A knowledge of anatomy and physiology can be used to predict the body's responses to stimuli when healthy or diseased.

Anatomy

• Anatomy is the study of the structures of the body.
• Systemic anatomy is the study of the body by organ systems. Regional anatomy is the study of the body by areas.
• Surface anatomy uses superficial structures to locate deeper structures, and anatomical imaging is a noninvasive method for examining deep structures.

Physiology

• Physiology is the study of the processes and functions of the body.

Structural and Functional Organization

• The human body can be organized into seven levels: chemical (atoms and molecules), organelle (small structures within cells), cell, tissue (groups of cells with similar structure and structure), organ (two or more tissues that perform one or more common functions), organ system (groups of organs with common functions), and organism.
• The 11 organ systems are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems (see figure 1.2).

Characteristics of Life

• The characteristics of life include organization, metabolism, responsiveness, growth, differentiation, and reproduction.

Homeostasis

• Homeostasis is the condition in which body functions, fluids, and other factors of the internal environment are maintained within a range of values suitable to support life.
• Negative-feedback mechanisms operate to maintain homeostasis.
• Positive-feedback mechanisms make deviations from normal even greater. Although a few positive-feedback mechanisms normally exist in the body, most positive-feedback mechanisms are harmful.

Terminology and the Body Plan

Directional Terms

• A human standing erect with the feet forward, arms hanging to the sides, and palms facing forward is in the anatomical position.
• Directional terms always refer to the anatomical position, regardless of the body's actual position (see table 1.1).

Planes

• A sagittal plane divides the body into left and right parts, a transverse plane divides the body into superior and inferior parts, and a frontal plane divides the body into anterior and posterior parts.
• A longitudinal section divides an organ along its long axis, a transverse section cuts an organ at a right angle to the long axis, and an oblique section cuts across the long axis at an angle other than a right angle.

Body Regions

• The body can be divided into the limbs, head, neck, and trunk.
• The abdomen can be divided superficially into four quadrants or nine regions that are useful for locating internal organs or describing the location of a pain.

Body Cavities

• The thoracic cavity is bounded by the ribs and the diaphragm. The mediastinum divides the thoracic cavity into two parts.
• The abdominal cavity is bounded by the diaphragm and the abdominal muscles.
• The pelvic cavity is surrounded by the pelvic bones.

Serous Membranes

• The trunk cavities are lined by serous membranes. The parietal part of a serous membrane lines the wall of the cavity, and the visceral part covers the internal organs.
• The serous membranes secrete fluid that fills the space between the parietal and visceral membranes. The serous membranes protect organs from friction.
• The pericardial membrane surrounds the heart, the pleural membranes surround the lungs, and the peritoneal membranes line the abdominopelvic cavity and cover its organs.
• Mesenteries are parts of the peritoneum that hold the abdominal organs in place and provide a passageway for blood vessels and nerves to organs.
• Retroperitoneal organs are found "behind" the parietal peritoneum.  The kidneys, urinary bladder, and pancreas are examples of retroperitoneal organs.