Embryology Quiz: Fertilization and Development

Study Notes

Sperm releases genetic material, combining with female genetic material to form 46 chromosomes in a zygote.
The zygote travels through the fallopian tube to the uterus for further development into a human.

After fertilization, the zygote undergoes mitosis forming a morula, then a blastocyst consisting of around 100 cells in about five days.
Outer layers of the blastocyst will develop into the placenta, while the inner cell mass develops into the embryo.

The blastocyst attaches to the endometrium (uterine lining) for nourishment, a process called implantation.
Hormones estrogen and progesterone, produced first by the corpus luteum and later by the placenta, prevent menstruation and maintain the endometrium.

Inner cell mass of the blastocyst contains stem cells that can specialize into various cell types.
Three primary germ layers are formed during the second week: ectoderm, mesoderm, and endoderm, giving rise to various organs.

The placenta is formed from both fetal and maternal tissues, providing nutrients and waste removal for the fetus.
It also functions as an endocrine organ, producing hormones necessary for sustaining pregnancy.

Week 4: Rapid brain and nervous system development; heart begins to beat and may be detectable via ultrasound.
Week 5: Umbilical cord forms; facial features such as mouth and nostrils begin developing.
Week 6: Initial formation of fingers and toes; eyes begin developing pigment; genitals start forming.
Week 7: Head growth accelerates; embryo begins movement; internal reproductive organs begin to form.
Week 8: All vital organs are formed and functioning; separation of fingers and toes occurs; marks the end of the embryonic period.

Depo-Provera: Injection providing hormones for 12 weeks, similar to a mini pill.
Implant (Implanon NXT): Hormonal release through a plastic device in the upper arm, effective for 3 years.
Vaginal Ring: Soft ring releasing hormones for three weeks, preventing ovulation without daily intake.

Hormonal IUD: Releases progestin, thickens cervical mucus, thins the endometrium. Example: Mirena (effective for 5 years).
Copper IUD: Impedes sperm movement and prevents implantation; works as emergency contraception within 5 days.

Utilized after unprotected sex (e.g., broken condom); types include the morning-after pill and copper IUD.
Morning-after pill effectiveness declines within 72 hours; side effects may include nausea and dizziness.

Male Sterilization (Vasectomy): Involves cutting the vas deferens; generally does not affect sexual desire.
Female Sterilization (Tubal Ligation): A minor surgical procedure to block uterine tubes; considered a permanent method.

Chlamydia: Diagnosed via urine tests; treated with antibiotics; vaccine research ongoing.
Gonorrhea: Affects reproductive and excretory systems; can lead to severe complications if untreated, with treatment involving antibiotics.
Syphilis: Caused by bacteria through direct contact; affects men and women equally; early treatment is crucial.