Wednesday, July 18, 2012

In relation to the breathing system

Gas exchange in the lungs

Breathing in supplies us with oxygen needed for cellular respiration, while breathing out removes waste carbon dioxide from our body, air is breathed to the lungs oxygen passes into the blood by diffusion (movement of molecules or particles from regions of higher concentration to regions of lower concentration)along a concentration gradient. At the same time, carbon passes out of the blood into the air of the lungs also by diffusion along a concentration gradient. This gas exchange takes place in the alveoli which are the tiny are sacs with large surface area that make up much of the structure of the lungs.
The movement of oxygen into the blood and carbon out of the blood take place at exactly the same time-there is swap or exchange between the two, so this process is known as gaseous exchange.


Gas exchange in Alveoli

Air in the lungs ends up in the alveoli which are tiny air sacs that provide an ideal site for most effective possible diffusion. They have a large surface are which is always kept moist. This is effective for most effective diffusion of the gases. The alveoli also have a rich blood supply so that a concentration gradient is maintained in both directions, oxygen is removed into the blood and more carbon dioxide is delivered to the lungs. This makes sure that the gas exchange can take place along the steep concentration gradients for it to occur as rapidly as effectively as possible.


1- Explain fully, the function of  the lungs, alveoli, diaphragm and ribs

2- True or false :

a) The breathing movements do not cause change in the volume only in the pressure of chest during ventilation.

b) The movement of air is brought about by both the ribs and the diaphragm.

c)  Oxygen in the lungs from the air diffuses into the blood stream a while after carbon dioxide from the blood diffuses out of the bloodstream into the air.

d) The alveoli provides a very large moist surface area, richly supplied with blood capillaries to allow most efficient possible gas exchange.


- Fullick, Ann (2001). Biology for AQA. Chicago: Heinemann Educational.

- Brain, J. D. (2006, August). The merck manual home health handbook. Retrieved from

- Tamarakin, D. (2011, October 9). Stcc foundation press. Retrieved from

- Peter. (2012). Anaerobic respiration articles. Retrieved from


    A. The lungs: The chest contains two lungs, one lung on the right side of the chest, the other on the left side of the chest. Each lung is made up of sections called lobes. The lung is soft and protected by the ribcage. The purposes of the lungs are to bring oxygen (abbreviated O2), into the body and to remove carbon dioxide (abbreviated CO2). Oxygen is a gas that provides us energy while carbon dioxide is a waste product or "exhaust" of the body.

    B. The alveoli: At the end of each alveolar duct there are a number of sac-like structures called alveoli, it is within these structures that surfactant is produced. The alveoli are grouped together like a lot of interlinked caves, rather than existing as separate individual sacs.

    Gas exchange of oxygen and carbon dioxide takes place in the alveoli. Oxygen from the inhaled air diffuses through the walls of the alveoli and adjacent capillaries into the red blood cells. The oxygen is then carried by the blood to the body tissues. Carbon dioxide produced by the body’s metabolism returns to the lung via the blood. It then diffuses across the capillary and alveolar walls into the air to be removed from the body with expiration. The alveoli have a structure specialised for efficient gaseous exchange:

    1.Walls are extremely thin; 2.They have a large surface area in relation to volume; 3.They are fluid lined enabling gases to dissolve; 4.They are surrounded by numerous capillaries.

    C. The diaphragm: The diaphragm is located directly below the lungs. Along with the intercostal muscles (the muscles between the ribs), the diaphragm is a major respiration muscle. The diaphragm is a large, dome-shaped muscle that contracts and flattens during inhalation, which causes the chest cavity to expand. This maneuver creates a vacuum which pulls air into the lungs. During exhalation, the diaphragm then relaxes, returns to its previous shape, and air is forced out of the lungs.

    2) a. False b.true c. false d.true

  2. 2) a. False
    b. True
    c. False
    d. True

  3. Thank you emma for answering the long type questions and both you and Amani got the truw and false part right