The document discusses the development and anatomy of the genital systems in vertebrates, highlighting the embryonic origins of reproductive organs and the roles of different ducts such as mesonephric and paramesonephric ducts. It details the structure and function of gonads, oviducts, and the male and female genital ducts across various vertebrate classes, including fishes, amphibians, reptiles, birds, and mammals. The text emphasizes the complex differentiation processes influenced by genetic and hormonal factors that lead to the formation of reproductive systems prone to abnormalities.

1. Genital system in vertebrates
(Vertebrate Kidneys and Ducts)
Dr. P.B.Reddy
M.Sc,M.Phil,Ph.D, FIMRF,FICER,FSLSc,FISZS,FISQEM
PG DEPARTMENT OF ZOOLOGY
GOVERTNAMENT PG COLLEGE, RATLAM.M.P
reddysirr@gmail.com

3. Introduction: The male and female reproductive systems develop initially
embryonically "indifferent", it is the product of the Y chromosome SRY gene
that makes the "difference".
♂ - Male ♀ - Female
The reproductive organs are developed from the intermediate
mesoderm.
 The permanent organs of the adult are preceded by a set of
structures which are purely embryonic, and which with the exception
of the ducts disappear almost entirely before the end of fetal life.
 These embryonic structures are the mesonephric ducts (also
known as Wolffian ducts) and the paramesonephric ducts, (also
known as Müllerian ducts). The mesonephric duct remains as the
duct in males which gives rise to seminal vesical, epididymes and vas
deferens, and the paramesonephric duct as that of the female.
 Importantly its sex chromosome dependence, late embryonic/fetal
differential development, complex morphogenic changes, long time-course,
hormonal sensitivity and hormonal influences make it a system prone to
many different abnormalities.

4. Gonads:
 Gonads Produce eggs and sperm cells,
transport and sustain egg and sperm cells, nurture
developing offspring, and produce hormones.
The gonads, ovary or testis, also develop in the
intermediate mesoderm.
 They originally form as swellings that lie just
ventral to the anterior mesonephric kidney.
 A mullarian duct also develops in the
intermediate mesoderm near the mesonephric
duct.
Due to fusion or failure of 1st ridge to
differentiate, some vertebrates (agnathans, some
female lizards & crocodilians, & most female birds)
have a single testis or ovary.
 Hormones cause differentiation of early gonads
into either testes or ovaries.
 As males develop the mesonephric duct makes
connection with the testis as the primary sperm
conducting duct, and the mullerian duct is lost.

5. Ovaries:
•In some teleosts, ovaries are hollow sacs,
either because the ovary develops around
coelom or the ovary becomes hollow at
ovulation (eggs are discharged into cavity
which is continuous with the oviduct).
•In other teleosts plus agnathans, the
ovaries are compact & eggs are discharged
into coelom.
•Amphibians - ovaries are hollow & eggs are
discharged into the coelom.
•Reptiles, birds, & monotremes - ovaries
solid but develop irregular, fluid-filled
lacunae (cavities); eggs discharged into
coelom.
•Mammals - ovaries compact; no large
chambers or lacunae.

6. Testes:
•Usually smaller than ovaries because sperm are much smaller than
eggs (especially eggs with yolk).
•In mammals, testes are larger than ovaries.
Translocation of testes in mammals:
•Testes descend permanently into scrotal sacs in many mammals.
•Some mammals - testes lowered into scrotal sacs & retracted at will.
•Inguinal canal - passage between abdominal cavity & scrotum.
•Scrotal sacs - do not develop in some mammals; testes remain in
abdomen.

7. Male genital ducts:
•Some fishes (e.g., gar & sturgeon) & amphibians - mesonephric duct
transmits sperm & urine.
•Some amphibians - mesonephric duct transports only sperm; new
accessory urinary duct drains the kidney.
•Sharks - mesonephric duct is used primarily for sperm transport;
accessory urinary duct develops.
•Teleosts - mesonephric duct drains kidney; separate sperm duct
develops.
•Amniotes - embryonic mesonephric ducts transport sperm in adults.

