3. In all the vertebrates the excretory and reproductive
organs are closely related to each other.
Therefore the two systems together are known as
urino- genital system and the organs as urino-genital
organs.
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4. In Dogfish (Scoliodon), the sexes are separate and the
sexual dimorphism is conspicuous.
The male Scoliodon possesses two cylindrical hollow
copulatory organs, the claspers which are
modifications of pelvic fins.
The claspers are absent in female.
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5. Male Urino-genital Organs:
1. Excretory Organs:
Kidneys
Ureters
Uriogenital sinus
2. Genital organs
Paired testes
Vasa deferentia
Ampullae or Seminal vesicles
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6. kidney
Brownish red, elongated, flattened ribbon shaped
Ophisthonephros kidney- anterior part is reduced
and non functional, posterior part is well
developed and functional
Location- dorsal, deep in trunk region
Attached to dorsal abdominal wall above
peritoneum
Extend from base of liver to side of cloaca
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7. Anterior slender part- genital
kidney
Posterior thick part- renal
kidney.
In male- anterior part is
reduced, non excretory and it
convey genital products –
called epididymis
Posterior part is organ of
excretion
In female- anterior part –
highly atrophied , no
connection with genital organ
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8. Histology of kidney
Each kidney composed of numerous uriniferous
tubules
Tubules- bowman’s capsule and glomerulus at blind
end = Malpighian body
In fishes- glomerulus shows characteristics
mesangial areas –mesangial cells (controls filtration
of plasma in bowman’s capsule
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9. Nusrat Perween, AISC Pune
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Scoliodon: Histology of Kidney
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10. Behind Malpighian body –
coiled renal tubule – neck
(lined with ciliated,
cuboidal epithelial cells ,
proximal segmented distal
segment
Proximal and distal
segment –coiled – form
parallel arrangement
which helps in effective
reabsorption of elements
Last part of tubules –
collecting ducts which lead
to ureter
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11. Ureter
Receives collecting ducts from kidney
Thin tubules
Open in wide chamber- urinogenital sinus
Female- both ureter (Wolffian ducts) join to open
in sinus while genital ducts open separately
In male – ureter take over reproductive function
and in continuation of testes
Therefore accessory urinary duct receives the
collecting tubules from renal corpuscles or
nephrons
Both accessory urinary ducts joint and open in the
urino-genital sinus
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12. Urinogenital sinus
Wide chamber –
posterior end and open
in cloaca at the tip of
short urinogenital
papilla
Urine formation shows
the usual three steps-
ultrafiltration, selective
reabsorption and
tubular secretion
12
13. Rectal gland – whitish yellow gland situated dorsal
to the intestine. Removes excess NaCl from body
fluids
Gills: they also play a minor role of excreting
sodium and chloride ions through the chloride
cells present on the primary lamellae
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16. 1. Testis
Present in trunk dorsal to the gut
Attached to body wall dorsally by a double fold of
peritoneum called the mesorchium
posteriorly with caecal or rectal gland by a non
glandular tissue.
Each testis is ribbon like and extend anteriorly
upto the Leydig gland and posteriorly upto the
end of trunk
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17. Arising from each testis anteriorly
there are numerous fine tubules
called vasa efferentia which
traverse through the mesorchium
towards the anterior end of the
large duct called vas deferens
Each testis can be divided into
anterior two third testis proper
and posterior one third epigonal
or lymphomyeloid organ which
contains abundance granulocytes.
The mature sperms are carried to
the vas deferens
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18. Histology of testis
Each testis is enclosed in thin, connective tissue
capsule and is divided internally into small, oval
compartments by connective tissue strands or
trabeculae.
Inside, there is a region of thin sheets of cells
called the germinal zone from which develop
the spermatocytes.
The spermatocytes contain the sperms in a
particular stage of development and a few Sertoli
cells.
The Sertoli cells provide nutrition to the
developing sperms, may engulf the unused
sperms and produce hormonal secretions.
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19. 2. Vas deferens
large, narrow, very much coiled tube and runs along the
entire ventral surface of the anterior kidneys.
Its anterior part is known as the epididymis. It produces
the fluid which nourishes the sperms.
Along with the epididymis is the Leydig’s gland and
both represent the anterior kidney which is associated
with the male genital system.
The spermatophore are formed in the Leydig’s gland
spermatophore - protein capsule containing a mass of
spermatozoa, transferred during mating
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20. 3. Ampullae or seminal vesicles
Posteriorly, the vasa differentia enlarge to form thin
walled opaque ampullae.
