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
John (given name) Yônāṯān, which means "Gift from YHWH" and thus is a longer version of Nathan. John (given name) John is a common masculine given name in the English language of originally Semitic origin. The name is derived from the Latin "Ioannes" and "Iohannes", which are forms of the Greek name "Iōannēs" (), originally borne by Hellenized Jews transliterating the Hebrew name "Yohanan" (), "Graced by Yah", or (), "Yahweh is Gracious". There are numerous forms of the name in different languages; these were formerly often simply translated as "John" in English but are increasingly left in their native forms (see sidebar).