Gas Exchange: The Structure of the Lungs in a Snap! Unlock the full A-level Biology course at http://bit.ly/2ZagyJm created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.

The key points covered of this video include:

1. Introduction to the Lungs
2. Trachea and Bronchi
3. Bronchioles
4. Alveoli

Introduction to the Lungs

Mammals require a large amount of oxygen and produce a large amount of carbon dioxide. They are large organisms, they have a high metabolic rate and level of activity. To deal with these constraints mammals evolved lungs.

The Trachea and Bronchi

The trachea and bronchi connect the lungs to the mouth. They contain many C-shaped rings of cartilage to provide support and flexibility. This diagram shows a cross-section of a bronchus as would be seen under a microscope. Smooth muscle allows them to constrict to reduce air flow. The walls are line with ciliated epithelial tissue containing goblet cells. Goblet cells secrete mucus that traps dirt and pathogens. Ciliated epithelium wafts mucus up out of the airways.

Bronchioles

The bronchioles lead from the two bronchi to the alveoli. The bronchi consist mainly of smooth muscle and epithelial cells. Larger ones may have cartilage but most do not.

The Alveoli

The lungs consist mostly of millions of alveoli. Alveoli consist of squamous epithelial tissue and elastic fibres. This is a micrograph of a section of lung tissue showing alveoli. The alveoli show a variety of adaptations that suit them to gas exchange: Large surface area and good blood supply, short diffusion distance for gasses to travel.

Summary

Lungs are highly complex gas exchange organs
The alveoli are gas-filled sacs specialised for gas exchange
The trachea, bronchi and bronchioles deliver gasses to and from the alveoli
The functions on different parts of the lungs are represented in their structures that show their specific adaptations towards carrying out their roles