Difference Between Intracellular and Interstitial Fluid

The key difference between intracellular and interstitial fluid is that intracellular fluid is the fluid that is contained within cells, while interstitial fluid is the fluid between blood vessels and cells.

Human body fluid can be conceptually divided into various fluid compartments. The two main fluid compartments are intracellular and extracellular fluid compartments. The intracellular fluid compartment is the space within the cells of humans. The extracellular fluid compartment is outside the cells that are separated from the intracellular fluid compartment by cell membranes.  Extracellular fluid or compartment further divides into three types: interstitial fluid (surrounds cells), intravascular fluid (blood plasma and lymph), and transcellular fluid (ocular and cerebrospinal fluid). Therefore, intracellular and interstitial fluids are two types of body fluids.

CONTENTS

1. Overview and Key Difference
2. What is Intracellular Fluid
3. What is Interstitial Fluid
4. Similarities – Intracellular and Interstitial Fluid
5. Intracellular vs Interstitial Fluid in Tabular Form
6. Summary – Intracellular vs Interstitial Fluid

What is Intracellular Fluid?

Intracellular fluid is the fluid contained within cells. It consists of cytosol and fluid within the cell nucleus. The cytosol is the matrix in which cellular organelles are suspended. Cytosol and organelles together make the cytoplasm. The fluid component of the nucleoplasm in the cell nucleus is called the nucleosol. Intracellular fluid (ICF) makes up about 60% of total water in the human body. Intracellular fluid accounts for about 28 litres or 7.4 gallons of fluid. The fluid volume of ICF tends to be very stable. This is because the amount of water within living cells is closely regulated.

When the water inside a cell falls to a very low level, the cytosol becomes very concentrated with solutes. Therefore, it will be very difficult to carry out normal cellular activities. On the other hand, if too much water enters a cell, the cell may burst and destroy. Therefore, in ordinary conditions, the cell is always in osmatic equilibrium. Furthermore, it contains moderated amount of magnesium and sulphate.

What is Interstitial Fluid?

The fluid between blood vessels and cells is called interstitial fluid. Interstitial fluid, intravascular fluid, and transcellular fluid are three types of extracellular fluid compartments. The interstitial fluid compartment sometimes is called tissue space. It is present outside the blood. It usually surrounds tissue cells. Interstitial fluid and plasma make about 97% of the extracellular fluid. This interstitial fluid is not stable.

In the human body, the interstitial fluid compartment has 10.5 litres or 2.8 gallons of fluid. It contains nutrients diffused from capillaries and waste products discharged from cells due to metabolism. Interstitial fluid and plasma are quite similar. It also consists of a water solvent containing sugars, fatty acids, amino acids,  coenzymes, hormones, neurotransmitters, white blood cells, and cell waste products. This fluid accounts for 26% of the water in the human body. Furthermore, the lymphatic system returns proteins and excess interstitial fluid to the circulation. The ionic compositing of the interstitial fluid and blood plasma vary due to the Gibbs- Donnan effect.

What are the Similarities Between Intracellular and Interstitial Fluid?

• Intracellular and interstitial fluids are two types of body fluids.
• Both fluids have a high percentage of water.
• Both fluids do not contain blood cells.
• These fluids have proteins.
• These fluids have waste products.

What is the Difference Between Intracellular and Interstitial Fluid?

Intracellular fluid is the fluid that lies within cells. In contrast, interstitial fluid is the fluid present between blood vessels and cells. So, this is the key difference between intracellular and interstitial fluid. Furthermore, intracellular fluid accounts for about 28 litres or 7.4 gallons of fluid, while interstitial fluid accounts for about 10.5 litres or 2.8 gallons of fluid.

The below infographic lists the differences between intracellular and interstitial fluid in tabular form.

Summary – Intracellular vs Interstitial Fluid

Body fluids are mainly two types as intracellular and extracellular fluids. The intracellular fluid is within the cells of humans. Extracellular fluid is outside the cells and is separated from the intracellular fluid by cell membranes. Extracellular fluid is further divided into three types: interstitial fluid, intravascular fluid, and transcellular fluid. Therefore, the fluid that is found within cells is called intracellular fluid. On the other hand, the fluid between blood vessels and cells is called interstitial fluid. Thus, this is the summary of the difference between intracellular and interstitial fluid.

Reference:

1. “Body Fluids and Fluid Compartments.” Lumen.
2. “Interstitial Fluid.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “2703 Distribution of Water in the Human Body in Terms of ICF and ECF Pie Chart” By OpenStax College – Anatomy & Physiology, Connexions Web site.  Jun 19, 2013 ( CC BY 3.0) via Commons Wikimedia
2. “2702 Fluid Compartments ICF ECF” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia