Physiology Fundamentals Quiz Cells, Fluids & Body Systems - 1 скачать в хорошем качестве

Physiology Fundamentals Quiz Cells, Fluids & Body Systems - 1

Physiology is a branch of biology that explains the functions of living organisms and their parts, focusing on the physical and chemical mechanisms responsible for life. Human physiology specifically studies how different systems of the human body work together to maintain life. Survival depends on complex control mechanisms that regulate behaviors such as hunger, temperature regulation, fear responses, and reproduction. These mechanisms involve coordinated actions of genes, cells, tissues, organs, and regulatory systems like the nervous and hormonal systems. The cell is the basic living unit of the body. Each tissue or organ is composed of many cells supported by intercellular structures. Although cells differ in shape and function, they share fundamental characteristics. All cells obtain energy through oxidation of nutrients such as carbohydrates, fats, and proteins using oxygen. They also release the products of metabolism into surrounding body fluids. Many cells retain the ability to reproduce, allowing replacement when cells are damaged or destroyed. The human body contains approximately 35–40 trillion cells, including about 25 trillion red blood cells, which transport oxygen from the lungs to body tissues. In addition to human cells, the body hosts trillions of microorganisms called microbiota, particularly in the gastrointestinal tract. These microbes often live in harmony with the host and contribute to digestion, immunity, and nutrition. About 50–70% of the human body consists of fluid. Most of this fluid is intracellular (inside cells), while about one-third forms the extracellular fluid, which surrounds cells and serves as the body’s internal environment (milieu intérieur). This fluid contains essential nutrients, ions, oxygen, and waste products. Extracellular fluid is circulated through the bloodstream and exchanged with tissues by diffusion across capillary walls. Maintaining stable conditions in this internal environment is essential for proper cellular function and overall survival.