8. Intromittent organs:
 Useful when fertilization is internal; introduce sperm into female
reproductive tract.
 Found in some fish, some birds, reptiles, & mammals.
 Cartilaginous fish - appendages of pelvic fins called claspers direct
sperm into female reproductive tract.
 Snakes & lizards - have pair of HEMIPENES (pocket like diverticula of
wall of cloaca).
 Turtles, crocodilians, a few birds, & mammals - exhibit an unpaired
erectile penis.
 Penis - usually a thickening of floor of cloaca consisting of spongy
erectile tissue (corpus spongiosum) with grooves to direct sperm &
ending in a glans penis (sensory endings that reflexly stimulate
ejaculation).
 Mammals (except monotremes) - penis extends beyond body. The
embryonic corpus spongiosum becomes a tube with urethra inside & 2
additional erectile masses develop (corpus cavernosa).

9. Female genital ducts:
Consists of a pair of
gonoducts (or oviducts) that
extend from ostia to the cloaca.
 Different segments of ducts
perform special functions.
 When internal, fertilization
occurs near beginning of ducts,
the mullerian duct becomes the
passage for eggs.
The females of fish and
amphibians retain the
mesonephric duct as a urinary
duct.
In reptiles, birds, and
mammals (amniotes) the
metanephric kidney replaces the
mesonephric kidney.

10. Anatomy in various vertebrate groups:
 Cartilaginous fish - 2 ostia fuse to form single
ostium (or osteum); shell gland secretes albumen &
a shell; uterus holds eggs until laying.
 Teleosts - ducts are continuous with cavity of the
ovary.
 Lungfish & amphibians - oviducts long &
convoluted; lining secretes jelly-like material around
each egg.
 Crocodilians, some lizards, & nearly all birds
(diagram below) - 1 coiled oviduct lined with glands
that add albumen, shells, &, sometimes, pigment
 Monotremes - tract is reptilian; caudal end
secretes a shell before egg passes into the cloaca.
 Placental mammals - embryonic ducts give rise to
oviducts, uteri, & vaginas. Adult tract is paired
anteriorly & unpaired posteriorly (typically
terminating as an unpaired vagina). oviducts
(fallopian tubes) are relatively short, small in
diameter, convoluted, & lined with cilia; begin at
ostium bordered with fimbria.
Uterus:
Marsupials - no fusion of embryonic ducts
so there are 2 tracts (DUPLEX UTERUS)

11. Other placental mammals - varying degrees of
fusion:
 Bipartite uterus - 2 uterine horns, a uterine body
(with 2 lumens), & a single vagina.
 Bicornuate uterus - 2 uterine horns, a uterine body
(with a single lumen), & a single vagina.
 Simplex uterus - no uterine horns & oviducts open
directly into body of uterus.
 Vagina - fused terminal portion of oviducts that
opens either into urogenital sinus or to the
exterior; receives male intromittent organ.

13.  Both Müllerian and Wolffian
ducts are present at the bipotential
stage.
 In males, the Müllerian ducts
degenerate under the influence of
Anti-Müllerian hormone (AMH)
secreted by the testicular Sertoli
cells.
 Wolffian ducts differentiate into
epididymides, vasa deferentia, and
seminal vesicles under the control
of androgens produced by Leydig
cells.
 In females, the Wolffian duct
regresses and the Müllerian duct
differentiates into oviduct, uterus,
and upper vagina.

