How are rats fertilized? - briefly
Rats fertilize internally: during copulation the male deposits sperm in the female’s vagina, which ascends to the oviduct where it meets the ovulated egg. Implantation of the resulting zygote occurs in the uterine lining about four to five days after mating.
How are rats fertilized? - in detail
The reproductive cycle of female rats consists of a four‑day estrous phase followed by a non‑receptive diestrus. Ovulation occurs spontaneously on the afternoon of estrus, releasing a single oocyte into the ampulla of the oviduct.
During copulation, the male inserts the glans penis into the female’s vagina, delivering a ejaculate that contains 1–2 × 10⁶ sperm cells. Sperm travel through the cervix, uterus, and into the oviduct via muscular contractions and ciliary action. Within minutes, a proportion of motile sperm reach the ampulla, where they encounter the ovulated oocyte.
Fertilization takes place in the ampulla. Capacitated sperm bind to the zona pellucida, undergo the acrosome reaction, and fuse with the oocyte plasma membrane. The male pronucleus and female pronucleus then migrate toward each other, complete syngamy, and form the zygote.
Key physiological factors include:
- Estrogen surge on the day of estrus, priming the reproductive tract for sperm passage.
- Progesterone rise after ovulation, supporting embryo development.
- Prostaglandins in the ejaculate, enhancing uterine contractions and sperm transport.
Following fertilization, the zygote progresses to the uterus, where it implants after approximately 5 days. Successful breeding therefore depends on precise timing of estrus, effective sperm delivery, and the coordinated hormonal environment that guides sperm migration and oocyte activation.