Question

During human implantation a. cytotrophoblast cells spread along the basal lamina of the uterine epithelium b. the blastocyst usually invades the cervical region of the uterus c. the blastocyst is present during the proliferative phase of the uterine cycle d. syncytiotrophoblast cells will invade uterine stroma following endometrial contact e. the anterior pituitary begins secreting high amounts of hCG

Answer 1

d.Syncitiotrophoblast cells will invade uterine stroma following endometrial contact

The zona pellucida starts disintegrate & blastocyst inside will be free to contact with endometrium - Proliferation of the endometrial lining occurs to form crypts - The outer cell layers of the proliferated endometrium comes into contact with the Blastocyst 'Apposition' - The outer cell layer called trophoblast gets multiplied and invades through the proliferation -'Adhesion' - Endometrial proliferation overlaps and embeds the trophoblast within it - The apposing cells of the trophoblast keep dividing and starting to get bigger and fuse to the endometrium through invasion 'Syncitiotrophoblast' - The cells that doesn't take part in the fusion is called 'Cytotrophoblasts' - Syncitiotrophoblast continue to grow and form finger like projections called 'Villi' - Uterine blood vessels continue to grow - The cytotrophoblast layer begin to line the periphery of villi - Within the villi fetal blood vessels are formed - The membrane of trophoblast layer blocks the mixing of uterine and fetal blood vessels - The nutrients from uterine blood vessels are exchanged with the waste products of the fetal blood vessels - Eventually these structure begin to fill the uterus called 'placenta'