In Vitro Fertilization - Anatomy & Physiology

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Oocyte Collection

• Donor is superovulated to provide large numbers of mature follicles.
• Pre-ovulatory follicles collected by surgical procedure involving aspiration of the follicular content.
• Oocytes captured in vitro.

• Direct follicle aspiration:
  • A hyperdermic needle is inserted into the follicle.
  • Follicular fluid is aspirated.
  • Follicular fluid forcefully returned to the follicle.
  • Repeated 2-3 times to dislodge oocytes.

• Transvaginal Aspiration in the Mare:
  • Prior to the procedure, mares are injected with propatheline bromide (sedative) to relax the rectum.
  • Lubricated ultrasound transducer is inserted into the vagina and held in the fornix vagina.
  • Ovary transrectally positioned against the dorsal vaginal wall directly over the transducer head so that the follicle can be visualized.
  • Hypodermic needle is advanced through the vaginal wall into the antral follicle.
  • Follicular fluid containing the oocyte is aspirated under constant vacuum.

• Aspirated oocytes are placed in a culture vessel with capacitated spermatozoa.
  • Could also be cultured in a 'nurse animal' in vivo.
• Embryos are incubated for a further period to the appropriate stage for transfer.
• Embryos transferred to recipient female.
• Can be transferred at the correct stage of the recipient's oestrous cycle.
• Embryos transferred around the blastocyst stage.
• Success rates are improving.
• Embryos can be frozen, eliminating the need for tight synchronisation. This allows them to be shipped to other locations.
• Increases incidence of large offspring syndrome.