphragm which separates the lungs from the liver, spleen and fundus of stomach. There are some differences between the right and left lung which are as fall:

Right lungLeft lung
Larger in sizeSmaller in size
Weight is about 625gmWeight is about 565gm
It contain three lobes and two tissuesIt contain two lobes and one fissure
Cardiac notch is absentCardiac notch is present
Lingula is absentLingual is present

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Lungs diagram

The thoracic cavity is made up of bone and cartilage. The thorax is a coil shaped cavity which is pointed above end and boarder below. It is formed by twelve thoracic vertebra at the back and twelve pairs of ribs from the lateral side and the sternum from the front and diaphragm at the below. The sides of the thoracic cavity are completely filled by the lungs. The mediastinum is the space between two lungs.

The mediastinum contains the heart great blood vessels, oesophagun, descending aorta and superior vena cava and maximum lymphatic glands.

Pleura: Each lung is surrounded by a double serous membrane.

The pleura divide the lobes of the lungs from each other. The pleura are the lining of the ribs is called as costal pleura. The portion covering the diaphragm is called as the diaphragm pleura. The portion which lies in the neck are covered by cervical pleura between the pleural layers, there is present a fluid which protects the friction between the lungs and the chest wall during the respiratory movements.

Physiology of respiration:

The Physiology of respiration takes place as following:

  1. Entrance of air (O2) in the lungs and going out of air (CO2) out of the lungs.
  2. Exchange of O2 and CO2 at surface of the air cells.
  3. Tissues respiration.

Entrance of air in the lungs and going out of air out the lungs: Due to the contraction of the intercostal muscles and the movement of the diaphragm in the lower direction. The movement of the ribs takes place outside as a result of this the size of the thoracic cavity increases and the lungs expands maximum. Therefore the maximum air from outside enters in the lungs this is called as the inspiration. When the intercostal muscles relax and the diaphragm moves in the upwards direction the ribs move inside as a result of this the size of the thoracic decreases & the air from the lungs goes outside which is called as expiration. This process takes place alternately.

Exchange of O2 and CO2 on the surface of air cells: When the air reaches the air cells the exchange of O2 and CO2 takes place the air cells are surrounded by the maximum blood capillaries. The blood present in these blood capillaries takes the oxygen due to high pressure of O2 similarly the CO2 is given out during expiration due to high pressure of CO2. This called as exchange of O2 and CO2 on the surface of the air cells.

Tissue respiration: in this process when the O2 is taken by the blood to the different tissues of the body as a result of metabolism the O2 is used and the energy + CO2 is produced. This CO2 is taken by the blood for excretion this is called as the tissues respiration. This complete process is called as the physiology of respiration.

The normal person’s rate of respiration is about 12-14 times/min, about 1.5 liters of air is always present in the lungs and other parts of the respiratory system. There is only one artery of the body which carries the CO2 blood this is called as pulmonary artery. There is one vein of the body which carries the O2 blood these are four pulmonary veins.

Vital capacity: The total volume of the air that can be taken by the lungs or given by the lungs by the most forcibly inspiration or expiration. In a normal man this is 4-5 liters and in women this is 3-4 liters. This is measured by spirometer and the test is called as the spirometry.

Artificial respiration:

This is a technique for providing the air for a person who is not breathing his own but whose heart still beating.

The breathing may stop as a result of drowning or due to gas (carbon monoxide) poisoning. The artificial respiration is given to save the life. In the mouth to mouth breathing method the patient is made to lie on his back. The operator places his hand below the neck by lifting closes the nostrils of the patient with fingers and applies own mouth and around the patient mouth and blows about 1 liter air in the patients lungs then allow the expiration. This process is repeated 10-15 times/min this is called as the artificial respiration.

Definitions related to respiratory system:

  1. Hypoxia: This is the oxygen deficiency at the tissue level.
  2. Dyspnea: The difficulty in breathing is called as dyspnea.
  3. Cyanosis: This is the blue color of the skin tissue due to the reduced hemoglobin. The cyanosis is most commonly seen in the nail ends, lips, car lopes, and mucus membrane.
  4. Spirometry: This is a simple PFT (Pulmonary function test) that is the study of the lungs volume.

