User:Anchalkanwar/sandbox

Anatomy: The little information published on the morphology of the ostrich lung indicates that the structure conforms to that of the other avian species, but is designed like that of highly aerobic volant birds. The trachea branches into two primary bronchi, one to each lung, where they continue directly through to become mesobronchi, attaching the most posterior air sacs (abdominal and post-thoracic) to the lungs. The connection from the main mesobronchi to the more anterior air sacs includgin the interclavicular, lateral clavicular, and pre-thoracic sacs known as the ventrobronchi region. The largest air sacs found within the respiratory system of are those of the post-thoracic region, while the others, change with decreasing size, and include the interclavicular(unpaired), abdominal, pre-thoracic, and lateral clavicular sacs. The adult 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 share an exchange in the blood capillary or an avascular epithelial plate.

Function: Intussusceptive angiogenesis is a novel mechanism of blood vessel formation, which has been shown to characterize many organs. It is not only involved in vasculature expansion, but also in angioadaptation of vessels to meet physiological requirements. The use of such mechanisms has demonstrated to increase the later stages of lung development, associated with elaborate parabronchial vasculature, and reorientation of the gas exchange blood capillaries to establish a crosscurrent system at the gas exchange interface.

Kidney Function:

The kidneys and ureters of ostriches are similar to those of other birds. They are chocolate brown in color, granular in texture, and lie in a depression in the pelvic cavity of the dorsal wall. Urine is secreted continuously as it passes down from the ureters to the urodeum. Although there is no bladder, a dilated pouch of ureter stores the urine until discharged.

Ostrich kidneys are fairly large in size, and so are able to hold significant amounts of solutes. Hence, ostriches drink relatively large volumes of water daily, and excrete generous quantities of highly concentrated urine. It is when drinking water is unavailable or withdrawn, that the urine becomes highly concentrated with uric acid and urates. It seems that ostriches who normally drink relatively large amounts of water tend to rely on renal conservation of water when drinking water is scarce within the kidney system. Though there have been no official detailed renal studies conducted on the flow rate (Poiseuille's Law) and composition of the ureteral urine in the ostrich, knowledge of renal function has been based on samples of cloacal urine, and samples or quantitative collections of voided urine. Studies have shown that the amount of water intake, and dehydration impacts the plasma osmolality and urine osmolality within various sized ostriches. During a normal hydration state of the kidneys, young ostriches tend to have a measured plasma osmolality of 284 mOsm, and urine osmolality of 62 mOsm. Adults have higher rates with a plasma osmolality of 330 mOsm, and a urine osmolality of 163 mOsm. The osmolality of both plasma and urine can alter in regards to whether there is an excess or depleted amount of water present within the kidneys. An interesting fact of ostriches is that when water is freely available, the urine osmolality can reduce to 60–70 mOsm, not losing any necessary solutes from the kidneys when excess water is excreted. Dehydrated or salt-loaded ostriches can reach a maximal urine osmolality of approximately 800 mOsm. When the plasma osmolality has been measured simultaneously with the maximal osmotic urine, it is seen that the urine:plasma ratio is 2.6:1, the highest encountered among avian species. Along with dehydration, there is also a reduction in flow rate from 20 L/day to only a mere 0.3-0.5 L/day.

In mammals such as ostriches, the increase of the glomerular filtration rate (GFR) and urine flow rate (UFR) is due to a high protein diets. As seen in various studies, scientists have measured clearance of creatinine, a fairly reliable marker of glomerular filtration rate (GFR). It has been seen that during normal hydration within the kidneys, the glomerular filtration rate is approximately 92 ml/min. However, when an ostrich experiences dehydration for at least 48 hours (2 days), this value diminishes to only a mere 25% of the hydrated GFR rate. Thus in response to the dehydration, ostrich kidneys secrete small amounts of very viscous glomerular filtrates that have not been broken down, and return them to the circulatory system through blood vessels. The reduction of GFR during dehydration is extremely high, and so the fractional excretion of water (urine flow rate as a percentage of GFR) drops down from 15% at normal hydration to 1% during dehydration.