Anaesthesia Fundamentals | Physiology | Osmolarity: Partition of Fluids Across Membranes

Osmolarity: Partition of Fluids Across Membranes
Session overview
Description
This session describes the physical processes by which molecules traverse cell membranes.

Learning objectives
By the end of this session you will be able to:

• Specify the routes by which ions and molecules enter cells and the factors that restrict their movement
• Describe the transport mechanisms that cells use to facilitate the absorption or removal of specific substances
• Explain the origin of the transmembrane potential and its significance

Prerequisites
Before commencing this session you should:

• Have knowledge of the physics of colligative properties and physical laws of transfer across a membrane

The cell membrane divides the cytoplasm from the extracellular fluid (Fig 1). The permeability of the membrane determines which substances can enter or leave.

Two types of transport determine the distribution of ions in the body. These types are distinguished by the use of metabolic energy and the directional flow of the molecules:

• Passive transport
• Active transport

This session explores these processes, giving you the knowledge to interpret the movement of solutes into cells and the electrical gradients produced.