Editing Capillary (section)

{{Use dmy dates|date=September 2021}}
{{Short description|Smallest type of blood vessel}}
{{About|the blood vessel|the lymphatic vessel|lymph capillary|other uses|capillary (disambiguation)}}
{{Infobox anatomy
| Name        = Capillary
| Latin       = vas capillare<ref name="Terminologica Histologica">{{cite book |author1=Federative International Committee on Anatomical Terminology |title=Terminologia Histologica: International Terms for Human Cytology and Histology |date=2008 |publisher=Lippincott Williams & Wilkins |location=Baltimore |isbn=9780781766104 |page=87}}</ref>
| Image       = Capillary.svg
| Caption     = Diagram of a capillary
| Image2      = Capillary system CERT.jpg
| Caption2    = A simplified illustration of a capillary network
| Precursor   =
| System      = [[Circulatory system]]
| Pronunciation = {{IPAc-en|US|ˈ|k|æ|p|ə|l|ɛr|i}}, {{IPAc-en|UK|k|ə|ˈ|p|ɪ|l|ər|i}}
| Artery      =
| Vein        =
| Nerve       =
| Lymph       =
}}

A '''capillary''' is a small [[blood vessel]], from 5 to 10 [[micrometre]]s in diameter, and is part of the [[microcirculation]] system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the [[tunica intima]] (the innermost layer of an artery or vein), consisting of a thin wall of simple squamous [[endothelial cell]]s.<ref>{{Cite web|title=Structure and Function of Blood Vessels {{!}} Anatomy and Physiology II|url=https://courses.lumenlearning.com/suny-ap2/chapter/structure-and-function-of-blood-vessels/#:~:text=Capillaries%20have%20only%20a%20tunica,smooth%20muscle%20and%20connective%20tissue.|access-date=2021-11-19|website=courses.lumenlearning.com}}</ref> They are the site of the exchange of many substances from the surrounding [[interstitial fluid]], and they convey blood from the smallest branches of the arteries ([[arteriole]]s) to those of the veins ([[venule]]s). Other substances which cross capillaries include water, [[oxygen]], [[carbon dioxide]], [[urea]],<ref>{{cite book |last=Maton |first=Anthea |title=Human Biology and Health |publisher=Prentice Hall |year=1993 |location=Englewood Cliffs, New Jersey |isbn=978-0-13-981176-0 |url-access=registration |url=https://archive.org/details/humanbiologyheal00scho|pages=87, 114, 120}}</ref> [[glucose]], [[uric acid]], [[lactic acid]] and [[creatinine]]. [[Lymph capillaries]] connect with larger [[lymph vessel]]s to drain [[lymph]]atic fluid collected in microcirculation.