Editing Common ostrich (section)

===Respiration===
====Anatomy====
[[File:Ostrich Respiratory Anatomy.svg|thumb|Diagrammatic location of the air sacs]]
 
Morphology of the common ostrich [[lung]] indicates that the structure conforms to that of the other [[bird anatomy|avian species]], but still retains parts of its primitive [[ratite]] structure.<ref name=Makanya /> The opening to the respiratory pathway begins with the [[larynx|laryngeal]] cavity lying posterior to the [[posterior nasal apertures|choanae]] within the [[Mouth|buccal cavity]].<ref name=Deeming /> The tip of the tongue then lies [[anatomical terms of location|anterior]] to the choanae, excluding the nasal respiratory pathway from the buccal cavity.<ref name=Deeming /> The trachea lies [[Anatomical terms of location|ventrally]] to the cervical vertebrae extending from the [[larynx]] to the [[Syrinx (bird anatomy)|syrinx]], where the trachea enters the [[thorax]], dividing into two primary [[bronchus|bronchi]], one to each lung, in which they continue directly through to become mesobronchi.<ref name=Deeming /> Ten different air sacs attach to the lungs to form areas for respiration.<ref name=Deeming /> The most [[Anatomical terms of location|posterior]] [[air sacs]] (abdominal and post-thoracic) differ in that the right abdominal air sac is relatively small, lying to the right of the [[mesentery]], and [[Anatomical terms of location|dorsally]] to the liver.<ref name=Deeming /> While the left abdominal air sac is large and lies to the left of the mesentery.<ref name=Deeming /> The connection from the main mesobronchi to the more [[Anatomical terms of location|anterior]] air sacs including the [[clavicle|interclavicular]], lateral clavicular, and pre-thoracic sacs known as the ventrobronchi region. While the [[Anatomical terms of location|caudal]] end of the mesobronchus branches into several dorsobronchi. Together, the ventrobronchi and dorsobronchi are connected by intra-pulmonary airways, the [[bird anatomy|parabronchi]], which form an arcade structure within the lung called the paleopulmo. It is the only structure found in primitive birds such as ratites.<ref name=Deeming />
[[File:Struthio_syrinx.jpg|thumb|The syrinx has simple muscles. The only sounds that can be produced are roars and hisses.]]
The largest air sacs found within the respiratory system are those of the post-thoracic region, while the others decrease in size respectively, the interclavicular (unpaired), abdominal, pre-thoracic, and lateral clavicular sacs.<ref name=Schmidt-Nielsen /> The adult common ostrich lung lacks connective tissue known as interparabronchial septa, which render strength to the non-compliant avian lung in other bird species. Due to this the lack of connective tissue surrounding the parabronchi and adjacent parabronchial lumen, they exchange blood capillaries or [[blood vessel|avascular]] epithelial plates.<ref name=Makanya /> Like mammals, ostrich lungs contain an abundance of type II cells at gas exchange sites; an adaptation for preventing lung collapse during slight volume changes.<ref name=Makanya />

====Function====
The common ostrich is an [[endotherm]] and maintains a body temperature of {{cvt|38.1|-|39.7|C}} in its extreme living temperature conditions, such as the heat of the savanna and desert regions of Africa.<ref name=King/> The ostrich utilizes its respiratory system via a costal pump for ventilation rather than a [[thoracic diaphragm|diaphragmatic pump]] as seen in most mammals.<ref name=Deeming/> Thus, they are able to use a series of air sacs connected to the [[bird anatomy|lungs]]. The use of air sacs forms the basis for the three main avian respiratory characteristics:
# Air is able to flow continuously in one direction through the lung, making it more efficient than the mammalian lung. 
# It provides birds with a large residual volume, allowing them to breathe much more slowly and deeply than a mammal of the same body mass. 
# It provides a large source of air that is used not only for gaseous exchange, but also for the transfer of heat by evaporation.<ref name=Deeming/>

[[File:Struthio camelus portrait Whipsnade Zoo.jpg|frameless|right|alt=Ostrich portrait showing its large eyes and long eyelashes, its flat, broad beak, and its nostrils]]

Inhalation begins at the mouth and the nostrils located at the front of the beak. The air then flows through the anatomical dead space of a highly vascular trachea ({{circa}} {{cvt|78|cm}}) and expansive bronchial system, where it is further conducted to the posterior air sacs.<ref name=zool241/> Air flow through the [[bird anatomy|parabronchi]] of the paleopulmo is in the same direction to the dorsobronchi during inspiration and expiration. Inspired air moves into the respiratory system as a result of the expansion of thoraco abdominal cavity; controlled by [[bird anatomy|inspiratory muscles]]. During expiration, oxygen poor air flows to the anterior air sacs<ref name=Schmidt-Nielsen/> and is expelled by the action of the [[bird anatomy|expiratory muscles]]. The common ostrich air sacs play a key role in respiration, since they are capacious, and increase surface area (as described by the [[Fick Principle]]).<ref name=zool241/> The oxygen rich air flows [[wikt:unidirectional|unidirectionally]] across the respiratory surface of the lungs; providing the blood that has a crosscurrent flow with a high concentration of oxygen.<ref name=zool241/>

