The organs of the reproductive system

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Human Reproductive Biology

TAQ 1

The female reproductive system carries out several functions. Producing the ova/oocytes, the design of this system transports oocytes to the fertilisation site. However, if fertilisation doesn’t occur the reproductive system menstruates. This system releases sex hormones to maintain its cycle. Main organs of this system include; vagina, uterus (connecting to fallopian tubes. This surrounds/supports foetus during pregnancy containing endometrium), ovaries (produce female sex hormones, a mature ovum is released monthly travelling through fallopian tubes) and fallopian tubes (muscular tubes from the uterus to the ovaries, containing fimbriae help transmit ova to the infundibulum for transport to the uterus).

There are three main functions of the male reproductive system:

  • Produce, maintain and transport sperm
  • Secrete sperm into female reproductive tract during sex
  • Produce and release male sex hormones to maintain reproductive system

Main organs of the male reproductive system include; penis, urethra, scrotum (thick skin that surrounds/protects the testes), testes (have two main functions; producing sperm containing male genes and producing testosterone, the main male sex hormone), epididymis (coiled microscopic tubes collecting sperm from the testes providing environment for sperm to mature), vas deferens (strong tube carrying sperm from the epididymis), seminal vesicles and prostate (produces fluid allowing nourishment for sperm).

TAQ 2

Source of hormone

Hormone

Function

Hypothalamus

GnRH/Gonadotrophin releasing hormone

Encourages the release of luteinising hormone and follicle stimulating hormone.

Pituitary

Luteinising Hormone

In males this stimulates the release of testosterone from leydig cells in the testes. Crucial for menstruation in women.

Pituitary

Follicle stimulating hormone

In males this hormone stimulates spermatogenesis. Crucial for ovaries in women.

Testes (leydig cells)

Testosterone

The final stages of sperm maturation is stimulated by testosterone.

Gonads, pituitary gland, placenta and corpus luteum.

Inhibin

This reduces the amount of FSH production, slowing down the production of sperm when an adequate amount is reached.

Placenta

Human chorionic gonadotrophin

This hormone is used to detect pregnancy, this hormone helps to ensure a healthy pregnancy and affects the development of the foetus. The amount of this hormone in the blood during pregnancy is also used as a health screening for the foetus.

Corpus luteum

Progesterone

This hormone increases blood flow to the womb, which prepares the environment for the foetus. It also ensures the walls of the uterine do not contract prematurely. As well as stimulating the production of the endometrium.

Corpus luteum

Oestrogen

This hormone helps the stimulation of progesterone as without oestrogen it would not be able to carry out some of its functions. Oestrogen has the role of controlling and maintaining the production of other pregnancy hormones, as well as stimulating the development of the placenta.

Hypothalamus

Oxytocin

This hormone plays a crucial part in the stimulation of contractions and releases other hormones to also help with the preparation of parturition.

TAQ 3

Method of contraception

Evaluation of advantages

Evaluation of disadvantages

Overall evaluation

Condoms

  • 98% effective if used correctly
  • Protect against STI’s
  • No medical side effects
  • Only needed during sex
  • Easily accessible with many size, flavour and shape options.
  • Must be used correctly
  • Can split, this can lead to pregnancy or transmission of STI’s
  • Suggestions of interrupted sex and decreased sensation
  • Allergy to latex
  • Male must pull out before penis softens to prevent it slipping off.

Condoms are a good method of contraception. Disadvantages can be avoided. People can learn how to apply and use them correctly. If a couple feels diminished sensation, this can be helped by the different variety of condoms. Avoiding lubricants whilst using condoms can help keep good effectiveness.

Pill

  • 99% effective
  • Doesn’t interfere with sex
  • Can reduce the risk of some cancers, can help periods, can reduce acne and can reduce symptoms of PMS.
  • Temporary side effects such as; migraines, mood swings and nausea.
  • Possible raised blood pressure
  • Links to serious health problems such as; DVT’s and breast cancer.
  • Does not protect against STI’s.

Over all the contraceptive pill is extremely effective. Having risks of health problems, there are also some health benefits. Anyone taking the pill are required to attend regular check-ups with a health professional where questions will be asked and blood pressure will be checked.

