Editing Circulatory system (section)

====Capillaries====
Arteries branch into small passages called [[arteriole]]s and then into the [[Capillary|capillaries]].<ref>{{cite web | url =https://www.nhlbi.nih.gov/health/health-topics/topics/hlw/printall-index.html | title =What Are the Lungs? | author =National Institutes of Health | publisher =nih.gov | url-status=dead | archive-url =https://web.archive.org/web/20141004200807/https://www.nhlbi.nih.gov/health/health-topics/topics/hlw/printall-index.html | archive-date =2014-10-04 | author-link =National Institutes of Health }}</ref> The capillaries merge to bring blood into the venous system.<ref>{{cite web | url =https://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20100/Bio%20100%20Lectures/Organ%20Systems/Circulatory%20System/Circulatory%20System.htm | title =The Circulatory System | author =State University of New York | publisher =suny.edu | date =February 3, 2014 | url-status=dead | archive-url =https://archive.today/20140203084650/http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20100/Bio%20100%20Lectures/Organ%20Systems/Circulatory%20System/Circulatory%20System.htm | archive-date =February 3, 2014 | author-link =State University of New York }}</ref> The total length of muscle capillaries in a 70 kg human is estimated to be between 9,000 and 19,000 km.<ref>{{Cite journal |last1=Poole |first1=David C. |last2=Kano |first2=Yutaka |last3=Koga |first3=Shunsaku |last4=Musch |first4=Timothy I. |date=March 2021 |title=August Krogh: Muscle capillary function and oxygen delivery |journal=Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology |language=en |volume=253 |issue=110852 |url=https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC7867635&blobtype=pdf |doi=10.1016/j.cbpa.2020.110852 |pmc=7867635 |pmid=33242636}}</ref>