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Introduction to the Human Body Help

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By — McGraw-Hill Professional
Updated on Aug 18, 2011

Introduction to the Human Body

Anatomy and Physiology are subdivisions of the science of biology, the study of living organisms. Human anatomy is the study of body structure and the relationships between body structures. Human physiology is concerned with the functions of the body parts. In general, function is determined by structure.

Humans as Biological Organisms

Human beings (Homo sapiens) are biological organisms. The basic physical requirements of humans, as with all organisms, are: water, for a variety of metabolic processes; food, to supply energy, raw materials for building new living matter, and chemicals necessary for vital reactions; oxygen, to release energy from food materials; heat, to promote chemical reactions; and pressure, to allow breathing.

Levels of Organization of the Human Body

The levels of organization of the human body are, from the simplest to the most complex: chemical, cellular, tissue, organ, system, and organism. Each level of body organization represents an association of units from the preceding level.

Chemical and cellular levels are the basic structural and functional levels.

A tissue is an aggregation of similar cells that performs a specific function. There are four types of tissues found in humans.

An organ is composed of several tissue types that are integrated to perform a particular function.

A system is an organization of two or more organs and associated tissues working as a unit to perform a common function or set of functions. The body systems are:

  1. The muscular and skeletal systems function in body support and locomotion.
  2. The endocrine and nervous systems function in integration and coordination by maintaining consistency of body functioning.
  3. The digestive, respiratory, circulatory, lymphatic, and urinary systems are involved with processing and transporting body substances. The digestive system mechanically and chemically breaks down foods for cellular use and eliminates undigested wastes. The respiratory system supplies oxygen to the blood, eliminates carbon dioxide, and helps regulate acid-base balance. The circulatory system transports respiratory gases, nutrients, wastes, and hormones; helps regulate body temperature and acid-base balance; and protects against disease and fluid loss. The lymphatic system transports lymph from tissues to the blood stream, defends the body against infections, and aids in the absorption of fats. The urinary system functions to remove wastes from the blood; regulate the chemical composition, volume, and electrolyte balance of the blood; and helps to maintain the acid-base balance of the body.
  4. The integumentary system functions to protect the body, regulate body temperature, eliminate wastes, and receive sensory stimuli.
  5. The reproductive system functions to produce gametes for sexual reproduction and to produce sex hormones.

Homeostasis

Homeostasis is the process by which a nearly stable internal environment is maintained in the body so that cellular metabolic functions can proceed at maximum efficiency. Homeostasis is maintained by muscles or glands that are regulated by sensory information from the internal environment.

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