Physiology of Reproduction
Sexual Differentiation
Genetic
XY
Indifferent gonads
XX
Ovary
Gonadal Testes
Spermatogonia
Germ cells
Oogonia
Sertoli cells
Leydig cells
Granulosa cells
Somatic cells
Theca cells
Mullerian Female
Wolffian
Male
Antimullerian Androgen
hormone
No androgen No AMH
Male genital tract
Male external genitalia
(Penis, scrotum)
Female genital tract
Female external genitalia
(Labia, Vulva, clitoris)
Male Reproductive system
Functio :
• Develop Spermatozoa
• Deliver Sperm to the
female reproductive
system
• Produce male sex
hormones
Functional anatomy of Male Reproductive System
. Testicles
. Site of sperm production and testosterone synthesis
. Sperm contains ½ of genetic makeup
. Epididymis
. Sperm storage and maturation
. Scrotum
. Protects testes and regulates temperature
. Vas Deferens
. Transports sperm from epididymis to urethra
. Urethra
. Tube inside of penis, transports sperm or urine to the
exterior
. Penis
. organ of copulation
Testes:
•The primary sex organs of male
•they are housed in the scrotal sac by
the spermatic cord
Function:
•Spermatogenesis: production of
sperms
•Hormone production (androgen)
. Development of male
secondary sex characteristic
. Male libido
. General anabolic effect
Scrotum:
• is a two-lobed sac developed from the
inguinal skin to accommodate the testes.
Function of the scrotum
• Support and protect the testes
• Regulate testicle temperature to be 4-5 C
below normal body temperature.
• Thermoregulation of testis:
• Cremaster Muscles:
. During hot condition: cremaster muscle relaxes dropping the testes
far from the heat of the body.
. During the cold season: the cremaster muscle contracts, retracting
the scrotum and bringing the testes nearer to the body.
• Sebaceous and sweat glands: The large number on the scrotum help in
lowering the scrotal temperature.
• Pampiniform plexus: The testicular vein are coiled around the testicular
artery and cools the warm blood of artery before reaching testes
Cryptorchidism
• is a condition in which testes fails to descend into the
secrotum .
• Unilateral Cryptorchidism:
• Only one testis is retained inside the abdomen and
fails to perform its function, while other testis is
normal
• The animal may be fertile.
• Bilateral Cryptorchidism:
• both testes fail to descend and are retained in
abdomen
• The animals are always infertile in this case.
Regulation of Male Reproduction
• Gonadotropin-releasing hormone
(GnRH):
• produced by the hypothalamus
• Stimulate follicle-stimulating
hormone (FSH) and luteinizing
hormone (LH) production
• Luteinizing hormone (LH):
• produced by the pituitary gland
• causes the synthesis and
secretion of (testosterone)
from Leydig cells
• Follicle-stimulating hormone (FSH):
• Produced by the pituitary
• stimulates the production of
androgen-binding protein from
Sertoli cells and the formation
of the blood-testis barrier.
Function of testicular cells:
•Leydig cells:
• Produce testosterone
• Functions of Testosterone:
• Support spermatogenesis
• Stimulate growth and development of secondary sex organs
(prostate gland, bulbourethral gland)
• Stimulate masculinization characters of male
• enhance libido
•Sertoli cells:
• Nourish developing sperms during spermatogenesis
• Phagocytosis of defective sperms
• Provide the blood testes barrier
• Secretions
• Luminal fluid
• Androgen binding protein
• Inhibin
• Secret mullerian inhibiting substance
Spermatogenesis: is The production of
spermatozoa which occurs in the sertoli
cells of the seminiferous tubules
• Spermatogonia divide by mitosis, and
mature into primary spermatocytes.
• primary spermatocyte undergoes
meiosis:
• meiosis I yields 2 haploid secondary
spermatocytes
• meiosis II (like mitosis) yields 4 equal-
sized spermatids.
• spermatids migrate toward the lumen
(central opening).
Spermiogenesis: differentiation of spermatids into mature spermatozoa
• Formation of acrosom
• Condensation and elongation of the nucleus
• Formation of flagellum
Epididymis :
• convoluted tubule arises from the testes
• Functions:
. Transport sperms
. store sperms
. Provide nutrition to the sperm cells
. Sperm get ability to move here.
