Body Fluid Water & Electrolyte Balance P01 II Assoc. Prof. Dr. Refat Tabassum

Summary

In this lecture, Dr. Rifata Basum, an associate professor at Bhushundharathi Medical College, explains the concept of body fluid and water balance. She covers topics such as the role of water in biochemical reactions, the different fluid compartments in the body, and how fluid is distributed between intracellular and extracellular spaces. The lecture also explores methods to measure body fluid compartments, water balance, and mechanisms regulating fluid intake like thirst and ADH. Dr. Basum also highlights the causes of dehydration and overhydration, and how the body maintains homeostasis through complex physiological processes.

Takeaways

• 😀 Body fluid refers to the total body water and its dissolved constituents like electrolytes and non-electrolytes.
• 😀 Water plays a crucial role in transporting solutes, serving as a medium for biochemical reactions, and regulating body temperature.
• 😀 Body fluid constitutes about 55-60% of a female's body mass and 60-65% of a male's body mass, while infants have about 70-80% body fluid.
• 😀 The body fluid is divided into two compartments: intracellular fluid (inside cells) and extracellular fluid (outside cells).
• 😀 Extracellular fluid is further divided into interstitial fluid, plasma, and transfer fluids.
• 😀 Transfer fluids are separated by epithelial membranes and include cerebrospinal fluid (CSF), pericardial fluid, and synovial fluids.
• 😀 There are two methods to measure body fluid compartments: direct (indicator or dilution technique) and indirect methods.
• 😀 Suitable dyes or isotopes are used in direct measurement, with different substances for measuring total body water, extracellular fluid, and plasma volume.
• 😀 Water balance refers to the equilibrium between fluid intake and output, impacting hydration status. An imbalance can lead to overhydration or dehydration.
• 😀 Positive water balance occurs when water intake exceeds output, such as during pregnancy or recovery from illness. Negative water balance happens when output exceeds intake, as in cases of vomiting or diarrhea.
• 😀 Water balance is regulated through two main mechanisms: thirst mechanism (driven by changes in plasma volume and osmolarity) and ADH (antidiuretic hormone) regulation, which affects water reabsorption in the kidneys.

Q & A

What is body fluid, and what are its constituents?

Body fluid refers to the total body water, which includes dissolved constituents such as electrolytes and non-electrolytes. Electrolytes include sodium, potassium, chloride, bicarbonate, and calcium, while non-electrolytes include glucose, cholesterol, urea, creatinine, and bilirubin.

What are the main functions of water in the body?

Water serves as a transport vehicle for solutes, provides an aqueous medium for biochemical reactions, participates as a reactant in several metabolic processes, and plays a crucial role in regulating body temperature.

How much of an adult male's body mass is made up of body fluid?

In a 70 kg adult male, approximately 60 to 65 percent of the total body mass is composed of body fluid.

What are the two main compartments of body fluids?

Body fluids are divided into two main compartments: intracellular fluid (inside the cells) and extracellular fluid (outside the cells). Intracellular fluid accounts for about two-thirds of the body fluid, while extracellular fluid includes interstitial fluid, plasma, and transcellular fluids.

What is the composition of extracellular fluid (ECF)?

Extracellular fluid is made up of three components: plasma (15% of ECF), interstitial fluid (80% of ECF), and transcellular fluid (1% of ECF).

What is the transfer of fluid, and what are some examples?

Transfer of fluid refers to fluid that is separated from another by an epithelial membrane. Examples include cerebrospinal fluid (CSF), pericardial fluid, peritoneal fluid, synovial fluid, and fluids in the gastrointestinal tract.

What are the methods for measuring body fluid compartments?

There are two methods: direct (indicator or dilution technique) and indirect methods. The direct method involves using a dye or radioactive isotope to measure fluid volumes, while the indirect method measures interstitial and intracellular fluid volumes.

What substances are used to measure total body water and extracellular fluid?

Substances like deuterium oxide, titrated water, anti-firing agents, and amino pyrin are used to measure total body water. For extracellular fluid, sucrose, inulin, mannitol, sodium bromide, and chloride are commonly used.

What happens in positive water balance?

Positive water balance occurs when water intake exceeds water output, leading to water retention in the body. This can happen during growth, recovery from illness, or pregnancy.

How does the body regulate water balance?

Water balance is regulated through two mechanisms: the thirst mechanism, which is triggered by a decline in plasma volume or an increase in plasma osmolarity, and the ADH mechanism, which responds to changes in plasma osmolarity and blood volume to adjust water reabsorption in the kidneys.