What is Red blood cell?
[[File:Redbloodcells.jpg|150px|right]] [[File:Statistical-Dynamics-of-Flowing-Red-Blood-Cells-by-Morphological-Image-Processing-pcbi.1000288.s005.ogv|thumb]] '''Red blood cells''' (also known as '''RBCs''', '''red blood corpuscles''' or '''erythrocytes''') are [[Cell (biology)|cells]] in the [[blood]] which transport [[oxygen]].<ref name=tb>{{cite book|title=Edexcel IGCSE Biology Student Book|url=https://archive.org/details/edexceligcsebiol0000brad|author1=Bradfield, Phil|author2=Potter, Steve|publisher=Pearson Education|year=2009|isbn=9780435966881}}</ref><ref>{{cite web|publisher=Wisc-Online|title=General Anatomy & Physiology: Red Blood Cells|url=http://www.wisc-online.com/objects/ViewObject.aspx?ID=ap14604|author=Liang, Barbara|accessdate=2011-03-22}}</ref> In women, there are about 4.8 million red blood cells per [[microliter]] of blood. In men, there are 5.4 million red blood cells per microliter of blood.<ref>{{cite web|url=https://www.webmd.com/a-to-z-guides/complete-blood-count|title=What Is a Complete Blood Count?|website=WebMD}}</ref> Red blood cells are red because they have [[hemoglobin]] in them. Quantity of Red Blood Cells in the Human Body. The average male adult has about '''5 million red blood cells per cubic millimeter''' of blood, while the average female adult has about '''4.5 million red blood cells per cubic millimeter of blood'''. This may vary by about 300,000 to 500,000 red blood cells. == Function == The most important function of red blood cells is the transport of [[oxygen]] (O<sub>2</sub>) to the [[tissue (biology)|tissues]]. The [[hemoglobin]] [[wikt:absorption|absorbs]] oxygen in the [[Lung|lungs]]. Then it travels through [[Blood vessel|blood vessels]] and brings oxygen to all other cells via the [[heart]]. The blood cells go through the lungs (to collect oxygen), through the heart (to give all cells oxygen). They go back to the heart to be re-pumped to the lungs (to again collect oxygen), so the blood in your body travels in a double circuit, going through your heart twice befor