Reproduction

• Spermatogenesis: 

  1. Spermatogonia undergoes mitosis to produce two spermatogonium; one to undergo spermatogenesis.
  2. The spermatogonia becomes a primary spermatocyte, which undergoes meiosis 1 to produce two secondary spermatocytes.
  3. The two secondary spermatocytes each undergo meiosis 2 to produce 4 spermatids.
  4. The spermatids develop into sperm
• The head of the sperm contains acrosome to dissolve the egg cell wall.
• The sperm flagella is made of actin microtubules
• Oogenesis:

  1. The diploid oogonia undergoes mitosis before birth to produce a primary oocyte, which is arrested in prophase 1 until puberty. 
  2. After puberty, the primary oocyte releases a polar body and undergoes meiosis to become a secondary oocyte, which is stuck in metaphase 2 until fertilization.
  3. After ovulation, the sperm penetrates the haploid egg and meiosis completes, producing a diploid zygote. 
• The menstrual cycle begins with a drop in estrogen and progesterone
• The follicular phase is marked by increase in estrogen, causing increase in LH which triggers ovulation
• The luteal phase is marked by increase in progesterone and estrogen, which decreases LH and FSH. If no implantation occurs, then the progesterone and estrogen levels drop. If implantation occurs, HCG increases.
• Capacitation occurs in the oviduct
• Capacitation prepares the sperm for the acrosomal reaction, and makes the sperm more permeable to calcium so that the flagella can beat faster
• The fast block to prevent polyspermy is egg membrane depolarization through the influx of Na to prevent additional sperm from binding
• The slow block to prevent polyspermy is called the cortical reaction, which forms an impenetrable fertilization envelope
• Sperm is produced in the seminiferous tubules and matures, during spermatogenesis, in the epididymis