How many organs (no matter how minor it is) does a human being have? And what are they?

How many organs (no matter how minor it is) does a human being have? And what are they?

This is really a question with no clear cut answer. It is a human characteristic to want to divide things into discrete categories, but nature itself is not nearly so discriminating. The Terminologica Anatomica lists over 7,500 named parts of the human body. Of course, many of these terms apply to parts of the body that may not be considered organs, and some apply to parts of individual organs. However, this large number of names points to the complexity of the human body.

Before we can even attempt to answer this question, we must first have a definition of what an organ is. A widely accepted definition of an organ is a collection of tissues that act together to perform a function or functions. By this definition, each individual bone of the skeleton could be considered an organ. But to give an idea of the complexity of the issue, we could then ask whether the cranium comprises a single organ, or is it itself a collection of all the individual bones (organs) which comprise it? Then, is the mandible a separate organ, or is it a portion of the organ we call the skull? Are the teeth part of the skull, or are they 32 individual organs of the digestive system? Likewise with the musculature, we could say that each muscle is an individual organ. But then what constitutes a muscle? For example, the multifidus is a muscle that runs from the transverse processes of vertebrae to insert into the spinous processes of the vertebrae 3 to 4 levels superior to the vertebra of origin. Is each slip arising from each transverse process an individual organ, or does the whole multifidus collectively constitute a single muscle or organ? If we count each bone and each muscle as a separate organ, we rapidly approach 1,000 individual organs in the body, and we have not yet taken account of anything but the skeletal and muscular systems of the body. Likewise, with the organs of the digestive system, for example, we run into a similar problem. Is the small intestine a single organ, or is it three organs: the duodenum, the jejunum and the ileum?

Another approach would be to attempt to come up with a minimally acceptable list of individual organs of the body. One way to look at this is to list the systems of the body and the major organs in each system. Just as an organ can be described as a collection of tissues that act together to perform a function or functions, a system can be defined as a collection of organs that act together to perform a function or functions. Such a minimal list could look something like the following:

Circulatory system

  • heart
  • arteries
  • veins
  • capillaries
  • cisterna chyli
  • spleen
  • Lymphatic system (a part of the circulatory system):
    • thoracic duct
    • right lymphatic duct
    • lymph vessels
    • tonsils,
    • adenoids
    • thymus
    • spleen.
    • lymph nodes

Digestive system

  • teeth
  • tongue
  • salivary glands (3 pair)
  • esophagus
  • stomach
  • liver,
  • gallbladder
  • pancreas
  • small intestine
  • large intestine
  • rectum
  • anus

Endocrine system

  • hypothalamus
  • pituitary gland
  • pineal body
  • thyroid gland
  • parathyroids
  • suprarenal glands

Integumentary system

  • skin, hair and nails and associated glands, including mammary glands.
  • The skin with its associated structures is sometimes considered an organ.

Muscular system

  • The individual muscles of the body.

Nervous system

  • brain,
  • spinal cord
  • peripheral nerves

Reproductive system

  • ovaries,
  • fallopian tubes
  • uterus
  • clitoris
  • vagina

  • Male:
  • testes
  • vas deferens
  • seminal vesicles
  • prostate
  • penis

Respiratory system

  • pharynx
  • larynx
  • trachea
  • bronchi
  • lungs
  • diaphragm

Skeletal system

The individual bones of the skeleton and associated ligaments and other structures.
In a normal human adult there are 206 regularly occurring bones, plus a variable number of sesamoid bones that may appear in tendons of muscles.

Excretory system

  • kidneys
  • ureters
  • bladder
  • urethra

Organs of Special Sense

  • eyes
  • olfactory bulbs
  • vomeronasal organ
  • vestibulocochlear organ
  • taste buds of the tongue

Even with such a minimal list, we still have a list of over 60 individual organs or pairs of organs.

In short, there is no clear answer to this question. So much depends upon the definition of an organ. This list should not be viewed as a list for memorization. Continuity from the subcellular to the whole organism is a central concept in anatomy. Organelles are collections of macromolecules and tissues are collections of cells and their products, each arranged to cooperate to carry out a particular set of functions. Organs are collections of tissues similarly organized to carry out related, but more complicated sets of functions. Organ systems carry this concept to the next level of complexity, followed by organisms and their structure-function relationships.

Federative Committee on Anatomical Terminology (1998) Terminologica Anatomica. Theime, Stuttgart, Germany.

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