To compensate for the large "dead" space, the common ostrich trachea lacks valves to allow faster inspiratory air flow.<ref name=MainaSingh/> In addition, the [[lung volumes|total lung capacity]] of the respiratory system, (including the lungs and ten air sacs) of a {{cvt|100|kg}} ostrich is about {{cvt|15|L|cuin}}, with a [[tidal volume]] ranging from {{cvt|1.2|-|1.5|L|cuin}}.<ref name=Schmidt-Nielsen/><ref name=MainaSingh>{{Cite journal 
| last1 = Maina | first1 = J.N. 
| last2 = Singh | first2 = P. 
| last3 = Moss  | first3 = E.A. 
| doi = 10.1016/j.resp.2009.09.011 
| title = Inspiratory aerodynamic valving occurs in the ostrich, ''Struthio camelus'', lung: A computational fluid dynamics study under resting unsteady state inhalation 
| journal = Respiratory Physiology & Neurobiology 
| volume = 169 
| issue = 3 
| pages = 262–270 
| year = 2009 
| pmid = 19786124 
| s2cid = 70939 
}}</ref> The tidal volume is seen to double resulting in a 16-fold increase in ventilation.<ref name=Deeming/> Overall, ostrich respiration can be thought of as a high velocity-low pressure system.<ref name=Schmidt-Nielsen/> At rest, there is a small pressure difference between the ostrich air sacs and the atmosphere, suggesting simultaneous filling and emptying of the air sacs.<ref name=MainaSingh/>

The increase in respiration rate from the low range to the high range is sudden and occurs in response to [[hyperthermia]]. Birds lack sweat glands, so when placed under stress due to heat, they heavily rely upon increased evaporation from the respiratory system for heat transfer. This rise in [[respiration rate]] however is not necessarily associated with a greater rate of oxygen consumption.<ref name=Deeming/> Therefore, unlike most other birds, the common ostrich is able to dissipate heat through panting without experiencing [[respiratory alkalosis]] by modifying ventilation of the respiratory medium. During [[hyperpnea]] ostriches pant at a respiratory rate of 40–60&nbsp;cycles per minute, versus their resting rate of 6–12&nbsp;cycles per minute.<ref name=Schmidt-Nielsen/> Hot, dry, and moisture lacking properties of the common ostrich respiratory medium affect oxygen's diffusion rate ([[Henry's Law]]).<ref name=zool241>{{cite book |last1=Hill |first1=W.R. |last2=Wyse |first2=A.G. |last3=Anderson |first3=M. |name-list-style=amp |year=2012 |title=Animal Physiology |edition=3rd |publisher=Sinauer Associates |place=Sunderland, MA}}{{page needed|date=November 2013}}</ref>

Common ostriches develop via [[Angiogenesis|Intussusceptive angiogenesis]], a mechanism of [[blood vessel]] formation, characterizing many organs.<ref name=Makanya/> It is not only involved in vasculature expansion, but also in angioadaptation<ref>{{cite journal |pmid=12270956 |year=2002 |last1=Zakrzewicz |first1=A. |last2=Secomb |first2=T.W. |last3=Pries |first3=A.R. |title=Angioadaptation: Keeping the vascular system in shape |volume=17 |issue=5 |pages=197–201 |journal=News in Physiological Sciences |doi=10.1152/nips.01395.2001 }}</ref> of vessels to meet physiological requirements.<ref name=Makanya /> The use of such mechanisms demonstrates an increase in the later stages of [[lung]] development, along with elaborate parabronchial [[vasculature]], and reorientation of the [[gas exchange]] blood capillaries to establish the crosscurrent system at the blood-gas barrier.<ref name=Makanya/> The [[blood-air barrier|blood–gas barrier]] (BGB) of their lung tissue is thick. The advantage of this thick barrier may be protection from damage by large volumes of blood flow in times of activity, such as running,<ref name=Maina/> since air is pumped by the air sacs rather than the lung itself. As a result, the [[capillaries]] in the parabronchi have thinner walls, permitting more efficient gaseous exchange.<ref name=Deeming/> In combination with separate pulmonary and systemic circulatory systems, it helps to reduce stress on the BGB.<ref name=Makanya/>