Arch, aortic: The second section of the aorta following the ascending aorta. As it continues from the heart, it gives off the brachiocephalic trunk, and the left common carotid and subclavian arteries. The brachiocephalic trunk splits to form the right subclavian and the right common carotid arteries, which supply blood to the right arm and the right side of the neck and head. The left common carotid artery and left subclavian artery, the second and third branches off the aortic arch, perform parallel functions on the left side.
- Arch, zygomatic
Arch, zygomatic: The bone that forms the prominence of the cheek. The zygomatic bone is also known as the zygoma, the zygomatic arch, malar bone, yoke bone. The word “zygomatic” comes from the Greek “zygon” meaning a yoke (as for oxen).
Archaea: A unique group of microorganisms that are called bacteria (Archaeobacteria) but are genetically and metabolically different from all other known bacteria. They appear to be living fossils, the survivors of an ancient group of organisms that bridged the gap in evolution between bacteria and multicellular organisms (eukaryotes).
Archaeogenetics: The study of the past using the techniques of molecular genetics. The application of genetics to archeology. The term “archaeogenetics” was coined in the 1990s by the archeologist Colin Renfrew from the Greek archaios (ancient) + genetics = archaeogenetics, literally, ancient genetics. In archaeogenetics, information on the DNA of different ethnic groups from around […]
Archaeology: The scientific study of the material remains of past peoples. In archaeology today, a range of biological techniques, including DNA analysis, enter into what has been termed bioarchaeology.
- Arcuate neuron
Arcuate neuron: A neuron in the arcuate nucleus of the brain. See: Arcuate nucleus.