Reproductive Physiology

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Reproductive Physiology

• Dr. Mickey A. Latour
• Purdue University, Smith Hall,
• West Lafayette, IN 47907

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Reproduction

• The following topics will be discussed
• - Male reproduction
• - Female reproduction
• - Embryonic Development and Implantation
• - Gestation and Parturition

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Reproduction

• The role of the male is less complicated than
  the female.

• Whether boar, bull, ram, stallion, tom, or
  rooster, all males
• have the same basic function

(a) to produce ample amounts of viable sperm
(b) to be willing and able to deliver semen
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Reproduction

• Male reproduction system consist of

(a) the testicles, which produce sperm
(b) the duct system, which delivers sperm and
semen
(c) the accessory glands, which produce fluid to
lubricate, buffer and to carry the sperm
(d) the penis, or male organ of copulation, which
deposits the semen in the female
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Reproduction (Terms)

• Testicles
• Seminiferous tubules
• Vas deferens
• Rete testis
• Sperm vs Semen
• Acrosome
• Epididymis
• Bulbourethral gland
• Urethra

Where spermatogeneis is carried out and the major
site of testosterone production, the male hormone.
Where spermatozoa are produced, haploid cell
number (1N)

Leads from the epididymis to urethra
Where the seminiferous tubules converge
Sperm from testicles, whereas semen contains both
sperm and seminal fluid
Cap on the head of sperm
Provides both a pathway storage site for the
immature sperm
A mixing of sperm and seminal fluid
Opening through the entire penis
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Reproduction
Bulbourethral gland
Seminal Vessicles
Testes
Diverticulum (pouch)
External Orifice
Epididymis
Glands Penis
Sigmoid Flexure
Retractor Penis
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Reproduction

• Pathway for sperm

Seminiferous tubules----Rete testis---Epididymis--
vas deferens---Urethra
Tail
Nucleus/Head
Acrosome
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Reproduction
Controlling the production of sperm

• Sperm production is regulated by production of
  the male hormone, testosterone
• which is consequently regulated by pituitary
  hormone, follicle stimulating hormone
• (FSH) and leuteinizing hormone (LH).

• Both FSH and LH are time dependent, i.e.,
  sexual maturity and further regulated by
• Gonadotropin Releasing Hormone (GnRH).

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Reproduction (Sperm Production)

• Scrotum
• Cremaster muscle
• Pampiniform plexus
• Tunica dartos

Aids in sperm production by keeping the testicles
4-8 degrees cooler than body temperature.
The muscle with allows the testicles to move
close to the body (cold weather) or away from
the body (hot weather).
A network of blood vessels above the testicles to
assist in providing cooler blood to the testicles
The elastic tissue and muscle fibers with the
scrotal wall that contract and relax to aid in
temperature control of testicles.
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Reproduction Factors Affecting Sperm Production

• Nutrition
• Temperature
• Age Genetics
• Castration
• Cryptorchids

Vitamin A and protein seem to be the critical
nutrients involved in sperm production.
This is usually a temporary effect.
As animals age, they exhibit less libido, and
this can be directly related to the genetics of
the animal.
Removal of the testicles.
When one or both testicles fail to descend into
the scrotum.
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Reproduction (Terms)

• Ovaries
• Oviduct
• Horns
• Cervix
• Vagina
• Vulva

Is the site of gamete formation (ova). Like the
testes, the ovaries receive stimulation from FSH
and LH.
Connects the ovary to the uterine horn, thus the
passage way for the ova. The portion of the
oviduct surrounding the ovary is call the
infundibulum.
Mostly called the uterus, where the embryo
implants.
Is the passage way between the uterus and vagina.
Female organ of copulation.
External genitalia of the female.
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Reproduction
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Reproduction
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Reproduction (Female Hormones)

• Gonadotropin-releasing hormone (GnRH)
• FSH
• LH
• Estrogen
• Progesterone
• PGF2?

Is produced in the hypothalamus and controls the
release of FSH and LH.
Stimulates follicle development within the
ovaries.
Triggers ovulation/release of the ova.
Major production site is the ovaries and causes
increase in LH release from anterior pituitary.
Produced by a functional corpus luteum and
maintains pregnancy.
Is a hormone-like substance produced in the
uterine wall, which causes regression of the CL.
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Reproduction
Estrus cycle

• Proestrus the beginning stages of follicle
  development
• Estrus the period where the female is receptive
  to breeding
• Metestrus following estrus and development of
  the CL
• Diestrus highly active CL to a reduction in
  estrogen production

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Reproduction
Species Cycle(d) Heat (h) Time of
Ovulation Suggested Breeding Time
Cow 21 12-18 12-15 after ovulation 4-8 h before
end of estrus Sow 20-21 48-72 18-40 after start
of estrus 24 h after start of estrus Ewe 16-17 24-
36 18-26 after start of estrus 12-18 after start
of estrus Mare 19-23 90-170 1 d before 1 d
after est. alternate d during estrus Fowl nearly
every day usually occurs at dusk at ovulation
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Reproduction
Gestation Length
Ewe 150 days
Sow 114 days
Cow 282 days
Mare 336 days
Fowl 1 day
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Reproduction
Embryo Development and Implantation
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Fertilization

• Usually occurs within 24 to 36 hours of
  copulation in mammals. In birds, fertilization
  occurs within 15 to 20 minutes of ovulation.
• For fertilization to occur, the sperm must have
  to penetrate the egg (i.e.,undergone
  capacitation).
• Only one sperm fertilizes the egg via enzymes
  present on the head surface.

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Following Fertilization - Implantation of Embryo

• Embryos implants in the uterus which is rich in
  blood and provides fluids to the developing
  embryo.
• Following implantation, the embryo begins to
  develop extra-embryonic membranes, called
  placentation.
• Chicks are developed completely in the egg laid
  and are independent of maternal care.

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Following Fertilization - Implantation to
Placentation

• Development of extra-embryonic membranes
  (placenta).
• Placenta functions to a) provide nutrients and
  vital gases, b) removal of waste products, and c)
  production of hormones to maintain pregnancy
• Chicks develop a placenta like structure and
  provides an avenue for nutrients.

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Embryo Structure
Chorion
Embryo
Amnion
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Parturition

• Defined as giving birth.

• Towards to final days of gestation, estrogen
  production is increased by the
• placenta, which in turn stimulates
  prostaglandins (PGF2?) from the
• uterine wall.
• The PGF2? lowers progesterone levels. While
  the CL is regression it begins
• to release relaxin a hormone which relaxes
  the pelvic muscles and ligaments in
• the pelvic area.

• Around the time of birth, the hormone prolactin
  increases to stimulate milk
• synthesis.

• The hormone, oxytocin brings about steady
  contractions during the birth
• process.

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Breeding (Artificial Insemination)
A) more genetic improvement through use of sires
B) reduction or elimination of sires (not true
for turkeys)
C) reduces the risk of spreading certain
reproductive diseases
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