Final answer:
The statement is true, as the percentage of total body water in humans ranges from 45% in older adults to 75% in infants. This proportion varies with age, organ content, and overall body composition.
Step-by-step explanation:
The statement that normal values for total body water as a percentage of body weight vary from 45% to 75% is true. Human beings are mostly water, with the percentage of body water changing throughout different stages of development. Infants tend to have approximately 75% of their body mass as water, which reduces to about 50-60% in adults, and can drop further to as low as 45% in old age.
The distribution of water in the body is vital for various physiological functions, with the brain and kidneys having the highest water content (80-85%), and the teeth having the lowest (8-10%).
Body water is not static; it continually moves through the body's tissues and cells via osmosis, responding to the concentration gradients of water and solutes. It's crucial to maintain appropriate balances of solutes both inside and outside cells for normal functioning. Water content varies in different body organs and tissues and also inversely varies with fat content in the adult body.