| 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: | portion of tissue | 
|---|---|
| Synonyms: | |
| Definition: | Anatomical structure, that consists of similar cells and intercellular matrix, aggregated according to genetically determined spatial relationships. | 
| Ontology: | Anatomy Ontology [ZFA:0001477] |