MALE REPRODUCTIVE SYSTEM
  • Structure and Function

The organs of the male reproductive system are specialized for three major functions:
  1. To produce, maintain and transport sperm (the male reproductive cells) and protective fluid (semen)
  2. To discharge sperm within the female reproductive tract
  3. To produce and secrete male sex hormones

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Male Reproductive Diagram


External Organs (see picture left)
Most of the male reproductive system is located outside of the man’s body. The external structures of the male reproductive system are the penis, the scrotum and the testicles.
Penis- The penis is the male organ for sexual intercourse (Obviously). I don’t feel the need to describe everything I am learning about it because I don’t think it is too important, plus everybody knows the fundamentals of penises.
Scrotum- The scrotum is a loose pouch like sack of skin that hangs behind the penis. It contains the testicles (testes). The scrotum has a protective function and acts as a climate control system for the testes. For sperm development, the testes must be at a temperature slightly cooler than normal body temperature. Special muscles in the wall of the scrotum allow it to contract and relax, moving the testicles closer to the body for warmth and protection or vice versa.
Testicles (testes) - Located inside of the scrotum, the testicles are secured by a structure called the spermatic chord. Most men have two testes. Testes are responsible for making testosterone (see below).Within the testes are coiled masses of tubes called seminiferous tubules. These tubules are responsible for producing the sperm cells through a process called spermatogenesis.
Epididymis - The epididymis is a long, coiled tube that rests on the backside of each testicle. It functions in the transport and storage of the sperm cells that are produced in the testes.
Internal Organs (see picture above)
The internal organs of the male reproductive system are the ones that are more unspoken of and are also called accessory organs,
Vas deferens - The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports mature sperm to the urethra in preparation for ejaculation.
Ejaculatory ducts - These are formed by the fusion of the vas deferens and the seminal vesicles. The ejaculatory ducts empty into the urethra.
Urethra - The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of expelling (ejaculating) semen when the man reaches orgasm. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at orgasm.
Seminal vesicles - The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder. The seminal vesicles produce fructose that provides sperm with a source of energy and helps with the sperms’ ability to move. The fluid of the seminal vesicles makes up most of the volume of a man’s ejaculatory fluid, or ejaculate.
Prostate gland - The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum. The prostate gland contributes additional fluid to the ejaculate. Prostate fluids also help to nourish the sperm. The urethra, which carries the ejaculate to be expelled during orgasm, runs through the center of the prostate gland.
Bulbourethral glands - The bulbourethral glands, or Cowper’s glands, are pea-sized structures located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra.
How does the male reproductive system function?
The entire male reproductive system is dependent on hormones, which are chemicals that stimulate or regulate the activity of cells or organs. The primary hormones involved in the functioning of the male reproductive system are follicle-stimulating hormone, luteinizing hormone, and testosterone.

There are six major hormones involved in the male reproductive system:
Gonadotropin Releasing Hormone (GnRH)
Follicle Stimulating Hormone (FSH) - this is released by the anterior pituitary gland, it stimulates the production of sperm.
Luteinizing Hormone (LH) - released by the anterior pituitary gland, it stimulates testosterone production, which is made by the interstitial cells of the testes.
Aldosterone - it is made in the adrenal cortex and is very similar to testosterone, it regulates the electrolytes in the body, and responsible for the absorption of sodium in to the bloodstream.
Testosterone - made in the interstitial cells, it stimulates the sex drive, and is the hormone that makes men angry.
Inhibin- made by the sertoli cells when they are low in nutrients to feed developing sperm cells, it acts as a negative feedback, it goes to the brain to slow the release of Follicle Stimulating Hormone and Gonadotropin Releasing Hormone.

