ANS 2: Week 3 Notes
ANS 2: Week 3 Notes ANS 002
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This 8 page Class Notes was uploaded by Mackenzie Hayes on Friday April 15, 2016. The Class Notes belongs to ANS 002 at University of California - Davis taught by Dr. James Murray in Spring 2016. Since its upload, it has received 102 views. For similar materials see Introductory Animal Science in Animal Science and Zoology at University of California - Davis.
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Date Created: 04/15/16
ANS 2: Week 3 Notes 4/11: ● Hormones in Female Reproduction: ○ Hypothalamus → GnRH → anterior pituitary ○ Anterior pituitary → FSH + LH → ovary ■ LH stimulates ovulation ○ Ovary → causes corpus luteum to develop / causes ova to develop ■ Corpus luteum (CL)→ progesterone ■ Releases progesterone + becomes CA (scar where CL used to be) ■ Progesterone= vital for pregnancy (must be regulated) ○ Uterus: -pregnantr-prostaglandin → CL regressesOT pregnant ○ Cells that were producing estrogen switch to produce progesterone ○ Humans can use hormones to control the cycling of animals ● Embryo releases a “signal” to let mom know they’re there ○ Pigs have minimum 3 embryo - any less the signal isn’t “strong enough” ○ Signal → maintain CL → production of progesterone → keep pregnant ● ^Diagram WILL BE ON AN EXAM (be able to recreate / label it) ○ Day 0 = when ovulation occurs (and again at day 20ish) ○ Cycle = period from ovulation to ovulation ○ FSH = always “wandering” in the background (levels not cyclical) ○ Progesterone: ■ Loss of CL → drop in progesterone (day 0) ■ After ovulation: new CL forming → rise in progesterone ○ Estrogen: ■ Follicle grows, then levels drop @ ovulation ■ Cells switch to produce progesterone ○ *when labeling take the time to write “ovulation” at day 0 and 20* ● Luteal Phase: area where progesterone is high (between ovulations) ○ Dog luteal phase lasts 5-7 months ○ Because it is longer than gestation no need for embryo to send “signal” ■ Progesterone constantly high during long period ● Feedback in Female Reproduction: ○ Feedback is negative or positive depending on time ● Stress / Parturition: ○ “Triggered” by release of cortisol from fetus ○ → increased release of estrogen by placenta ○ → estrogen causes uterus to start contracting ○ Uterus releases prostaglandins which cause regression of CL ■ → drop in progesterone ○ Progesterone inhibits the contractions of uterus ■ → drop in progesterone = stimulates contractions ○ Oxytocin = posterior pituitary hormone ■ Stimulates contraction + mammary production ■ Makes other systems “forget” about pregnancy 4/13: ● Mature Ovary (turkey): ○ Follicle labeled in order of “readiness” to release egg ○ Looks different because they ovulate once a day ○ Egg has to carry all nutrients for embryo development ○ Stigma = area on follicle that’s not vascularized (no blood vessels) ■ Where the follicle ruptures to release egg (to prevent blood loss) ■ LH causes this rupture ● Anatomy of Female Bird Reproduction: ○ Magnum - lays down nutrients ○ Isthmus - lays down membranes ○ Shell gland- lays down calcified shell ○ Sperm storage tubules - hold sperm to release later ■ Can hold for up to 2 weeks ● Ovulation: ○ Release of LH causes enzymatic “digestion” of stigma ○ Follicle ruptures → release of egg = start of ovulation ○ Smooth muscles in the theca externa contract ○ Granulosa cells remain metabolically active for 24-48 hours ■ Producing progesterone and prostaglandins ○ *very dependent upon light* ● Oogenesis: ○ Primordial germ cell differentiates into oogonium ○ Oogonium enters meiosis ○ Primary oocyte = 2N, 4C → has replicated DNA ○ Arrested development ■ Essentially stops at metaphase 1 of meiosis ○ LH activates meiotic “machinery” ○ 1st metabolic division is very uneven (at ovulation, 1N, 2C) ○ If fertilized then second division occurs ■ 1N, 1C ■ Restores diploid state with sperm DNA added ■ Why do we “throw away” 3 copies of DNA? (unlike males) ● Allows for cell to be big and retain almost all cellulose and nutrients, DNA is all that’s wasted ● Maximizes cell survival ● Arrested development + uneven division ○ Differentiate oogenesis from spermatogenesis ● Fertilization: ○ Homunculus - little man inside sperm ○ Physical union of male and female gametes (sperm and ova) ● After fertilization egg divides and develops ● Embryo stage = n o longer reliant on maternal RNA, produce own ○ Zygote - one celled embryo ● Early Development: ○ From conception to death: ○ Embryonic: rom fertilization until all essential organs are formed ○ Fetal:end of embryonic stage until parturition ○ Gestation length:varies (don’t need to memorize lengths) ● E = morula stage (inner cell mass) ● F = blastocyst stage (fluid filled space = blastocele) 4/15: ● A = zygote ● B = 2 cell ● C = 4 cell ● E = morula, still held together by zona pellucida ● F = 72 hours after fertilization ○ Dark clump of cells is what actually becomes fnner Cell Mas) ○ Mass eventually “hatches” out of zona pellucida ● Definitions: ○ Blastocyst:a hollow sphere of cells composed of two cell layers (the trophoblast) with a clump of cells inside (the ICM or inner cell mass) ○ Blastocoele: fluid filled interior of blastocyst ○ Trophoblast: cells form the extraembryonic membranes ● In ruminants, embryo turns into a worm-like thing ● Extra-embryonic membranes: ○ Provide protection for embryo - fetus and nutrient / waste exchange ○ Amnion: fluid filled sac like airbag around embryo ○ Yolk sac: stores yolk (essentially empty in mammals) ○ Chorion and Allantois:(often fused) ■ Chorion = outer layer contributing to placenta ■ Allantois = outgrowth of bladder for nutrient/waste exchange, respiration, and storage of urine ● Recognition of Pregnancy: ○ Primates: (aka humans) ■ Blastocysts secrete chorionic gonadotropin (CG) ■ CG binds to LH receptors in the CL and stimulates continued secretion of progesterone ○ Ruminants: ■ Not Pregnant: CL regresses at end of cycle ● Due to endometrial secreting PGF ■ Pregnant: ● (bovine) embryo secretes interferon tau which decrease PGF secretion ● (sheep) embryo secretes ovine trophoblast protein which inhibits production of PGF ○ Pigs: ■ Release estradiol to block PGF ■ Minimum 3-4 embryos ○ Dogs: monoestrous (basically keep secreting progesterone anyway) ● Gestation: differs by species DON’T MEMORIZE THE NUMBERS ● To know for Midterm 1: ○ Structures and functions ○ Oogenesis ○ Hormones, site of synthesis, target organ (or cell), and function ○ Stages of early development ● Manipulating Reproduction: ● Males: ○ Artificial Insemination: ■ Depends on ability to collect semen and cryopreservation (pig semen can’t be stored like other animals’) ■ Used in: broad breasted turkeys, cattle, sheep, horses, dogs ■ Also for captive / endangered species preservation ○ IntraCytoplasmic Sperm Injection: ■ In Vitro Fertilization: inject single sperm + shock egg into thinking fertile (most widely used in humans) ● For infertility ● Preservation of genetics ■ Controversy: may pass on infertility if genetic ● Females: ○ Estrous Synchronization: (so all can be inseminated at once) ■ Ruminants: ● Melengestrol Acetate (MGA) - orally administered, acts like progesterone ● CIDRs - controlled internal drug release ○ 10% progesterone by weight ● GnRH + PGF ■ Pigs: ● PG600 - pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) - induces fertile heat ○ Superovulation: ■ Artificially induced ovulation of more oocytes than normal for species ■ 2 methods: ● Intramuscular injection of PMSG + luteolytic dose of PGF ● 8-10 injections of FSH at half-day intervals ○ Best to synchronize ovulation (shot of GnRH) slims down time frame by hours ○ In Vitro Fertilization: ■ Oocytes collected from ovaries after slaughter or ovum pick up following superovulation ■ Matured and fertilized in vitro ■ Embryos transferred immediately or following culture ○ Ovum Pickup: (OPU) ■ Ultrasound guided - noninvasive - aspiration inside the cow ■ Highly repeatable ○ Induced Abortion: ■ PGF - causes CL breakdown ■ Dopamine agonists - decline of prolactin in dogs ○ Frozen Zoo: sperm, embryo, cells, ovaries
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