Cough reflex:

The cough reflex is very necessary to the life, by the cough the passage of the lungs are maintained free from any foreign material. The bronchi and the trachea are so sensitive that if there is any foreign material or other reason of irritation it causes the cough reflex.

The afferent impulses pass from the respiratory impulses through the VAGUS nerve to the medulla oblongata in the brain in this portion the following takes place:

  1. First of all a moderate amount of air is taken inside the lungs.
  2. The epiglottis closes and the vocal cords are shut lightly to hold the air within the lungs.
  3. During the 3rd step the muscles of the abdomen contract very forcefully pushing the diaphragm up in the chest and the intercostal muscles contract very forcefully. As a result of this the pressure in the lungs rises usually about +30mmHg.
  4. During the 4th step the vocal cords and the epiglottis suddenly opens widely so that the air under the pressure in the lungs comes out this air comes so fact that it carries the any foreign material which is present in the trachea this a called as the cough reflex. Sometimes the air is expelled at a velocity of 75miles/hour.

Sneeze reflex:

The sneeze reflex is very much like the cough reflex except that it is applied to the nasal pathways instead of the lower respiratory passage. The sneeze reflex is the irritation in the nasal passage the afferent impulses from the fifth cranial nerve (Trigeminal) passes to the medulla oblongata of the brain. The initial air blocks at takes place at soft palate uvula. The pressure is built up in the lungs and pharynx behind the uvula then suddenly the uvula is depressed so that the large amount of air passes quickly through the nose this helps to clear the nasal passage from the foreign materials. This called as the sneeze reflex.

Muscles of inspiration: The following muscles are involved during inspiration:

  1. Diaphragm
  2. External intercostal
  3. Sternocles- domostoids
  4. Scapular elevators + Anterior serrati

Muscles of expiration:

  1. Abdominals
  2. Internal intercostal
  3. Posterior inferior serrati

Clinical and applied aspects:

  1. Bronchial asthma: There are two types of Bronchial asthma 1. Extrinsic and 2. Intrinsic In both the cases the mucus membrane and muscle get thick and the mucus gland enlarges reducing the air flow during an asthmatic attack the spasmodic contraction of brachial muscle contract the air passage and there is access of the thick sticky mucus which further reduces the air ways the inspiration is normal but expiration rate is slow. There is severe dyspnea and wheezing the duration of attack may be from few muscles to few hours.

Non Specific Factors:

  1. Cold air
  2. Cigarette smoking
  3. Air Pollution
  4. URTI (Upper Reparatory Track Infection)
  5. Emotional Stress
  6. Very Hard Exercise

Extrinsic Asthma: It is also called as allergic asthma this type of asthma occurs in the children and young adults. The attack reduces with the age.

Intrinsic Chronic Asthma: It occurs in the old age and there is no history of childhood there is chronic inflammation of URTI difficulty in breathing (hypoxia)

  1. Pneumonia: It occurs when the protective process fail to prevent the taken harmful micro-organisms in the lungs with the air.


  1. When the coughing isn’t possible due to the damage of sensory nerve ending in the walls of the respiratory passage.
  2. Damage to the diaphragm or the intercostal muscles.
  3. Damage to epithelial living of respiratory track.
  4. Damage to respiratory center medulla oblongata

The other reasons like smoking, alcohol, tobacco and O2 toxicity

  1. Tuberculosis: It is caused by one of the mycobacteria.
  2. Mycobacterium tuberculosis: The man is the main host the microorganism cause the pulmonary tuberculosis and is spread by the infected person by the sputum.
  3. Mycobacterium bovis: Animals are the main cause; the microorganism is normally spread to the man by untreated milk from the cows or buffaloes coursing the infection of alimentary canal.
  4. Bronchial cancer: The main cause is the blood and lymph due to tumor in the primary bronchial part. The local spread may be within the lung to other lung or to blood vessels nerves by absorption.
  5. Laryngitis: The larynxand trachea are infected by bacterial or viral infection in the nose and the pharynx. The infection may become chronic especially in the tobacco smokers or the people who live or work in the thick populated area.