There are three major purposes of the male reproductive system: production of spermatozoa, secretion of sex hormones and to transport spermatozoa from male to the female. The organs in this system are mainly external and consist of a penis and the scrotum, which contains and protects testes. Because the testes require lower temperature than the rest of the body, the scrotum regulates temperature for normal spermatozoa development. When the testes need to cool down, the cremaster muscle relaxes and allows them to hang further from the body; however when the warmth or protection is required, the muscle contract to pull testes closer. (Rogers, 2011)
The main purpose of the testes is to produce spermatozoa and testosterone. Each testis is an oval body that averages 4 to 7 centimetres in length and 20 to 25 millilitres in volume. Attached to each testis is an epididymis, a tightly coiled tube that is almost 6 meters in length. This tube collects the spermatozoa and provides an environment for it to mature. (Rogers, 2011)
The spermatozoa then travels to the vas deferens which transports it into the abdominal cavity and then empty into the ejaculatory duct which runs through the centre of the prostate gland, where it is connected to the secretory ducts of the seminal vesicles. See diagram 1.
The seminal vesicles, which are two sacs on each side of the bladder, along with the prostate and bulbo-urethral glands, produce nutrients-rich fluid that provides energy for the spermatozoa following ejaculation and make up most of the volume of the semen. During sexual arousal erectile tissue fills up with blood due to nerve impulses. The semen is then expelled by urethra through the shaft of the penis to the outside of the body. This is achieved by muscle contractions as a result of stimulation to the sympathetic nerves of the epididymis, prostate, vas deferens and seminal vesicles. Once ejaculated, the maximum life span of spermatozoa is 24 to 72 hours at body temperature. (Rhoades and Pflanzer, 1996)
Female reproductive system
The main functions of the female reproductive system are the secretion of oestrogen and progesterone, production of ova, gestation and delivery of the foetus. The secretion of sex hormones and production of ova functions are carried out by the ovary. The gestation and delivery are performed by the uterus and cervical canal. See diagram 2.
The external female genitalia are called the vulva and include the labia majora, the labia minora, the clitoris and the vaginal opening. The labia majora are two folds of skin that protect the vaginal and urinary openings. The labia minora are the two small folds of skin that contain a large number of small blood vessels and provide protection for the clitoris. They lie within the labia minora and on average are about 4 centimetres long. (Rogers, 2011)
The clitoris is a small erectile structure that is partly concealed by the labia minora. The external part of the clitoris is called the glans clitoris which is highly sensitive. The clitoris and the penis are derived embryologically from the same tissue; however there is currently no known reproductive function for the clitoris. The external opening of the urethra is immediately in front of the vaginal opening and is about 2.5 centimetres away from the clitoris. (Rogers, 2011)
The internal female reproductive system includes vagina, uterine tubes, the uterus and ovaries. The vagina extends from the cervix of the uterus down to the opening in the vulva. Because vagina is a muscle organ, the walls have the ability to expand and contract to allow the passage of the baby during childbirth. The cervix is a part of uterus that extends into the vagina therefore forming recesses around it. There are two lateral fornices on each side, an anterior fornix which is located at the front of the cervix and posterior fornix, which is the largest and it is located at the back.
The uterus is composed of smooth muscles and it is located in the lower abdomen. The lining of the uterus is called the endometrium and the thickness of it changes during the menstrual cycle. When the fertilised ovum enters the uterus, it implants in the endometrium. During sexual stimulation and labour myometrium, the muscular walls of the uterus, expand and contract.
Attached to the uterus are the fallopian tubes. These tubes extend from the uterus into the abdominal cavity. At the end, each tube has long extensions called the fimbriae which terminate near the ovaries. The fallopian tubes are lined with cilia, which transfer the ovum to the uterus.