Coitus interruptus

  • Always available
  • No prescription or costs
  • This requires no planning
  • Believed to be effective and has pregnancy rates of those similar to a male condom providing this is done perfectly.
  • Requires self-control
  • There is no protection against STI’s
  • Lower in effectiveness than other methods.

Using this as a contraception method is not the most ideal option although statistics suggest 4% pregnancy with this. Perhaps this would be more appropriate to long term couples? It would not be a method that I’d recommend.

Intrauterine device

  • 99% effective
  • Can be removed
  • No effects on partner
  • Can alleviate symptoms of periods
  • This can last up to 5 years.
  • Does not protect against STI’s,
  • Invasive and
  • Infections risk
  • Removed by a health professional
  • Painful when it’s inserted.

This is an effective form of contraception and lasts a long time without interference. However, according to research this method is better suited to those who have already experienced pregnancy.

Rhythm method

  • Low in cost
  • No side effects
  • No need for prescriptions or medical devices.
  • Does not protect against STI’s,
  • Requires cooperation of both partners
  • Fertile days require no sex or use alternative contraception
  • Requires tracking of menstrual cycle for six months
  • High failure rate.

Overall this method is not very reliable and would be too risky for those not wanting to become pregnant. However, for a couple wanting to conceive in the future this could be beneficial knowledge.

TAQ 4 – Part 1

Huntington’s disease is inherited by a defect in a single gene, it is autosomal dominant disease. This means that a person only needs one copy of the defective gene to develop Huntington’s. People inherit two copies of every gene, a copy from each parent. This means that if a parent has a defective Huntington’s gene, this could be passed along or the non-defective gene could be passed on meaning that each child would have a 50% chance of inheriting the disorder. This disease usually causes movement disorders and cognitive and psychiatric disorders. Onset in a child normally results in death.

Part 2

Sickle cell anaemia is a blood disorder, this disease is inherited through genes. This disorder involves the red blood cells which carry oxygen to be abnormal. This is caused by a mutation in a particular gene, the one that tells the body to produce haemoglobin. However, to suffer this a person must inherit the defective gene from both parents but if a person inherits the gene from only one parent, they’ll be known to have sickle cell traits. If two people have sickle cell traits this gives a potential chid 1 in 4 chance of suffering with sickle cell anaemia.

Part 3

Cystic fibrosis causes the digestive system and lungs to become clogged with excess mucus. Cystic fibrosis is caused by a mutation of a gene, CFTR. However, to develop this condition a defective gene would have to be inherited from both parents. If a person has inherited this gene from one parent they are known as a carrier. If two carriers reproduce, there’ll be 1 in 4 chance the offspring will not be a carrier, 1 in 2 chance the offspring inheriting one defective gene and a 1 in 4 chance the child will inherit both faulty genes (suffering cystic fibrosis).

TAQ 5

Genetic counselling is a service provided to those who are at risk of having inherited any disorder, this service provides advice and information on potential inherited conditions, and they will look at their risk and probability of passing faulty genes to future children and advice regarding family planning management. The process of genetic counselling includes; evaluating family and medical history, requesting genetic tests, evaluation of results and helping patients understand and to assist in making decisions of the next step. There’s a number of methods to genetic counselling which include; construction and analysis of pedigree, calculation of risk reoccurrence (mendelian or empirical), estimation of the consanguinity coefficient and more specific analysis. Factors that indicate counselling; known or presumed disorder/illness in relative, congenital malformation, mental retardation, consanguinity and infertility or repeated miscarriage.

Construction and analysis of pedigree involves mapping genes that are responsible for certain disorders, following and diagnosing heritable conditions, to form family trees and lineages and to provide accurate family records. The construction division involves using a standard set of symbols to determine each character taking part. Analysing involves trial and error, assumption and results. However, there are limitations with construction; unreliable medical records, inaccurate/misinterpreted information, unavailable family members, concealed adoptions, miscarriages, variable expressivity of genotype and incomplete penetrance of genotype. Pedigree can often rule out, although not prove modes of inheritance.

