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From Wikipedia, the free encyclopedia

In biology and anatomy, an organ (Latin: organum, "instrument, tool", from Greek ὄργανον - organon, "organ, instrument, tool"[1]) is a collection of tissues joined in structural unit to serve a common function.[2]

Usually there is a main tissue and sporadic tissues. The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are the nerves, blood, connective etc.. Functionally related organs often cooperate to form whole organ systems. Organs exist in all higher biological organisms, in particular they are not restricted to animals, but can also be identified in plants. In single-cell organisms like bacteria, the functional analogues of organs are called organelles.

A hollow organ is a visceral organ that is a hollow tube or pouch (as the stomach or intestine) or that includes a cavity (as of the heart or urinary bladder).[3]


Organ systems

The functions of organ systems often share significant overlap. For instance, the nervous and endocrine system both operate via a shared organ, the hypothalamus. For this reason, the two systems are combined and studied as the neuroendocrine system. The same is true for the musculoskeletal system, which involves the relationship between the muscular and skeletal systems.

Plant organs and organ systems

The flower is the angiosperm's reproductive organ. This Hibiscus flower is hermaphroditic, and it contains stamens and pistils.
Strobilus of Equisetum.

Organs of plants can be divided into vegetative and reproductive. Vegetative plant organs are root, stem and leaf. The reproductive organs are variable. In angiosperms, they are represented with the flower, seed and fruit. In conifers, the organ that bears the reproductive structures is called a cone. In other divisions of plants, the reproductive organs are called strobili (in Lycopodiophyta) or simply gametophores (in mosses).

The vegetative organs are essential for maintaining the life of a plant (they perform the vital functions, such as photosynthesis), while the reproductive organs are essential in reproduction. However, if there is asexual vegetative reproduction, the vegetative organs are those that create the new generation of plants (see clonal colony).

The two main organ systems in vascular plants are the root system and the shoot system.

Animal organs and organ systems

The organ level of organisation in animals can be first detected in flatworms and the more advanced phyla. The less-advanced taxons (like Placozoa, Porifera and Radiata) do not show consolidation of their tissues into organs.


List of major human organ systems

There are typically considered to be eleven major organ systems of the human body. Humans have a variety of systems due to the complexity of the species' organism. These specific systems are widely studied in Human anatomy. "Human" systems are also present in many animals.

See also


  1. ^ Organon, Henry George Liddell, Robert Scott, A Greek-English Lexicon, at Perseus project
  2. ^ Widmaier EP, Raff H, and Strang KT (2003) Vander's Human Physiology. 11th Ed. McGraw-Hill. ISBN 987-0-07-304962-5.
  3. ^ > hollow organ Citing: Merriam-Webster's Medical Dictionary, 2002

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