- published: 22 Dec 2012
- views: 41034
In biology, an organ is a collection of tissues joined in a structural unit to serve a common function.
Usually there is a "main" tissue, parenchyma, and "sporadic" tissues, stroma. The main tissue is the one that is unique for the specific organ. For example, the main tissue in the heart is the myocardium, while sporadic tissues include the nerves, blood and connective tissues. 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, such as the stomach or intestine, or that includes a cavity, like the heart or urinary bladder.
Two or more organs working together in the execution of a specific body function form an organ system, also called a biological system or body system. 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 because of the relationship between the muscular and skeletal systems.
Organ may refer to the following:
Anatomy (from the Ancient Greek ἀνατέμνειν, anatemnein: ana, "separate, apart from", and temnein, "to cut up, cut open") is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy (zootomy), and plant anatomy (phytotomy). In some of its facets anatomy is closely related to embryology, comparative anatomy and comparative embryology, through common roots in evolution.
Anatomy is subdivided into gross anatomy (or macroscopic anatomy) and microscopic anatomy.Gross anatomy is the study of anatomical structures that can, when suitably presented or dissected, be seen by unaided vision with the naked eye.Microscopic anatomy is the study of minute anatomical structures on a microscopic scale. It includes histology (the study of tissues), and cytology (the study of cells). The terms microanatomy and histology are also sometimes used synonymously (in which case the distinction between histology and cell biology isn't strictly made as described here).