Foetal Development Medical Illustrations

The Week by week Development of the Human Foetus

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Foetal – Human Foetus (Fetus) Development

Foetal (Fetal) development in human’s is the process from fertilisation where fusion of the male and female gametes has occurred. This is the fusion of female gametes called an ova or egg and male gametes called sperm. Gametes are specialised haploid cells and each cell carries only one copy of each chromosome. Therefore, fertilisation has completed when the nuclei of the ova or egg and sperm have combined, creating a single cell that is then capable of development by dividing into further cells.

When the sperm and egg meet fertilisation occurs inside one of the fallopian tubes. The journey of the now fertilised egg continues its journey and carries along the fallopian tube for about four days. During this time the single cell has been dividing until it finally a ball of cells that surround a fluid filled inner cell called a blastocyst. The blastocyst inner cell mass is what subsequently forms the embryo.

The blastocyst enters the uterus via the fallopian tube and implantation into the uterine endometrium occurs. The blastocyst ‘buries’ itself in the uterine endometrium and this initial phase of the implantation process is called “adplantation”. Subsequent developments are the forming a placenta so the embryo can gain nutrients to grow and the placenta is what allows for the maternal support during foetal development.

Dating Your Pregnancy

The actual exact age of a developing foetus and the due date of a baby’s birth given to an expectant mother, differs by approximately two weeks. These medical illustrations of the foetus are dated from the actual day of fertilisation. A woman’s pregnancy dates differ because it is not possible to know exactly when a woman’s egg was fertilised, plus there are also several days around ovulation when fertilisation could have taken place.

So a GP will estimate the length of the pregnancy using the dates of the last period, or menstrual cycle. Therefore, pregnancy is calculated using the date of the first day of the period, which means a woman will be considered to be 4 weeks pregnant by the time the next period has been missed.

The actual foetus, however, which had been fertilised right at the start of ovulation, has already been developing for approximately two weeks, although for the first seven days it would only have been a collection of dividing cells. So week tow of our illustrations is predicted by the GP to be your week 4 and so forth. This is why the date of when labour is due can sometimes by out by two weeks.

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