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More complex animals are composed of different organs, which have evolved over time. For example, the liver and heart evolved in the chordates about 550-500 million years ago, while the gut and brain are even more ancient, arising in the ancestor of vertebrates, insects, molluscs , and worms about 700–650 million years ago.
There are other systems in the body that are not organ systems—for example, the immune system protects the organism from infection, but it is not an organ system since it is not composed of organs. Some organs are in more than one system—for example, the nose is in the respiratory system and also serves as a sensory organ in the nervous ...
This article contains a list of organs in the human body. It is widely believed that there are 79 organs (this number goes up if you count each bone and muscle as an organ on their own, which is becoming a more common practice [1] [2]); however, there is no universal standard definition of what constitutes an organ, and some tissue groups' status as one is debated. [3]
On the organ and tissue scale in mammals and other animals, examples include the circulatory system, the respiratory system, and the nervous system. On the micro to the nanoscopic scale, examples of biological systems are cells , organelles , macromolecular complexes and regulatory pathways.
The term "homology" was first used in biology by the anatomist Richard Owen in 1843 when studying the similarities of vertebrate fins and limbs, defining it as the "same organ in different animals under every variety of form and function", [6] and contrasting it with the matching term "analogy" which he used to describe different structures ...
That might be an organ, a region in the body, or an anatomical structure. For example, the central nervous system and the peripheral nervous systems. Central (from Latin centralis) describes something close to the centre. [33] For example, the great vessels run centrally through the body; many smaller vessels branch from these.
It was written around 350 BC. The whole work is roughly a study in animal anatomy and physiology; it aims to provide a scientific understanding of the parts (organs, tissues, fluids, etc.) of animals and asks whether these parts were designed or arose by chance.
The dead bodies of vertebrate animals and insects are sometimes called carcasses. The human body has a head, neck, torso, two arms, two legs and the genitals of the groin, which differ between males and females. The branch of biology dealing with the study of the bodies and their specific structural features is called morphology. [2]