Reproductive System and Development Exam Notes

Structural Abnormalities and Surgery

  • Individuals with structural abnormalities, such as missing portions of their skull due to encephalitis, face a higher risk of injury.
  • Surgery involving artificial skull plates (e.g., titanium) is often required to protect the brain.
  • Multiple surgeries may be necessary as the child grows to accommodate the increasing brain and skull size.

Exam Review: Reproductive Systems and Development

  • The unit is divided into two main sections: reproductive systems and development/labor processes.
  • Expect anatomy questions where you identify a structure based on its function and location (e.g., "a band of tissue held tight by a ligament").
  • Hormonal questions will be prevalent, so understand testosterone, inhibin, and the menstrual cycle (follicular, ovulation, and luteal phases).

Menstrual Cycle Hormone Graphs

  • Assignments involving hormone graphs had issues with the proper division between follicular, ovulatory, and luteal phases.
  • Ensure you can clearly distinguish between these phases and the corresponding hormonal changes.

Spermatogenesis and Oogenesis

  • Spermatids mature in the epididymis, while spermatozoa are fully mature and located in the vas deferens.
  • The primary oocyte is the stage before ovulation, the secondary oocyte is after ovulation but before fertilization, and the ovum is the fully fertilized egg. Do not use "ovum" as a blanket term for all.

Evolutionary Perspective of Reproduction

  • Consider the goal of reproduction (pregnancy) to understand the purpose of the menstrual cycle and hormonal fluctuations.
  • The hypothalamus detects when pregnancy hasn't occurred and initiates the cycle anew by releasing gonadotropic releasing hormone (GnRH).
  • FSH (follicle-stimulating hormone) is released to mature another follicle. LH (luteinizing hormone) needed to rupture one.

Sex Hormones

  • Both males and females share GnRH, FSH, and LH. The target tissues and subsequent hormones differ.
  • Female sex hormones: GnRH, FSH, LH, estrogen, and progesterone.
  • Male sex hormones: GnRH, FSH, LH, testosterone, and inhibin.
  • Inhibin regulates sperm production.

Sertoli and Leydig Cells

  • Sertoli cells are support cells that provide nutrients and remove waste for sperm cells (which lack cytoplasm).
  • Spermatogenic cells produces the inhibit

Ovum Terminology

  • Primary oocyte: Before ovulation.
  • Secondary oocyte: After ovulation, before fertilization.
  • Ovum: Fully fertilized egg.

Birth Control Hormonal Mechanisms

  • Birth control often releases high amounts of progesterone, mimicking the luteal phase.
  • This suppresses follicle development, preventing ovulation and pregnancy.

Breastfeeding Hormonal Perspective

  • Be able to explain breastfeeding from a hormonal perspective, including potential problems when breastfeeding during pregnancy.

Follicle Development and Ovulation

  • FSH stimulates follicle growth in the ovary.
  • As the follicle grows, it produces estrogen and a small amount of progesterone.
  • A surge in estrogen triggers a final surge of FSH, which then triggers a surge in luteinizing hormone (LH).
  • LH causes the follicle to rupture, leading to ovulation.
  • Ovulation is the release of the secondary oocyte.

Secondary Oocyte Journey

  • The secondary oocyte ruptures into the abdominal cavity.
  • Fimbriae sweep the oocyte into the oviduct.
  • Cilia facilitate movement down the oviduct.
  • If cilia aren't functioning, the oocyte can get stuck, leading to ectopic pregnancies (implantation outside the uterus).
  • The most common site for ectopic pregnancy is the oviduct.

Fertilization Window

  • The secondary oocyte is viable for approximately 24 hours after ovulation.
  • Sperm can potentially live in the female reproductive system for up to three days.

Luteal Phase and Implantation Timelines

  • After ovulation, the woman enters the luteal phase, a period of uncertainty regarding fertilization.
  • Fertilization to implantation takes 10-14 days.
  • Cleavage occurs within 30 hours of fertilization (2 to 4 to 8 cells).
  • By 72 hours, there are 16 cells, forming a morula.
  • Blastulation occurs around days 4-5, forming a blastocyst.
  • Implantation begins between days 5-7, with the blastocyst embedding into the endometrium lining.
  • Complete implantation takes an additional 3-7 days, totaling 10-14 days.

Corpus Luteum and Hormone Production

  • After implantation, trophoblast cells produce hCG (pregnancy hormone).
  • hCG signals the hypothalamus to stop the menstrual cycle.
  • The corpus luteum, formed from the remnant of the ruptured follicle, produces progesterone and a small amount of estrogen.
  • These hormones maintain the endometrial lining by suppressing FSH and LH.

