Interstitial Liquid: Definition, Formation, Composition and Functions of This Fluid in the Body

It acts as a medium for intercellular communication, the delivery of nutrients to cells, and the elimination of metabolic wastes.

Interstitial fluid is a fluid that surrounds the cells of the body.

If there were no mechanism to remove it, body parts would swell under pressure.

Fortunately, the lymphatic system is a network of vessels and tissues that actively removes fluid from tissue and returns it to the blood plasma.

Once in the lymphatic vessels, the fluid contains many other cells and substances that aid in the immune response by allowing white blood cells to find and digest harmful bacteria and virus-infected cells.

Many cells also shed their metabolic waste in the interstitial fluid, and the debris is cleaned out through the lymphatic system.

The human body is made up of many cells. Each organ contains cells specialized in its structure and function.


These cells are connected with the help of intercellular junctions. However, there is a solution between these cells that bathes the cells. This solution is known as interstitial fluid.

It can be defined as the main component of the extracellular fluid found in the interstitial tissue spaces.

It is an essential component of the body and, in fact, on average, a person has eleven liters of interstitial fluid. Below are some more details about the formation, composition, and function of this fluid.

Interstitial fluid formation

Every time the heart pumps blood to the arteries, which supply this blood to various organs, it does so under pressure. Due to this hydrostatic pressure, it expels the water from the capillaries.

This differential water potential is established because the small solutes can move beyond the capillary walls.

Because of this, there is osmosis, and thus the water passes from the point of high concentration to the end of low concentration.

This same osmotic pressure also eventually manages to push this water into the circulatory system.

This pressure is different in different places in the body. The pressure is higher in the arteries and lowers in the veins, in direct correspondence with the pressure, speed, and direction of blood flow and the presence of solutes.

Composition of interstitial fluid

The elemental composition of the interstitial fluid is water, along with solutes such as sugars, fatty acids, amino acids, salts, urea, white blood cells, etc.

Therefore, it contains nutrients and waste products. Although the elemental composition of this fluid remains the same, it differs slightly depending on the region of the body where the liquid is present.

The composition of this fluid is very similar to the design of lymphatic fluid since the lymphatic fluid is also considered interstitial fluid.

However, this composition varies slightly depending on the location of the fluid, as the lymphatic fluid will contain more white blood cells to fight any infection.

Also, certain other types of interstitial fluid, such as peritoneal fluid, are present primarily for lubrication purposes, so this fluid is more transparent and contains fewer cells.

Interstitial fluid function

The interstitial fluid serves many functions. This fluid is responsible for maintaining homeostasis in the cell and the body.

It also helps supply nutrients to cells and transport waste from cells to other organs such as the kidneys, from where they are removed.

Also, this liquid may contain hormones that will reach the target organ through this liquid. It can even have neurotransmitters.

There are certain diseases associated with this condition, as ideally, this fluid must be removed from the cells and put back into circulation.

If this fluid is not removed, then there is a buildup of this fluid, leading to swelling and a condition commonly known as elephantiasis, which is a severely disfiguring condition that causes buildup and swelling of the ankle and feet, which is exacerbated due to gravity.

Sometimes the accumulation of fluid can be due to an obstruction of the flow of lymph, which can even affect the functioning of the entire lymphatic system.

Therefore, if there is a buildup of this fluid, it should be diagnosed and treated as soon as possible.

Disclaimer: This is for informational purposes only and should not be used as a replacement for expert medical advice.