뒤로Anatomical Terms, Body Planes, and Body Cavities: Foundations of Human Anatomy & Physiology
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Anatomical Terms and Body Orientation
Standard Anatomical Position
The standard anatomical position is a universally accepted starting point for describing the human body. In this position, the body stands erect, feet slightly apart, with palms facing forward and thumbs pointing away from the body. All directional terms are based on this position, ensuring consistency in anatomical descriptions.
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 locations of structures relative to other structures or locations in the body. These terms are essential for clear communication in anatomy and medicine.
Term | Definition | Example |
|---|---|---|
Superior (cranial) | Toward the head end 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 breastbone. |
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
The body is divided into two major regions for anatomical reference:
Axial region: Includes the head, neck, and trunk.
Appendicular region: Includes the limbs (arms and legs).
Regional terms specify particular areas within these divisions, aiding in precise location identification.
Body Planes and Sections
Major Body Planes
Body planes are imaginary flat surfaces that divide the body or organs into sections for anatomical study. The three most common planes are:
Sagittal plane: Divides the body into right and left parts.
Midsagittal (median) plane: Lies exactly in the midline.
Parasagittal plane: Offset from the midline.
Frontal (coronal) plane: Divides the body into anterior (front) and posterior (back) parts.
Transverse (horizontal) plane: Divides the body into superior (upper) and inferior (lower) parts; also called a cross-section.
Oblique section: Cuts made at angles 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 organ movement and growth. The two main sets of cavities are:
Dorsal body cavity: Protects the nervous system and has two subdivisions:
Cranial cavity: Encases the brain.
Vertebral cavity: Encases the spinal cord.
Ventral body cavity: Houses internal organs (viscera) and is divided by the diaphragm into:
Thoracic cavity: Contains pleural cavities (lungs), mediastinum (including the pericardial cavity for the heart), and other thoracic organs.
Abdominopelvic cavity: Subdivided into the abdominal cavity (digestive organs, spleen, liver) and pelvic cavity (urinary bladder, reproductive organs, rectum).
Membranes of the Ventral Body Cavity
The serosa (serous membrane) is a thin, double-layered membrane that covers the walls of the ventral body cavity and the outer surfaces of the organs it contains. The parietal serosa lines the cavity walls, while the visceral serosa covers the organs. The space between these layers is filled with serous fluid, reducing friction.
Pericardium: Serosa around the heart
Pleurae: Serosa around the lungs
Peritoneum: Serosa around the abdominopelvic cavity
Abdominopelvic Quadrants and Regions
For clinical and anatomical reference, the abdominopelvic cavity is divided into quadrants and regions:
Quadrants: Right upper (RUQ), left upper (LUQ), right lower (RLQ), left lower (LLQ)
Nine regions: Right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right iliac (inguinal), hypogastric, left iliac (inguinal)
Other Body Cavities
In addition to the main body cavities, there are several smaller cavities:
Oral and digestive cavities (mouth and digestive tract)
Nasal cavity (within and posterior to the nose)
Orbital cavities (house the eyes)
Middle ear cavities (contain tiny bones for hearing)
Synovial cavities (joint cavities, not exposed to the environment)
Clinical Connections
Homeostatic Imbalances
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.
Serous membrane inflammation: Infections or other causes can lead to inflammation of serous membranes (e.g., pleurisy, peritonitis), resulting in pain and impaired organ function.
