Male Reproductive system

 Reproductive system 

Sexually reproducing animals possess a functional reproductive system . Animals which are having both male and female reproductive structures for e.g. in liver fluke, tape worm and earth worm are called monoecious animals on the other hand animals which are having separate reproductive structures in both male and female is known as dioecious animals.

Humans are dioecious animals i.e both sexes are separate.

The reproductive system of human consists of 

1. Primary sex organs

2. Secondary sex organs 

3. Accessory sex organs 

The primary sex organ produses gametes ,testis in males and ovary in females . It also secretes sex hermones.

Secondary sex organs consists of  prostate, seminal vesicle, vas defferens and penis in male . The female Secondary sex organs  consists of fallopian tube, uterus, vagina and mammary gland.

These are have important functions in reproduction. 

Accessory sex organs distinguish between male and female.  There is difference in appearance in male and female due to accessory sex organs.  This includes distinct external charecters such as pitch of voice, body hair distribution pattern with facial pattern and body shape. 

Male reproductive system 

The male reproductive system is divided into three groups of structures according to their function .

1. Glands

2. Ducts

3. Supporting structure 

The glands includes- A pair of testis, a pair of seminal vesicle, pair of bulbourethal gland ( cowper's gland) and a prostate gland.

Ducts include vasa efferentia,epididymis, vas differens( ductus deferens), ejaculatory duct and urethra. 

The supporting structure includes scrotum, a pair of spermatic chords and penis.

Testis-

There is a pair of oval shaped testis in human scrotal sac which produces male gamete i.e sperm and also secretes male sex hermone andogen.

It is measuring about 4.5 cm in length, 2 to 3 cm wide and 10 to 15 gm in weight.

The male gonads testes develope in the abdominal cavity during fetal stage. And then descends in to the scrotum through inguinal canal during 7th month of gestetion period or shortly before birth. The inguinal canal is then closed. The testes are held in position in the scrotal sac by means of a cord known as inguinal cord or spermatic chord.

When one or both testis is failed to descend from abdominal cavity to the scrotal sac , this condition is known as cryptorchidism.

Inguinal hernia is a condition in which , inguinal canal is fail to close after the testes have descended down or are reopened at a latter stage in life.

Scrotum,  is a loose pouch like structure hangs below the abdomain in between thighs and posterior to penis .

The presence of testis in the outside of body cavity have a significant role. It has temperature 2⁰ - 3⁰c less than body temperature,  which is vital for viable sperm production in spermatogenesis.

When the temperature is low the testis is drawn close to body by a special type of muscle known as dartos muscle to get warmth. 

The testis have three protective layers 

1.The outermost protective serous coat i.e  Tunical vaginalis .

2.Middle Tunica albuginea made up of fibrous tissues .

3. The inner most Tunica vasculosa , consists of loose networks of capillaries. 

The Tunica albuginea is extended to form conical compartments called testicular lobules. Each lobule contains 1-3 highly coiled sperm producing seminiferus tubules.

The seminiferus tubules are internally lined by a single layer of germinal epithelium.

The germinal epithellium have two types of cell i.e  spermatogonia and sertoli cell.

Most of the germinal cells are cuboidal spermatogonia, which multiply by mitosis to form primary spermatocytes. The primary spermatocyte cell then undergoes meosis to form haploid spermatids, which differentiate into spermatozoa or sperms and released in to the lumen of the tubule.

The process of formation of spermatozoa( sperms) from the spermatogonia is called spermatogenesis.

Another type of cell, 

Sertoli cells are large ,elongated,pyramidal cells whose bases are lined in uriniferus tubules and epices are project into lumen. 

Function of sertoli cells-

1. They nourish the spermatozoa. 

The process of differentiation in to spermatozoa, spermatid cytoplasm discarded as residual bodies and phagocytosed by sertoli cells

2. It secretes androgen binding proteins (ABP) which concentrates testosteron hermone in the seminifrous tubule.

3. It also secretes inhibin hermone  stimulated by  FSH ,and secretes antimullerian hermone during Fetal life which prevents the formation of mullerian duct (latter developes in to female reproductive tract).

