The urinogenital system of pigeons includes excretory and reproductive organs that are closely connected structurally. The excretory system includes paired kidneys and ureters. Adult pigeons lack a urinary bladder to reduce weight for flight. The reproductive system is sexually dimorphic. In males it includes paired testes that produce sperm and vas deferens, while in females it includes a left ovary and oviduct that produces eggs. During development and egg-laying, these organs undergo changes regulated by hormones to carry out their excretory and reproductive functions.

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.

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

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

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

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

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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