How do hormone levels change in pregnancy?

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Biology – Human reproductive Biology TAQ 1 Assessment Criterion 1.1 1.1 Explain the relationship between structure and function of the male and female reproductive systems Explain the process of reproduction with particular reference to the role of the different structures within the male and the female reproductive systems (200 words) Word Count: 200 In coitus, the male’s penis stiffens and is inserted into the female’s vagina. During orgasm the male ejaculates, releasing semen containing sperm cells through the urethra travelling up the female’s fallopian tubes to reach the egg and tries to penetrate its outer coating. If successful, the head of the sperm enters the egg, fusing with the nucleus and the egg implants in the lining of the uterus which is thicker after ovulation. Between puberty and menopause, females experience a monthly menstrual cycle in preparation for reproduction. A mature egg is released and the endometrium becomes thicker in order for a fertilised egg to implant and if not fertilised, it exits the body during menstruation. The fallopian tubes deliver eggs to the uterus where a foetus will develop. Sperm cells are produced in the testes and then kept cool in the scrotum in order to be produced efficiently. Mature sperm then leave the testes through an epididymis where stored before travelling to the vas deferens. During sexual intercourse, the vas deferens contracts and pushes sperm towards the urethra for ejaculation. Muscular contractions at the base of the penis then enable sperm to be forced through the male urethra into the vagina. Fig 1 – Female Reproductive System Fig 2 – Male Reproductive System

Source of hormone

Hormone

Function(s)

Placenta

Human chorionic gonadotropin (hCG)

Maintains pregnancy and affects foetal development. It is produced from 6 days after fertilisation, rises over 5-6 weeks and reaches maximum concentrations by 8-10 weeks. It rapidly decreases from 11-13 weeks and plateaus from 20 weeks for the remainder of pregnancy.

Ovaries

Progesterone

Maintains the uterus lining’s thickness so that it is ready for the implantation of an embryo. In the first few weeks levels are double that of non-pregnant levels and this rises throughout.

Ovaries

Oestrogen

Stimulates the uterus lining in order to thicken. It also rebuilds the uterus lining after menstruation. Levels range until 34 weeks pregnant and then steadily increase.

Hypothalamus

Oxytocin

Helps during lactation of milk during breastfeeding, contraction during birth and is released during sexual orgasm. During labour, it is released in a pulsatile way . It is at its highest level during early labour with two to three times more than during pregnancy and increases from late pregnancy to labour.

Hypothalamus

Gonadotrophin releasing hormone (GnRH)

Stimulates LH and FSH and maintains reproductive function in males and females.

Anterior pituitary gland

Luteinising hormone (LH)

Stimulates ovulation and the development of the corpus luteum. This then stimulates the ovaries in producing progesterone from the corpus luteum. In the male, it aids the production of sperm.

Anterior pituitary gland

Follicle stimulating hormone (FSH)

Stimulates the follicles in the ovary to develop. This allows the ovaries to then produce oestrogen. In males, it aids the production of sperm.

Testicles

Testosterone

Stimulates sperm production.

Biology: Human Reproductive Biology TAQ 3 Assessment Criterion 2.1 2.1 Critically evaluate the advantages / disadvantages of different methods of contraception Using a table, critically evaluate the different forms of contraception using both the advantages and disadvantages of each before reaching a conclusion as to which are seen as the best methods (400 words) Word count: 400

Method of contraception

Evaluation of advantages

Evaluation of disadvantages

Final evaluation

Condoms

Effective protection from STDs and conception. They are free from family planning clinics or can be bought elsewhere meaning that they are easily accessible. 97% effective.

Condoms can split. There is still a risk of contracting certain STDs when wearing a condom. Female condoms have a 15% failure rate and are not free through the NHS.

With its high effectiveness rate, this method of contraception is one of the best options. However, if the condom splits it will not be effective.

Pill

The combined pill is almost 100% effective with a very low pregnancy rate. Impenetrable to sperm and makes it difficult for sperm to travel up the fallopian tubes.

There are side effects and an increased risk of a stroke due to the pill causing blood to clot easier. Missing a pill could affect its effectiveness.

As there is such a high effectiveness rate, the pill is one of the best options for contraception. However, there are side effects and missing one day can change the effectiveness.

Coitus interruptus

There aren’t any advantages with coitus interruptus.

When withdrawing before ejaculation, there is still a high risk of leakage of seminal fluid beforehand and therefore is not considered an effective method at all.

Due to the high risk of premature ejaculation before withdrawal, coitus interruptus is a highly ineffective use of contraception.

