Editing Common ostrich (section)

===Circulation===

====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 />

====Blood composition====

The [[red blood cell]] count per unit volume in the ostrich is about 40% of that of a human; however, the red blood cells of the ostrich are about three times larger than the red blood cells of a human.<ref name=metabolism1>{{Cite journal | last1 = Isaacks | first1 = R. | last2 = Harkness | first2 = D. | last3 = Sampsell | first3 = J. | last4 = Adler | first4 = S. | last5 = Roth | first5 = C. | last6 = Kim | first6 = P. | last7 = Goldman | first7 = R. | doi = 10.1111/j.1432-1033.1977.tb11700.x | title = Studies on Avian Erythrocyte Metabolism. Inositol Tetrakisphosphate: The Major Phosphate Compound in the Erythrocytes of the Ostrich (Struthio camelus camelus) | journal = European Journal of Biochemistry | volume = 77 | issue = 3 | pages = 567–574 | year = 1977 | pmid =  19258| doi-access = free }}</ref> The blood oxygen affinity, known as [[P50 (pressure)|P<sub>50</sub>]], is higher than that of both humans and similar avian species.<ref name=metabolism1 /> The reason for this decreased [[Oxygen–haemoglobin dissociation curve|oxygen affinity]] is due to the hemoglobin configuration found in common ostrich blood.<ref name=metabolism1 /> The common ostrich's [[tetramer]] is composed of [[hemoglobin]] type A and D, compared to typical mammalian tetramers composed of hemoglobin type A and B; hemoglobin D configuration causes a decreased oxygen affinity at the site of the respiratory surface.<ref name=metabolism1 />

During the [[embryo]]nic stage, [[Hemoglobin E]] is present.<ref name=metabolism2>{{Cite journal 
| doi = 10.1016/S0300-9629(76)80046-1 
| last1 = Isaacks | first1 = R. E. 
| last2 = Harkness | first2 = D. R. 
| last3 = Froeman | first3 = G. A. 
| last4 = Goldman | first4 = P. H. 
| last5 = Adler | first5 = J. L. 
| last6 = Sussman | first6 = S. A. 
| last7 = Roth | first7 = S. 
| title = Studies on avian erythrocyte metabolism—II. Relationship between the major phosphorylated metabolic intermediates and oxygen affinity of whole blood in chick embryos and chicks 
| journal = Comparative Biochemistry and Physiology A 
| volume = 53 
| issue = 2 
| pages = 151–156 
| year = 1976 
| pmid = 2411
}}</ref> This subtype increases oxygen affinity in order to transport oxygen across the allantoic membrane of the embryo.<ref name=metabolism2 /> This can be attributed to the high metabolic need of the developing embryo, thus high oxygen affinity serves to satisfy this demand. When the chick hatches hemoglobin E diminishes while hemoglobin A and D increase in concentration.<ref name=metabolism2 /> This shift in hemoglobin concentration results in both decreased oxygen affinity and increased P<sub>50</sub> value.<ref name=metabolism2 />

Furthermore, the P<sub>50</sub> value is influenced by differing organic modulators.<ref name=metabolism2 /> In the typical mammalian RBC 2,3 – DPG causes a lower affinity for oxygen. 2,3- DPG constitutes approximately 42–47%, of the cells phosphate of the embryonic ostrich.<ref name=metabolism2 /> However, the adult ostrich have no traceable 2,3- DPG.In place of 2,3-DPG the ostrich uses inositol [[polyphosphate]]s (IPP), which vary from 1–6 phosphates per molecule.<ref name=metabolism2 /> In relation to the IPP, the ostrich also uses [[Adenosine triphosphate|ATP]] to lower oxygen affinity.<ref name=metabolism2 /> ATP has a consistent concentration of phosphate in the cell<ref name=metabolism2 /> {{endash}} around 31% at [[incubation period]]s and dropping to 16–20% in 36-day-old chicks.<ref name=metabolism2 /> However, IPP has low concentrations, around 4%, of total phosphate concentration in embryonic stages, but the IPP concentration jumps to 60% of total phosphate of the cell.<ref name=metabolism2 /> The majority of phosphate concentration switches from 2,3- DPG to IPP, suggesting the result of the overall low oxygen affinity is due to these varying polyphosphates.<ref name=metabolism2 />

Concerning immunological adaptation, it was discovered that wild common ostriches have a pronounced non-specific immunity defense, with blood content reflecting high values of [[lysosome]] and [[phagocyte]] cells in medium. This is in contrast to domesticated ostriches, who in captivity develop high concentration of [[immunoglobulin]] [[antibodies]] in their circulation, indicating an acquired immunological response. It is suggested that this immunological adaptability may allow this species to have a high success rate of survival in variable environmental settings.<ref name= Cooper/>