For example, the fact that the tissues of the mesentery are continuous was something that was simply not known for sure until it was demonstrated with microscopy. Plant life and animal life rely on many organs that coexist in organ systems. For example, the liver evolved in the stem vertebrates more than 500 million years ago, while the gut and brain are even more ancient, arising in the ancestor of vertebrates, insects, and worms more than 600 million years ago. All parts of the plant above ground (in non-epiphytes), including the functionally distinct leaf and flower organs, may be classified together as the shoot organ system.. Humans and other mammals have many organ systems. The main tissues that make up an organ tend to have common embryologic origins, such as arising from the same germ layer. Definition noun, plural: organs A group of tissues that perform a specific function or group of functions Supplement An organ pertains to a group of tissues that perform a specific function or group of functions. The term "visceral" is contrasted with the term "parietal", meaning "of or relating to the wall of a body part, organ or cavity" The two terms are often used in describing a membrane or piece of connective tissue, referring to the opposing sides. , Some alchemists (e.g. Continued Organ Transplant Waiting Times, Policies, Procedures. organ [or´gan] organum.  Because humans cannot predict all future scientific discoveries, they cannot build a unified ontology that is totally certain and will never again change. United Network for Organ Sharing (UNOS) is the private, non-profit organization that manages the nation’s organ transplant system under contract with the federal government. Given the ancient origin of most vertebrate organs, researchers have looked for model systems, where organs have evolved more recently, and ideally have evolved multiple times independently. See the full definition for organ in the English Language Learners Dictionary, Thesaurus: All synonyms and antonyms for organ, Nglish: Translation of organ for Spanish Speakers, Britannica English: Translation of organ for Arabic Speakers, Britannica.com: Encyclopedia article about organ. The organ procurement team sometimes inspects the donor's heart for damage or blockage by sticking a thin tube into an artery or vein and threading it through their blood vessels to the heart. lung - Goes back to an Indo-European word for "light," because of the lightness of the organ. Multiple organ failure is the failure of two or more systems, such as the cardiovascular, and renal systems, and is a common consequence of sepsis (the presence of bacteria in the bloods) and of shock (very low blood pressure). These specific systems are also widely studied in human anatomy. ), both meaning "musical instrument," both from Latin organa, plural of organum "a musical instrument," from Greek organon "implement, tool for making or doing; musical instrument; organ of sense, organ of the body," literally "that with which one works," from PIE *werg-ano-, from root *werg-"to do." Organ Donation Facts In the United States, there is a large shortage of organ donors. The study of human and animal tissues is known as histology or, in connection with disease, histopathology. The heart, liver, and stomach are examples of organs in humans. Organ failure: The failure of an essential system in the body. Examples of organs include the eyes, ears, heart, lungs, and liver. Non-placozoan animals such as humans have a variety of organ systems. An organ is a self-contained group of tissues that performs a specific function in the body. These example sentences are selected automatically from various online news sources to reflect current usage of the word 'organ.' Plant organs are made from tissue composed of different types of tissue.