Intrauterine device

All IUCDs contain silver or copper threads which increase efficiency with a spermicidal effect which repels sperm and reduces the speed at which the ovum travels along the fallopian tube. The new Mirena coil is statistically more effective than sterilisation and can be used for 3 years but other IUDs that remain effective for 5-7 years.

Due to the reduction in tubular contraction, it has been found that infrequent ovulation can occur. If a pregnancy does occur; there is a raised risk of mid-trimester miscarriage.

The IUD is statistically better than sterilisation so very effective. However it doesn’t come without risks.

Rhythm method

If done correctly - 80 – 87% effectiveness.

There are between one to two days where an egg can be fertilised by sperm, however sperm can survive for 5 – 7 days so there is still a chance of conception. It is also very difficult for most women to predict their ovulation.

Although there is an effectiveness rate of 80-87% when used correctly, this is not always an effective method of contraception due to the difficulty in predicting a woman’s ovulation.

Biology: Human Reproductive Biology TAQ 4 Assessment Criterion 3.1 3.1 Describe the cause of a range of common genetic conditions What causes each of the following genetic conditions? (300 words total) 1. Huntington’s disease (100 words) Huntington’s disease is caused by inheritance of a mutant dominant gene from one of the parents, with carriers having a 50% possibility of passing it on to all of their children and the disease developing. It is the chromosome number four that is the faulty gene that causes Huntington’s disease and is inherited in autosomal dominant mutation from either of the carrier parent’s two copies of a gene called huntingtin. Growth of a cytosine, adenine and guanine triplet within the huntingtin gene causes a different form of the protein huntingtin to be produced which in time damages brain cells. Word Count: 99 Diagram showing a father carrying the gene and an unaffected mother leading to some of their offspring being affected; those affected are also shown with some affected offspring; those unaffected have no affected offspring Fig 1. 2. Sickle Cell Anaemia (100 words) Sickle Cell Anaemia is a blood disorder where red blood cells are sickle-shaped that is inherited by both parents in autosomal recessive mutation and people of a black ethnicity or African descent are affected. If only one parent has the abnormal gene; the children will have sickle-cell trait which doesn’t provide symptoms or need treatment. It is caused by an abnormality in haemoglobin from a lowered amount of oxygen which makes the blood cells distorted and sickle shaped. As the sickle shape makes the cells fragile, they could end up being destroyed early resulting in anaemia. Word Count: 96 3. Cystic Fibrosis (100 words) Cystic Fibrosis a condition inherited from an abnormal CFTR gene in both parents in a autosomal recessive mutation which is most common in people of a Caucasian ethnicity from Europe and North America and carried by 1 in 25 people. CFTR creates proteins that monitor sodium and chloride levels in the cells but if defective; there will be thick mucus in the tubes and passages within the body. It is the chromosome number 7 that contains the faulty gene and there are approximately 1,500 variations of abnormalities with the most common being delta F508. This condition is present at birth. Word Count: 100

Biology: Human Reproductive Biology

TAQ 5

Assessment Criterion 3.2

3.2 Explain different methods of genetic counselling

Genetic counselling is an important consideration, particularly for couples at risk of a range of genetic based conditions and predispositions. What different kinds of genetic counselling are there and what are they used for? Write a short essay explaining the use of such counselling. (600 words) Genetic counselling can help couples who are looking to start a family by seeing if there are any potential inherited diseases that they will develop or pass on to their children and options available to them in order to reduce the risk of children being born with the disease or disorder. This is where family histories are researched and advice is given. Conditions detectable by genetic counselling include; down syndrome, sickle-cell anaemia, Tay-Sachs disease, spina bifida, cystic fibrosis, Huntington’s disease, muscular dystrophy and mental retardation. Disorders such as cystic fibrosis and sickle-cell anaemia require both parents to pass on their genes in order for it to occur whereas Huntington’s disease and DiGeorge syndrome only needs one parent to pass it on. A sample of blood or tissue can be taken and this sample contains the parent’s DNA which can then be tested to see if there are any conditions that could be developed or mutations that could occur. For certain conditions, it could be necessary to examine the samples in a special genetics laboratory. The triple test can predict if a baby could be Down’s syndrome. Pre-implantation genetic diagnosis is an option sometimes considered when there is a risk of the child inheriting a serious genetic condition and involves in-vitro fertilisation. This is where the mother’s eggs will be removed from her ovaries and fertilised with the father’s sperm in a laboratory. The embryos can then be tested a few days later to see if a particular genetic condition has occurred and unaffected embryos are implanted into the uterus. Gene / DNA probes can be used in order to analyse the parents’ DNA and can see if certain DNA sequences are contained within the parent or foetus’ genetic material. This involves separating DNA from the human cell and taking a copy of a sequence as a sample. DNA is extracted from the parent and digested by a restriction endonuclease and cut into segments which then identify sets of nucleotides that occur in a fixed order. Fragments are separated into sizes by electrophoresis and information on the pattern of cleavage sites on chromosomes is gained. Women are routinely scanned by Ultrasound during pregnancy and they can be used to predict chromosomal abnormalities in the foetus by measuring the amount of fluid behind the fetus’ neck. The nuchal fold thickness is recorded and can assess the risk of Down’s syndrome. Amniocentesis is carried out between the 15th - 20th weeks in pregnancy and is where a hollow needle is inserted into the mother’s uterus and 20ml of amniotic fluid surrounding the foetus is aspirated through a syringe after locating the placenta via ultrasound. The fluid aspirated can then be tested for abnormalities by looking at the accumulation of metabolites. There is a small risk of miscarriage with 1 in 100 women miscarrying. A higher risk method is a Chorionic Villus biopsy which is carried out between the 10th - 13th weeks of pregnancy and this is where a fine catheter or needle is inserted through the cervix or the abdominal wall into chorionic tissue under ultrasound guidance and a few villi are removed via gentle suction to make a sample. This sample is analysed for any chromosomal or genetic abnormalities, inborn errors of metabolism, haematological disorders or gene defects. There is a higher risk of miscarriage than that of amniocentesis but a diagnosis can be made earlier than amniocentesis. Fetoscopy is another method wherby the foetus is studied through a fine fibre-optic telescope and samples of foetal tissue can be taken under direction vision which can detect haemophilia, haemoglobinopathy or skin diseases. Word Count: 600

