Anatomical Terminology

Anatomy is the study of body structures and their relationships to each other. When studying anatomy it is important to first know anatomical terminology. In anatomy, when we refer to the location of a body structure we always assume anatomical position. The anatomical position is when the body is standing with the head and toes pointing forward, feet together, arms to the side and palms of the hands facing forward.  Left and right directions always refer to the body in the anatomical position and not the observer.

The body can be divided into sectional planes in order to describe organs and structures and their characteristics and locations. The frontal or coronal plane separates the body into anterior (front) and posterior (back) halves. The transverse or horizontal plane separates the body into superior (upper) and inferior (lower) halves. The mid-sagittal or median plane separates the body into equal left and right halves. The para-sagittal plane separates the body into unequal left and right halves. 

 

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Directional terms allow us to describe of the location of body organs or structures in relation to each other. Anterior or ventral refers to towards the front and posterior or dorsal refers to towards the back or behind. Superior or cranial or cephalic refers to towards the head or above and inferior or caudal refers to away from the head and towards the tail or below. Medial refers to towards the midline and lateral refers to away from the midline. Proximal refers to closer to the point of attachment or trunk and distal refers to further away from the point of attachment or trunk.  Superficial or external refers to towards the body surface and deep or internal refers to away from the body surface. Bilateral means the structures are on both sides of the reference point, contralateral means the structures are on opposite sides as the reference point and ipsilateral means the structures are on the same side as the reference point.

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The body can be divided into the axial part referring to the main axis of the body including the head, neck and trunk and the appendicular part referring to the limbs. 

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Regional terms allow for a precise description of the location of body structures. 

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The abdominopelvic regions and abdominopelvic quadrants are subdivisions of the abdominal and pelvic areas that are used to describe the location of organs or structures and to pinpoint areas of interest in the event of pain or injury.

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The body cavities are fluid-filled spaces that are closed off from the external environment and most often contain organs. The two major body cavities are the dorsal body cavity which includes the cranial and vertebral cavities and the ventral body cavity which includes the thoracic, abdominal and pelvic cavities.  The thoracic cavity contains the pleural cavities and mediastinum which contains the pericardial cavity.

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serous membrane or serosa is a thin double-layer membrane that lines and encloses body cavities. The serous cavity is filled with serous fluid and lubricates the space between serous membranes and organs to reduce friction. The parietal serosa is the outer membrane that lines the inside of the body wall. The visceral serosa is the inner membrane that lines the organs. To envision the serosa, imagine pushing your hand into a blown-up balloon. The outer balloon wall represents the parietal serosa, the inner balloon wall in contact with your hand represents the visceral serosa and the space filled with air in the balloon is the serous cavity. There are various serous cavities enclosing organs that include the pleural cavity that surrounds the lungs, the pericardial cavity that surrounds the heart and the peritoneal cavity that lines the abdominopelvic cavity.  Some other body cavities include oral, nasal, orbital, middle ear and synovial cavities. 

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