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 litter- bearing 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