When and how does the blastocyst use proteases?
A - The blastocyst uses proteases to hatch from the zona pellucida when it reaches the uterus, and then it uses proteases again to digest the extracellular matrix of the uterine wall which allows the blastocyst to bury itself in the uterine wall.
B - The blastocyst uses proteases to degrade proteins which would allow it to attach to the wall of the fallopian tube.
C - The blastocyst uses proteases to hatch from the zona pellucida when it is in the fallopian tube.
D - The blastocyst uses proteases to digest the extracellular matrix of the uterine wall which allows the blastocyst to bury itself in the uterine wall.
E - The blastocyst uses proteases to hatch from the zona pellucida when it reaches the uterus.
Answer: A. Once the blastocyst reaches the uterus, it uses a protein digesting enzyme, or protease, to make a hole in the surrounding zona pellucida. It then squeezes through the hole to hatch out of the zona pellucida. Proteins on the outer surface of the blastocyst bind to the extracellular matrix of the uterine wall and allow the blastocyst to attach. Once attached, the blastocyst secretes a number of different proteases that digest the extracellular matrix of the uterus and allow the blastocyst to bury itself in the uterine wall.