Urinogenital system of pigeon

Excretory and Reproductive System

1. Urino -genital System of Pigeon

2. Urinogenital System of Pigeon The excretory and reproductive organs of pigeon are very closely connected with each other structurally, so are studied together under the heading urinogenital system. But, both systems, that are, excretory and reproductive, are physiologically independent, so should be studied separately as follows

3. Excretory System The excretory system of pigeon includes pair of kidneys and pair of ureter The urinary bladder is absent in adults to reduce the body weight (flight adaptation ) Among birds, ostrich only has the urinary bladder

4. 1) Kidneys : The main excretory organs of pigeon (birds) are paired, dark brown, flattened, three-lobed metanephric kidneys. A small yellowish, elongated and streak-like adrenal body lies attached ventrally to the anterior lobe of each kidney. It is an endocrine gland . Each kidney consists of masses of numerous tightly packed, convoluted uriniferous tubules . Birds have comparatively more tubules than those of mammals Each uriniferous tubule has small glomerulus and a specialized portion, called the loop of Henle Loops of Henle are long The glomerulus filters the blood and filtrate passes through the long loop, where much of its water is reabsorbed. T hus , much concentrated urine passes down the ureter

5. 2) Ureter : Uriniferous tubules of each kidney unite to form a ureter or metanephric duct. The ureter is a narrow, straight tube, arising ventrally from the anterior lobe of the kidney and running backwards to open into the middle compartment of the cloaca , the urodaeum , through its dorsal wall . Physiology of Excretion The excretory system is highly specialized for water-saving. The birds are urecotelic like reptiles, because in them the end product of urinary excretion is relatively insoluble uric acid which is synthesized in liver. Semisolid viscous urine comes from the kidneys into the urodaeum from where it passes up into the coprodaeum and large intestine, where further water is resorbed and the mixed faeces and urinary products are then excreted as the characteristic semisolid white guano. Birds also excrete salt by nasal glands, especially well developed in marine forms.

6. Male Reproductive System Sexes are separate and sexual dimorphism is absent in pigeon. The male reproductive organs of pigeon are testes and vasa deferentia and there occurs no penis like mammals. Ostrich and ducks only have an erectile penis.

7. Testes: Two oval and white testes, each attached to the anterior end of a kidney by mesorchium . The right testis is slightly smaller than the left. The testes increase many times in size during the breeding season. The weight of testis is about 1000 times greater in the breeding season than it is in the non-breeding period, when it contains only spermatogonia . Both testes have masses of coiled seminiferous tubules with groups of interstitial cells between them. The cells of lining epithelium of seminiferous tubules produce spermatozoa by undergoing spermatogenesis. The interstitial cells are also called Leydig cells and produce sex hormone testosterone. The seminiferous tubules join to form a long epididymis . The testes are permanently retained within the body cavity.

8. Vasa Deferentia : From the inner border of each testis arises a convoluted Wolffian or mesonephric duct, its anterior end is an epididymis and the rest is a vas deferens . The epididymis is connected with the seminiferous tubules of the testis by extremely fine tubules, the vasa efferentia . Vas deferens runs backwards along the outer side and parallel to the ureter of that side to open into the urodaeum on a very small erectile papilla posterior to the ureter It is the only copulatory organ of most birds . For temporary storage of spermatozoa, the hind end of each vas deferens becomes swollen, called the seminal vesicle There is no copulatory organ in pigeon

9. Female Reproductive Organs: The adult female has only the left ovary and left oviduct as main reproductive organs. In the embryo there are two ovaries and two oviducts, but during development, the ovary and oviduct of right side become more or less completely atrophied.

10. Ovary: A large-sized, irregular-shaped left ovary occurs at the ventral side of anterior lobe of left kidney. During breeding season, the size of the ovary increases considerably due to the influence of FSH and LH of anterior pituitary. The ovary secretes estrogen which modifies the accessory sexual organs and behavior. The surface of ovary remains filled with numerous follicles or ovisacs of different sizes and each contains a single ovum or oocyte . The ova are at various stages of development. These follicles project from the surface of the ovary in birds. Of the large number of oocytes only few ripen to make the large follicles. Each follicle produces a large yolky ovum which when mature escapes by the rupture of the follicle into the coelom . After each follicle has bursted it quickly regresses. There is no corpus luteum . The released ova in the coelom are caught by the enlarged ciliated and muscular funnel of the oviduct. Ovulation depends on the cyclic release of luteinizing hormone (LH).

11. Oviduct: The left oviduct ( Mullerian duct) is a long, broad, thick-walled, convoluted tube passing backwards to the cloaca . The oviduct anteriorly has an expanded muscular and ciliated coelomic funnel or ostium or infundibulum with fimbriated margin. It opens by a wide, slit-like aperture into the coelom near the ovary. The oviduct has various parts. As an ovum enters the ostium and passes down, the walls of ostium secrete the thin chalaziferous layer of dense albumen around the egg. The succeeding part of the oviduct, called glandular part or magnum, has tubular glands which secrete the albumen or egg white. The magnum is followed by isthmus which secretes a parchment-like double shell membranes around the albumen . The next portion is called uterus. Uterus is thin walled and is lined by nidamental glands which form an outer hard calcareous shell around the shell membranes. The last portion of oviduct is vagina which is muscular, thick-walled and contains mucus secreting unicellular glands which secrete pigment, external cuticular layer of the cell and mucus for expelling the egg. The oviduct opens into urodaeum or c loaca .

12. Cloaca : It is the terminal part of alimentary canal and urino -genital system. It is common opening for rectum, ureter and genital ducts. It opens to outside as cloacal aperture.

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