Editing Giraffe (section)

===Internal systems===
[[File:GiraffaRecurrEn.svg|thumb|right|alt=Sketch of the path of the recurrent laryngeal nerve in giraffe|Scheme of path of the recurrent laryngeal nerve in giraffe]]

In mammals, the left [[recurrent laryngeal nerve]] is longer than the right; in the giraffe, it is over {{cvt|30|cm}} longer. These nerves are longer in the giraffe than in any other living animal;<ref name="Wedel">{{Cite journal|author=Wedel, M. J.|year=2012|title=A monument of inefficiency: the presumed course of the recurrent laryngeal nerve in sauropod dinosaurs|journal=[[Acta Palaeontologica Polonica]] |volume=57 |issue=2 |pages=251–256 |doi=10.4202/app.2011.0019|s2cid=43447891 |doi-access=free |archive-date=29 October 2013 |url-status=live |url=http://www.app.pan.pl/archive/published/app57/app20110019.pdf |archive-url=https://web.archive.org/web/20131029184627/http://www.app.pan.pl/archive/published/app57/app20110019.pdf}}</ref> the left nerve is over {{cvt|2|m}} long.<ref>{{cite book|author=Harrison, D. F. N. |year=1995 |title=The Anatomy and Physiology of the Mammalian Larynx|publisher=Cambridge University Press |page=165 |isbn=978-0-521-45321-9}}</ref> Each nerve cell in this path begins in the [[brainstem]] and passes down the neck along the [[vagus nerve]], then branches off into the recurrent laryngeal nerve which passes back up the neck to the larynx. Thus, these nerve cells have a length of nearly {{cvt|5|m}} in the largest giraffes.<ref name=Wedel/> Despite its long neck and large skull, the [[brain]] of the giraffe is typical for an ungulate.<ref>{{cite journal |author1=Graïc, J.-M.|author2=Peruffo, A. |author3=Ballarin, C.|author4=Cozzi, B. |year=2017|title=The brain of the giraffe (''Giraffa camelopardalis''): surface configuration, encephalization quotient, and analysis of the existing literature|journal=The Anatomical Record |volume=300 |issue=8 |pages=1502–1511 |doi=10.1002/ar.23593 |pmid=28346748 |s2cid=3634656|doi-access=free}}</ref> Evaporative heat loss in the nasal passages keep the giraffe's brain cool.<ref name=Mitchell2004/> The shape of the skeleton gives the giraffe a small [[lung]] volume relative to its mass. Its long neck gives it a large amount of [[Dead space (physiology)|dead space]], though this is limited by its narrow windpipe. The giraffe also has a high [[tidal volume]], so the balance of dead space and tidal volume is much the same as other mammals. The animal can still provide enough oxygen for its tissues, and it can increase its [[Breathing|respiratory]] rate and oxygen diffusion when running.<ref name=SkinnerJD2011>{{Cite journal |author1=Skinner, J. D.|author2= Mitchell, G.|year= 2011|title=Lung volumes in giraffes, ''Giraffa camelopardalis'' |journal=Comparative Biochemistry and Physiology A |volume=158 |issue=1 |pages=72–78 |doi=10.1016/j.cbpa.2010.09.003 |pmid=20837156 |url=http://137.215.9.22/bitstream/handle/2263/16472/Mitchell_Lung(2011).PDF?sequence=1 |hdl=2263/16472|hdl-access= free|access-date= 27 November 2011|archive-date=20 November 2018 |url-status=live |archive-url=https://web.archive.org/web/20181120033132/https://137.215.9.22/bitstream/handle/2263/16472/Mitchell_Lung(2011).PDF?sequence=1}}</ref>
[[File:Flickr - Rainbirder - Reticulated Giraffe drinking.jpg|thumb|left|[[Reticulated giraffe]] bending down to drink in Kenya. The circulatory system is adapted to deal with blood flow rushing down its neck.|alt=Photograph of a giraffe bending down to drink]]
The giraffe's [[circulatory system]] has several adaptations to compensate for its great height.<ref name=Holmes>{{cite magazine |last1=Holmes |first1=B. |title=Heads up! The cardiovascular secrets of giraffes |magazine=Knowable Magazine |date=2021 |doi=10.1146/knowable-051821-2 |s2cid=236354545 |doi-access=free |url=https://knowablemagazine.org/article/living-world/2021/heads-up-cardiovascular-secrets-giraffes |access-date=1 August 2022 |archive-date=6 July 2022 |archive-url=https://web.archive.org/web/20220706111325/https://knowablemagazine.org/article/living-world/2021/heads-up-cardiovascular-secrets-giraffes |url-status=live}}</ref> Its {{cvt|25|lb|kg|order=flip}} and {{cvt|2|ft|cm|order=flip|-1}} [[heart]] must generate approximately double the blood pressure required for a human to maintain blood flow to the brain. As such, the wall of the heart can be as thick as {{cvt|7.5|cm}}.<ref name="Prothero 2003"/> Giraffes have relatively high heart rates for their size, at 150 beats per minute.<ref name=anatomy/>{{rp|76}} When the animal lowers its head, the blood rushes down fairly unopposed and a [[rete mirabile]] in the upper neck, with its large [[Cross section (geometry)|cross-sectional]] area, prevents excess blood flow to the brain. When it raises again, the blood vessels constrict and push blood into the brain so the animal does not faint.<ref>{{cite journal|author1=Mitchell, G. |author2=Skinner, J. D. |year=1993|title=How giraffe adapt to their extraordinary shape |journal=[[Transactions of the Royal Society of South Africa]]|volume=48|issue=2 |pages=207–218 |doi=10.1080/00359199309520271|bibcode=1993TRSSA..48..207M }}</ref> The [[jugular vein]]s contain several (most commonly seven) valves to prevent blood flowing back into the head from the [[inferior vena cava]] and [[right atrium]] while the head is lowered.<ref>{{cite journal |doi=10.3957/056.039.0210 |author1=Mitchell, G.|author2=van Sittert, S. J.|author3=Skinner, J. D. |title=The structure and function of giraffe jugular vein valves |journal=South African Journal of Wildlife Research |volume=39 |issue=2|pages=175–180 |url=http://137.215.9.22/bitstream/handle/2263/13994/Mitchell_Structure(2009).pdf?sequence=1 |year=2009 |hdl=2263/13994 |s2cid=55201969 |hdl-access=free|access-date=21 November 2011|archive-date=20 November 2018|archive-url=https://web.archive.org/web/20181120033146/https://137.215.9.22/bitstream/handle/2263/13994/Mitchell_Structure(2009).pdf?sequence=1|url-status=live}}</ref> Conversely, the blood vessels in the lower legs are under great pressure because of the weight of fluid pressing down on them. To solve this problem, the skin of the lower legs is thick and tight, preventing too much blood from pouring into them.<ref name=MacDonald/>

