What is Blood?
[[File:1GZX Haemoglobin.png|right|thumb|[[Hemoglobin]], a [[globular protein]]<br />green = haem (or heme) groups<br />red & blue = protein subunits]] [[Image:Red White Blood cells.jpg|thumb|right|A [[scanning electron microscope]] (SEM) image of a normal [[red blood cell]] (left), a [[platelet]] (middle), and a [[white blood cell]] (right)]] '''Blood''' is a [[liquid]] in [[human]]s and many [[animal]]s. There are about 5 litres of blood in the human body.<ref>{{Cite web|last=updated|first=Laura Geggel last|date=2016-03-03|title=How Much Blood Is in the Human Body?|url=https://www.livescience.com/32213-how-much-blood-is-in-the-human-body.html|access-date=2024-08-08|website=livescience.com|language=en}}</ref> Blood is pushed through the [[organism]] by the [[heart]]. It brings [[nutrient]]s and [[oxygen]] to the [[Tissue|tissues]] of the body. It also takes away [[waste]] and [[carbon dioxide]] from tissues.<ref>{{cite web| url = http://www.fi.edu/learn/heart/blood/blood.html| title = Blood – the human heart| accessdate = 19 March 2009| author = The Franklin Institute| archive-date = 5 March 2009| archive-url = https://web.archive.org/web/20090305043654/http://www.fi.edu/learn/heart/blood/blood.html| url-status = deviated| archivedate = 5 March 2009| archiveurl = https://web.archive.org/web/20090305043654/http://www.fi.edu/learn/heart/blood/blood.html}}</ref> Blood is made up of [[blood plasma]] and various [[cells]]. These include [[red blood cells]], [[white blood cells]] and [[platelets]]. Platelets help [[blood clot|blood to clot]]. [[Hemoglobin]] is in red blood cells. White blood cells help fight [[infection]]s and heal [[wound|wounds]]. == Plasma == Blood plasma is the yellow liquid in which blood cells float. Plasma is made up of nutrients, [[electrolyte]]s ([[salts]]), [[gas]]es, non-protein hormones, waste, [[lipid]]s, and proteins. These proteins are [[albumin]], [[antibody|antibodies]] (also called ''immunoglobulins''), clottin