Fluid and Electrolyte Distribution: Intracellular and Extracellular Fluid

A key component of homeostasis is the makeup of bodily fluids. Disease develops anytime the volume or chemical composition of these fluids deviates even slightly from normal. The kidney, along with the respiratory, integumentary, nervous, and endocrine systems, maintains the constancy of body fluids.

Body Fluids

Each and every cell in the body has some water, and water typically surrounds cells. Water, which makes up 60% of the total weight of the body, is its main component. For life to exist, there must be an enough amount of water, electrolytes, and an acid-base balance in the water. Lethargy, fever, and dryness of the mucous membranes often result after a 10% loss of total body water, while a 20% loss results in death.

Blood, stomach fluid, intestinal fluid, cerebrospinal fluid, vaginal and semenal secretions, perspiration, tears, and the aqueous and vitreous humor of the eye are all examples of body fluids. Their actions have an impact on a person's daily activities.

Composition of Body Fluids

Each sub-fluid compartment's has a somewhat different composition from the fluid in the other sub-compartments, yet there is constant and widespread component exchange. Along with water, it also includes non-electrolytes and electrolytes. Organic substances like glucose, lipids, creatinine, and urea make up the majority of non-electrolytes. Electrolytes include salts that are both organic and inorganic, as well as certain proteins.

Fluids Distribution in the Body

The cell either has bodily fluids within or outside of it. Additionally, these fluids are housed in a number of smaller compartments that also aid in the transfer of organic components. Two body compartments receive the majority of the bed fluids:

• Intracellular compartment:
  • The intracellular compartment is the term for the area inside the cell. Intracellular (within the cell) fluid is the substance that fills these gaps. Of all bodily fluid, intracellular fluid (ICF) makes up two-thirds (023). The ICF acts as a conduit for the basic elements required for the development and efficient operation of each cell.
• Extracellular compartment:
  • The extracellular compartment is the term for the area outside the cell. Extracellular (outside the cell) fluid is the fluid that is present with spaces. Of all bodily fluid, extracellular fluid (ECF) accounts for 173 of it. Interstitial fluid, blood plasma and lymph, cerebral fluid, synovial fluids of the eye and ear, pleural, pericardial, and peritoneal fluids are all examples of ECF present in the body. renal filtrate is contained in the gastrointestinal and GR compartments. Two primary sub compartments further split the extracellular compartment:
  • Interstitial compartment:
    • The void between the tissues is what is meant. The most significant and numerous ECFs are the fluids found in these spaces, known as interstitial fluids.
  • Intravascular compartment:
    • The area found inside blood arteries is referred to as an intravascular compartment. These liquids are referred to as intravascular fluids. The primary intravascular fluids are lymph and blood plasma.

Comparison of Fluid distribution in Adults and Newborn (In relation to total body weight)

Proposition of body fluid in liters(volume)

Movement of fluids among compartments

Two forces regulate the flow of water from one body part to another: 

• Hydrostatic pressure:
  • The force a fluid applies to the surface of a fluid-filled compartment is known as hydrostatic pressure. Fluid is usually moved out of the compartment by it.
• Osmotic pressure: 
  • A solution permeable membrane must be subjected to osmotic pressure in order to stop the flow or compartment of pure water.

Differentially permeable cell membranes exist between the two compartmental membranes. Proteins and other substances have a limited ability to get through cell membranes, although many smaller molecules and ions can pass through. As a result, most big molecules (such as proteins) stay inside the cell.

Water moves from the intracellular space to the extracellular space through the process of osmosis when the solute concentration of the ECF is increased (interstitial). Edema is the term for this phenomena. Water builds up abnormally in the interstitial compartment, causing edema.

Regulation of Water Content (Body Fluids Balance)

The amount of water in the body is controlled to maintain a consistent overall volume. Consequently, the amount of water the body consumes is equal to the amount it loses each day.

The majority of water that enters the body comes from drinking, while a lesser quantity comes from eating and an even smaller amount results from the oxidation of food in cells. In an adult, the total amount of water that enters the body each day is around 2500ml.

Electrolytes, which are vital mineral solutes for the body, are taken in by food and drink. Water helps to maintain homeostasis since it is ingested by the body and expelled when things are normal. The neurological system, specifically the thirst center in the brain, and hormonal processes control how much water is consumed (Antidiuretic hormone). The organs governed by homeostatic feedback response are the kidneys. They are in charge of eliminating the majority of the body's water.

Dehydration, characterized by a decrease in bodily fluid volume and an increase in osmolality of body fluids, happens when water loss exceeds water gain. The ratio of solutes to solvent volume in a solution is known as osmolality. Thus, the ratio of hydration solutes to water in blood plasma is known as plasma osmolality. A person's state can be inferred from their plasma osmolality value.

A series of physiological processes known as the thirst response are activated as the blood gets more concentrated. The sensory receptors known as osmoreceptors in the thirst center of the hypothalamus keep track of the blood's osmolality, or solute content. A conscious awareness of thirst is brought on by signals sent by the hypothalamus when blood osmolality rises over its optimal level. To remedy the situation, the person should drink water to replenish their body's fluid levels. Antidiuretic hormone (ADH) is also released by the hypothalamus of a person who is dehydrated via the posterior pituitary gland. The kidneys receive a recovery signal from ADH, which effectively dilutes the blood plasma.