You are not currently logged in. Please create an account or log in to view the full course.

Gas Exchange

1. The Alveolus and the Capillary

This is the course trailer. Please create an account or log in to view this lecture.

  • Description
  • Cite

About this Lecture


In the first mini-lecture, we take a look at the mechanism of gas exchange in the lungs. In this lecture we learn how carbon dioxide and oxygen are constantly exchanged between structures in the lung called alveoli and vessels in the circulatory system called capillaries. To begin, we outline some of the key cellular features of the alveolus: the exchange surface of the respiratory system, understanding the structure and function of alveolar type I and type II cells. Then, we move onto Dalton’s Law to appreciate how partial pressures of different gases interact with one another. With this gained knowledge, we return to the respiratory system and learn about its adaptations in making gas exchange efficient, and then understand how these exchange surfaces can be compromised in diseased patients.


In this lecture, Dr Helen Wallace (University of Liverpool) teaches us about the microscopic structures in our lungs and blood that allow for the exchange and transport of the two gases involved in respiration: oxygen and carbon dioxide. To do so, we: (i) introduce the alveoli and capillaries as the exchange surfaces that allow for oxygen and carbon dioxide to be exchanged, using Dalton’s Law to explain how diffusion is maintained in the desired direction, before then (ii) appreciating how oxygen and carbon dioxide are then transported in the lungs by haemoglobin.


Dr Helen Wallace is a senior lecturer in Women's and Children's Health at the University of Liverpool. Her primaryprimary interests focus on all aspects of physiology education, from A level students, undergraduates and postgraduates, to healthcare professionals. She has contributed to many physiology text books, and in addition to this she is the Programme Director of MRes in Clinical Studies, the Physiology Course Lead for the MBChB programme, the Respiratory System Science Lead for the MBChB programme, and Education Lead for the Institute of Life Course and Medical Sciences.

Cite this Lecture

APA style

Wallace, H. (2022, August 30). Gas Exchange - The Alveolus and the Capillary [Video]. MASSOLIT.

MLA style

Wallace, H. "Gas Exchange – The Alveolus and the Capillary." MASSOLIT, uploaded by MASSOLIT, 30 Aug 2022,

Get instant access to over 6,200 lectures