AEMCA Practice Exam

What is oncotic pressure?

1. A pressure caused by atmospheric conditions

2. A pressure caused by large proteins in the blood that control membrane pressure

3. A form of pressure related to blood flow

4. A type of pressure experienced within the lungs

The correct answer is: A pressure caused by large proteins in the blood that control membrane pressure

Oncotic pressure refers specifically to the form of osmotic pressure exerted by large molecules, especially proteins, in a solution. In the context of the human body, this mainly pertains to the proteins found in blood plasma, such as albumin. These proteins are too large to easily pass through capillary membranes. Consequently, they draw water into the circulatory system from surrounding tissues, which helps maintain fluid balance within the blood vessels. This phenomenon is crucial for maintaining the proper distribution of fluids between the vascular system and the interstitial spaces, thus preventing edema (swelling due to fluid accumulation). Understanding oncotic pressure emphasizes the importance of proteins in vascular health and fluid dynamics within the body, which is a central concept in medical and physiological studies. While the other options mention various forms of pressure, they do not accurately capture the specific nature and role of oncotic pressure as it relates to large proteins and fluid balance within the body.