Editing Blood (section)

===Cell production and degradation===
In vertebrates, the various cells of blood are made in the [[bone marrow]] in a process called [[hematopoiesis]], which includes [[erythropoiesis]], the production of red blood cells; and [[myelopoiesis]], the production of white blood cells and platelets. During childhood, almost every human bone produces red blood cells; as adults, red blood cell production is limited to the larger bones: the bodies of the vertebrae, the breastbone (sternum), the ribcage, the pelvic bones, and the bones of the upper arms and legs. In addition, during childhood, the [[thymus]] gland, found in the [[mediastinum]], is an important source of [[T lymphocytes]].<ref>{{cite book |last1=Williams |first1=Peter W. |url=https://archive.org/details/graysanatomy0000gray_m7a1 |title=Gray's anatomy |last2=Gray |first2=Henry David |publisher=C. Livingstone |year=1989 |isbn=978-0-443-02588-4 |edition=37th |location=New York |url-access=registration |name-list-style=vanc}}</ref>
The proteinaceous component of blood (including clotting proteins) is produced predominantly by the [[liver]], while hormones are produced by the [[endocrine gland]]s and the watery fraction is regulated by the [[hypothalamus]] and maintained by the [[kidney]].

Healthy [[erythrocytes]] have a plasma life of about 120 days before they are degraded by the [[spleen]], and the [[Kupffer cells]] in the liver. The liver also clears some proteins, lipids, and amino acids. The kidney actively secretes waste products into the [[urine]].