Pregnancy

• Ejaculation

  1. 300 million sperms move from the testes through the vas deferens into the area of the prostate

  2. Prostate contracts closing off the opening between the bladder and the urethra, releasing fluid into the urethra and pushing semen on through

  3. Seminal fluid forms a thick alkaline fluid to protect sperm from the acidic environment of the female vagina

  4. Gel is liquefied by enzymes from the prostate gland and contains sugars to nourish the sperm

  5. Sperm use their tails to swim through layers of cervical mucus guarding the entrance to the uterus

  6. During ovulation, the barrier becomes thinner and changes acidity, creating a friendlier environment for the sperm

  7. After releasing the egg, it arrives at the ampullary-isthmic junction in the tube and rests for 30 hours

  8. Fertilization occurs in this portion of the tube

  9. Once the sperm has entered the uterus, contractions propel the sperm upward into the fallopian tubes to meet the waiting egg

  10. Sperm must travel from the vagina to the fallopian tubes, a tough journey that few sperm survive

  11. First sperm enter the tubes a few minutes after ejaculation, but the first sperm are not likely to fertilize the egg

  12. Most sperm can survive in the female reproductive tract for up to five days

  13. Fallopian tube pushes the egg towards the uterus, cilia push the sperm towards the egg

  14. Surrounding cells of the egg produce a chemical that attracts sperm

  15. Sperm burrow through the cells of the corona radiata and bind to receptors in the zona pellucida

  16. The acrosome of the sperm releases its stored digestive enzymes upon contact with the zona pellucida

  17. Sperm must fuse with the egg plasma membrane, causing the egg membrane to change and prevent other sperm from attaching

  18. Sperm's nucleus enters the egg cell, combining genetic material to create a zygote
• The combined sperm and egg is called a zygote, the earliest developmental stage
• Zygote divides rapidly in the days following fertilization
• Zygote travels down the fallopian tube to the uterus after fertilization
• Zygote continues to divide and morph into a blastocyst, a ball of 16 cells, approximately five to six days after fertilization
• Only 20% to 30% of fertilized eggs will reach the blastocyst stage
• Embryos surviving the blastocyst stage have a high implantation potential
• Blastocyst hatches out of its shell and burrows into the uterine wall, endometrium, providing oxygen and nutrients
• Approximately four weeks from the beginning of the last period, the blastocyst begins to produce the pregnancy hormone to stop releasing eggs
• Blastocyst is called an embryo near the next period, and home pregnancy tests might show a positive result at week five
• Circulatory system, brain, and spinal cord begin to form at week six
• At weeks seven and eight, the embryo doubles in size, and little hands and feet start to grow
• At weeks 9 to 12, the embryo is called a fetus, almost fully formed with recognizable facial features, and the reproductive, circulatory, and urinary systems are at an advanced stage of development
• The fetus will urinate in the amniotic sac, a sign of proper functioning of the fetus's body
• If the baby is a girl, her ovaries contain millions of eggs; if a boy, his testicles start producing testosterone
• The fetus is about five centimeters in size and 14 grams in weight, growing and maturing until ready for birth