Mammalian Lungs

1. Mammalian Lungs • List the features of the mammalian lung that adapt it to efficient gaseous exchange • Describe, with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli of the mammalian gaseous exchange system; • Explain the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the mammalian gaseous exchange system;

2. Can you label the lungs?

3. Answers

4. Gaseous Exchange • Gaseous Exchange is the movement of gases by diffusion between an organism and its environment across a barrier such as the alveolus wall

5. The lungs are a large pair of inflatable structures lying in the chest cavity Air can pass into the lungs through the nose and along the trachea, bronchi and bronchioles Finally the air reaches tiny, air-filled sacs called alveoli. The walls of the alveoli are the surface where the exchange of gases takes place

6. The lungs are protected by the ribs. Movement of the ribs together with the action of the diaphragm (a layer or muscular tissue beneath the lungs) help to produce breathing movements (ventilation)

7. Gases pass both ways through the thin walls of the alveoli. Oxygen passes from the air in the alveoli to the blood in the capillaries. Carbon dioxide passes from the blood to the air in the alveoli.

8. Task • View the selection of lung slides • Complete a lung dissection • Then answer the following questions as fully as you can.... (you can use Biology 1 p55 to help you) • State 3 ways in which the structure of the lungs allows efficient gas exchange (4). • Explain why the barrier to diffusion must be as thin as possible (1). • Describe how a steep diffusion gradient is achieved in the lungs (4).

9. Answers • State 3 ways in which the structure of the lungs allows efficient gas exchange (4). Large surface area (1) provides more space for molecules to pass through (1), plasma membranes surrounding the cytoplasm create a permeable barrier allowing diffusion of oxygen and carbon dioxide (1), alveolus wall is one cell thick creating a thin barrier for diffusion (1) • Explain why the barrier to diffusion must be as thin as possible (1). It reduces the distance gases have to diffuse (1) • Describe how a steep diffusion gradient is achieved in the lungs (4). Blood brings carbon dioxide from the tissues to the lungs ensuring the carbon dioxide concentration in the blood is higher than that of the air in the alveoli (1), it also carries oxygen away from the lungs ensuring that the concentration of oxygen in the blood is kept lower than air inside the alveoli (1), the movement of the lungs (ventilation) ensures there is a fresh supply of oxygen entering the lungs increasing the concentration of oxygen in the alveoli (1), carbon dioxide is also removed by ventilation ensuring that the concentration in the alveoli is lower than that of the blood (1)

10. Think! Read the sentence below... Is it correct? If not, why not? Alveoli have thin cell walls- this decreases the distance that gases have to travel and speeds up rates of diffusion Alveoli have thin cell walls- this decreases the distance that gases have to travel and speeds up rates of diffusion Alveoli have thin walls- their walls are one cell thick!

11. Mammalian Lungs • List the features of the mammalian lung that adapt it to efficient gaseous exchange • Describe, with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli of the mammalian gaseous exchange system; • Explain the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the mammalian gaseous exchange system;

12. Mammalian Lungs • List the features of the mammalian lung that adapt it to efficient gaseous exchange • Describe, with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchi, bronchioles and alveoli of the mammalian gaseous exchange system; • Explain the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the mammalian gaseous exchange system;