science
Blood is pumped around the body by a muscular organ divided into separate chambers that keep oxygen-rich and oxygen-poor blood from mixing.
The human heart has four chambers: two upper chambers called atria that receive incoming blood, and two lower chambers called ventricles that pump blood back out, with the right side sending blood to the lungs to pick up oxygen and the left side pushing oxygen-rich blood out to the rest of the body.
A heart with only two or three chambers wouldn't be able to keep oxygen-rich and oxygen-poor blood properly separated, which is exactly the job the four-chamber design accomplishes in humans and other mammals, unlike some simpler animals that do have fewer heart chambers.
The heart's familiar 'lub-dub' sound comes from four one-way valves snapping shut in sequence, preventing blood from flowing backward and keeping it moving through the chambers in a single, efficient direction.
science
Why does the sky appear blue?Which gene did they show links ALS and frontotemporal dementia?What can two magnets do without touching?What do scientists hope to make using clues from animals like this?What is this two-layer solar cell design called?What do we call the hardened remains of ancient animals that scientists dig up and study?Which element makes bananas slightly radioactive?Why does the spoon look bent where it enters the water?What is really pushing the blades and making them spin?Which one?What is happening to the apple when it turns brown in the air?What is trapped inside the cup that keeps the water out?Quration — Quration Play