. Sperms get mature here.
. Phagocytosis of Dead sperms
Vas deferens (ductus deferens): a muscular tube connecting the tail the
epididymis to the urethra.
Erection: the enlargement of the penis that prepares for breeding.
• Mechanism:
• Dilation of the arteries which allow for increasing the blood
flow into the organ.
• Compression of the veins carrying blood away from the
penis by contraction of ischiocavernosus muscles
• The net effect is that more blood enters the penis than
leaves it.
• Ejaculation: is the reflex of semen ejection from the penis.
• Closure of the muscle sphincter around the neck of the
urinary bladder to prevent the movement of semen into the
bladder.
• Rhythmic contractions of the urethra that pump the semen
out into the female reproductive tract.
Functional anatomy of Female Reproductive system
Ovaries:
•Produce reproductive cells (ova)
•Produce Sex hormones (Estrogen
and Progesterone)
Oviduct :
•guide ova from the ovary to the
uterus
•serve the usual site of fertilization
Uterus:
•It is the site of fertilized ova
implantation
Cervix:
•muscular valve that seals off the
uterus from outside
Dictyate stage
Meiosis inhibiting factor
Folliculogenesis: Is the progression
of a number of primordial
follicles into preovulatory which
occurs during the reproductive
cycle
Follicular phase
• Recruitment: Primordial follicle
develop to primary follicle
• Primordial follicle developed
to this stage before birth
• Growing follicle: stimulated by
FSH
• Cells of recruited follicles
start multiplication and form
multiple layer of granulose
which produce estrogen that
prepare animal for breeding
and pregnancy.
Luteal phase
• Ovulation: (induced by LH)
• rupture of mature follicle and release of the ovum
• Corpus luteum formation: granulosa and theca cells become luteal cells and
shift from estrogen to progesterone production
Hormonal production and regulation during reproductive cycle
Reproductive Cycles (Estrus Cycle)
(The interval between two successive ovulation)
• E2 reach the peak level
• Period of Sexual receptivity
•The period of follicular development
•Increased estrogen
(heat) keyed by Estrogen
Proestrus
Estrus
• E2 priming followed by P4 is
required for dog
• Previous exposure to P4 is
required for E2 to cause
signs of heat in sheep
Anestrus
occur near
Ovulation
the end of this phase
Corpus luteum reach its
maximum size and activity
A period of temporary
inactivity of ovaries seen
in seasonal breeder
Diestrus
Metestrus
•The period after ovulation and initial
corpus luteum formation
•Increased progesterone
Pregnancy
Pregnant animal signal for corpus luteum persistence
Hormonal profile during the estrus cycle
Surge
Pineal gland is the translator of photoperiod
Photoperiod and reproductive cycles
decreased light suppress the inhibitory
neurons of the pineal gland which allow
for melatonin release
Inhibitory neurons
• Melatonin:
• tune on the reproductive system
of short day breeders (sheep and
goats)
• shut down the reproductive
system of long day breeders (Cat
and horses)
Superior cervical
gangilion
• Suppressive effect of photoperiod can be overcome by:
• Exposure to artificial lighting regimens (cats and horses)
• Administration of melatonin (sheep)
Animal Type of
Length of
Duration of
Time of Ovulation
12 hours after
At or near the
estrous cycle estrous cycle estrus
(days)
Cattle
Sheep
Horse
Polyestrous
19-23 Average 6-30 hours
21
average 18 hrs end of estrus
Seasonal
polyestrous
In Fall
14-20 days
Average 17
20-42 hours
average 30 hrs end of estrus
Seasonal
polyestrous
In spring
10-37 days
Average 21
2-6 days
average 4
days
24-48 hours
before the start
of estrus to24
hours after the
end of estrus
Goat
Seasonal
polyestrous
In Fall
12-24
Average 20
1-4 days
Average 39
hours
30-36 hours after
start of estrus
Puberty: is the age of first ovulation
In sheep puberty is associated with increase in the
synthesis and release of GnRH from the hypothalamus
and gonadotropin which drive follicular development.