Each ampulla anteriorly gives out a thin walled sac,
the sperm sac.
Both the sperm sacs unite posteriorly and form the
urinogenital sinus.
The ampulla store the spermatophores .
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21. Accessory organs :
1. Claspers
2. Siphon
1. Claspers :
These are paired structures which are the modified
pelvic fins and also called myxoptergium.
They are the accessory reproductive organs.
The claspers are erectile, receive sperms and pass
them to the cloaca of female to ensure internal
fertilization .
In a mature male they measure about 6 cm in
length.
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22. Each clasper is a tube partially open on the dorsal side
forming a triangular groove due to the infolding of the
dorsal skin.
The anterior opening of the groove lies near the cloaca
and called the apopyle while the posterior exit is the
hypopyle which opens on a sharp, pointed style.
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23. 2. Siphon:
On the ventral side of the body, below the skin, there
is a pair of elongated, glandular and muscular sac, the
siphons
They anteriorly extend upto the posterior region of the
pectoral fin and end blindly.
Posteriorly, they open into the groove of claspers.
They force the sea water into the grooves and help
push the spermatophores in the cloaca of female.
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26. Nusrat Perween, AISC Pune 26
1. Ovaries
These are large, yellowish,
lobulated bodies.
They are located in the
abdominal cavity and attached
to the anterior abdominal wall
mid-dorsally by the fold of
peritoneum called
mesovarium,
The surface shows developing
ova.
They extend back from the base
of liver and merge into epigonal
organ.
27. 2. Oviduct
Large tubes extending along
the complete length of the
body
Also known as Mullerian
ducts
Open into the coelom by
zigzag slit like aperture called
ostium or oviducal funnel
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28. 3. Shell gland
Both oviducts enlarge
posteriorly and known as
shell gland
Also known as oviducal or
nidamental gland
Heart shaped
Shows a narrow middle
mucus secreting zone and
posterior large shell
secreting zone
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29. 4. Uterus
Behind the shell gland
each oviduct narrows and
finally dilates posteriorly
into wide uterus
The uteri from both the
sides unites to form a
short vagina
Vagina opens into the
cloaca by a large aperture
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30. The vagina is separate from the cloaca by fold of
mucous membrane which functions as a valve and
closes the aperture between vagina and the cloaca
during the development of the embryo
The mature ova released in the abdominal cavity and
then by the action of the body muscles and beating of
the cilia of the external lining of the visceral organs
They are carried to the oviducal funnel and ultimately
to the oviducts
There is no direct connection between ovaries and
oviducts
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32. Fertilization
Fertilization is internal
Takes place in the section of
oviduct between the oviducal
funnel and shell gland
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33. During copulation the claspers are inserted into cloaca
of the female.
The spermatic fluid is transferred through the grooves
of the claspers into the oviducts.
The siphon sacs force the stored sea water into the
grooves and push the sperms in the body of the female
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34. Scoliodon is ovoviviparous
Development of egg occurs
in uteri and give birth to
living youngs
The fertilized egg or
zygotes descends from the
shell gland into the uterus
The uteri is divide into
compartments as per
number of embryo
34
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35. Uteri is filled with uterine fluid which surrounds the
developing embryo and protect them.
The embryo is enclosed in a thin membrane called egg
case which contains nutritive and protective fluid.
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36. In early stage of development each embryo is provided
with a tubular yolk-stalk which is connected at one
end with the gut of the embryo and other with the
yolk-sac containing yolk for the nourishment of the
young
36
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37. In later stage when the yolk is used up, the yolk-sac
becomes greatly folded and embedded in the uterine wall
to form yolk sac placenta
37
Umbilical cord with
Appendicula
Placenta
Uterine attachment
Uterus
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38. Each embryo develops
villi and fuse with
grooves in yolk-sac this
give rise to simple yolk
sac placenta
Now the embryo receives
nutrient through the
placenta from the
uterine tissue of the
mother
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Scoliodon: Embryo with yolk-sac placenta
39. When the embryo is 3 to 4 mm in size, the primary
yolk sac gets elongated and changes to the placental
cord.
The placental cord produces many finger like
processes called appendicula which absorb the
nutrient from the maternal uterine wall
Each appendiculum consist of central core of loose
connective tissue and many layers of epithelial cells
around it
The gestation period is about 6 month and young
Scoliodon are born
No further parental caring to new born babies
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