Osmotic/oncotic, and hydrostatic pressures modify blood capillary transfer of nutrients and waste.

Introduction

Three features of water’s chemistry, osmotic pressure, oncotic pressure, and hydrostatic pressure support the primary purpose of the cardiovascular system, capillary transfer into blood of nutrients and transfer out of metabolic waste products like lactic acid.

In this article, I summarize cardiovascular capillary transfer in the three short videos. The first video is a discussion of osmotic pressure and oncotic pressure. Osmotic pressure is often a difficult concept for students when it is first encountered.

The second video deals with hydrostatic pressure as it is defined in physiology for the cardiovascular system. You will notice this definition of hydrostatic pressure is somewhat different than the physics definition.

The third video explains how these three properties of water-based systems work to efficiently transfer material in and out the tissue capillaries. 

Osmotic/oncotic pressure influence on capillary transfer

Osmotic pressure is a numerical value that predicts the ability of a watery solution to attract more water molecules. In physiology, watery solutions are frequently separated from each other by a lipid membrane.

Water molecules will move from the side of the lipid membrane with the lowest osmotic pressure to the side with the highest osmotic pressure if there are water channels present.

A high osmotic pressure signifies a solution with a high attraction for water molecules. To discover how osmotic pressure is calculated, view the video by clicking on the image below.

Role of hydrostatic pressure in capillary transfer

To explain capillary exchanges, hydrostatic pressure on blood must also be considered. While osmotic pressure DRAWS water through membrane water channels, hydrostatic pressure FORCES water through them. Check out the video by clicking the   image below.

Capillary transfer, filtration and reabsorption

In blood capillary beds, osmotic/oncotic and hydrostatic are opposing pressures. Filtration occurs at the arterial end because hydrostatic pressure is the dominant influence. When hydrostatic pressure drops at the venous end, osmotic/oncotic pressure favors reabsorption of the filtered water. View the video by Clicking on the image below.

Capillary transfer worksheet

Click here for a worksheet that will help you consolidate these concepts which explain blood capillary transfer. Just, a little further investigation of this topic on your own using the worksheet will strengthen your memory of them.

Learning human physiology:

These videos and the worksheet are from Day 21 of my course the 30-Day Challenge: Craft Your Plan for Learning Physiology. To read at the other topics covered over the 30 days of this challenge course click here.

Further Reading:

Water’s Chemistry Governs Physiology

Tips for how to study the cardiovascular system

Do you have questions?

Please put your questions in the comment box or send them to me by email at DrReece@MedicalScienceNavigator.com. I read and reply to all comments and email.