Analyse the features of fertilisation, implantation and hormonal control

Analyse the features of fertilisation, implantation and hormonal control of pregnancy and birth in mammals (ACSBL075)

Features of fertilisation in mammals:

Occurs when sperm and ovum fuse and the result is a single celled zygote.
For successful fertilisation to occur, sperm must be deposited in the vagina within 24-72 hours after ovulation since they have very limited lives.
Once deposited within the vagina, the sperm swim through the cervix and into the uterus, and then up into the fallopian tubes where the ovum resides.
The movement of sperm on this long journey is helped by muscular contraction of the walls of the uterus and the fallopian tubes. Fertilisation of the ovum occurs in the fallopian tube.
Only one sperm will succeed in fertilising the ovum by penetrating its cell membrane and depositing the male genetic material into the female cell, where the two nuclei fuse.
The fertilised ovum (zygote) immediately becomes resistant to penetration by any other sperm arriving later. After fertilisation occurs, the zygote remains in the fallopian tube for about 72 hours, and during this time it develops rapidly, as you will see in the next section.

Features of implantation in mammals:

Between five to seven days after fertilisation, the blastocyst reaches the uterus and embeds itself in the thickened endometrium (lining of the uterus). This process is called implantation, and if the embryo survives it is the beginning of a pregnancy.
If the blastocyst implants successfully in the uterus, the cells go on multiplying by cell division and moving around into new locations to form two distinct structures:
- Three or four blastocyst cells develop into the inner cell mass, which over the next few weeks will form into the recognisable structures of a human embryo, with a head, beating heart and tiny limbs. Some of these cells also develop into the fetal membranes that form a fluid-filled protective ‘bag’ around the embryo.
- The remaining 100 or so blastocyst cells form a structure called the trophoblast, which will provide the baby’s contribution to the placenta. The first stage of development of the placenta is when the trophoblast cells burrow into the endometrium.

Hormonal Control of pregnancy:

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Analyse the features of fertilisation, implantation and hormonal control of pregnancy and birth in mammals (ACSBL075)

Features of fertilisation in mammals:

Occurs when sperm and ovum fuse and the result is a single celled zygote.
For successful fertilisation to occur, sperm must be deposited in the vagina within 24-72 hours after ovulation since they have very limited lives.
Once deposited within the vagina, the sperm swim through the cervix and into the uterus, and then up into the fallopian tubes where the ovum resides.
The movement of sperm on this long journey is helped by muscular contraction of the walls of the uterus and the fallopian tubes. Fertilisation of the ovum occurs in the fallopian tube.
Only one sperm will succeed in fertilising the ovum by penetrating its cell membrane and depositing the male genetic material into the female cell, where the two nuclei fuse.
The fertilised ovum (zygote) immediately becomes resistant to penetration by any other sperm arriving later. After fertilisation occurs, the zygote remains in the fallopian tube for about 72 hours, and during this time it develops rapidly, as you will see in the next section.

Features of implantation in mammals:

Between five to seven days after fertilisation, the blastocyst reaches the uterus and embeds itself in the thickened endometrium (lining of the uterus). This process is called implantation, and if the embryo survives it is the beginning of a pregnancy.
If the blastocyst implants successfully in the uterus, the cells go on multiplying by cell division and moving around into new locations to form two distinct structures:

Three or four blastocyst cells develop into the inner cell mass, which over the next few weeks will form into the recognisable structures of a human embryo, with a head, beating heart and tiny limbs. Some of these cells also develop into the fetal membranes that form a fluid-filled protective ‘bag’ around the embryo.
The remaining 100 or so blastocyst cells form a structure called the trophoblast, which will provide the baby’s contribution to the placenta. The first stage of development of the placenta is when the trophoblast cells burrow into the endometrium.

Hormonal Control of pregnancy:

Hormones play a vital role during pregnancy. A wide range of hormones are involved and their roles have been described below:

hCG is mainly responsible for the early pregnancy symptoms ranging from missed menstruation to nausea, vomiting and fatigue.

This hormone maintains the functionality of placenta and prevents sudden movement and contraction of the uterus.

It is an ovarian hormone that is controlled by luteinising (hormone that triggers ovulation and develops in the corpus luteum).
An important role of estrogen is to facilitate the maturation of lungs, kidneys, adrenal gland, liver and bone density of the unborn baby. Besides this it also aids the flow of blood to fetus. Estrogen also protects the female baby from the masculine effects of androgen.

Human chorionic somatomammotropin hormone (HCS) also known as Human placental lactogen (HPL) hormone facilitates fetal development and formation of lactation glands.
Oxytocin facilitates the delivery process by helping in the contraction of uterus and also stimulates the mammary glands to produce milk.
Calcitonin is useful in calcium metabolism and prevents the bone calcium form entering the blood system.
Prolactin and oxytocin help the woman to get rid of post pregnancy problems.