Male Reproductive System

 Male Reproductive System

The male reproductive system consists of 

 i) scrotum which acts as thermoregulator and maintaining the temperature of testes

ii) testes which are the primary sex organs

iii) Vasa Efferentia

iv) Epididymis

v) Vas deferential

vi) Ejaculatory ducts 

vii) Urethra

viii) penis

ix) Accessory glands

The male reproductive system is functional for the sexual activity and urinary functions.

1) Scrotum:- 

It is a pouch of pigmented skin arising lower abdominal wall and hanging between the legs. It's dermis contains a continuous layer smooth muscle fibres called dartos tunic. The scrotum is divided into right and left scrotal sacs called septum scrotum. The scar like raphe marks the position of septum externally. The testes passes to the scrotal sacs by the inguinal canals. Tearing of inguinal tissues may leads bulging out of loop of intestine into the scrotum. This condition is called inguinal hernia.

      The scrotum acts as thermoregulator, maintaining the temperature of testes and protect the sperms against the high body temperature.

2) Testes 

The testes are the primary sex organs. They are soft , smooth, pinkish, oval organ. They are suspended in the scrotal sacs by spermatic cords.

i) protective coats ( Tunicae) 

    

A testis is enclosed in a dense fibrous coat, the Tunica albuginea. Outside the Tunica albuginea,there is a visceral layer of peritoneum called Tunica vaginalis. There is also a part of scrotal sac act as a parietal peritoneum.

ii) Testicular Lobules:-

There is septa which divides the testis into 200-300 lobules. Each Testicular Lobule contains 1-4 convoluted seminiferous tubules, blood vessels and nerves embedded in loose connective tissue. The ends of the seminiferous tubules converge towards the middle of the posterior surface of the testis and join to form short straight tubules called tubuli recti. The tubuli recti open into a network of wider , irregular tubules called rete testis.

What are seminiferous tubules ?

These are the tubules which are present in the Testicular Lobule.Each seminiferous tubule is lined by germinal epithelium. Major of the cells in this epithelium are cuboidal spermatogenic cells but a few are large pyramidal , supporting Sertoli or nurse cells. The cuboidal cells produce spermatogonial into the lumen of the seminiferous tubules. The spermatogonia grow into primary spermatocytes, which undergoes meiosis producing haploid cells , first secondary spermatocytes and then spermatids and then into spermatozoa. Differentiation of spermatozoa from the spermatogonia is called spermatogenesis.

3) Vasa Efferentia 

From the rete testis, 50-20 fine convoluted, ductules, the Vasa Efferentia, pierce the tunica albuginea to enter the head of the Epididymis. The Vasa Efferentia at places bear cilia to aid in sperm transport.

4) Epididymis 

It is a long tube which is greatly coiled and tightly packed to form an elongated, flattened body attached to the hind surface of the testis. It shows three regions -

 a)upper wider head or caput epididymis that receives the Vasa efferentia

 b)middle narrower body or Corpus epididymis

c) lower tail or cauda epididymis

5) Vasa deferentia

The Vasa deferens is a continuation of the cauda epididymis. It is about 40cm.long and is slightly coiled at first but becomes straight as it enters the abdominal cavity through the inguinal canal. Here, it passes over the urinary bladder, curves round the ureter and joins the duct of a seminal vesicles to form an ejaculatory duct. The Vasa deferens is enlarged to form a spindle like ampulla for the temporary storage of spermatozoa.

6) Ejaculatory ducts 

These are about 2 cm. Long thin walled tubes, pass through the prostate gland and open into the urethra.

7) Urethra 

It is the urinary duct leading from the bladder. It carries urine as well as spermatozoa and secretion of the seminal vesicles. It also receives secretions of the prostate and cowper's glands. It is 20 cm, long and passes through the penis. The urethra has 3 region

i) prostatic urethra which is surrounded by prostate gland

ii) membranous urethra without any covering 

iii) penial urethra that passes through the penis.

The urethra has 2 sphincter : 

a) internal sphincter of smooth muscle fibres at its beginning

b) external sphincter of straight muscle fibres around its membranous part.

8) Penis 

The penis is an external intromittent organ through which the urethra runs.It consists of 3 columns of spongy tissue:
a) 2 corpora cavernosa
b) 1 Corpus spongiosum
Near the tip of the penis, the Corpus spongiosum is enlarged to form a soft and highly sensitive glans penis. It is covered by a loose , retractable fold of skin , the prepuse,  or foreskin. The urethra opens out at the tip of the penis

9) Accessory Sex Glands 

These includes a pair of seminal vesicles, a prostate gland and a pair Cowper's , or bulbourethral glands.

a) Seminal vesicles:-

The seminal vesicles are elongated, coiled sacs about 4cm. long. They are located near the ampullae of the Vasa deferentia. The seminal vesicles do not store sperms. They contribute yellowish, slightly alkaline, viscous seminal fluid that contains the sugar fructose, a coagulating enzymes ascorbic acid and harmone like prostaglandins. Fructose provides energy to the spermatozoa for swimming. The prostaglandins stimulate contractions in the female reproductive tract to help the meeting of sperm and ovum in the oviduct. Their ducts join the Vasa deferentia.

b) Prostate gland:-

It surrounds the first portion of the urethra. It is large, chestnut - shaped spongy and lobulated gland. It secreted a thin, milky, slightly acidic fluid, which is discharged into the prostatic part of urethra. It contains citrate and anticoagulant enzymes. The secretion nourishes and activates the spermatozoa to swim.

c) Cowper's Glands or Bulbourethral glands :-

These lie below the prostate gland. They are about the size of pea seeds. They secrete alkaline mucus which is discharged into the membranous part of the urethra. This serves to neutralize any acid urine remaining in the urethra.

d) Other Glands :-

Prepuse contains preputial gland which produce  a sebaceous substance which together with desquamated epidermal cells forms a whitish, pasty , foul smelling accumulation called smegma, about the base of the glans penis beneath the prepuse.

The urethra also has mucus secreting cells in its lining.

 What  is Semen? 

The secretion of accessory Sex Glands and mucus are added to the sperms to form the seminal fluid or semen or seminal plasma. It is rich in fructose, calcium and some enzymes.

 What are the main  functions of semen?

It has many functions:-

i) They provides a fluid medium for the transmission of sperms into the vagina of female.

ii) They nourish and Activate the sperms to keep them viable and motile.

iii) They neutralize the acidity of urine in the urethra of male and vagina of the female to protect the sperms.

iv) They facilitate the sexual activity by lubricating the reproductive tract of the female. The semen has a pH of 7.35-7.5.