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University Degree: Developmental & Reproductive Biology
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Everest, not nearly enough pressure for an adult. How then, can a fetus survive on such low oxygen pressure? A fetus is able to cope with this low amount of oxygen pressure in several ways: 1. A fetal heart beats extremely fast - an average of 150 times per minute. A normal adult, on the other hand, has an average heartbeat between 70-80 times per minute. 2. A fetus has more red blood cells per cubic millimeter than an adult (seven million compared to five million in an adult!). A fetus' heart must beat quickly in order to allow such large amounts of red blood cells to pick up the much-needed placental oxygen.
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External respiration is the diffusion of O� from the alveoli of the lungs to the blood in capillaries and diffusion of CO� in the opposing direction. In the lungs deoxygenated blood coming from the right side of the heart is converted into oxygenated returning to the left side of heart. O� is uploaded through the pulmonary capillaries and CO� is unloaded into the alveolar air. Internal respiration is the gas exchange of O� and CO� between systemic capillaries and tissue cells throughout the whole body.
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As soon as the chromosomes begin to condense, the DNA becomes inactive. The condensation of the chromosomes into separate structures enables them to be moved easily. During Interphase they are diffuse and would become entangled if they were moved about the nucleus. In the later stages of Prophase, pairs of sister chromatids can be seen. These chromatids are attached at a point called the centromere. The nucleoli disappear, the nuclear membrane breaks down and a spindle apparatus is formed. The spindle apparatus is made up of microtubules which control the movements of the chromosomes.
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However this is not so with the oldest living organism on the planet being 3000 years old - a tree, still producing saplings! How the number of eggs in a female declines throughout the years: At 16 weeks, the female foetus contains 7 millions eggs, however this number decreases as the cells die - apoptosis (cell death). By birth, nine weeks, a female baby has only 2 million eggs contained in her uterus. Despite these relatively large numbers, females only use 360 eggs in a lifetime, although as mentioned above, the eggs a female releases later in her life are much less fertile.
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However meiosis is made much more complicated by a processed called crossing over; this means that the chromosomes can be broken up and sections of the chromosome can switch over and exchange with each other making a unique combination of 23 chromosomes which can be passed on to the offspring When the gametes from each parent combine at fertilisation 'a zygote (fertilized egg cell) with the full complement of chromosomes is produced' (Pinel J.P.J, 2000, 36,)  thus creating an even more unique combination of genetic material.
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The combination of complementary and conventional care works well but more importantly; it can give the couple the highest potential for success." http://www.positivehealth.com/permit/Articles/Womens%20Health/infertil.htm When fertility drugs are used many people believe that they just do one thing and increase fertility however they can have many harmful side effects. Many people can over look this when they decide to use them to increase their fertility. "The effectiveness of fertility drugs such as Clomiphene and Bromocriptine are overshadowed by their many, and often very harmful, side effects.
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The doctor can then perceive when the eggs are mature by monitoring the blood level hormone of the women, on an ultrasound. When the eggs are ready to be retrieved, the doctor will remove them using a fine hollow needle. The eggs are then combined with the partner's sperm in a dish containing a nutrient, which is then refined in an incubator. Two days later any fertilised eggs will become a ball of cells called an embryo, two or three embryos are transferred into the uterus through the cervix with a thin catheter.
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Prolactin stimulates the mammary glands of the breast, to promote and sustain milk production. Follicle-stimulating hormone (FSH) encourages the production of eggs in women and sperm in men, whilst the luteinizing hormone motivates the release of the eggs and the creation of progesterone in women, and the emission of testosterone in men. The thyroid is generated into hormone production by the thyroid-stimulating hormone (TSH) in the pituitary gland, whereas the adrenal gland is prompted into action by the adrenocorticotrophic hormone. The posterior lobe of the pituitary contains oxytocin and antidiuretic hormones, formed in the hypothalamus, and transported to the pituitary within nerve fibres.
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This allowed only the female embryos to be selected and implanted into the potential mothers. After this process was carried out, both of the patients gave birth to healthy female twins. This process would not have been possible if it were not for the discovery of PCR by Kary Mullis in 1985. The technique used is now called Pre-implantation Genetic Diagnosis, and to date it allows the screening of more than 100 different genetic diseases (Strode. A, 2011). This technique allows the identification of embryos that carry inherited mutations in single genes. PGD involves several steps and can be used to select embryos without a genetic disorder, to have less cancer predisposition, to match a
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