Giraffes have [[Esophagus|oesophageal muscles]] that are strong enough to allow regurgitation of food from the stomach up the neck and into the mouth for [[wikt:ruminate|rumination]].<ref name=anatomy/>{{rp|78}} They have [[Ruminant#Digestive system of ruminants|four-chambered stomachs]], which are adapted to their specialized diet.<ref name=Dagg1971/> The [[intestine]]s of an adult giraffe measure more than {{cvt|70|m}} in length and have a relatively small ratio of [[small intestine|small]] to [[large intestine]].<ref name="PerezEtAl2009">{{cite journal |author1=Pérez, W. |author2=Lima, M. |author3=Clauss, M. |year=2009 |title=Gross anatomy of the intestine in the giraffe (''Giraffa camelopardalis'') |url=https://www.zora.uzh.ch/id/eprint/24084/5/P%C3%A9rez_giraffe_intestine_AHE_revised-1.pdf |archive-url=https://web.archive.org/web/20180722150740/http://www.zora.uzh.ch/id/eprint/24084/5/P%C3%A9rez_giraffe_intestine_AHE_revised-1.pdf |archive-date=22 July 2018 |url-status=live |journal=Anatomia, Histologia, Embryologia |volume=38 |issue=6 |pages=432–435 |pmid=19681830 |doi=10.1111/j.1439-0264.2009.00965.x|s2cid=28390695}}</ref> The giraffe has a small, compact liver.<ref name=anatomy/>{{rp|76}} In fetuses there may be a small [[gallbladder]] that vanishes before birth.<ref name="Dagg1971"/><ref>{{cite journal |author=Cave, A. J. E. | title=On the liver and gall-bladder of the Giraffe |journal=[[Proceedings of the Zoological Society of London]] |volume=120 |pages=381–93 |year=1950 |doi=10.1111/j.1096-3642.1950.tb00956.x | issue=2}}</ref><ref>{{cite journal |author1=Oldham-Ott, C. K. |author2=Gilloteaux, J. |title=Comparative morphology of the gallbladder and biliary tract in vertebrates: variation in structure, homology in function and gallstones |journal=[[Microscopy Research and Technique]] |volume=38 |issue=6 |pages=571–579 |year=1997 |doi=10.1002/(SICI)1097-0029(19970915)38:6<571::AID-JEMT3>3.0.CO;2-I |pmid=9330347 |s2cid=20040338}}</ref>