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
Riley (given name) Riley (given name) Riley is a unisex given name, which first appeared as "Raghallach", which was originated on a man who died in the Battle of Clontarf. Its source gives its meaning as "valiant". Riley in the United States is mostly a girl's name. In 2017, it was the twenty-fifth most popular girl's name, and the 253rd most popular boy's name. The opposite is true for the UK, where it is primarily a boy's name, being the fortieth most popular name given to baby boys in 2016. Riley is also a popular surname. The surname's first variant is Ó Raghallaigh