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Renin Angiotensin Mechanism.

Organs of Male Reproductive System.

 

Introduction.

  • Reproduction is the ability of an individual to produce a new individual, and is considered as one of vital signs of living organisms,

  • Human life starts when a male gamete called “Sperm” fuses with a female gamete called “Ovum” to form a single cell called “Zygote”.

  • Male and female reproductive organs are called “Gonads” they are responsible for production of sex hormones and gametes.

  • The medical specialty which deals with the male reproductive system and urological problems found only in men is called “Andrology”.

Male reproductive system

  • Male reproductive system is divided into internal organs and external organs.

  • External Organs include,

    • Penis.

    • Scrotum.

    • Testes.

  • Internal Organs include,

    • Vas deferens

    • Seminal vesicles

    • Ejaculatory ducts.

    • Prostate gland,

    • Cowper’s Gland (Bulbourethral gland.)

    • Urethra.

Penis:

  • The penis is the male organ of copulation (sexual intercourse). 

  • It is flaccid for non-sexual actions, such as urination, and turgid and rod-like with sexual arousal. 

  • When erect, the stiffness of the organ allows it to penetrate into the vagina and deposit semen into the female reproductive tract.

  • Penis consists of 

    • body, 

    • glans penis

    • root. 

  • The body of the penis is made up of three cylindrical masses of erectile tissue.

  • The two lateral masses are called the corpora cavernosa.

  • The corpora cavernosa is an erectile tissue, it gets filled with blood on sexual arousal to make penis rigid.

  • The smaller middle part which contains the urethra is called corpus spongiosum.

  • Corpora spongiosum is also an erectile tissue with less capabilities than corpora cavernosa. It helps keep the urethra open to pass sperm during intercourse. 

  • The lower end of the corpus spongiosum is slightly enlarged, called the glans penis. 

  • The glans penis is covered with the folded skin called the prepuce (foreskin).

  • The urethra opens in the glans penis in a form of slit called “Urethral orifice”.

  • The root of penis is made up of,

    • Bulb of the penis.

    • Crus of the penis. And these structures enable attachment of penis to the urogenital diaphragm.

  • An erection and the enlargement of penis are maintained by parasympathetic division of the spinal cord.

Scrotum:

  • It is a muscular sac covered with highly pigmented skin, present behind penis, held hanging between the legs.

  • Scrotum is divided into two compartments by the scrotal septum, one housing each testes.

  • The scrotum is supplied with two muscles,

    • Dartos Muscle.

    • Cremaster Muscle.

  • These muscles relax and contract as per body's temperature to keep the temperature of the testes 2 to 4 degrees lower than body temp.

Testes:

  • These are male gonads.

  • They produce male gamete “Sperm” and androgen “Testosterone.”

  • They are “Two” in number, oval in shape and are housed in each compartment of the scrotal sac.

  • Length is 4-5 cm.

  • They are covered with two layers of connective tissues,

    • Tunica vaginalis: Outer.

    • Tunica albuginea: Internal.

  • Tunica albuginea also distributes parts of testes in 300 to 400 compartments called “Lobules” by forming curtain-like structures called “Septa”.

  • Each lobules contain “Seminiferous tubules” , the site where sperm production takes place.

  • Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH).

  • The process of sperm production is called “Spermatogenesis.”

  • Spermatogenesis starts from the basement membrane of seminiferous tubules resulting in maturation of Germ cells to sperm. 

  • In between the developing Germ cells there are some elongated cells called “Sertoli cells” that form a protective”Blood-testis barrier” and also control sperm production by forming a hormone called “Inhibin'.

  • The formed sperms are then stored in a structure adjoining testes called “Epididymis”, which acts as a “Storage and maturation site of sperms”

  • During ejaculation the sperm are transferred from epididymis to vas deferens (ductus deferens).

Vas deferens:

  • There are two vasa deferentia.

  • Also called “ductus deferens”

  • They are thick muscular tubes arising from the epididymis and go through the “Inguinal canal” into the pelvic cavity.

  • They can be accessed in the scrotum as they form a part of the “Spermatic cord”; they can be cut to prevent the transfer of sperm into the semen.

  • The surgical removal of small parts of vas deferens is called a “Vasectomy” and is a “Permanent Sterilization method” for males.

  • Vas deferens ends behind the prostate gland by forming a flask like structure called ampoula which forms an “ejaculatory duct” along with seminal vesicle.

Seminal Vesicle:

  • These are slender glandular structures present on either side of the prostate gland.

  • The seminal vesicle along with the ampulla of vas deferens forms a structure called “ejaculatory duct” where sperms coming from vas deferens mix with secretion of seminal vesicles.

  • Seminal vesicle’s secretion forms 60% of the bulk of Semen (A thick milky white liquid ejaculated by male during sexual intercourse).

  • Secretion of seminal vesicles is rich in fructose which is utilized by sperm as an energy source for travel in the female reproductive system.

Prostate Gland:

  • It is a walnut shaped gland located at the base of the urinary bladder.

  • The prostate glands surround a part of urethra called “prostate urethra”.

  • The ejaculatory ducts carrying semen join the urethra in the prostate gland.

  • Prostate glands secrete an alkaline secretion which is essential for,

    • Neutralizing the acidity of urethra to protect sperm.

    • Coagulating and decoagulating the semen in the female reproductive system (This provides time for the sperm to utilize fructose in semen for further movement).

Bulbourethral Glands:

  • Also called “Cowper’s Glands”.

  • They are situated at the base of the penis and joined to the urethra.

  • They secrete a thick salty secretion that neutralizes the acidic environment of urethra present in penis called “Penile Urethra” and in the female vagina.

  • The secretions are secreted just before the ejaculation and also called pre-ejaculate, it doesn't contain sperm but may carry sperm present in urethra.

Commonly Asked Questions.

  1. With a well labelled diagram, discuss Male Reproductive System.

  2. Draw a well labelled diagram of Male Reproductive System.

  3. With a well labelled diagram describe structure of testes.

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