뒤로Anatomical Orientation, Terms, Body Planes, and Cavities: Study Notes for Anatomy & Physiology
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Anatomical Position and Directional Terms
Standard Anatomical Position
The anatomical position is a universally accepted reference for describing locations and directions on the human body. In this position, the body stands erect, feet slightly apart, arms at the sides, palms facing forward, and thumbs pointing away from the body. All directional terms are based on this position.
Right and left always refer to the subject's right and left, not the observer's.
Directional Terms
Directional terms are used to describe the location of one body structure relative to another. These terms are essential for clear communication in anatomy.
Term | Definition | Example |
|---|---|---|
Superior (cranial) | Toward the head or upper part of a structure or the body; above | The head is superior to the abdomen. |
Inferior (caudal) | Away from the head end or toward the lower part of a structure or the body; below | The navel is inferior to the chin. |
Anterior (ventral) | Toward or at the front of the body; in front of | The breastbone is anterior to the spine. |
Posterior (dorsal) | Toward or at the back of the body; behind | The heart is posterior to the sternum. |
Term | Definition | Example |
|---|---|---|
Medial | Toward or at the midline of the body; on the inner side of | The heart is medial to the arm. |
Lateral | Away from the midline of the body; on the outer side of | The arms are lateral to the chest. |
Intermediate | Between a more medial and a more lateral structure | The collarbone is intermediate between the breastbone and shoulder. |
Term | Definition | Example |
|---|---|---|
Proximal | Closer to the origin of the body part or the point of attachment of a limb to the body trunk | The elbow is proximal to the wrist. |
Distal | Farther from the origin of a body part or the point of attachment of a limb to the body trunk | The knee is distal to the thigh. |
Superficial (external) | Toward or at the body surface | The skin is superficial to the skeletal muscles. |
Deep (internal) | Away from the body surface; more internal | The lungs are deep to the skin. |
Regional Terms
Body Divisions and Specific Areas
The body is divided into two major regions: axial (head, neck, trunk) and appendicular (limbs). Regional terms specify particular areas within these divisions, aiding in precise anatomical description.
Axial region: Includes cephalic (head), cervical (neck), thoracic (chest), abdominal, pelvic, and back (dorsal).
Appendicular region: Includes upper and lower limbs.
Body Planes and Sections
Planes of the Body
Body planes are imaginary lines used to divide the body for anatomical study. The three most common planes are:
Sagittal plane: Divides the body into right and left parts. A midsagittal (median) plane is exactly at the midline; a parasagittal plane is off-center.
Frontal (coronal) plane: Divides the body into anterior (front) and posterior (back) parts.
Transverse (horizontal) plane: Divides the body into superior (top) and inferior (bottom) parts; produces a cross section.
Oblique section: A cut made at an angle other than 90° to the vertical plane.
Body Cavities and Membranes
Major Body Cavities
The body contains internal cavities that protect organs and allow for their movement. There are two main sets of cavities:
Dorsal body cavity: Protects the nervous system; includes the cranial cavity (brain) and vertebral cavity (spinal cord).
Ventral body cavity: Houses internal organs (viscera); divided into thoracic and abdominopelvic cavities, separated by the diaphragm.
Ventral Body Cavity Subdivisions
Thoracic cavity: Contains two pleural cavities (each surrounds a lung), the mediastinum (contains pericardial cavity and other thoracic organs), and the pericardial cavity (encloses the heart).
Abdominopelvic cavity:
Abdominal cavity: Contains stomach, intestines, spleen, and liver.
Pelvic cavity: Contains urinary bladder, reproductive organs, and rectum.
Clinical Example: Hiatal Hernia
A hiatal hernia occurs when part of the stomach protrudes through the diaphragm into the thoracic cavity, potentially causing heartburn and requiring surgical repair in severe cases.
Membranes in the Ventral Body Cavity
The ventral body cavity is lined by serous membranes (serosa), which are thin, double-layered membranes:
Parietal serosa: Lines internal body cavity walls.
Visceral serosa: Covers internal organs.
The space between these layers is filled with serous fluid, reducing friction.
Pericardium: Associated with the heart.
Pleurae: Associated with the lungs.
Peritoneum: Associated with the abdominopelvic cavity.
Clinical Example: Serous Membrane Inflammation
Inflammation of serous membranes, such as pleurisy (lungs) or peritonitis (abdominal cavity), can cause pain and organ dysfunction.
Abdominopelvic Quadrants and Regions
Quadrants
Medical personnel often use four abdominopelvic quadrants to localize pain or pathology:
Right upper quadrant (RUQ)
Left upper quadrant (LUQ)
Right lower quadrant (RLQ)
Left lower quadrant (LLQ)
Regions
Anatomists use nine abdominopelvic regions, arranged in a tic-tac-toe grid, for more precise localization:
Right hypochondriac region
Epigastric region
Left hypochondriac region
Right lumbar region
Umbilical region
Left lumbar region
Right iliac (inguinal) region
Hypogastric (pubic) region
Left iliac (inguinal) region
Other Body Cavities
Smaller Cavities
In addition to the main body cavities, several smaller cavities exist:
Oral and digestive cavities: Mouth and digestive tract.
Nasal cavity: Within the nose.
Orbital cavities: Eyes.
Middle ear cavities: Contain tiny bones for hearing.
Synovial cavities: Joint cavities (not exposed to the environment).
Summary Table: Major Anatomical Terms
Term | Definition |
|---|---|
Superior | Above; toward the head |
Inferior | Below; away from the head |
Anterior | Front; toward the front of the body |
Posterior | Back; toward the back of the body |
Medial | Toward the midline |
Lateral | Away from the midline |
Proximal | Closer to the point of attachment |
Distal | Farther from the point of attachment |
Superficial | Toward the body surface |
Deep | Away from the body surface |
Example: The heart is medial to the lungs and posterior to the sternum.
Additional info: These terms are foundational for describing anatomical relationships and are used throughout all chapters of Anatomy & Physiology.
