Bio2/ Topic One: Introduction to the Human Body

In This Hand- Out:

            Humans as Biological Organisms

            Levels of Organization of the Human Body

            Homeostasis

            Anatomical Positions and Terminologies

            Body Regions and Body Cavities

• Human anatomy: study of body structure and the relationship between body structures
• Human Physiology: 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 well as with all organisms are:

(a)    water- for a variety of metabolic processes

(b)    food- to supply energy; raw materials for building new living matter and chemicals necessary for vital reactions

(c)    oxygen- to release energy from food materials

(d)    heat- to promote chemical reactions

(e)    pressure- to allow breathing

Levels of Organization of the Human Body

(Arranged from simplest to the most complex)

chemical à cellular à tissue à organ à system à  organism

            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:

• Epithelial tissue: cover body and organ surfaces, lines body cavities, and forms glands; is involved with protection, excretion, secretion, diffusion, and filtration
• Connective tissue: binds, supports, and protects body parts, stores energy and minerals
• Muscle tissue: contracts to produce movement
• Nervous tissue: initiates and transmits nerve impulses that coordinate body activities

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:

• Muscular and skeletal systems: function in body support and locomotion
• Endocrine and nervous systems: function in integration and coordination by maintaining consistency of body functioning.
• Digestive, Respiratory, Circulatory, Lymphatic and Urinary systems: involved with processing and transporting body substances
• Integumentary system: functions to protect the body, regulate body temperature, eliminate wastes, and receive sensory stimuli
• 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 the 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.

Anatomical Position and Terminology

• Anatomical position: all terms of direction that describe the relationship of one body part to another; in this position, the body is erect, feet are parallel and flat on the floor, eyes are directed forward, and arms are at the sides of the body with the palms of the hands turned forward and the fingers pointing downward
• Three planes of reference that are used to locate and describe structures within the body:

(a)    mid- sagittal plane

(b)    coronal plane

(c)    transverse (horizontal or cross- sectional) plane

• Commonly Used Anatomical Descriptive and Directional Terms

Body Regions and Body Cavities

• Principal body regions: head, neck, trunk, upper extremity and lower extremity
• Body cavities: confined spaces in which organs are protected, separated, and supported by associated membranes; principal divisions are anterior (ventral) cavity and posterior (dorsal) cavity
• Posterior (dorsal) cavity: includes the cranial and vertebral cavities and contains the brain and spinal cord
• Anterior (ventral) cavity: includes the thoracic, abdominal, and pelvic cavities and contains the visceral organs
• Body membranes: composed of thin layers of connective and epithelial tissue, serve to cover, protect, lubricate, separate, or support visceral organs or to line body cavities
• 2 principal types of body membranes: mucous membranes and serous membranes
• mucous membranes: secrete a thick, viscous substance called mucous that lubricates and protects the body organs where it is secreted.
• Serous membranes: line the thoracic and abdominopelvic cavities and cover the visceral organs; composed of thin sheets of epithelial tissue that lubricate, support, and compartmentalize visceral organs
• Serous membranes of the thoracic cavity: parietal and visceral pleura, parietal and visceral pericardium, parietal and visceral peritoneum and the mesentery.