14. Fish male FROG -MALE - URENOGENITAL SYSTEM
L. Testes are very long and ribbon like. 1. Testes are small and rod-like.
2. Testes are attached to the kidneys
anteriorly.
2. Testes are attached to the kidneys
above the middle region with
mesorchium.
3. Testes are connected with the rectal
gland by epigonal organs.
3. The epigonal organs are absent.
4. Vasa efferentia leave the testis at its
anterior end.
4. Vasa efferentia leave the testis alone
its inner border.
5. These open into the wolffian duct.
5. open into .the Bidder's canal which
drains into the wolffian duct.
6. Wolffian duct is differentiated into an
anterior narrow closely convoluted
epididymis and the posterior wide less
convoluted vesiculus seminalis.
6.Wolffian duct is not differentiated into
the parts except having a small seminal
vesicle near its beginning.
7. Wolffian ducts act only as genital
ducts.
7. Wolffian ducts act as both urinary
and genital duct. Hence they are known
as urinogenital ducts.
8. A pair of club-shaped sperm sac open
into the urinogenital sinus
8. Sperm sacs are absent
9. The copulatory apparatus comprising
siphons and claspers.
9. Copulatory apparatus is absent.
10. Sperms are released into the genita
iuct of female, hence fertilization is
internal.
10. Sperms are released over the eggs
tithe fresh water, hence fertilization is
external. Sperms are released as milt'
11. There are no fat bodies attachec to
the testes.
11. There is a large branched fai-bodv
attached to the anterior end of ead
testis.
12. There is a single urino-genital
12. Urino-genital papillae are paired.
SHARK -FEMALE -
REPRODUCTIVE SYSTEM
FROG -FEMALE - REPRODUCTIVE
SYSTEM
1. Ovaries are small, tabulated
bodies
1. Ovaries are large, hollow,
lobed sacs
2. connected with rectal glands
by long epigonal organs.
2. Epigonal organs are absent.
3. Oviducts (Mullerian ducts) are
long but not convoluted.
3. Oviducts (Mullerian ducts) are
very long and greatly convoluted.
4. Oviducts converge and unite in
front of the ovaries leaving a slit
'ostium tubae! The oviducal
funnels are on either side of
ostium tubae.
4. Oviducts converge infront of
the ovaries but do not unite.
Each oviduct has its own ostium
at the lip of oviducal funnel.
5. shell glands are present. 5. There is no shell gland
6. The oviducts are expanded to
form large uteri in the region of
renal part of kidneys
6. The oviducts are expanded to
form small ovisacs behind the
kidneys.
7. The oviducts join to form a
median sac-'vagina' which opens
into the cloaca.
7. The oviducts independently
open into the cloaca. The vagina
is absent.
8. There are no fat bodies.
8, There is a large fat body
attached to the anterior end of
each ovary.
9 Since the fertilization in
internal, there is no question of
releasing the egg out side the
body
9. The mass of eggs is called
"spawn* which is released
outside the body Fertilization is
external.

15. FEMALE-CALOTES FEMALE-PEGION FEMALE-RABBIT
1, Two ovaries are present. 1. Only left ovary is present. 1. A pair of ovaries are present on the left and
right sides. They are small and compact bodies.
2. Ovaries are irregular bodies situated
asymmetrically and hanging from the dorsal wall
of the body cavity by mesovaria.
2. The single left ovary is attached to anterior
lobe of the left kidney by mesovarium.
2. The ovaries lie behind the kidneys and
attached to dorsal wall of the abdominal cavity
by mesovaria.
3. Right ovaiy is a little anterior to the left one. 3. Right ovary is absent. 3. Right and left ovaries are at the same level.
4. Oviducts are paired. 4. Only left oviduct is developed. 4. Oviducts are paired.
5. Oviducts give striated appearance over
greater part of their length.
5. Oviduct doesnot give striated appearance. 5: Striated appearance is absent.
6. Oviducts extend well ahead of ovaries and
follow straight course.
6. Oviduct starts'just behind the ovary and
follow a convoluted course.
6. Oviducts start just outside the ovaries and
follow convoluted course.
7. Oviducal funnel are large and have externally
directed Ostia with the entire margin.
7. Single Left oviducal funnel is very large and
membranous. It has fimbricated margins it lies
close to the ovary with it; ostium.
7. Oviducal funnel are small and have internally
directed ostia with fimbricated margin.
8. Each oviduct dilates to form an oval shell
gland along the ventral surface of the kidney
uteri are not demarcated. Oviducts are enlarged
into small ovisacs. These are two vaginae.
Vaginae open into the urodaeum.
8. The oviduct is divided into anterior oviducal
funnel, behind it magnum which is thick walled
& secretes albumen. The posterior most part is
the thick walled and muscular vagina.
8. The oviducal funnel leads distally in a narrow
and convoluted tube - Fallopian tube. The
posterior most parts of the two oviducts form
uteri. The paired uteri open into median and
highly muscular chamber-vagina. Associated
with urethra, the vagina forms the urino-genital
canal or vestibule.
9. Urodaeum opens outside by a cloaca 9. Urodaeum opens out by a cloaca. 9. Urino - genital canal opens outside by a
longitudinal aperture - vulva in front of the
anus.
10. There are no special glands associated with
female reproductive system.
10. Same as in calotes. 10. Cowper's and perineal glands are associated
with female reproductive system.
11. Milk glands are absent. 11. Milk Glands are absent. 11. On the ventral surface of trunk region 4 or 5
pairs of milk glands open through their tears.
12. Fertilization is internal oviparous animal. 12. Same as in calotes. Oviparous animal 12. Same as in calotes and columba. Viviparous
animal

