Monday, 16 February 2015

Male reproductive system

The male reproductive system is located in lower abdomen of males. It consists of  scrotum, testes, spermatic ducts,  glands, and penis.The function of male reproductive system is to produce millions of sperms within viscous fluid called semen and depositing it in to vagina, with the use of erectile organ called Penis.Males are driven by natural instincts to carry out this biological act as it is very essential for perpetuation of race.Testes also produces male sex hormone Testosterone which is responsible for development of secondary sexual characters in boys.


Scrotum
The scrotum is a sac-like organ made of skin and muscles that accommodates the testes. It is located below to the penis in the pubic region. The scrotum is made up two pouches with a testis located in each pouch. . When the testes become too warm to support spermatogenesis, the scrotum relaxes to move the testes away from the body’s heat.This mechanism maintains -2 degrees less than usual body temperature of 37 degrees centigrade which is necessary for normal production of sperm. In contrary the scrotum can shrink closer to body during cool climate keeping it warm.

Testes
There are two testes, also known as testicles which are responsible for production of sperms and testosterone. The testes are egg shaped glandular organs around 1.5 to 2 inches long and an inch in diameter. Each testis is found inside its own pouch on one side of the scrotum and is connected to the abdomen by a spermatic cord and cremaster muscle. The cremaster muscles contract and relax along with the scrotum to regulate the temperature of the testes. The inside of the testes is divided into small compartments known as lobules. Each lobule contains a section of seminiferous tubule lined with germinal epithelial cells. These epithelial cells contain many stem cells that divide by mitotic division followed by meotic division and form sperm cells through the process of spermatogenesis.Seminiferous tubules open into reticulate network called Rete testis. Rete testis opens into Head of epididymis through serveral efferent ductules (Vas efference) as you see in figure below.

Epididymis

The epididymis is folded tube like structure on testes. The epididymis is made up of  long, thin tubules that are tightly coiled into a small mass. Sperm produced in the testes moves into the epididymis to mature before being passed on through the male reproductive organs. The length of the epididymis delays the release of the sperm and allows them  to mature.

 Vas Deferens

Within the scrotum, a pair of spermatic cords connects the testes to the abdominal cavity. The spermatic cords contain the vas deferens along with nerves, veins, arteries, and lymphatic vessels that support the function of the testes. The vas deferens , also known as the ductus deferens, is a muscular tube that carries sperm superiorly from the epididymis into the abdominal cavity to the ejaculatory duct. The ductus deferens is wider in diameter than the epididymis and uses its internal space to store mature sperm. The smooth muscles of the walls of the ductus deferens are used to move sperm towards the ejaculatory duct through peristalsis a wave like movement.

Seminal Vesicles

The seminal vesicles are a pair of lumpy exocrine glands that store and produce some of the liquid portion of semen. The seminal vesicles are about 2 inches in length and located posterior to the urinary bladder and anterior to the rectum. The liquid produced by the seminal vesicles contains proteins and mucus and has an alkaline pH to help sperm survive in the acidic environment of the vagina. The liquid also contains fructose to feed sperm cells so that they survive long enough to fertilize the oocyte.

Ejaculatory Duct

The ductus deferens passes through the prostate and joins with the urethra at a structure known as the ejaculatory duct. The ejaculatory duct contains the ducts from the seminal vesicles as well. During ejaculation, the ejaculatory duct opens and expels sperm and the secretions from the seminal vesicles into the urethra.

Urethra
Semen passes from the ejaculatory duct to the exterior of the body via the urethra, an 8 to 10 inch long muscular tube. The urethra passes through the prostate and ends at the external urethral orifice located at the tip of the penis. Urine exiting the body from the urinary bladder also passes through the urethra.

Prostate gland
The prostate is a walnut-sized exocrine gland that borders the inferior end of the urinary bladder and surrounds the urethra. The prostate produces a large portion of the fluid that makes up semen. The prostate gland contributes about 30 percent of the seminal fluid; the constituents of its secretions are mainly citric acid, acid phosphatase, calcium, sodium, zinc, potassium, protein-splitting enzymes, and fibrolysin (an enzyme that reduces blood and tissue fibres) The prostate also contains smooth muscle tissue that can constrict to prevent the flow of urine or semen.

Cowper’s Glands
The Cowper’s glands, also known as the bulbourethral glands, are a pair of pea-sized exocrine glands located inferior to the prostate and anterior to the anus. The Cowper’s glands secrete a thin alkaline fluid into the urethra that lubricates the urethra and neutralizes acid from urine remaining in the urethra after urination. This fluid enters the urethra during sexual arousal prior to ejaculation to prepare the urethra for the flow of semen.

Penis
The penis is   copulatory organ located superior to the scrotum. The penis is roughly cylindrical in shape and contains the urethra and the external opening of the urethra.It has expanded sensitive end called glans penis which is purposeful during penetration into vagina. Large pockets of spaces corpora cavernosa (erectile tissue) in the penis allow it to fill with blood and become erect. The erection of the penis causes it to increase in size and become turgid and retains the state for a while due to  blocking of veins carrying blood away from penis. The function of the penis is to deliver semen into the vagina during sexual intercourse.At the beginning of the glans penis, a circular fold of skin, commonly called the foreskin (or prepuce), extends forward to cover the glans. At birth or during early childhood, the foreskin may be removed by an operation called circumcision.Sensitive spots around rim of glans of penis give a feel of excitement and pleasure during the intercourse and finally semen gets ejaculated in a state called Climax. In addition to its reproductive function, the penis also allows  the excretion of urine through the urethra to the exterior of the body.

Semen
Semen, also called seminal fluid.Semen is the fluid produced by males for sexual reproduction and is ejaculated out of the body during sexual intercourse. Semen also contains other liquids, known as seminal plasma, which help to keep the sperm cells viable.Semen contains sperm, the male reproductive cells, along with a number of nourishing components and enzyme called Hyaluronidase suspended in a liquid medium. The chemical composition of semen gives it sticky consistency and a slightly alkaline pH. The total volume of semen for each ejaculation of a human male averages between 2 and 5 ml.In human beings each ejaculation contains normally 200 to 300 million sperm.These traits help semen to support reproduction by helping sperm to remain within the vagina after intercourse and to neutralize the acidic environment of the vagina. In healthy adult males, semen contains around 100 million sperm cells per milliliter. These sperm cells fertilize oocytes inside the female fallopian tubes.This semen can be artificially ejected by stimulating the penis.

No comments: