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Reproduction, Early Development, Pregnancy 1. From 2 cells l • • • …a 3-layer embryo …a yolk sac, amniotic cavity, chorionic cavity …a placenta 2. Pregnancy and Childbirth l • • Changes to female anatomy Labor and birth Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Ovulation Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy 1o oocytes arrested in Meiosis I in female fetus After puberty, 1 primary oocyte/month completes Meiosis I as follicle matures Follicle ruptures-ATTENTION--CELL LOOSE IN CELOM Oocyte enters Fallopian tube If fertilization occurs, Meiosis II occurs and oocyte becomes ovum Ovulation and Meiosis Fig. 24.15 Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Spermatogenesis Fig. 24.3 Sperms form in walls of seminiferous tubules Spermatogenic cells within sustentacular cells Meiosos proceeds as spermatocytes move towards lumen (4 sperm from each spermatocyte) Seminiferous tubulerete testis head/body/tail epididymis vas deferens (through spermatic cord around bladder) urethra Seminiferous tubulerete testis head/body/tail epididymis vas deferens (through spermatic cord around bladder) urethra Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Form thick epithelial lining of seminiferous tubules Tight junctiones between keep sperm proteins from entering bood Produce testicular fluid which helps move sperm Concentrate testosterone to stimulate sperm production Produce inhibin which slows sperm production Sustentacular cells Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Fig. 24.4 First week of development From oocyte to blastocyst Fig. 3. 3 Oocyte(fertilization)zygote4-cell stage (2 days) morula (ball)blastocysteinner cell mass (embryo) Trophoblast (extraembronic membranes) Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Implantation Endometium ready for implantation Blastocyst implants with ICM against uterine wal Ectopic pregnancy--implantation outside built-up endometrium (potential for bleeding since embryo stimulates vascularization) Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Endometrium Fig. 24.18 Two layers – Stratum basalis – Stratum functionalis Stratum functionalis builds up each month in response to ovarian hormones Uterine glands secrete glycoproteins--nutrients for potential zygote--into uterine cavity At menstruation, functional layer self-digests, spiral arteries kink and constrict so cells die. Just before menstrual flow starts, spiral aa. Open wide, capillaries burst and functional layer sloughs off. Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Fig. 24.19 Endometrium and menstrual cycle Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Menstrual Phase (Days 1-5): Sloughed Functional layer of endometrium expelled through vagina as menstrua flow Proliferative phase (Days 6-14): In response to estrogen from growing ovarian follicle, new functional layer elaborates Ovulation (about Day 14) Secretory phase (Days 15-28): – Spiral aa. Elongate and coil – Uterine glands secret glycoproteins – More estrogen (and progesterone) from corpus luteum If pregnancy, secretory phase continues due to embryonic estrogen production If no pregnancy, corpus luteum degenerates, estrogen drops leading to menstruation Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Endometrium and menstrual cycle Meanwhile…back in the embryo Implantation with ICM towards uterine wall Trophoblast Fig. 24.25 – Cytotrophoblast (cells around ICM) –Human Synctiotrophoblast (synctium of cells that becomes placenta) Frolich, Anatomy, Reproduction, Early Dev., Pregnancy Placenta formation Fig. 24.25 Lacunae form within synctiotrophoblast--maternal blood fills these spaces Vili form with embryonic capillaries down middle Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Placenta formation Villi bathed in maternal blood in lacunae--exchange of nutrients, O2, CO2 Fig. 24.25 After 13 weeks, full placenta--pancake-shaped organ. Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Other extraembryonic tissues Cellular trophoblast forms amnion, yolk sac Fetal cells shed into amniotic cavity which fills with fluid from fetal kidneys extreted through ureter, bladder, urethra Amniocentesis--sample of amniotic fluid taken with hypodermic needle Part of yolk sac “sucked” into embryo to form endermic bladder Fig. 3.4 Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Embryo proper ICM forms hypoblast (yellow-becomes endoderm) and epitblast (blue--becomes ectoderm) See handout for all adult derivatives of embryonic tissues--HOW FAR WE’VE COME!! Animated movie of fetal deveopment http://www.cvillepregnancy.org/fetal.html Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Fig. 3. 4 Pregnancy--changes in female anatomy Shift in organs – Bladder, rectum pushed superiorly, squeezed--change in urination, defecation patterns – Stomach compressed--eat more often, less at each meal – Immune response may change appetite to avoid possible poisons for fetus Postural changes to compensate for anterior weight Breasts enlarge--first milk production Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Birth Stage 1. Dilation Stage – Ligaments loosen – Cervix dilates Stage 2. Expulsion – Baby moves through pelvic girdle--head is rotated 90 degrees – Floor of pelvis Kegel exercises Perineal support Avoid ripping or episiotomy – Baby skull--sutures not fused, bones can be slide on top of each other giving pointed look Stage 3. Placenta. – Detaches and is expulsed within one hour. Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy Fig. 24.27 Frolich, Human Anatomy, Reproduction, Early Dev., Pregnancy