Chapter 13: Reproduction
• Chapter overview:
– Chapter 13 presents the anatomy and
physiology of reproduction, including:
• anatomical views and parts identification
• estrous cycle and gestation
• new developments and related technologies
Selected Reproduction Terms:
• Puberty - sexual maturity
• Ovulation - release of ovum (egg)
from ovary
• Copulation - the act of mating
• Fertilization - union of male and
female sex cells
• Conception - becoming pregnant
Selected Reproduction Terms:
• Estrous cycle - the interval between two
estrus periods
• Estrus - the time of receptivity to mating
during the estrous cycle; also termed “heat”
• Gestation - pregnancy
• Parturition - the act of giving birth
Reproductive Tract: Male Mammals
• Scrotum - container for the testes external
to the body; functions in temperature
regulation
• Testicles - paired within the scrotum
• Epididymis - long tortuous tubule encased
and lying along the surface of the testis
Reproductive Tract: Male Mammals
• Vas deferens - simple tubule carrying
sperm from the epididymis to the ampulla
or urethra
• Ampulla - widened area at juncture of vas
deferens and urethra; not found in all
species
• Urethra - single tubule leading from vas
deferens through penis to exit
Reproductive Tract: Male Mammals
• Sigmoid flexure - curvature in the penis
structure of bull and boar allowing for
extension during mating
• Accessory glands - glands associated with
the male reproductive tract to provide fluids
for volume, nutrient source, and protection
of the sperm
Terms: Male Reproduction
• Castration - removal or destruction of the
testes by surgical or other physical or
chemical methods
• Cryptorchid - male mammal with one or
both testicles failing to descend into the
scrotum
Reproductive Tract: Female Mammals
• Ovary - structure containing the
reproductive cells (ova); paired
• Infundibulum - associated with each
ovary; captures the ova after ovulation
• Oviduct - tubule connecting infundibulum
to the uterine structure; site of fertilization
Reproductive Tract: Female Mammals
• Uterine horn - leads from oviduct to body
of uterus; well developed in litter-bearers,
small or absent in nonlitter-bearers;
implantation occurs here in many litterbearing species
• Uterus - body of the uterine structure
between cervix and horns; site of
implantation in nonlitter-bearers
Reproductive Tract: Female Mammals
• Cervix - muscular opening between uterus
and vagina; remains reasonably constricted
except for relaxation to allow birth
• Vagina - structure external to the cervix;
accepts penis of male for mating
• Vestibule - general area of vagina posterior
to entrance of urethra
Major Hormones of Reproduction:
• Testosterone - produced in cells of Leydig
in testis; causes growth of reproductive
tract, development of male physical
character, and onset of sexual drive
• Estrogen - produced in cells lining mature
ovarian follicles; induces estrus, mammary
duct growth, and development of secondary
sex character
Fetal Membranes:
• Membranes develop from the fetus to
provide contact for nourishment and a
protective barrier
– Amnion: innermost membrane surrounding
fetus
– Chorion: outer layer making contact with
uterus
– Allantois: layer fused with amnion and chorion
to create a fluid filled space
“Freemartins” in Bovines:
• Occurrence: female born twin to a male
• Result: female generally has incomplete
reproductive tract; over 90% are infertile
• Reason: fetal membranes anatomose
(connect); compounds from male fetus
inhibit normal development of female
Estrus Synchronization:
• Manipulation of estrous cycle to
synchronize ovulation and breeding of
female groups
• Generally focus on use of prostaglandin
injection protocols to lyse the corpus luteum
Superovulation:
• Manipulation of ovulation to dramatically
increase simultaneous release in a single
genetically superior individual
• Generally involves use of follicle
stimulating hormone and prostaglandin
• Multiple ova may be fertilized in vivo or in
vitro
• Ova are manually collected from dam
• Recipient females are utilized to implant
fertilized ova
Embryo Transfer (ET):
• Transferring embryos from one genetically
superior female to another
• Embryos may be recovered from a donor
female or may be fertilized and grown in
vitro
• Often linked with superovulation
• Transfer of frozen embryos also common,
allowing longer-term storage
• Also used to expand populations of
endangered species
Cloning:
• An ovum recovered from a female is
enucleated and genetic material from a
diploid donor cell is inserted
• The new cloned embryo is implanted in a
recipient female
• An offspring is created from one genetic
parent
• Note: natural born identical twins are
actually clones of each other
Transgenics:
• Transgenic - an animal with the genetic
makeup of more than two parents
• What: recombinant technology creating the
inclusion portions of foreign DNA into
DNA of another cell via splicing techniques
• Why: to attempt to “insert” a cure or control
for a genetic disease; to create organisms
that produce pharmaceuticals; to advance
the science of medicine