Embryology

1 Question: After how many days of ovulation embryo implantation occurs (AIIMS) Options: (1 ) 3 - 5 days
(2 ) 7 - 9 days ✅
(3 ) 10 - 12 days
(4 ) 13 - 15 days

Important facts :
1. From the time of ovulation it takes 3-4 days(or 18-19 days from the last menstrual cycle) --- for Fertilized Ovum in the Ampulla (Tube) to reach the Uterus.

2. From the time of ovulation it takes 7-9 days (or 21 – 22 days from the last menstrual cycle) --- for Implantation (During this time the Uterine milk /secretions provide nutrition for early dividing Ovum) – The predominant morphological feature is edema of the endometrial stroma.

3. Oogenesis begins in ovary – 6-8 weeks of gestation

4. Maximum number of oocytes (6-7 million) are attained at 20 weeks (5th Month) of gestation.

5. At birth total content of Both ovaries is 2 million primary oocytes.
6. At puberty number is decreased further and is – 300000 – 500000 of which only 500 are destined to mature during an Individual’s life !

7. All the primary oocyte in the ovary of a newborn till puberty – arrested in Late prophase

8. First polar body is released just prior to ovulation

9. Second division starts just after it and is -- arrested in metaphase

10. Thus second polar body release occurs only at the time of fertilization.

11. LH surge precedes ovulation by 34 – 36 hrs.
12. LH peak precedes ovulation by 10 – 16 hrs

13. Prior to ovulation : a) Follicle reaches a size of 18 – 20 mm (KCET 2009) b) Endometrium is 9 – 10 mm thick c) Endometrium shows triple line on USG

14. Maximum action of Corpus Luteum is at 22 days of Menstruation
15. In the absence of fertilization – corpus Luteum persists for – 12–14 days

16. Maximum Growth of Corpus Luteum is at 8th week of Gestation and degenerates at 6th month of gestation