The human gas exchange system
Every cell in your body needs a steady supply of oxygen and a constant way to get rid of carbon dioxide, and the gas exchange system is the elegant set of tubes and air sacs that makes this happen. In this lesson we follow air from the nose down the trachea, into the two bronchi, through the branching bronchioles, and finally into the millions of tiny alveoli where gases actually swap with the blood. We meet the ribs, intercostal muscles and diaphragm that move the air, and we look closely at the tissues that build the airway walls — cartilage, ciliated epithelium, goblet cells, smooth muscle, elastic fibres and the ultra-thin squamous epithelium of the alveoli — learning both where each is found and what each one does. We see how goblet cells and mucous glands trap dirt in mucus and how cilia sweep it up the 'mucus escalator', and we finish with the star of the show: the alveolus, and exactly how oxygen and carbon dioxide diffuse between the air and the blood.
By the end you should be able to (NSSCAS Biology (AS) 2.10.1):
- Describe the gross structure of the human gas exchange system
- Investigate and observe the gross structure of lungs and associated organs of a sheep or other mammal (dissect)
- Describe the distribution in the gas exchange system of cartilage, ciliated epithelium, smooth muscle, capillaries and squamous epithelium of alveoli
- Recognise cartilage, ciliated epithelium, smooth muscle, capillaries and squamous epithelium of alveoli in microscope slides, photomicrographs and electron micrographs
- Recognise trachea, bronchi, bronchioles and alveoli in microscope slides, photomicrographs and electron micrographs and make plan diagrams of transverse sections of the walls of the trachea and bronchus
- Describe the functions of ciliated epithelial cells, goblet cells and mucous glands in maintaining the health of the gas exchange system
- Describe the functions in the gas exchange system of cartilage, smooth muscle, elastic fibres and squamous epithelium
- Describe the process of gas exchange between air in the alveoli and the blood in the capillaries