Body parts and regions

SNOMED CT uses the Foundation Model of Anatomy (FMA) definition of body part and body part subdivision for some concepts. For example, the joint regions discussed below are classified as body part subdivisions, since that is what is intended by the diseases and procedures that use these terms in their definitions. They are not body parts because they are defined, not by a set of bones, but rather by a particular joint and its surrounding structures. However, our interpretation of the word region is based on common usage and is intended as a three-dimensional structure, not the FMA two-dimensional definition of body region. In other words, these regions are not simply surface regions (skin), but also include the three dimensional underlying structures (subcutaneous tissues, bones, muscles, tendons, fascia, vessels and etc.).

Surface regions

Many concepts contain the phrase surface region. These could be interpreted as massless (immaterial) mathematical surfaces, but a clinical terminology would have no direct use for such meanings in clinical records. They could be interpreted as having mass (not immaterial), but the depth then is arbitrary. Should it be just skin deep, or should it include deeper layers of the surface? If only skin deep, the meaning of these concepts would overlap with concepts for skin regions. If deeper, the meaning would possibly be the same as the generic structure concepts.

Abdominal regions

The named regions of the abdomen are by tradition divided horizontally by the transpyloric plane and the interspinous plane, and vertically by the midclavicular plane. The lateral regions are therefore bounded above by a plane that is inferior to the ribs. In contrast, the flank is the lateral region of the abdomen bounded above by the ribs. Thus some parts of the hypochondriac regions, which are superior to the transpyloric plane but inferior to the ribs, would be considered also part of the flank. The hypogastric region is also sometimes called the pubic region.

Abdominal cavity, pelvic cavity

The term abdominal cavity has two meanings, one including the pelvic cavity, the other excluding it. Abdominal cavity structure includes both. Abdominal cavity proper excludes the pelvic cavity.

Organs, organ system subdivisions

The FMA definition of body organ is also used. Organs include individual bones, joints, muscles, arteries, veins, lymph vessels, nerves, and etc. Concepts that include groups of organs are frequently used in SNOMED CT. In most cases, these have been part of the subsumption hierarchy (IS A hierarchy) of the particular organ type, that is, they are kinds of organs.

For concepts that refer to the collection of organs (rather than organs in a collection), there is another concept that is a, kind of, organ system subdivision. Many such collections do not yet have corresponding organ system subdivision concepts. The default is to interpret concepts as denoting organs, rather than organ system subdivisions.

Cell, tissue, organ

In general, organs are made up of tissue, and tissue is made up of cells. However, a cell is not necessarily part of tissue, and tissue is not necessarily part of a named organ. 

Tree structured organs

Arteries, veins, nerves, and the bronchi form tree-like structures that distribute across multiple regions. Because of their size and links with other structures, they require slightly different modeling. FMA divides tree structured organs as: organs with organ cavities and organs that are solid.

Hollow tree organs

Organ with organ cavity has a subtype, hollow tree organ. The hollow tree organs are:

• Tracheobronchial
• Biliary
• Vascular
  • Arterial
    • Systemic arterial
    • Pulmonary arterial
  • Venous
    • Systemic venous (superior, inferior, and 4 cardiac trees)
    • Pulmonary venous (superior and inferior left and superior and inferior right)
    • Portal venous
  • Lymphatic (right lymphatic duct and thoracic duct)

Among the solid organs, there is one category, neural, that is tree-structured (see: Nervous system; neural tree).