Before puberty the hypothalamus is highly sensitive to
the negative feedback of estrogen
Species
cows
Age of Puberty (months)
8-12
12-18
7-8
horses
Sheep
goat
7-8
dogs
6-12
6-12
cat
Spontaneous ovulators
LH surge is stimulated by positive feedback of follicular estrogen
Induced Ovulators
Rabbit
Cat
Camelids
Luteolysis:
• Occur 14 days after ovulation)
• LH is important to maintain Corpus
luteum
• PGF2-a from the uterus of large
Domestic Animals (cattle, goats,
horses, pigs, and sheep) causes
regression of corpus luteum.
• Follicular Estrogen causes initial
release of PGF2a
• Progesterone Stabilized Oxytocin
Receptors
Countercurrent Exchange
Pregnancy
Parturition
Lactation
Fertilization and pregnancy:
• Transport of Spermatozoa:
• Spermatozoa reach the site of fertilization in minutes
• The process of transport aided by
• Contraction of the uterus and the oviduct
• Contraction is stimulated by oxytocin of the pituitary
gland
• Capacitation:
• Includes changes of a spermatozoa which occurs in the
female reproductive tract
• most dramatic change is the release of the acrosome
enzymes which help the spermatozoa to penetrate through
the layers surrounding the ovum to accomplish fertilization.
• Fertilization of the ovum
A single spermatozoon
allowed to enter the
ovum the
The zygote:
• The fertilized ovum
contain the male
pronucleus and the
female pronucleus.
• Each carries the
haploid chromosome
number
• The male and female
pronuclei quickly join
together to restore
the diploid number of
chromosomes
Cleavage:
• Zygote begins to divide
rapidly by the normal
process of mitosis until
reach morula stage .
• While cleavage is taking
place, the zygote is slowly
moving down the oviduct
toward the uterus by
• The muscular
contractions and the
movements of cilia of
the oviduct.
• The cells of the morula continue to divide and gradually form a hollow
cavity in the center.
• By the time it reaches the uterus (a few days later), it is formed blastocyst
• Hatched blastocyst is ready to implant itself in the lining of the uterus.
PREGNANCY: (Gestation period).
It is the time from fertilization to
delivery of the newborn.
• Divided into trimesters.
• The first trimester: (embryo
period) starts when the newly
implanted zygote is getting
itself organized and developing
its placenta.
• The second trimester: (fetus
period)
• All the body tissues, organs,
and systems develop during
this period.
• The third trimester:
• is the last period of fetal
growth and preparation for
parturition .
Maternal Recognition of Pregnancy:
• If pregnancy happened, the corpus luteum should persist and continue
to produce sufficient amount of progesterone to support pregnancy
• Embryo signals for the persistence of Cl and modify the uterine
production of PGF2a
• The embryo of Cow and Ewe produce trophoplastin 14 days after
ovulation
• Mares:
. Produce Pregnant Mare Serum Gonadotropin PMSG or Equine
chorionic gonadotropin (eCG) from the endometrial cup which
enhance progesterone production by the primary CL and aid in
the formation of secondary CL
. Movement of embryo throughout both horns before being fixed at
day 16
• Human trophoblastic cells produces Human Chorionic gonadotropin
(HCG)
PARTURATION: Cortisol from the fetus initiate parturition
•Progesterone during pregnancy maintain the
quiescence of the myometrium
•Estrogen during later part of gestation increases
the contractile potential of the myometrium
Stages of parturition
First: presentation of fetus
at the internal os of the
cervix by myometrium
contraction
Cow
Goat
Dog
cat
Source of relaxin
Cl in Cow and pigs
Placenta in
Second: is the actual
delivery process aided
by maternal abdominal
muscles
Cat, dog, horses
Delivery in Mare occur
While P4 is high
Third: delivery of fetal membranes
Lactation: is the process of milk
production.
• It begins toward the end of
pregnancy and is obvious at the
time of parturition.
• Stimulated by Prolactin and
growth hormone
Milk letdown:
• stimulation of teat activate
sensory impulse which
stimulate the hypothalamus and
the posterior pituitary gland to
secret oxytocin
• Oxytocin causes contraction of
the myoepithelial cells around
the alveoli and small ducts
• This squeezes milk down into
the large ducts and sinuses,
where it can be removed by
nursing or milking.