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  • Published on: 15th October 2019
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Chelsea Brackley

Student ID: 20001574

The reproductive system- Mary the Midwife

In reference to the case study, it is clear that Donna and Dan need some advice on the aspects of contraception as well as conception and pregnancy. In doing this, Mary the midwife thought it would benefit them to sit down and discuss this.

Summarise the journey taken by the gametes to achieve fertilisation.

The eggs are found in the Fallopian tube of the woman’s reproductive system, in their ovaries. The mans sperm are found in the testes.

The gametes contain of the egg and sperm. The egg is around 20 times bigger than the sperm and is surrounded in a thick layer called the membrane. This helps to protect the nucleus and if the egg is fertilised, it would protect the zygote. It is also surrounded by a load of cells known as granulosa cells. The sperm contains of the head, which is where the genetic material is carried; the acrosome, which is on the head of the sperm, which helps to penetrate the egg, which has enzymes to help this process. The sperm also has a tail (flagella), which helps the sperm to move up into the female genital tract and the mitochondria, which gives the sperm cell energy to achieve this. Once the sperm has been released from the penis, it travels up into the cervix and uterus, where many will die through this process. The ones that survive, make their way to the fallopian tube, where they will try to penetrate the membrane of the egg. Only one sperm cell will be successful in fertilising the egg. Once this has happened, the sperm cells will start to fuse with the eggs nucleus.

After this process has happened, and the sperm cells start to fuse with the egg, it creates and forms a new cell. In this cell, called the zygote, it contains 23 chromosomes from each parent, totalling at 46 chromosomes all together. Around 3 days after the egg was fertilised, the zygote will begin to divide creating a cluster of cells, which is known as the blastocyst. After it continues this process, the blastocyst becomes the embryo.

Explain what is meant by the terms fertilisation and implantation with reference to structure of formed cell/cells.

The term fertilisation is when the egg gamete and the sperm gamete fuse together. Once they fuse, they begin to divide in the process known as mitosis, splitting into four cells, each with their own set of chromosomes, which will come together and create a zygote. The chromosomes will also fuse, totalling at 46 chromosomes all together. After this happens, it soon forms a morula which is a cluster of cells (a ball). When the ball of cells divide, the cells become a embryo. This happens around 7-14 days after fertilisation. It is known as implantation. The term implantation is when an egg attaches itself to the uterus lining, after being fertilised, and implants itself.

Here is a diagram of fertilisation.

Here is a diagram of the stages of implantation

Describe the early stages of a developing embryo.

For the first 8 weeks of a pregnancy, the ‘baby’ is known as an embryo.

The first organs to develop in an embryo are the heart and brain in which the heart should beat within the 4th week of development. This is also when other muscles will start to develop; followed by the nervous system which begins to grow by the third week of pregnancy. By the end of the 4th week (a month), the embryo would have 4 limb buds, which is where the limbs, such as arms and legs, will eventually grow. By the end of the 2nd month, the embryo is clearly seen as a human and can be recognised through a scan. If the embryo is a male, by the end of the 2nd month, the testes would have formed and would be able to release testosterone.

The embryo will continue to grow into the fetal stage after week 8, where the organs will continue to mature until birth.

Please see diagram below, which shows the embryonic development in stages.

Explain the role of the placenta during pregnancy.

As the embryo grows, it needs nutrients to keep it growing so the placenta plays this role after implantation occurs. It is the organ in which it supplies nutrition, respiration and excretion whilst the embryo grows. Gases, such as, oxygen and carbon dioxide are exchanged between the mother and the embryo through the maternal blood as is it to get rid of waste too. In getting rid of the waste, chorion,  which forms projection in the endometrium, breaks down endometrial tissue. The embryo is attached to the placenta, through tissue, which will later become the umbilical cord. The umbilical cord is how blood is transported to and from the embryo, it consists of two arteries and a vein, where the arteries carry low oxygenated blood from the embryo to the placenta and the vein carries oxygenated blood to the embryo. Some of which, the oxygenated blood, is carried to the liver of the embryo and can also bypass this and deliver blood through the pulmonary artery. Although after travelling through the tissue of the embryo, the blood returns to the placenta to pick up more oxygen through the two arteries in the umbilical cord.

Compare and contrast the role of the hormones during birth and lactation.

Progesterone is important during birth as it helps the uterine muscles to contract. It is also important during lactation because it prepares the breasts for milk secretion which leads me on to say that oestrogen is important during lactation and birth as it increases breast size as well as enlargement of the uterus.

Bibliography

• Ted Smart, 2001, human biology. First UK edn, pg. 258-259

• BBC, 2014, Gametes and Fertilisation, pg. 3. Available at: http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/celldivision/celldivision3.shtml

• Dawn Stacey, 2018, implantation and the start of pregnancy, pg. 1. Available at: https://www.verywellfamily.com/implantation-906754

• https://www.online-sciences.com/wp-content/uploads/2015/09/sexual-reproduction-333.gif

• https://www.ovulationcalculator.com/ovulation/

• Taylor/Cohen, 2013. Memmlers structure and function of the human body. 10th edn. Baltimore: Lippincott Williams & Wilkins

• http://www.assignmentpoint.com/science/medical/embryonic-development.html

• Taylor/Cohen, 2013. Memmlers structure and function of the human body. 10th edn. Baltimore: Lippincott Williams & Wilkins

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