Conception and Birth

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Task 1, Pass 1

 

Describe the process of conception, embryonic and foetal growth, and factors that can affect this development.

 

Conception and Birth

Conception is the process that occurs as a result of sexual intercourse or IVF (in vitro fertilisation) – in either case, a sex cell from both the male’s sperm, and the female’s ovum is needed, to create the embryo. The menstrual cycle releases the ovum, and a bad lifestyle can influence the timing of the ovum’s release.

            The menstrual cycle is controlled by the pituitary gland situated in the base of the skull – four different hormones are released over the 28 day cycle, and all of these are essential in the process of conception. When the ovum is released, it is taken in the direction of the fallopian tubes, where the tiny hairs guide the ovum to travel through the tube where it reaches the uterus. If the ovum comes into contact with a male’s sperm cell, the sperm will pierce the outer coating of the ovum, before penetrating the nucleus of the ovum. The sperm and ovum then fuse together to create a zygote, one cell. A set of 46 chromosomes is created, 23 chromosomes from the sperm, and 23 chromosomes from the ovum, making 23 pairs – if one chromosome is damaged, a chromosomal abnormality can be created such as Down’s syndrome.

            The zygote then splits into two, and continues dividing quickly, with cells forming both the embryo and the placenta, these cells take 4 days to reach the uterus where it is then called a blastocyst, which gets attached to the uterus wall by hair like projections called villi. It is when the blastocyst is implanted into the soft wall of the uterus that it connects to the bloodstream and it starts to absorb both oxygen and nutrients for growth, and when this occurs, 10-14 days after conception, it is then referred to as an embryo.

            By day 26, the hormone progesterone will continue to be produced throughout the pregnancy, the menstrual cycle will discontinue for the duration of the pregnancy, and some muscles will become softer, such as in the uterus, intestine, and bladder.

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            During the first trimester, in week 3, the first missed period will occur, the brain and nervous system start to form, and the placenta acts as some vital organs (liver, lungs, kidneys) for the embryo, and is connected to the embryo by the umbilical cord. Soon after this, the embryo is approximately 6.4mm long, and the neural tube closes. In week 5, the heartbeat can be detected, and the embryo is the size of a small seed.

            By the eighth week of pregnancy, the embryo contains 10,000 cells, and is 2.5cm long, and the startle reflex is developed. ...

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