Human Anatomy and Physiology - N. I. Fedyukovich 2003

Metabolism and Energy
Water and Mineral Metabolism

Water is an essential component of any Cell, serving as the liquid foundation of Blood AND Lymph. In humans, water content varies across different Tissues. For instance, adipose tissue contains about 10% water, bones — 20%, Kidneys — 83%, the Brain — 85%, and blood — 90%, averaging roughly 70% of total body mass.

Water performs a range of vital Functions within the body. Numerous chemical substances are dissolved in it, and it plays an active role in metabolic processes, facilitating The excretion of Metabolic waste products. Water also exhibits a high heat capacity and thermal conductivity, which contributes to thermoregulation.

The bulk of the body's water is located intracellularly, within Blood Plasma, and in the extracellular space.

Under normal conditions, an adult human consumes about 2.5 liters of water per day. Additionally, the body generates approximately 300 ml of metabolic water as a byproduct of METABOLISM/26.html">Energy Metabolism. To maintain balance, a person daily loses about 1.5 liters of water through urine, 0.9 liters via evaporation through the Lungs and Skin (excluding sweating), and roughly 0.1 liters in feces. Thus, under normal conditions, water turnover does not exceed 5% of body weight per day. Elevated BODY Temperature AND high-calorie food promote water loss through the skin and lungs, thereby increasing water intake.

The Regulation of Water metabolism is primarily controlled by Hormones secreted by the Hypothalamus, Pituitary Gland, and Adrenal Glands.

Mineral Substances enter the body through food and water. The body's requirement for mineral salts varies. The main group comprises seven elements: calcium, phosphorus, sodium, sulfur, potassium, chlorine, and magnesium, known as macrominerals. They are essential for skeletal formation (calcium, phosphorus) and for maintaining the Osmotic Pressure of biological fluids (sodium). These ions influence the physicochemical state of Proteins, the normal functioning of excitable structures (К⁺, Na⁺, Ca²⁺, Mg²⁺, Сl^-), Muscle contraction (Са²⁺, Mg²⁺), and energy accumulation (Р⁵⁺).

However, the body also requires another 15 elements, the total amount of which accounts for less than 0.01% of body mass. These are termed Trace Elements (or microminerals). Key Examples include iron (a constituent of Hemoglobin and tissue Cytochromes); cobalt (a component of cyanocobalamin); copper (a component of cytochrome c oxidase); zinc (a factor enhancing Insulin's effect on cell membrane permeability to glucose); molybdenum (a component of xanthine oxidase); manganese (an activator of certain enzyme systems); silicon (a regulator of bone Collagen synthesis); fluorine (involved in the synthesis of bone structures and the strength of tooth enamel); iodine (a constituent of THYROID HORMONES), as well as nickel, vanadium, tin, arsenic, selenium, and others. In most cases, these elements serve as constituents of Enzymes, hormones, and Vitamins, or act as catalysts for their enzymatic processes.

The specific role of various inorganic ions in sustaining vital body functions primarily depends on their intrinsic properties: charge, size, ability to form chemical bonds, and reactivity with water.