Editing Perch (section)

=== Internal anatomy ===
The [[esophagus]] is a flexible tube that goes from the mouth to the stomach. The [[stomach]] is connected to the intestine via the [[pyloric sphincter]].<ref name=":1" /> The [[intestines]] of perch consist of the [[small intestine]] and [[large intestine]]; the intestines have many [[Pyloric caecae|pyloric caeca]] and a [[Spiral valve|spiral value]], the small intestine consists of a part called the [[duodenum]]. The [[spleen]] is located after the stomach and before the spiral value. The spleen is connected to the [[circulatory system]], not part of the [[digestive tract]]. The [[liver]] is composed of three lobes: one small lobe (includes the gall bladder) and two large lobes. Perch have long and narrow [[kidney]]s that contain clusters of [[nephron]]s which empty into the [[mesonephric duct]].<ref name=":02">{{Cite book |last1=Parker | first1=Blair | first2= Wakee | last2= McKenzie |url= https://www.worldcat.org/oclc/1132388392 |title=Origin and Evolution of Vertebrates |date=2019 |publisher=EDTECH |isbn= 978-1-83947-454-5 |oclc=1132388392}}</ref> They have a two-chambered [[heart]] consisting of four compartments: the [[Sinus venosus|sinus venous]], one [[Atrium (heart)|atrium]], one [[Ventricle (heart)|ventricle]], and [[Infundibulum (heart)|conus]].<ref name=":11">{{Cite journal |last=Randall |first=D. J. |date=1968-05-01 |title=Functional Morphology of the Heart in Fishes |journal=American Zoologist |volume=8 |issue=2 |pages=179–189 |doi=10.1093/icb/8.2.179 |pmid=5738636 |issn=0003-1569|doi-access=free }}</ref> Perch have a [[swim bladder]] that helps control [[buoyancy]] or floating within the water, the swim bladder is only found in bony fish. In perch, the duct connecting the swim bladder to the [[pharynx]] is closed so air is unable to pass through from the mouth, these fish are called [[Physoclistic|''physoclists'']]. Specifically in perch, the gas bladder can vary from 12% to 25% of [[oxygen]] and 1.4% to 2.9% of [[carbon dioxide]] gas.<ref>{{Cite book |last1= Chiasson| first1= Robert |first2= William J. | last2= Radke |url=http://worldcat.org/oclc/640832481 |title=Laboratory anatomy of the perch |date=1991 |publisher=Wm. C. Brown |oclc=640832481}}</ref> Perch [[Reproductive organs of fish|reproductive organs]] include either a pair of [[testes]] (sperm-producing) or a pair of [[Ovary|ovaries]] (egg-producing).<ref name=":02" /> [[File:Oste082p labelled.png|thumb|The above picture is a labeled image of the internal anatomy of the species Perch Perca flavescens. Each letter corresponds to an internal body part, A: gills, B: auricle of the heart, C: ventricle of the heart, D: liver, E: stomach, F: digestive cecum, G: swim bladder, H: intestine, I: testis, and J: urinary bladder.<ref>{{Citation |last=Houseman |first=Jon |title=English: Internal Anatomy of the Perch Perca flavescens. |date=2013-05-22 |url=https://commons.wikimedia.org/wiki/File:Oste082p_labelled.png |access-date=2022-05-10}}</ref>]]