Term: atrium mitochondrion
Name: atrium
Synonyms:
Definition: Cavitated compound organ that receives inflow of deoxygenated blood and delivers it to a muscular cardiac ventricle. Valves are present to direct flow. There are only two chambers present in the fish heart.
Ontology: Anatomy Ontology [ZFA:0000471]

Name: mitochondrion
Synonyms: mitochondria
Definition: A semiautonomous, self replicating organelle that occurs in varying numbers, shapes, and sizes in the cytoplasm of virtually all eukaryotic cells. It is notably the site of tissue respiration.
Ontology: GO: Cellular Component [GO:0005739]    QuickGO    AmiGO