Editing Blood cell (section)

==Red blood cells==
[[File:Blood cells 090304-F-5951M-108.jpg|right|220px|thumb|Red and white human blood cells as seen under a microscope using a blue slide stain]]
[[File:Venous and arterial blood.jpg|thumb|The darker red blood syringes have deoxygenated blood, whereas the brighter red have oxygenated blood.]]

[[Red blood cell]]s or ''erythrocytes'' primarily carry [[oxygen]] and collect [[carbon dioxide]] through the use of [[hemoglobin]].<ref>{{cite book |last1=Boron |first1=Walter F. |last2=Boulpaep |first2=Emile L. |title=Medical Physiology |date=2017 |publisher=Elsevier |location=Philadelphia |isbn=978-0-323-42796-8 |page=434 |edition=3rd}}</ref> Hemoglobin is an [[iron]]-containing protein that gives red blood cells their color and facilitates transportation of [[oxygen]] from the [[lung]]s to tissues and [[carbon dioxide]] from tissues to the lungs to be exhaled.<ref>{{Cite web |author=Basic Biology |date=2015 |title=Blood cells |url=https://basicbiology.net/micro/cells/blood |website=basicbiology.net}}</ref> Red blood cells are the most abundant cell in the blood, accounting for about 40–45% of its volume. Red blood cells are circular, biconcave, disk-shaped and deformable to allow them to squeeze through narrow capillaries. They do not have a nucleus. Red blood cells are much smaller than most other human cells.

RBCs are formed in the red bone marrow from [[hematopoietic stem cell]]s in a process known as [[erythropoiesis]]. In adults, about 2.4 million RBCs are produced each second. The normal RBCs count is 4.5 to 5 millions per cu.mm. RBCs have a lifespan of approximately 100-120 days. After they have completed their lifespan, they are removed from the bloodstream by the [[spleen]].

Mature red blood cells are unique among cells in the human body in that they lack a nucleus (although [[erythroblasts]] do have a nucleus).

The condition of having too few red blood cells is known as [[anemia]], while having too many is [[polycythemia]].

Erythrocyte sedimentation rate (ESR) is the rate at which RBCs sink to the bottom (when placed in a vertical column after adding an anticoagulant). Normal values of ESR are:

•  3 to 5 mm per hour in males.

•  4 to 7 mm per hour in females.