Editing Common ostrich (section)

====Heart anatomy====

The common ostrich heart is a closed system, contractile chamber. It is composed of [[myogenic]] muscular tissue associated with heart contraction features. There is a double circulatory plan in place possessing both a [[pulmonary circuit]] and systemic circuit.<ref name=zool241 />

The common ostrich's heart has similar features to other avian species, like having a [[Cone|conically]] shaped heart and being enclosed by a [[Fibrous pericardium|pericardium]] layer.<ref name=heartanatomy>{{cite journal|author=Tadjalli, M.|author2=Ghazi, S. R.|author3=Parto, P.|name-list-style=amp|url=http://ijvr.shirazu.ac.ir/article_1084_16026a1de1a104067949c765dc03ca9f.pdf|year=2009|title=Gross anatomy of the heart in Ostrich (''Struthio camelus'')|journal=Iran J. Vet. Res.|volume=10|issue=1|pages=21–7|access-date=17 March 2017|archive-date=18 March 2017|archive-url=https://web.archive.org/web/20170318004059/http://ijvr.shirazu.ac.ir/article_1084_16026a1de1a104067949c765dc03ca9f.pdf|url-status=dead}}</ref> Moreover, similarities also include a larger [[right atrium]] volume and a thicker [[left ventricle]] to fulfil the [[Circulatory system|systemic circuit]].<ref name=heartanatomy /> The ostrich heart has three features that are absent in related birds: 
# The right [[Heart valve|atrioventricular valve]] is fixed to the [[interventricular septum]], by a thick muscular stock, which prevents back-flow of blood into the atrium when [[Cardiac cycle|ventricular systole]] is occurring.<ref name=heartanatomy /> In the [[fowl]] this valve is only connected by a short septal attachment.<ref name=heartanatomy /> 
# [[Pulmonary vein]]s attach to the left atrium separately, and also the opening to the pulmonary veins are separated by a septum.<ref name=heartanatomy /> 
# [[Septomarginal trabecula|Moderator bands]], full of [[Purkinje fibers]], are found in different locations in the left and right ventricles.<ref name=heartanatomy /> These bands are associated with contractions of the heart and suggests this difference causes the left ventricle to contract harder to create more pressure for a completed circulation of blood around the body.<ref name=heartanatomy />

The [[atrioventricular node]] position differs from other fowl. It is located in the [[endocardium]] of the atrial surface of the right atrioventricular valve. It is not covered by connective tissue, which is characteristic of vertebrate heart anatomy. It also contains fewer [[myofibrils]] than usual myocardial cells. The AV node connects the atrial and ventricular chambers. It functions to carry the electrical impulse from the atria to the ventricle. Upon view, the myocardial cells are observed to have large densely packed chromosomes within the nucleus.<ref name =Parto/>

The [[Coronary circulation|coronary]] [[arteries]] start in the right and left aortic sinus and provide blood to the heart muscle in a similar fashion to most other vertebrates.<ref name =Henriquez/> Other domestic birds capable of flight have three or more [[Coronary circulation|coronary]] arteries that supply blood to the heart muscle. The blood supply by the coronary arteries are fashioned starting as a large branch over the surface of the heart. It then moves along the [[coronary groove]] and continues on into the tissue as [[Ventricle (heart)|interventricular]] branches toward the [[apex of the heart]]. The [[atrium (heart)|atria]], [[ventricle (heart)|ventricle]]s, and [[septum]] are supplied of blood by this modality. The deep branches of the coronary arteries found within the heart tissue are small and supply the interventricular and right [[atrioventricular node|atrioventricular]] valve with blood nutrients for which to carry out their processes. The interatrial artery of the ostrich is small in size and exclusively supplies blood to only part of the left auricle and interatrial [[septum]].<ref name =Bezuidenhout/><ref name =Bezuidenhout2/>

These [[Purkinje fibers]] (p-fibers) found in the hearts moderator bands are a specialized cardiac muscle fiber that causes the heart to contract.<ref name=purkinje>{{cite journal|author=Parto, P.|author2=Tadjalli, M.|author3=Ghazi, S. R.|author4=Salamat, M. A.|name-list-style=amp|year=2013|title=Distribution and Structure of Purkinje Fibers in the Heart of Ostrich (''Struthio camelus'') with the Special References on the Ultrastructure|journal= International Journal of Zoology|doi=10.1155/2013/293643|volume=2013|pages=1–6|doi-access=free}}</ref> The Purkinje cells are mostly found within both the endocardium and the sub-endocardium.<ref name=purkinje /> The [[sinoatrial node]] shows a small concentration of Purkinje fibers, however, continuing through the [[Electrical conduction system of the heart|conducting pathway]] of the heart the [[bundle of his]] shows the highest amount of these Purkinje fibers.<ref name=purkinje />