18 Jan 2016

Respiratory system anatomy

The Respiratory System is one of the vital systems in the Human body plays a major role in providing adequate oxygen to all the parts of the body and removing the waste like carbon dioxide during the process of Inhalation and Exhalation.  



A respiratory system is a group of organs like Airway, Lungs, pulmonary vessels and respiratory muscles which are responsible for taking in oxygen and sending out carbon dioxide.  


Oxygen is very essential for the proper function of each and every tissue within the Human body.


The respiratory system is divided into two main parts, Upper and Lower respiratory tract.



           A.  Upper respiratory tract        B. Lower respiratory tract:


              A. Nose                                                    A.  Trachea  

              B. Pharynx                                              B.  Lungs (Bronchial tree & Alveoli)  

              C. Larynx           


Air enters the nose/ mouth and passes the sinuses (hollow spaces in the skull). Sinuses (Frontal, Ethmoid, Maxillary and Sphenoid) help to regulate the temperature and humidity of the air.



Then air moves into Pharynx, Both food and air passes through the pharynx before reaching their appropriate destinations (Food to esophagus and Air to Larynx)



Then the air passes into the larynx, which is essential for speech, (contains twofold called vocal cords. Opening between the vocal cords are the glottis. As the air leaves the lungs, the vocal cords vibrate and produce sound).  Then the air passes into Trachea.



Epiglottis is like a lid over the opening of larynx, Attached to the root of the tongue. Which closes the larynx while food passing.



The Trachea (windpipe) filters the air that is inhaled. It branches into the bronchi (Right and left), which are two tubes that carry air into each lung. The bronchial tubes are lined with tiny hairs called cilia. Cilia move back and forth, carrying mucus up and out. Mucus - a sticky fluid collects dust, germs and other matter that has invaded the lungs. (Usually, we expel mucus when we sneeze, cough or spit).



The bronchial tubes lead to the lobes of the lungs. The right lung has three lobes whereas the left lung has only two lobes. Smallest branches are called Bronchioles.


  Bronchial tubes are lined with tiny hairs called cilia, move back and forth and carrying mucus up and out.


  Mucus a sticky fluid collects dust, germs and other matter that has invaded the lungs.



Lungs: Spongy organ present in the thoracic cavity, the left lung is smaller than the right lung due to the presence of the heart more towards the left. 



Lobes are filled with small, spongy sacs called alveoli, and this is where the gases exchange of oxygen and carbon dioxide occurs.  The alveolar walls are very thin. These walls are composed of a single layer of tissues called epithelial cells and tiny blood vessels called pulmonary capillaries. Blood passes through the capillaries.



Pleura are the outer covering of the lungs and pleural fluid present within act as a lubricant.

Consists of two layers


  Visceral pleura attached to the surface of the lung; inner layer closer to the lungs


  Parietal pleura attached to the chest wall; the outer layer, closer to the ribs



The pulmonary artery carries deoxygenated blood containing more carbon dioxide and less in oxygen to the lungs, where the carbon dioxide gas moves from the blood to the alveoli and oxygen moves from alveoli to blood. Finally the Oxygenated blood (Blood containing more oxygen) goes to the heart through the 4 pulmonary veins and the heart pumps it throughout the body.



The diaphragm is a dome-shaped muscle at the bottom of the lungs controls breathing and separate the chest cavity from the abdominal cavity.



     A.  Contracts - Moves downward, enlarge an area in the thoracic cavity, decreasing internal air pressure, so that air flows into the lungs to equalize the pressure.



     B.  Relaxes - When the lungs are full, the diaphragm relaxes and elevates, Makes the area in the thoracic cavity smaller, thus increasing air pressure in the chest, Air is expelled out of the lungs to equalize pressure.  



Inhalation - Air is taken in through nose/mouth.  Inhalation is initiated by the diaphragm and supported by the external intercostal muscles.


When the diaphragm contracts, the rib cage expands and the contents of the abdomen are moved downward. This results in a larger thoracic volume and negative pressure (with respect to atmospheric pressure) inside the thorax. As the pressure in the chest falls, air moves into the lungs.


While taking a deep breath, the external intercostal muscles and accessory muscles assist in further expanding the thoracic cavity.



Exhalation - is a passive process - air is moved or exhaled out. Active or forced exhalation is achieved by the abdominal and the internal intercostal muscles.


The lungs have a natural elasticity capacity, as they recoil from the stretch of inhalation. Air flows back out until the pressures in the chest and the atmosphere reach equilibrium.


During forced exhalation, expiratory muscles including the abdominal muscles and internal intercostal muscles generate abdominal and thoracic pressure, which forces air out of the lungs.



The average rate of breathing is dependent upon age,


For adults - The normal respiratory rate is 12 to 16 breaths per minute (It may reach 45 breaths per minute during strenuous exercise).



The newborn – The normal respiratory rate is about 40 breaths per minute (It may slow down to 20 breaths per minute when the baby is sleeping).


Common Disease of Respiratory System:

      1.  Asthma
           2.  Bronchitis                 
           3.  Pneumonia
           4.  COPD (Chronic obstructive pulmonary disease)
           5.  Emphysema
           6.  Tuberculosis
           7.  Pulmonary edema
           8.  Pulmonary embolism
           9.  Pulmonary hypertension
          10. Fibrosis
          11. Sarcoidosis
          12. Pleural effusion
          13. Asbestosis

Common Signs and Symptoms:
          1.  Shortness of breath
          2.  Apnea
          3.  Dyspnea
          4.  Hypoxia
          5.  Anoxia
          6.  Bradypnea
          7.  Tachypnea


1.    Nose                     - Rhino / Naso

2.    Sinus                     - Sino

3.    Larynx                  - Laryngo

4.    Pharynx                 - Pharyngo

5.    Trachea                 - Tracheo

6.    Bronchus              - Broncho

7.    Bronchiole           - Bronchiolo

8.    Lung                     - Pneumono / Pulmono

9.    Breath                   - Pnea

10.  Chest                    - Pectr/o,  Thorac/o

11.  Diaphragm           - Phreno

12.  Carbon-dioxide    - Capn/o

13.  Voice                    - Phon/o


1. ARDS - Adult or acute respiratory distress syndrome

2. COPD - Chronic obstructive pulmonary disease

3. DOE - Dyspnea on exertion

4. OSA - Obstructive sleep apnea

5. PAT - Paroxysmal atrial tachycardia

6. PFT - Pulmonary function test

7. RDS - Respiratory distress syndrome

8. SOB - Shortness of breath

9. URI - Upper respiratory infection

10. TB - Tuberculosis


Test your Knowledge:

                A. Respiratory System Anatomy Quiz 

                B. Terminology Quiz