16. MALE-CALOTES (GARDENLIZARD) MALE- (PIGEON) MALE (RABBIT)
1. Testes are white ovoid bodies. 1. Testis white ovoid bodies. 1. Testes are pink, ovoid bodies.
2. Testes lie in the abdominal cavity much ahead
of kidneys. Inguinal canal is absent.
2. Testes lie in the abdominal cavity under the
anterior parts of kidneys. Inguinal canal is
absent.
2. Testes are extra abdominal and lie in the
scrotal sacs which are the folds of the skin.
They are connected with perivisceral cavity by
inguinal canals.
3 Right testis is a little ahead of the left one. 3. Left testis is a little bigger than the right one. 3. Right and left testes are symmetrical.
4. Spermatic cord is not formed. 4. Same as in calotes. 4. A spermatic cord extends from each testis to
a little behind the kidney of its side.
5. Each testis is attached to the dorsal body wall
by a double fold of peritoneum the mesorchium.
5. Each testis is attached to the kidney of its
side by mesorchium.
5. Each testis is attached to the wall of scrotal
sac by a short, thick, elastic cord
'gubernaculum'.
6. From the inner end of each testis arises a
much convoluted tube-epididymis.
6. Epididymis is absent. 6. Epididymis is present.
7. Caput and cauda epididymis are not found 7. Same as in calotes. 7 Caput epididymis and cauda epididymes are
the extensions of epididymis in front and
behind the testis
8. Epididymis is continued behind as long,
narrow, coiled and delicate vas deferens. It
passes backwards along the ventral surface of
the kidney of its side and joins with the ureter to
form urino-genital sinus which opens into the
cloaca.
8 The vas deferens arises directly from the
inner border of the kidney in the form of a
narrow convoluted tube. It runs backwards
outside the ureter parallel to it and both open
dorsally by separate aperture in urodaeum of
the cloaca.
8. The vas deferens passes through the
inguinal canal and runs forward and enters into
the abdominal cavity. So that a loop around
the ureter of its side to open into sac-uterus
masculinus' which is present in the dorsal wall
of the urinary bladder.
9. Seminal vesicles are absent. 9. Posterior end of each vas deferens enlarges
to form seminal vesicle.
9. Seminal vesicles are absent.
10. There are no special glands associated with
male genital system.
10. Same as in calotes. 10. There are prostate, couper's and perineal
glands are associated with the male genital
system.
11. In male a pair of eversible copulatory organs
'hemipenis' lie under the skin behind cloacal
aperture
11. Copulatory organs are absent. 11. The copulatory organ in male is in the form
of a thick muscular 'Penis'. It is covered by skin
loose fold prepuce or foreskin penis is made
up of a spongy tissue containing blood vessels
and it is erectile.