References TAQ 1 Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. p490. Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. p467 - 469. Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. p457. Fig 1 taken from: http://medical-transcriptionist-reference.blogspot.co.uk/2012/08/female-reproductive-system.html Fig 2 taken from: http://brookingsapbiology.wikispaces.com/Male+Reproductive+System TAQ 2 The Distance Learning Centre (2014).Human Reproductive Biology Learning Materials. Yorkshire: Unknown. p8 & 12-13. Sweet, B (2003).Mayes' Midwifery. 12th ed. London: Balliere Tindall. P117-121. Burrows, C et al (2012).A2-Level Biology, A2 The Complete Course for AQA. Newcastle Upon Tyne: CGP. p161. Toole, G et al (2008).AQA Biology, A2 Biology. Cheltenham: Nelson Thornes Ltd. p215. UCSF. (1999).HORMONE INVOLVED IN REPRODUCTION MAY HAVE ROLE IN THE MAINTENANCE OF RELATIONSHIPS.Available: http://www.oxytocin.org/oxytoc/index.html. Last accessed 13th Jan 2015. Sweet, B (2003).Mayes' Midwifery. 12th ed. London: Balliere Tindall. P346 - 347. Unknown. (2013).Gonadotrophin-releasing hormone.Available: http://www.yourhormones.info/hormones/gonadotrophinreleasing_hormone.aspx. Last accessed 13th Jan 2015. Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. p425-426. TAQ 3 Sweet, B (2003).Mayes' Midwifery. 12th ed. London: Balliere Tindall. P749 - 759. Rodriguez, D. (2014).The Truth About the Rhythm Method.Available: http://www.everydayhealth.com/sexual-health/rhythm-method.aspx. Last accessed 15th Jan 2015. TAQ 4 Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. P333. Unknown. (2014).Huntington's Disease - Cause.Available: http://www.nhs.uk/Conditions/Huntingtons-disease/Pages/Causes.aspx. Last accessed 17th Jan 2015. Unknown. (2015).Huntington's Disease .Available: http://en.wikipedia.org/wiki/Huntington's_disease. Last accessed 17th Jan 2015. Fig 1 taken from Wikipedia: http://en.wikipedia.org/wiki/Huntington's_disease. Last accessed 17th Jan 2015. Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. P272. Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. P535. Unknown. (2014).Cystic Fibrosis.Available: http://www.nhs.uk/Conditions/Cystic-fibrosis/Pages/Introduction.aspx. Last accessed 17th Jan 2015. TAQ 5 Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. P151. Unknown. (2014).Genetic Counseling.Available: http://en.m.wikipedia.org/wiki/Genetic_counselling. Last accessed 17th Jan 2015. Unknown. (2014).Genetics - Genetic testing and counselling .Available: http://www.nhs.uk/Conditions/Genetics/Pages/genetic-testing-and-counselling.aspx. Last accessed 17th Jan 2015. Sweet, B (2003).Mayes' Midwifery. 12th ed. London: Balliere Tindall. P41-46. Peters, M (2010).British Medical Association Complete Home Medical Guide, The Essential Reference For Every Family. 3rd ed. London: DK. P509.

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