Heart depending on what is counted as a chamber. The atrium and ventricle are sometimes considered "true chambers", while the others are considered "accessory chambers". Primitive fish have a four-chambered heart, but the chambers are arranged sequentially so that this primitive heart is quite unlike the four-chambered hearts of mammals and birds. The first chamber is the sinus venosus, which collects deoxygenated blood from the body through the hepatic and cardinal veins. From here, blood flows into the atrium and then to the powerful muscular ventricle where the main pumping action will take place. The fourth and final chamber is the
Opal (given name) in the 1950s. It was the 344th most common name for females in the United States in the 1990 census. Eighty girls born in the United States in 2010 were given the name and 92 girls born in 2011 were given the name. Opal (given name) Opal is a feminine given name derived from the name of the gemstone opal. The gemstone is the birthstone for October. Its name is derived from the Sanskrit उपल or "upala", which means ""jewel". It came into use along with other gemstone names during the late Victorian era. Opal was among the 100 most