The possible genetic risks can be measured in two ways; theoretically using Mendelian laws or empirically using previous published data when it’s not inherited. Empirical recurrence risks apply to a number of multifactorial conditions, 1-5% following one affected child, increasing if there is more than one effected in the pedigree analysis. Mendelian laws are usually used for those who are thought to be or known to carry gene abnormalities, although it becomes more complex when predicting the inheritance of a specific gene for an individual through generations.

Estimation of the consanguinity coefficient involves looking for common ancestors on the genealogical tree, then calculating possibilities of inheritance. The probability of an unfavourable outcome in offspring of consanguineous couples is not a certain number. The estimation must be based upon background population, degree of consanguinity and relating family history. Background population risks cannot give a definitive result as to whether the offspring would suffer birth defects because evidence compiled varies. The simplest way of providing a genetic screening for consanguineous couples is to research the family’s medical history, going back 3-4 generations. A genetic evaluation would proceed with high suspicion of autosomal recessive disorders in the offspring of consanguineous couples. During the estimation, the consanguineous relationship should be looked at in pedigree form, the medical histories of relatives that are compatible with potential genetic disorders.

There are three divisions of gene testing; molecular testing, chromosomal testing and biochemical testing. The aim of these tests are to find if there’s an abnormality in a persons’ DNA (genes). Molecular testing involves looking at single genes or short lengths of DNA, identifying changes within the DNA strand. Although there are limitations, it’s only helpful in cases of knowing a specific genetic mutation causes a specific condition. Chromosomal testing looks at features in a person’s chromosomes, parts of these can sometimes be abnormal. There are two ways in which this testing can be done; karyotyping looking at all chromosomes identifying numerical changes and FISH which looks at specific parts of chromosomes allowing the detection of small abnormalities. Biological testing involves looking at the amounts and activities of proteins, abnormal amounts suggest abnormalities of genes. There are many ways of performing the tests; new born screening, diagnostic, carrier, pre-implantation, forensic, predictive and prenatal testing.

References

The Distance Learning Centre. (2014). Learning Materials: Biology, Human Reproductive Biology. 1-34

Sheeler, P. Essentials of Human Physiology: Reproduction and Inheritance, 2nd edition. Iowa: Wm. C. Brown Publishers, 1996.

Websites

Zimmerman, K. Live Science (2015). Reproductive System: Facts, Functions and Diseases. Available: http://m.livescience.com/26741-reproductive-system.html. Last accessed 12 May 2015

NHS Choices. (2014). Contraception Guide. Available: http://www.nhs.uk/conditions/contraception-guide/pages/which-method-suits-me.aspx. Last Accessed 13 May 2015

WebMD. (2014). Your Guide to the Female Reproductive System. Available: http://www.m.webmd.com/a-to-z-guides/your-guide-female-reproductive-system. Last Accessed 13 May 2015

InnerBody. (1999-2015). Female Reproductive System. Available: http://www.innerbody.com/image/repfov.html. Last Accessed 13 May 2015

WebMD. (2014). The Male Reproductive System. Available: http://www.m.webmd.com/a-to-z-guides/male-reproductive-system. Last Accessed 14 May 2015

RCN. (2013). Hormones of the Reproductive System. Available: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/SexHormones.html. Last Accessed 14 May 2015

The Shropshire and North Wales Fertility Clinic. (2008). Hormones. Available: http://www.shropshireivf.nhs.uk/about-fertility/hormones.asp. Last Accessed 15 May 2015

NHS Choices. (2013). Sickle Cell Anaemia. Available: http://www.nhs.uk/conditions/Sickle-cell-anaemia/Pages/Introduction.aspx. Last Accessed 15 May 2015

NHS Choices. (2013). Cystic Fibrosis. Available: http://www.nhs.uk/Conditions/Cystic-fibrosis/Pages/Introduction.aspx. Last Accessed 16 May 2015

NHS Choices. (2013). Huntington’s disease. Available: http://www.nhs.uk/conditions/Huntingtons-disease/Pages/Introduction.aspx. Last Accessed 16 May 2015

Centres for Disease Control and Prevention (2015). Genetic Counseling. Available: http://www.cdc.gov/ncbddd/genetics/genetic_counseling.html. Last Accessed 17 May 2015

MedlinePlus. (2014). Genetic Counseling. Available: http://www.nlm.nih.gov/medlineplus/geneticcounceling.html. Last Accessed 17 May 2015

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