瘦体质量和无脂肪体质量是相同的还是不同的身体组成部分? 一个批判性的视角

Life's biochemical processes occur within aqueous solutions. Solutes are substances that are dissolved within these solutions. The human body contains a variety of solutes, which can differ across various body parts. These can encompass proteins—such as those responsible for clotting and carbohydrate transport—as well as electrolytes. In medicine, an electrolyte is often described as a mineral ion derived from a salt possessing an electric charge. Examples include sodium ions...

Triglycerides are a form of long-term energy storage molecules. They are made of glycerol and three fatty acids. To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. This process, called lipolysis, takes place in the cytoplasm. The resulting fatty acids are oxidized by β-oxidation into acetyl-CoA, which is used by the Krebs cycle. The glycerol that is released from triglycerides after lipolysis...

The hypodermis (the subcutaneous layer or superficial fascia) is present directly below the dermis. It connects the skin to the underlying fascia (fibrous tissue) of the bones and muscles. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for...

Mass and weight are often used interchangeably in everyday conversation. For example,  medical records often show our weight in kilograms, but never in the correct units of newtons. In physics, however, there is an important distinction. Weight is the pull of the Earth on an object. It depends on the distance from the center of the Earth. Weight dramatically varies if we leave the Earth's surface, unlike mass, which does not vary with location. On the Moon, for example, the...

In mechanics, understanding the motion of objects is essential, and one tool that helps solve this problem is the free-body diagram. It is a simple but powerful graphical representation that succinctly represents all the forces acting on an object. A free-body diagram can represent a stationary or moving object, and is used in mechanics to explain the cause of an object's motion.
A free-body diagram transforms a complex problem into a simple representation, making it easy to understand the...

Solving problems that involve forces is easy using free-body diagrams. A free-body diagram is a sketch showing all the external forces that are acting on an object or system. The object or system is represented by a single isolated point (or free body). Only those forces acting on it that originate outside of the object or system—the external forces—are shown. The forces are represented by vectors extending outward from the free body. Imagine a person sitting on a chair. Here, the...