Water Distribution in the Body

Water content in the Human Body

Water is a key component in human body. Water is dispensed throughout the whole body including organs and cells. Water content in adult men is around 60% of the body weight. Water content in adult women is around 50-55% of the body weight. For a man that weighs 70 kg, water content is around 42 liters. The average content can vary among individuals due to differences in body composition. While in lean body mass, water content is constant in mammals at 73%, body fat or adipose tissue is only around 10% water. Total body water is influenced by body fat relative mass. This is related to influences of gender, age and aerobic fitness on total body water. Total body water content is lower in older persons and women due to lower fat-free mass. Total body water content is relatively high in athletes.

Water content of Different Organs

Water is distributed throughout the entire body and all organs. Composition of various organs determines their water content. The water content of different organs ranges from eighty three percent in blood to only ten percent in adipose tissues. Water content of organs and tissues by weight is as follows.

Water content of brain is around 75% of the weight. Water content in blood is around 83%. Water content in liver is around 68%. Water content in kidney is around 83 %. Water content in adipose tissue is around 10%. Water content in muscle is around 76 %. Water content in skin is around 72%. Water content in heart is around 79%. Water content in lungs is around 79%. Water content in spleen is around 76 %. Water content in intestine is around 75%. Water content in skeleton is around 22%.

Water Distribution among Body Compartments

Intracellular and extracellular are the two main compartments where water is distributed. The intercellular compartment contains about two thirds of body water. The extracellular compartment contains about one third of body water. The extracellular compartment consists of interstitial fluid and plasma fluid. Interstitial fluid and plasma fluid have similar electrolyte composition with chloride and sodium being the most abundant ions. There are also other compartments that contain water, such as eyeball fluid, lymph and cerebrospinal fluid. These compartments contain small amount of water and typically considered to be part of the interstitial fluid.

Absorption and Distribution of Water in the Body

Gastrointestinal tract absorbs water after ingestion. Water then gets into the vascular system and interstitial spaces respectively. Water eventually gets transported to every cell. Intracellular water accounts for about 65% of total body water.

After passing through stomach, water gets absorbed mostly in the early segments of small intestine including the jejunum and the duodenum. Small amount of water gets absorbed in the stomach and the colon. The colon absorbs 1.3 liter a day and the small intestine absorbs 6.5 liter a day. This amount of water is related to how much water is ingested daily and how much water is produced by secretions from liver, pancreas, stomach, salivary glands and the small intestine itself. Water absorption process is very rapid. According a study, after ingestion, it takes only about five minutes for water to appear in blood cells and plasma.

Water gets into plasma from intestinal lumen by passive transport, which gets regulated by osmotic gradients. Blood circulation then transports water molecules for distribution throughout the entire body, to the cells and to the interstitial fluids. In the interstitial compartment, water moves freely. The aquaporin or water specific channels help water move across cell membranes. Osmotic and hydrostatic pressure regulate fluid exchanges between compartments. Changes in the extracellular fluid osmolality regulates water flows.

The body keeps losing water. The water pool in the body gets renewed by ingestion of water. How fast water pool gets renewed depends on how much and how frequently water is ingested. For a person drinking two liters of water a day, water molecule stays in the body for about 10 days. In about 50 days, 99% of the body water gets renewed. Renewal of the body water pool helps maintain balance of body water.

Amazing is how water is distributed in the body and how it plays vital role in keeping the body functional.

Last update: July 23, 2017 05:33:49 pm

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