The ovaries are usually around 4 centimetres long, 2 centimetres wide and 1.5 centimetres thick and are located in the pelvic cavity under the open end of the fallopian tubes. The average weight of the both ovaries is 4 – 8 grams. (Rogers, 2011) Testes and ovaries have similar functions: germ cells and hormone production. (Rhoades and Pflanzer, 1996)
Hormone control
At the beginning of puberty in males hypothalamus begins secreting gonadotrophin-releasing hormone (GnHR). The pituitary gland responds by releasing follicle stimulating hormone (FSH) and luteinizing hormone (LH) into the system. By entering the testes, FSH stimulates the Sertoli cells, to begin facilitating spermatogenesis, and LH stimulates Leydig cells which begin making and releasing testosterone into the testes and blood. Testosterone stimulates spermatogenesis; it also triggers deepening of the voice, facial and pubic hair growth and beginning of sex drive. (Boundless, 2015)
If testosterone levels increase a negative feedback system occurs. When the sperm count is too high, the Sertoli cells produce inhibin and it is released into the blood to slow down the spermatogenesis. If the spermatozoa count reaches 20 million per millilitre, the production of inhibin stops allowing the count to increase. See diagram 3.
The hypothalamus also secretes GnHR in females while the anterior pituitary gland secretes the FSH, which usually increases in the last few days of the previous menstrual cycle. This stimulates the growth of ovarian follicles which in turn secretes oestrogen. This hormone inhibits FSH secretion and in the anterior pituitary acts on the uterus. As the levels of oestrogen increase, it stimulates production of GnHR, which in turn increases the production of LH. LH induces corpus luteum to ovulate and develop which secretes progesterone. See diagram 4. Progesterone stimulates uterus to prepare it for implantation of the fertilised ovum. ((Greenwood et al., 2013) (Boundless, 2015))
Contraception
To avoid pregnancy, there are several methods available, provided that the methods are used correctly, these can be quite effective (see table below); however, only the abstinence provides 100% guarantee.
MethodBenefitsRiskEffective AbstinenceHighly effective Prevents STIs No side effectsCould become difficult to abstain from sexual activity for a long period of time100% Combined oral contraceptive pillEasy to use – take one pill a day Helps control hormone levelsDoes not protect against STIs
Side effects: blood clots, nausea, weight gain and headaches92-97% ImplantLasts up to 3 years Only provides progestin – no oestrogen related side effectsPain during/ after the insertion Infection – if not done correctly Progestin related side effects99.9% Intrauterine device (IUD)Can be used for up to 10 years Nothing to put in place before conceptionHormonal side effects: breasts tenderness, mood swings and headaches Does not prevent STIs99.9% Male condomEasy to obtain – no prescription required Helps prevent STIsCould break during intercourse, especially if used improperly Decreases sensitivity98% VasectomyLong lasting contraceptionInvolves a surgical procedure Reversal procedure is complex and does not guarantee success99.5% Female condomHelps to prevent STIs Controlled by females Stronger than latex More comfortable for menDifficulties with insertion Cost more than male condoms95% InjectionLasts up to 13 weeks Can be used while breastfeedingDisruption of the normal cycle Weight gain, acne, headaches99%
Genetic Disorders During cell division a gene mutation can occur resulting in gene disorder. (Mackean, 1977) One example of this is Huntington disease (HD) which is a progressive brain disorder that affects cognitive ability; motor neurone functions and causes emotional instability. The disease is caused by mutation of the fourth gene which normally would have 10-35 CAG segments. 36-39 CAG repeats may or may not cause the symptoms to develop; however human with anything above 40 repeats will almost certainly develop the disorder. (Huntington disease, 2015). See diagram 5.(predictivetestingforhd.com, no date)
Another type of a genetic disorder is Turner syndrome which is caused by nondisjunction. This happens when the chromosomes fail to separate during the ovum or the spermatozoon formation which results in a missing X chromosome. Embryo missing such chromosome develops as a female. The syndrome affects development of the affected female however the intellectual levels are normal. (Turner syndrome, 2015) See diagram 6. (Turner syndrome, 2015)
Genetic Screening Genetic screening is usually used to evaluate a person’s predisposition to certain genetic disorders and possibility of a faulty gene being transferred to offspring. This is usually achieved by searching for markers within the DNA.
Genetic counselling is offered to the affected people and parents to educate and provide advice on how to deal with the genetic disorder they are or their child is diagnosed with and what they should expect as the symptoms develop. (Clarke, 2006)