Implantation

Welcome to this lesson on implantation. In this lesson today, you will be learning about the process involved in the implementation of a zygote into the uterus. Specifically, you will learn about:

1. Attachment to Endometrium
2. Stimulation of the Corpus Luteum
3. Ectopic Pregnancy

1. Attachment to Endometrium

Implantation occurs when a blastocyst attaches to the endometrium of the uterus. This process usually occurs between five days to seven days after fertilization. The zona pellucida, which was previously enclosing the blastocyst, will break open. Then the cells of the blastocyst's outer layer will attach to the connective tissue of the endometrium. Remember, the endometrium is the tissue lining the uterus and this is occurring within the uterus.

• Implantation
• A term used to describe when the blastocyst attaches to the endometrium of the uterus.
• Endometrium
• The inner layer of tissue within the uterus; the deepest tissue layer of the uterus where the blastocyst implants itself.

2. Stimulation of the Corpus Luteum

Once the blastocyst has attached to the endometrium it will start secreting human chorionic gonadotropin, abbreviated HCG. Once the blastocyst has attached and implanted in the endometrium it releases HCG. HCG stimulates the corpus luteum to secrete estrogen and progesterone to prevent menstruation.

If implantation has occured you don't want menstruation to occur because the blastocyst would be shed along with the lining of the uterus. Menstruation has to be prevented and that is accomplished by progesterone and estrogen being secreted by the corpus luteum. Generally, fertilization occurs within the fallopian tubes and the fertilized egg will move into the uterus where development begins.

• Human Chorionic Gonadotropin (HCG)
• A hormone secreted from the developing placenta(blastocyst) that prevents the destruction of the corpus luteum; the corpus luteum secretes estrogen and progesterone which prepares the female’s body for pregnancy.

3. Ectopic Pregnancy

Sometimes pregnancies can occur within the oviduct. Rather than the egg moving into the uterus and developing there, the pregnancy can actually occur in the oviduct or fallopian tube. This is called an ectopic or tubal pregnancy. Generally, those type of pregnancies cannot last and will lead to the death of the embryo and mother if medical intervention isn't taken.

• Ectopic Pregnancy
• Also called tubal pregnancy, an ectopic pregnancy occurs when implantation occurs in the oviduct instead of the uterus. Ectopic pregnancies result in abdominal pain that will eventually cause the oviduct to rupture if the pregnancy isn’t terminated.

So this lesson has been an overview on implantation. Specifically, the process of attachment to endometrium, the stimulation of the corpus luteum, and ectopic pregnancy.

Keep up the learning and have a great day!