Comprehensive Introduction to Anatomy, Orientation, and Direction

Anatomy: This is the science dedicated to studying the form and composition of the structures of the body.
Gross Anatomy: Also referred to as macroscopic anatomy, this is the study of the body's larger structures. These structures are typically observable with the unaided eye.
Physiology: This science focuses on the body's functions, specifically the chemistry, biochemistry, and physics that drive those functions.

Tissue: This refers to a group of similar or closely related cells that act together to perform a specific function.
Organ: An organ is a functionally distinct structure composed of two or more types of tissues.
Organ System: This term describes a group of organs that work together to carry out a particular function.
Organism: An organism is a living being that possesses a cellular structure and is capable of independently performing all physiologic functions necessary for life.

Anterior: Used to describe the front or the direction toward the front of the body. This is also referred to as ventral.
Dorsal: Used to describe the back or the direction toward the back of the body. This is also referred to as posterior.
Cranial: Used to describe a position that is above or higher than another part of the body proper. This is also referred to as superior.
Caudal: Used to describe a position below or lower than another part of the body proper, specifically near or toward the tail. In human anatomy, this refers to the coccyx, which is the lowest part of the spinal column. This is also referred to as inferior.
Medial: Used to describe the middle or the direction toward the middle of the body.
Lateral: Used to describe the side or the direction toward the side of the body.
Proximal: Describes a position that is nearer to the point of attachment or the trunk of the body.
Distal: Describes a position that is farther from the point of attachment or the trunk of the body.
Superficial: Describes a position that is nearer to the surface of the body.
Deep: Describes a position that is farther from the surface of the body.
Prone: A specific orientation where the body is lying face down.
Supine: A specific orientation where the body is lying face up.

Sagittal Plane: A two-dimensional, vertical plane that divides the body or an organ into right and left sides.
Frontal Plane: A two-dimensional, vertical plane that divides the body or an organ into anterior and posterior (front and back) portions.
Transverse Plane: A two-dimensional, horizontal plane that divides the body or an organ into superior and inferior (upper and lower) portions.

Homeostasis: The steady state of body systems that living organisms maintain to ensure survival.
Negative Feedback: A homeostatic mechanism that works to stabilize an upset in the body’s physiological condition. It functions by preventing an excessive response to a stimulus, typically occurring as the stimulus is removed.
Positive Feedback: A mechanism that intensifies a change in the body’s physiological condition in response to a specific stimulus.