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Male Reproductive System

INTRODUCTION

Reproduction is the mechanism by which the thread of life is sustained. Reproduction maintains the continuation of the species. The testes in the male and the ovaries in the female produce sperms cells and ova respectively. The testes and ovaries also produce hormones which are responsible for the development of male and female secondary sex characteristics (eg. hoarseness of voice in boys & enlargement of breast in girls). Does that ring a bell !!!


MALE REPRODUCTIVE SYSTEM

The male reproductive system consists of the following organs:

2 TESTES (with the Scrotum)
2 EPIDIDYMIDES (with the Scrotum)
2 SPERMATIC CORDS
2 SEMINAL VESICLES
2 EJACULATORY DUCTS
2 PROSTATE GLANDS
1 PENIS

Hi !! Feel free to view the diagrams provided and identify the parts. Enjoy your discovery.

SCROTUM
The scrotum is a pouch (pocket) containing the testes, the epididymides and lower part of the spermatic cords. It lies below the symphysis pubis (bone) and in front of the upper part of the thighs and behind the penis. It is covered with skin which is deeply pigmented (darker appearance) and thrown into folds. Beneath the skin lies a thin sheet of involuntary muscle (not under our control/acts automatically) - the dartos muscle. This muscle form a septum (wall) dividing the scrotum into two cavities, one testis lying in each cavity. Interior to the dartos muscle lies the cremaster muscle which elevates (pull up) the testes during sexual arousal and on exposure to cold. The location of the scrotum and contraction of its muscle fibres regulate the temperature of testes for the production of sperm which requires a temperature of 33 degrees Centigrade.

TESTES
The testes are the reproductive glands of the male and are equivalent of the ovaries in the female. The testes develop high on the embryo's (foetus) posterior abdominal wall, and usually enter the scrotum by 32 weeks of gestation (pregnancy). Full descent (going down into the scrotum) is not complete until just prior to birth.

When the testes do not descend the condition is known as undescended testes. At birth the scrotum is examined for the 2 testes.

All boys are advised to examine and feel for the 2 testes in the scrotum and learn to do testicular self-examination to exclude tumours (abnormal growth).

A surgical operation is needed to bring down the undescended testes in a young boy to avoid any problems of fertility in later life.

The testes produce sperms and male hormone testosterone. The production of sperm requires a temperature of 33 degrees Centigrade (ie. below body temperature which is 37 degrees Centigrade) which is automatically maintained by the muscles in the scrotum. The testes are suspended (supported) in the scrotum by the spermatic cord. The testes are approximately 4.5cm in length, 2.5cm in breath and 3cm in thickness. The testes are partially covered by serous membrane called tunica vaginalis. Internal to tunica vaginalis is a dense (thick) white fibrous capsule (covering) called tunica albuginae. In each testis there are also series of internal compartments called lobules. Each lobule contain 200-300 seminiferous tubules that produce sperms. The sperms are produced or matured at a rate of 300 million per day and once ejaculated into the vagina, have a life span (expectancy) of 48 hours within the female reproductive tract.
If confused rest, and view the diagrams.



Hi there take note. The male produces millions of sperms per ejaculate compared to female who produce only one egg (ovum) a month. There are rare occasions when the ovaries produce more than one egg.

EPIDIDYMIS



The epididymis is a coma-shaped organ that lies along the posterior border of the testes. It consist mostly of a tightly coiled tube, "the ductus epididymis". At the lower border of the testis the epididymis continues as the ductus was deferens. It commences at the tail of the epididymis and passes upwards on the posterior wall of the testis. At first it is a coiled tube then straightens out to leave the testis and the scrotum enclosed within the spermatic cord.

SPERMATIC CORD
These are two spermatic cords, one for each testis. Each spermatic cord, acts as a supporting structure and constitute the following structures:
· The testicular artery
· The testicular vein
· Lymphatic vessels
· Nerves
· The ductus (vas) deferens

Functionally, the ductus deferens stores sperm for up to several months and propels (move forward) them toward the urethra during ejaculation.

One method of permanent contraception is vasectomy, in which a portion of each ductus deferens is ligated (cut and tied up) consequently sperm is prevented from entering the vagina during ejaculation and thus preventing unwanted pregnancy


SEMINAL VESICLES
These are two membranous pouches (bags) located between the bladder and the rectum. They secrete (produce) a thick alkaline fluid and pass it into the ejaculatory duct. This secretion contribute to sperm viability (keep alive) and constitute 60% of the volume of semen. Semen (seminal fluid) is a mixture of sperm and the secretion of various glands, i.e seminal vesicles, prostate glands and the bulbourethral gland. The average volume of semen for each ejaculation is 2.5 to 6ml and the average range of sperms ejaculated is 50 to 100 million/ml

The volume of seminal ejaculate is less important criteria than sperm count in determining
" manliness". If the number of sperms is less than 50 million/ml, there may be problems of fertility i.e. difficulty in causing pregnancy.


EJACULATORY DUCT
The ejaculatory ducts (Diagram B) are located behind to the urinary bladder formed by the union of the duct from the seminal vesical and ductus (vas) deferens. It ejects sperms into the prostatic urethra.

The urethra is the terminal (end) duct of the reproduction system, serving as a passageway for sperms or urine. In the male, the urethra passes through the prostate gland and the penis. It measures 20cm in length and subdivided into three parts namely prostatic urethra, membranous urethra and spongy urethra. This spongy urethra alone is 15cm in length and enters the penis and terminates at the external urethral orifice (opening at the tip of the penis.)

PROSTATE GLAND (Diagram B)
This is a single doughnut - shaped gland, placed below to the urinary bladder and surrounds the upper portion of the urethra. The prostate gland is surrounded by fibrous connective tissue and smooth muscle. Inside, the prostate is made up of many individual glands which release their secretions into the prostatic urethra through separate ducts.

PENIS
The penis contains the urethra, which is the terminal duct for both urinary and reproductive tract. The penis is used to introduce sperms into the vagina. The distal (far) end of the penis is a slightly enlarged region called the glans, which means shaped like an acorn. Covering the glans is the loosely fitting prepuce or foreskin.

Circumcision is a surgical procedure in which part or all of the prepuce is removed.

Internally, the penis is composed of three cylindrical masses of erectile tissue bound together by fibrous tissue. Under sexual stimulation, the arteries supplying the penis dilate (expand) veins draining the penis are compressed. These vascular (blood supply) changes result in erection. The penis returns to its flaccid (soft) state when the arteries constrict and the pressure on the vein is relieved. During ejaculation the sphincter (rings of muscle) at the base of the urinary bladder is closed, thus urine is not expelled during ejaculation and the semen does not enter the urinary bladder.

Hi!! boys : Read once or twice to understand better your reproductive organs and review the diagrams to visualize your reproductive organs.



Reference: Tortora and Anagnostakos Principles of Anatomy and Physiology 4th Edition. Harper & Row, New York

SARADA, FFPAM


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