The body fluid or the physiologic fluid is essential for various physiological processes and the maintenance of body homeostasis. The functions of water in the body include temperature regulation, moistening of tissues, transportation of essential nutrients, elimination of waste from the body, and lubricating different joints and tissues. Some example of body fluid includes blood plasma, tears, synovial fluid, sweat, and urine.

In general, the cellular waste is excreted out of the cell in the intracellular fluid while in exchange, the nutrients are ingested from the intracellular fluid.

Intracellular body fluid is composed of a high amount of potassium, phosphate, and magnesium while low amounts of bicarbonate, chloride, sodium, and protein (Figure 3).

Excess fluid in the body or increased fluid results in edema whereas a reduced body fluid amount is referred to as dehydration. Edema can occur in any part of the body/tissue, for example, soft tissues, liver disease-induced edema, pulmonary edema, excess abdominal fluid or ascites, etc.

The maximum body fluid is present at the fetal development stage (~95%), which goes down to ~75% for an infant and eventually to ~50-60% in the adult stage (Figure 1).

While osmotic pressure pulls the fluid (water and the dissolved molecules it carries) back into the capillary, the hydrostatic pressure pushes the fluid out of the capillary. The fluid that exits the capillary moves into the interstitial fluid. This process is referred to as filtration. In contrast, the fluid from the interstitial fluid back into the capillaries is what drives the reabsorption process.

Males have a higher amount of body fluid as compared to females as females have higher body fat. Fat tissues tend to have less water than lead body mass.

Pulmonary edema, in particular, is a major health risk as it compromises gas exchange. Edema is seen when the body retaining fluid results in an accumulation of water in the tissue, for example, hand fluid retention results in hand edema. Diuretics help to manage edema. Conversely, reduced water intake or conditions like diarrhea and sweat can result in dehydration.

Skin turgor or skin elasticity is an indication of the hydration level of the body and is often used to diagnose dehydration. Decreased urine output is also an indication of dehydration.

Homeostasis is the relatively stable conditions of the internal environment that result from compensatory regulatory responses performed by homeostatic control systems. Know the different components of homeostatic control systems, homeostatic regulators, and the various biological processes that homeostasis entail...Read More

Biology Definition: A body fluid refers to any fluid produced by a living organism. In humans, the body fluid can be classified into two major types according to the location in the body:

Humans are capable of only one mode of reproduction, i.e. sexual reproduction. Haploid sex cells (gametes) are produced so that at fertilization a diploid zygote forms. This tutorial is an in-depth study guide regarding male and female reproductive physiology...Read More

What is body fluid? Literally, body fluid is the fluid of the body. The adult human body is ~50-60% composed of water, which is distributed inside the cells (intracellular) and outside the cells (extracellular). A total of intracellular and extracellular water forms the total body fluid.

Almost 20% of the total body weight is an extracellular body fluid (Figure 2). Extracellular fluid differs from intracellular body fluid in sodium, potassium, and protein content. In extracellular fluid, electrolytes that are abundant or in relatively high amounts are sodium, chloride, and bicarbonates. Other electrolytes present but are comparatively at lower levels (than the intracellular fluid) are potassium, phosphate, and magnesium.

Non-infectious body fluids (blood and blood products, sweat, saliva, excretion products, tissue fluids, and intracellular body fluids like synovial fluid) can be used for the diagnosis of any disease or medical condition.

Further, intercellular fluid and intracellular fluid are in dynamic equilibrium with each other as they are separated by a cellular membrane and fluid movement is in dynamic equilibrium.

A typical eukaryotic cell is comprised of cytoplasm with different organelles, such as nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, and so on. The cellular contents are surrounded by a double layer, cell membrane. These cellular structures and cell junctions are elaborated in this tutorial...Read More

The kidneys are responsible for the regulation of water and inorganic ions. Read this tutorial to learn about the different parts of the kidneys and its role in homeostasis...Read More

What percent of your body is water? or what percentage of water is the human body? The human body is primarily made up of water and the water distributed in different parts of the body organs and tissues is what defines the body fluid. The body fluid content of the body changes with the body’s development.

The fluid that is present inside the cell i.e., in the cytoplasm of the cell. The intracellular fluid largely remains unchanged and does not undergo rapid changes or fluctuations. Intracellular fluid forms ~40% or 2/3rd of the body fluid. Bodily fluids are distributed in different fluid compartments as shown in Figure 2.

The analysis of various body fluids helps to establish any medical condition. For the same, the sample can be obtained as follows:

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The body maintains tight control over total body water and total body osmolarity, thus ingestion and excretion of water are regulated. The water in different components of the compartment is maintained to match total body osmolarity and in process of maintaining a steady-state redistribution of water from the different compartments of the body can occur. The redistribution of water in different compartments of the body is controlled by:

The majority of the chemical/metabolic reactions of the body occur in the cytoplasm or the intracellular body fluid. Intracellular body fluid is also involved in maintaining osmolarity via sodium-potassium pump wherein potassium ions are primarily intracellularly distributed.

The human body is capable of regulating growth and energy balance through various feedback mechanisms. Get to know the events of absorptive and post-absorptive states. This tutorial also describes the endocrine and neural control of compounds such as insulin and glucagon. It also deals with the regulation of growth, heat loss, and heat gain. ..Read More

Examples of body fluids: amniotic fluid, aqueous humor, bile, blood plasma, breast milk, cerebrospinal fluid, cerumen, chyle, exudates, gastric juice, lymph, mucus, pericardial fluid, peritoneal fluid, pleural fluid, pus, saliva, sebum, serous fluid, semen, sputum, synovial fluid, sweat, tears, urine, vomit

Water movement occurs passively across the membrane depending on the osmotic gradient. Conversely, ion movement is not permitted across the membrane and occurs occasionally (depending on the cellular requirement) through active transport. Ions in the body fluids of a human are referred to as the electrolytes in the body.

Often a question arises, Is lymph extracellular fluid? The body’s circulating fluids include lymphatics and blood. Notably, blood plasma constitutes the intravascular fluid while lymph forms the interstitial fluid. Thus, lymph is an extracellular interstitial fluid.

This goes to show that similar to food intake having a major role in energy balance, fluid intake also is key to keeping a healthy body fluid balance. Body fluid homeostasis is thus essential in ensuring that the body fluid is kept stable and it does so by maintaining the body osmolality (the concentration of all particles dissolved in the body fluid) within the normal limits while the extracellular fluid and blood volume (the amount of fluid circulating inside the blood vessels) are kept adequate.

Apart from water, the body fluid is also composed of other molecules, such as electrolytes (sodium, potassium, etc), metabolites (urea, glucose, carbon dioxide, oxygen), and proteins (albumin, hormones, amino acids, antibodies). Depending on the location of the body fluid, the composition and amounts vary.

The circulatory system is key to the transport of vital biomolecules and nutrients throughout the body. Learn about the different components and functions of the human circulatory system dealt with in detail in this tutorial. The lymphatic system is also elucidated elaborately here...Read More

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Body fluid balance is essential for homeostasis. Water/sodium balance in the body is tightly regulated by the nervous system. Otherwise, any disturbance in the body fluid results in abnormal health conditions wherein there can be an increase in body fluid load/ fluid volume or a reduction in the body fluid.

Body fluid can also be a carrier of certain diseases like sexually transmitted diseases (HIV-AIDS) and viral diseases (hepatitis).

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