Activities to do. Read the explanations on the respiratory system and perform the first Multiple Choice Test and the Mute Picture. Then read the explanations on the process of breathing and perform the second Multiple Choice Test and the Crossword.

1.The human respiratory system
. It is the appararus that is in charge of capturing the oxygen (O2) from the air and releasing carbon dioxide (CO2) produced during mitochondrial respiration.

2. Parts of the respiratory system. The human respiratory system consists of the nose, pharynx, larynx, trachea, two bronchi and two lungs. The right lung has three lobes and the left lung has two. Each pulmonary lobe has hundreds of side lobes or lobules.

While entering to the lungs the bronchi divide into branches and emerge bronchioles, which ramify while each one enters into a lobule, where they branch again forming the bronchial capillaries that end in the lung sacs, which present walls with the globose expansions called pulmonary alveoli.

Most of the inner surface of the respiratory tract has cells that produce the mucosity (mucus). This is a very viscous substance inside of which the particles remain adherent, carrying the air and having antibacterial and antiviral substances. In addition, the nostrils, trachea, bronchi and bronchioles have internal ciliated cells that move mucus toward the pharynx where it passes to the esophagus due to the swallowing process.


3. The anatomy of the human respiratory system.

1. Nostrils. Are two orifices that connect the exterior with the nasal chamber, inside of which there are some hair which filter the air and mucus-secreting glands which retain dust and humidify the air.

2. Nasal cavity. Are two large cavities located above the mouth. Inside, they present folds called turbinate bones, which slow the flow of air, helping to humidificate and warm it.

3. Pharynx. Is a conduit of about 14cm long that allows the communication between the nostrils, the mouth cavity, the middle ear (through the Eustachian tubes), larynx and esophagus.

4. Mouth. It allows the entry of the air but without filtering dust nor humidifying which is provided by nostrils.

5. Tongue. This organ presses the food against the palate to introduce foods.

6. Epiglottis. It is a small tongue which when being pushed by a bolus descends upon the glottis closing the access and thus preventing the food being introduced into the trachea.

7. Larynx. Is a short conduit, about 4cm in length, which contains the vocal cords.

8. Vocal cords . Are two muscular and fibrous folds on the inside of the larynx. The space between them is called the glottis and leads into the trachea. They are the vocal organ of humans.

9 . Thyroid cartilage. It is the first cartilage in the trachea. Is more developed in men, which causes the presence of a bulge in the neck called the Adam's apple and a deeper voice.

10. Esophagus. It is a digestive system's duct, located behind the trachea.

11. Trachea. It is a conduit o12cm long and 2cm in diameter, that consist a serie of semiannular cartilages whose rear ends are joined by muscle fibers. This prevents friction with the esophagus, when the food passes through it.

12. Lungs. Are two globular masses. The right lung has three lobes and the left only two.

13. Pulmonary artery. Contains blood poor in oxygen and rich in carbon dioxide, which moves from the heart to the lungs.

14. Pulmonary vein. Contains blood rich in oxygen and low in carbon dioxide, which moves from the lungs to the heart.

15. External intercostal muscles. Are the ones lifting the ribs in order to increase the volume of the thorax and produce inhalation.

16. Ribs

17. Pleural cavities. Are the two membranes that surround the lungs. The space between them is filled with pleural fluid. Its purpose is to avoid friction between the lungs and ribs.

18. Thorax. Is the cavity formed by the ribs and sternum, where the lungs lie.

19. Bronchi. Are two pipes in which the trachea branches off.

20. Bronchioli (bronchioles). Are the branches of the bronchi. The ultimate ramifications originate the bronchial capillaries that end in the lung sacs, which are the cavities with a numerous globose expansions called plumonary alveoli.

Considering the two lungs there is about 500 million plumonary alveolis.

21. Heart cahmbers. Is a concavity in the left lung in where the heart is.

22. Diaphragm. Is a muscular membrane that during inhalation descends which allows the plumonary dilation and during the exhalation ascends the emptying of the lungs.