Gonadotropin Releasing Hormone is considered a neurohormone, which is a hormone produced in a specific neural cell and released at its neural terminal. GnRH is mainly made in the preoptic area of the hypothalamus, the neurons originate in the nose and migrate into the brain, where they are scattered throughout the medial septum and hypothalamus and connected by dendrites, which are branched filaments in nerve cells. The nuerons that make Gonadotropin Releasing Hormone have connections to an area of the brain known as the limbic system, which is heavily involved in the control of emothions and sexual activity. GnRH is secreted in the hyperphysical portal bloodstream. The portal blood carries the GnRH to the pituitary gland, which contains the Gonadotropin cells, where GnRH activates its own receptor. At the pituitary gland, the Gonadotropin Releasing Hormone stimulates the synthesis and secretion of the gonadotropins, follic-stimulating Hormone, and Luteinzing Hormone. These processes are controlled by the size and frequency of GnRH pulses, as well as by feedback from androgens and estrogens. Low-frequency GnRH pulses lead to follicle-stimulating hormone release, whereas high-frequency GnRH pulses stimulate luteinizing hormone release. The Gonadotropin Releasing Hormone is secreted in pulses at a constant frequency in both males and females, its pulses every one to two hours. Its secretion at the beginning of puberty triggers sexual development, and from then on it is essential for hormone.jpgnormal sexual physiology in both males and females. During the reproductive years, pulse activity is extremely important for successful reproductive function.

Follicle-Stimulating Hormone or FSH is one of two Gonadotropic hormones, or sex glands, produced by the pituitary gland. The Follicle-stimulating hormone, FSH, is called a gonadotropin because it stimulates the testes. It is not necessary for life, but is essential for reproduction. This hormone is secreted from cells in the anterior pituitary called Gonadotrophs. Most Gonadotrophs secrete only LH or FSH, but some appear to secrete both hormones. FSH is a glycoprotein that works with the luteinizing hormone. In the male, it promotes the development of the tubules of the testes and the differentiation of sperm. The presence of Follicle-Stimulating Hormone in males is necessary for the maturation of spermatozoa. The presence of additional FSH may not be required for months because testosterone can maintain this activity.
A follicle-stimulating hormone (FSH) test may be done to:
· To determine low sperm count.
· Determine if a child is going through puberty early. Puberty is early when it starts in boys younger than age 10.
· Determine why sexual features or organs are not developing when they should (delayed puberty).
· Help diagnose certain pituitary gland disorders, such as a tumor.

Luteinizing hormone or
LH is stimulated in both sexes; it secretes sex steroids from the gonads. In the testes, LH binds to receptors on Leydig cells, which stimulates the synthesis and secretion of testosterone. It also stimulates the testes to produce the hormone androgen.

Aldosterone is a mineral corticoid hormone, a type of hormone that is essential to life because it regulates the amounts of electrolytes in the body. Aldosterone is secreted by the adrenal cortex and responsible for the re-absorption of sodium into the bloodstream. It also stimulates the removal of potassium. Aldosterone is produced in the adrenal cortex which is part of the adrenal gland. Aldosterone simultaneously regulates sodium and potassium levels, helping to maintain both blood pressure and bodily fluids. If aldosterone levels in the body are out of sync, symptoms can result. High levels of aldosterone can cause high blood pressure, muscle cramps and weakness. Low levels may indicate disease, such as diabetes. Often, aldosterone levels vary between the sexes and may be affected by the amount of sodium in a person’s diet.

Testosterone is primarily secreted in the testes of males. It is essential for normal sperm development. Testosterone plays a huge role in the development of male reproductive tissues such as the testis and prostate as well as increased muscle, bone mass and the growth of body-hair. Testosterone is essential for health and well-being, as well as the prevention of osteoporosis. On average, an adult male produces about ten times more testosterone than an adult human female.




SOURCES
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http://www.cliffsnotes.com/study_guide/The-Male-Reproductive-System.topicArticleId-22032,articleId-22026.html
http://www.wisegeek.com/what-is-aldosterone.htm
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/lhfsh.html
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/H/Hypothalamus.html
http://projects.cbe.ab.ca/Diefenbaker/Biology/Bio%20Website%20Final/notes/reproductive/6_male_repro_hormones.htm

http://www.urologyspecialistskc.com/vasectomy.html

http://www.cchs.net/health/health-info/docs/2300/2376.asp