4. Sertoli cell act as blood testis barrier which prevents blood cells and other components to enter seminiferous tubule. It also prevents sperm from diffusing in to blood,  which may activate immunogenic response by creating sperm specific antibodies. 

Lydig's cell are interstitial cells present in between seminiferus tubules which secretes  testosteron hermones stimulated by  LH and ICSH (interstitial cell stimulating hermones).

 

Function of testosteron hermone- 

1. Development of male secondary sexual charecters. 

2. Stimulate germinal epithelium to go spermatogenesis. 

Function of testes-

1. Production and storage of sperm. 

2. Secretion and synthesis of androgen hermone.

Male accessory ducts 

The male accessory ducts consists of  Rate testis, vas efferentia,  epididymes, vas defferens, ejaculatory duct and urethra .

After the sperm is produced in spermatogenesis,  the pressure generated by the fluid secreted by sertoli cells pushes sperm and fluid in to the lumen of seminiferus tubules. 

From this sperm moves to a series of very short ducts called straight tubules. 

The straight tubules leads to a network of ducts in testis called rate testis. 

Vas efferentia-

There are 15- 20 small and thin ducts,  called vas efferentia, arises from rate testis and joins proximal duct of epididymis. 

 

Epididymis -

Epididymis is series of long , coiled ducts encircling the testis. 

It has three parts,  

Caput epididymis- located on superior pole of testis  connected with seminiferus tubules ,which stores sperms for maturation.

Corpus epididymis- middle part and 

Cauda epididymis- the part connected to vas differens and attached in to scrotal sac by a connective tissue called gubernaculum .

This part stores sperm for 2-3 months.

Testicle- it is the combination of both testis and epididymis .

Vas defferens/ ductus deferens 

It ia a single muscular tube arises from cauda epididymis and through the inguinal canal it goes to abdominal cavity and before joining to seminal vesicle of its side it forms a wide structure called ampulla( function as reservoir for sperm) form this the sperm goes to ejaculatory duct.

The cutting and tying of vas defferens is a process of permanent birth control in male known as vasectomy. 

Ejaculatory duct- 

This is a short duct ,formed by the union of vas defferens and ducts of seminl vesicle.  This duct enter in to prostate gland and then open in to urethra. 

Urethra-

It is the terminal duct which act as a passage for both semen and urine.  It has three segments- prostatic urethra, membranous urethra and penile urethra.

Penis-

 

It is the introminent ( copulatory)organ of male , also function as urinary duct.

It has three parts root , body and skin.

The body of penis is made of of spongy epithelium covered by a shaft of skin.

The skin also covers the head or tip of penis known as glance penis which is made up of expanded cap of Corpus spongiosum.

Accessory glands of male reproductive system 

Seminal vesicle-

A pair of this gland is present behind the urinary bladder. The secretions of seminal vesicle contains fructose, vitamins, mucus and more amount of prostaglandins ,fructose provides energy to the sperm and prostaglandin gives mobility and viability to sperm.

 

The ducts arises from this gland joins vas differens at ampula to form ejaculatory duct. 

Prostate gland-

It is a hard glandular organ present below the urinary bladder. It secretes thin, milky white alkaline fluid , which neutralises the acidity in semen, urethra and vagina. It also increases sperm motility.

Bulbourethal gland-

This is a small gland lies below the prostate gland,  this gland opens in to urethra at the base of penis.

During sexual excitement the bulbourethal gland secretes an alkaline mucus like fluid which neutralizes acidity of residual urine in urethra and act as lubricant in the glance penis during intercourse. 

Path of sperm-

Sperm-> rate testis-> vasa efferentia-> epididymis-> vas deferens-> ampula-> ejaculatory duct-> external urethra-> internal urethra-> vagina of female. 

Hermonal control of male reproductive system 

Hypothalamus secretes GnRH hermone which stimulates anterior pituitary gland to secrete LH and FSH.

LH also called  ICSH( interstitial cell stimulating hermones) stimulates lydig's cell which secretes androgen hermone. 

FSH inhibits the seminiferus tubules to produce seminiferus tubules which also releases inhibin hermone. 

FSH also stimulates production of androgen binding protein (ABP).