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Sunday, April 28, 2024

General embryology : PART 4 Implantation

 

Implantation

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The process during which the blastocyst attaches to the endometrium and subsequently embeds in it.

Time of implantation

It occurs at 6 days after fertilization and by the 11 th to 12th days of development the blastocyst is completely embedded in the endometrial stroma.

Implantation bleeding

Bleeding may occur at the implantation site as a result of increase blood flow into the lacanarspaces.

Implantation bleeding occur near the 28th day of menstrual cycle, it may confused with normal menstrual bleeding.

Mechanism of implantation:

 it has three stages:

(a) the blastocyst contacts the implantation site of the endometrium (apposition);

(b) trophoblast cells of the blastocyst attach to the receptive endometrial epithelium (adhesion); and

(c) invasive trophoblast cells cross the endometrial epithelial basement membrane and invade the endometrial stroma (invasion) 

Normal sites of implantation: The blastocyst implants in the endometrium along the anterior or posterior wall of uterus near the fundus.

(Trophoblast cells of blastocyst invade the epithelium and underlying endometrial stroma with the help of proteolytic enzymes)

Abnormal implantation:

1.        Implantation in abdominal cavity

2.        Implantation in the pouch  of Douglas

3.        Implantation in the ampullary region of f. tube (most common)

4.        Implantation in the internal os

5.        Ovarian implantation

6.        Interstitial implantation

7.        Tubal implantation


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