Answer
By about the 9th day after fertilization implantation is complete. The syncytiotrphoblast, however, continues to erode and disorganize endometrial tissue. One consequence of this activity is that small spaces or openings develop in the endometrium. Progressively, these spaces link up to form a network of larger and larger openings--the lacunar network
Work Step by Step
While the lacunar network is forming , the maternal capillaries adjacent to the conceptus expand to form what are called maternal sinusoids. The syncytiotrophoblast progressively expands the blood spaces, and erodes the endometrial glands ; the mixture of substances produced flows into the lacunae and through the network of spaces. The nutrient rich mixture-- of blood and endometrial secretions-- serves the blastocyst in two ways: it is a source of nutrients, and it removes embryonic metabolic wastes.