Multiple Choice Test (Spanish activity. Activity in English is under construction)

Mute picture (Spanish activity. Activity in English is under construction)

4. The external respiration or "ventilation" in humans.
The external respiration or ventilation includes the following three stages:

1 . Inhalation. In it the external intercostal muscles contract and raise the ribs and sternum, and the diaphragm descends. All this increases the capacity of the rib cage, causing the lungs to expand and between the air rich in the O2 enters.

2 .Gas exchange. In it the air rich in the O2 reaches the pulmonary alveoli, the walls of which are so thin that allow the gas exchange. Because of that they are covered with the fine blood capillaries that contain blood loaded with CO2 and low in O2, CO2 passes into the alveoli and O2 passes into the blood which is inside the blood capillaries.

3 . Exhalation. In it the external intercostal muscles relax and lower the ribs and sternum, and the diaphragm rises. All this diminishes the capacity of the rib cage, causing the lungs to contract and, therefore, the air rich in CO2 goes out.


5 . The gas exchange. The characteristics of the gas exchange that occurs in the pulmonary alveoli are:

1) The blood coming from the heart, which reaches the blood capillaries that cover the pulmonary alveoli, is charged with carbon dioxide and contains very little oxygen.

2) The air from outside, rich in oxygen, reaches to the pulmonary alveoli. Also comes the carbon dioxide from blood capillaries. The result is a gas mixture which contains mostly an oxygen.

3) The distance between the gases contained within the pulmonary alveoli and the gases inside of the blood capillaries is very little, only 0.6 microns (0.6µ) and the walls that separate them are permeable to them. Due to that the gases can pass from one to another. The result is that both of the gas mixtures end having a very similar composition.

4) The blood that goes from the blood capillaries which cover the pulmonary alveoli to the heart is very rich in oxygen and low in carbon dioxide.


6. The lung capacity

Tidal volume (TV). Is that colume of air moved into or out of the lungs during normal breathing. For men it is up to 0,5 liters.

Inspiratory reserve volume (IRV). Is the maximal volume that can be inhaled from the end-inspiratoty level. For men it is up to 3 liters.

Expiratory reserve volume (ERV). Is the maximal volume of air that can be exhaled frm the end-expiratory position. For men it is up to 1 liter.

Vital capacity (VC). Is the volume of air breathet out after the deepest inhalation. Equals to the sum of the three previous volumes (TV + IRV + ERV = VC). For men it is up to 4,5 liters.

Residual volume (RV). Is the volume of air remaining in the lungs after a maximal exhalation. For men it is up to 1,5 liters.

Total lung capacity (TLC). Is the volume in the lungs at maximal inflation. For men it is up to 6 liters.


7 . The main diseases of the respiratory system. The main ones are:

  • Shortness of breath. Decreased lung capacity to exchange gases. It can be caused by the deposits of the tobacco tar on the respiratory surface, by asthma, by infections, etc..
  • Bronchial asthma. Sudden contraction of the bronchial muscles usually due to an allergic reaction. Causes a very unpleasant choking sensation.
  • Pulmonary edema. Infiltration of fluid (serous fluid) that fills the interior of the lungs causing respiratory failure.
  • Lung infarction. Severe pain in the chest caused by a pulmonary embolism, ie by a clot blocking a vessel that supplies blood to the lung tissues.
  • Infectious diseases.
    • Viral. The main ones are the cold and the flu.
    • Bacterial. According to the affected section it is divided into the following diseases: sinusitis, tonsillitis, pharyngitis, laryngitis, bronchitis, pleurisy (pleura), pneumonia. Also is needed to mention tuberculosis (infection caused by Mycobacterium tuberculosis that results in the formation of caverns in the lungs), and pertussis (whooping cough that affects infants and little kids).
Multiple Choice Test (Spanish activity. Activity in English is under construction)
Crossword (Spanish activity. Activity in English is under construction)

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