Friday, 13 December 2013

Embryology

Golden points embryology
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 jProphaser 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

Extra points :
1. LH surge tends to occur at around 3 AM.
2. Ovulation occurs in morning between (midnight and 11 AM) in Spring
3. Ovulation occurs in evening between (4 PM and 7 PM ) in Autumn and winter .
4. Ovulation occurs more frequently from Right Ovary
5. Ovulation occurs alternatively between the two ovaries in younger women
6. In women more than 30 yrs age ..ovulation occurs frequently from the same ovary.

Remember :
1. The primitive germ cells takes origin from Yolk sac at 3rd week of gestation and migrate to the Genital ridge by 4th week of gestation .
2. 1st meiotic division – arrested in Prophase – completed just prior to Ovulation releasing
the 1st polar body.
3. 2nd meiotic division – arrested in Metaphase – completed at the time of fertilization releasing the 2nd Polar body.
4. Also, Primary Oocyte – 44XX; Secondary Oocyte – 22X;
5. Primary Oocyte(44X) – undergoes 1st meotic division – Arrested in prophase – completed just prior to ovulation – releases
First polar body (22X) + Secondary Oocyte (22X)
6. Secondary Oocyte (22X) – 2nd meiotic division – Arrested in Metaphase – At the time of fertilization – releases Second Polar Body (22X) + Ovum (22X)
7. In Males : Primary spermatocyte (44XX) – undergoes 1st meiotic division – forms secondary spermatocytes (2 in number)
8. Secondary spermatocytes (22X) (2 in number) – undergoes 2nd meiotic division –  forms Spematids (22X)(4 in number)
9. Spermatids undergoes transformation as spermeiogenesis – forms Sperma (4 in number)
10. Developmental process from Spermatogoonia to Sperma takes 74 days
(Some books 61days)and entire process till the transit to the ductal system takes 90 days (3 months)
11. So, in case of infertility of males the repeat sperm analysis is done after 3 months.

Age in days and development events 
1. 2 days – Embryo at 2 cell stage
2. 3 days – Morula is formed
3. 4 days – Blastocyst is formed
4. 8 days – Bilaminar disc is formed
5. 14 days – Prochordal plate & primitive streak seen
6. 16 days - Intra-embryonic mesoderm is formed / Disc is three germ layers

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