Menstrual Cycle Phases and Hormonal Control

  • Follicular phase: Maturing follicle in the ovary, shedding of the old endometrium lining in the uterus.
  • Luteal phase: Endometrium lining becomes thicker and richer, preparing for implantation.
  • If implantation occurs, hCG is released; if not, the cycle starts again.

Key Concepts for the Exam

  • Birth control mechanisms.
  • Phases of the menstrual cycle.
  • Primary vs. secondary sex characteristics.
  • Testosterone and inhibin pathways.
  • Spermatogenesis (order of events).
  • Role of the spermatogonia and where they are found.
  • Oogenesis (differences from spermatogenesis).
  • Fertility concepts.
  • Erection control (parasympathetic nervous system) and ejaculation control (sympathetic nervous system).
  • Corpora cavernosa tissue for erection.
  • Semen production and the role of the three glands.
  • Prostaglandins (uterine contractions, endometrial shedding, labor).
  • Positive feedback loop of labor.
  • Alkaline substances in semen (buffer against acidic environments).
  • Sperm survival rate through the cervix (1%).
  • Female anatomy (Bartholin's gland vs. Skene's gland).
  • Uterine layers: endometrium, myometrium, and parametrium.
  • Oogenesis start and stop points.
  • Superovulation and multiple births.

Twins

  • Monozygotic (identical) twins: One secondary oocyte fertilized by one sperm, followed by the zygote undergoing external cleavage rather than internal.
  • Complete Physical seperation of cells on division lead to twins.
  • Dizygotic (fraternal) twins: Two secondary oocytes fertilized by different sperm. They share the womb at the same time.

Menstrual Cycle and Hormonal Feedback

  • Ovulation is a process we want completed and have a positive feedback.
  • Make sure you get a really good grasp of that.
  • Make sure that you know which phase is positive feedback loop and which ones are negative

Sexually Transmitted Infections (STIs)

  • Know which STIs are caused by viruses and which are caused by bacteria.
  • Distinguish between curable and manageable STIs.

Pelvic Inflammatory Disorder (PID)

  • PID is inflammation or buildup of scar tissue in the oviduct.
  • Causes include infections (STIs, UTIs) and injury.
  • PID itself is not transmissible, but the underlying infection might be.

Follicular, Ovulatory, and Luteal Phases

  • Follicular and luteal phases are negative feedback loops (homeostatic control).
  • Ovulation phase is positive feedback loop (rupture of the secondary oocyte).

Prolactin and Oxytocin

  • Dopamine suppresses prolactin production.
  • Prolactin is trophic (affects the anterior pituitary), while oxytocin is non-trophic (affects the posterior pituitary).

Breastfeeding and Pregnancy Complications

  • Two potential complications when breastfeeding during pregnancy: overuse of resources and risk of early contractions due to oxytocin release.

Sperm and Egg Layers

  • Acrosome contains enzymes that allow the sperm to penetrate the egg layers.
  • Egg layers: corona radiata, zona pellucida, and cell membrane.
  • Only the sperm nucleus enters the egg; the rest remains outside.
  • After penetration, the cell membrane hardens to prevent other sperm from entering.

Fertility and Sterility

  • Sterile: Unable to have children (e.g., no uterus - requires hysterectomy).
  • Fertile: May be able to have children with reproductive assistance.
  • Hysterectomy does not affect hormonal production by the ovaries.

Reproductive Technologies

  • Intrauterine insemination: Occurs within the uterus.
  • In vitro fertilization: Occurs in a Petri dish, followed by implantation into the uterus.

Contraception

  • Contraceptives often produce high levels of progestin, mimicking the luteal phase.
  • This suppresses FSH and LH.

Embryonic Development

  • Sequence: zygote, cleavage, blastulation, implantation, gastrulation, morphogenesis, neurulation.
  • Know which primary germ layers become which tissues. The mesotherm produces muscle.
  • Heart development sequence.
  • Teratogen: Anything a female is exposed to during her pregnancy that crosses the placenta and causes some sort of structural abnormality.

Fetal Development

  • Day 18 : Heart beats.
  • Week 4 : Blood forms.
  • Week 5 : Heart pumps the blood.
  • Week 8 : Detect heart beat on ultrasound.

Placenta vs. Umbilical Cord

  • Placenta: Connection between the endometrium and chorion.
  • Umbilical cord: Tether allowing for transfer of material.
  • Sampling techniques: CVS, amniocentesis, ultrasound.

Week 3: the heart beats.