Reproduction

Last Day of Lecture

  • Official last day of lecture; one more short chapter to cover tomorrow at 11:00 AM (attendance not required but appreciated).
  • Next week is the final exam, marking the end of the semester.

Pregnancy and Gestation

  • Gestation period averages about nine and a half months.
  • Embryonic period: week three to week eight.
  • Fetal period: week nine until birth.

Primitive Streak and Embryo Research

  • US law restricts the study of human embryos to those no more than two weeks old (established in the 1970s).
  • Reasons for the two-week limit:
    • Approximately 50% of embryos are naturally shed within two weeks.
    • Identical twins are created before two weeks (conjoined twins if after two weeks).
    • The primitive streak, the first sign of the spinal cord, appears around two weeks.
  • Advancements now allow keeping embryos alive beyond two weeks, raising ethical questions about current laws.

Role of hCG

  • Blastocyst implants into the uterus; corpus luteum produces estrogen and progesterone to maintain the endometrium.
  • If pregnancy occurs, the blastocyst and later the placenta secrete human chorionic gonadotropin (hCG).
  • hCG prevents the corpus luteum from dying, ensuring continued estrogen and progesterone production.
  • Eventually, the placenta becomes the primary source of estrogen and progesterone.
  • hCG is the hormone detected in pregnancy tests, with higher levels in blood than urine.
  • Pregnancy tests are typically effective after about three weeks from blastocyst formation.
  • HCG is initially produced by the blastocyst and later by the placenta.

Contraceptives

  • Contraceptives primarily prevent pregnancy, not STDs.

Diaphragm and Cervical Cap

  • Placed in front of the cervix to block sperm from entering the uterus.
  • Often used with spermicide.
  • Effectiveness can vary.

IUD (Intrauterine Device)

  • T-shaped device inserted into the uterus by a doctor or nurse.
  • Highly effective (approximately 95% efficacy).
  • Long-lasting (3-5 years, depending on the type).
  • Types of IUDs:
    • Copper IUD: Copper acts as a spermicide and may kill eggs. Releases copper which causes inflammation and attacks sperm.
    • Progesterone IUD: Progesterone creates a mucus plug in the cervix, blocking sperm. May also inhibit fallopian tube contractions, preventing the egg from reaching the uterus.
  • Rare cases exist where pregnancy occurs with an IUD in place.
  • Copper IUDs can cause heavier menstrual cycles, while progesterone IUDs can lead to lighter or less frequent periods.

Birth Control Pills

  • Available as pills, injections, patches, or implants.
  • Contain either a combination of progesterone and estrogen or progesterone alone (mini-pill).
  • The choice depends on individual health factors (e.g., women over 35 may prefer progesterone-only due to lower risks).
  • Combination pills prevent the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), inhibiting follicle development, egg maturation, and ovulation.
  • Progesterone-only pills primarily cause the cervix to fill with mucus, blocking sperm.
  • Both types can prevent blastocyst implantation.
Implants
  • Implants, containing either combination hormones or progesterone alone, are inserted under the skin.
  • Last for five years or more.

Emergency Contraception

Morning-After Pill (Plan B)
  • Taken within three days after unprotected sex.
  • Contains high levels of progesterone to prevent blastocyst implantation.
RU-486 (Mifepristone)
  • Taken up to ten weeks after sex.
  • Blocks progesterone from binding to the endometrium, causing the uterine lining to shed.
  • Results in the shedding of any attached embryo or blastocyst.
  • Considered an abortion pill by some.
Cytotec (Misoprostol)
  • Taken up to fourteen weeks of pregnancy, typically with RU-486.
  • Causes uterine contractions to shed the endometrium.
  • Also used to treat stomach ulcers and postpartum bleeding.

Contraceptive Effectiveness

  • Effectiveness varies among different methods.

Essure Hysteroscopic Sterilization

  • Metal coils are inserted into the fallopian tubes, blocking them and releasing agents to kill sperm and eggs.
  • No contraceptive method is 100% guaranteed.

Diseases Affecting the Reproductive System

Bacterial Diseases

Chlamydia
  • Most common STD, often asymptomatic, and may not lead to drastic issues.
Gonorrhea
  • More obvious in men (discharge, burning during urination); women often asymptomatic.
Syphilis

  • Can be deadly if untreated, progressing through primary, secondary, and tertiary stages.

  • If untreated both Chlamydia and Gonorrhea can lead to pelvic inflammatory disease (PID), causing scarring and reduced fertility.

    • In males, scarring in the urethra reduces sperm count.
    • In females, scarring of the fallopian tubes can cause ectopic pregnancy.
    • Ectopic pregnancy requires surgical removal to prevent potentially fatal internal bleeding.

Viral STDs

Herpes
  • Oral and genital forms.
  • Usually benign in individuals with healthy immune systems but dangerous for immunocompromised individuals and newborns.
  • Neonatal herpes can be deadly, often requiring cesarean delivery for infected mothers.
    • Newborns that contract herpes from his or her mom, has at least a 30% chance of death.
HPV (Human Papillomavirus)
  • Common virus with many strains; can cause cervical cancer in women.
  • Vaccines available and recommended for individuals under 45.
  • Mandatory in some countries like Australia reducing cases of cervical cancer.
HIV/AIDS
  • HIV leads to AIDS, compromising immunity.
  • Drugs like HEART (for HIV-positive individuals) and PrEP (for HIV-negative individuals at risk) help manage the virus.
Trichomoniasis
  • Caused by the protozoan Trichomonas.
  • Typically diagnosed in women, causing intense itching and foul-smelling discharge.

Endometriosis

  • Endometrial cells grow outside the uterus (e.g., in fallopian tubes, ovaries).
  • Can cause cysts, pain, scarring, and reduced fertility.
  • Common in women with infertility issues.