Male Reproductive System

The male reproductive system of man is formed of the following parts:

(1) Scrotum  

(2) Testes 

(3) Accessory ducts 

(4) Glands 

(5) External genitalia

(1) SCROTUM:

The testes are situated outside the abdominal cavity in a pouch called scrotum. It helps in maintaining the low temperature about 2° to 2.50° C lower than  the body temperature. Hence it is a thermoregulator. Low temperature is necessary for the development of sperms.

(2) TESTES :

There is a pair of testes. Each testis is oval in shape.The size of the testis is (4.5*3*2.5)cms in length,width and thickness. They are pinkish in color. They are the primary sex organs in man. Each testis is attached to the scrotum by a thick band called gubernaculum.With the abdominal cavity the testes are connected by spermatic cord. The scrotum is attached to abdominal cavity by inguinal canal.

Anotomy of Testis:

Each testis is surrounded by the three layers:

• Tunica vaginalis : outer most covering of testes.
• Tunica albugenia : It is the middle layer.
• Tunica vasculosa : It is the inner most layer.

Each testis has about 250 compartments called testicular lobules. Each lobule contains 1-3 seminiferous tubules.

There are about 1000 seminiferous tubules in each testis.

Each seminiferous tubules is lined on its inner side by two types of cells called male germ cells or spermatogonia and sertoli cells. Spermatogonia form sperms and the sertoli cells provide nutrition to developing sperms

The region outside the seminiferous tubules is called interstitial spaces. These contain interstitial cells or the leydig cells. These secrete male hormones, the androgens (testosterome). They are large sized polyhedral cells with ecentric nucleus lipid vacuoles and yellow pigment grannules.

(3) Male Accessory Ducts:

The male accessory ducts include

• Rete testis 
• Vas efferentia 
• Vas defferens
• Epididymus 
• Ejaculatory duct & urethra

Rete-testis :

Rete testis is a network of channels present into the testis. Seminiferous tubules lead to rete testis. They open into vas efferentia

Vasa efferentia:

From rete testis arise a network of small ductules called vas efferentia. These collect sperms and transfer them to epididimus.

Vas deferens:

There are two long tubes originating from each testis.Each vas deferens is 30 cm long tube.It is a narraow,muscular and tubular. It starts from cauda-epididimus and and enters the abdominal cavity through inguinal canal.Their function is to conduct sperms.

Epididymes:

It is about 6 cm long tube. It is present in the posterolateral side of the testis.It is divided into 3 regions:-

Caput epididimes or head: It is the upper wider part which receives vas efferentia

Carpus epididimus or body: It is narrow middle part.

Cauda epididimus or tail: It is wider and is present on the caudal side of the testis.

Ejaculatory duct: 

There are two ejaculatory ducts. Each duct is formed by the union of vas deferens and duct of seminal vesicles. It is about 2cm long. After passing through prostate gland it joins urethra.

Urethra: It originates from urinary bladder and after passing through penis it opens outside. Its external opening is called urethral meatus. It has three parts

• Prostate urethra: It passes through prostate gland and carries urine only
• Membranous urethra: It is smallest part without any covering a carries both urine and semen
• Penile uthera: It passes through penis a carries both urine and semen. It passes through corpus spongiosum of the penis.

(4) External genitalia

In man the penis forms the external genitalia. It is a male copulatory organ.it contains three cylindrical mass of erectile tissue two dorsal carpora cavernosa and one ventral corpus spongiossum. The tip of the penis is called glans penis. There is a retractile fold of skin on glans penis called fore skin or prepuce.

(5) Male accessory glands

There are three male accessory glands viz seminal vesicles, prostate gland and cowper’s glands.

• Seminal vesicles:- There is a pair of sac like str. near the base of the urinary bladder. Each seminal vesicle is about 4cm long. The seminal vesicles produce an alkaline secretion. This secretion forms about 60% of semen volume.

The secretion of seminal vesicles contains- Fructose, Prostaglandins, Citrate, inositol(clotting proteins). Fructose provides energy to sperms for swimming while prostaglandins stimulate  uterine and vaginal contractions. This secretion neutralizes the acidic environment of the male urethra and that of female reproductive tract.

• Prostate glands:- The prostate gland is a single large gland which surrounds a part of urethra. It secretes a thin milky secretion which forms about 25% of the semen volume. It contains citric acid, lipids and enzymes (phosphotase,amylase) and prostaglandins. This secretion nourishes and activates the spermetazoa.

• Cowper’s glands or bulbourethral glands:-There is a pair of these glands. They are present on either side of membranous urethra. These glands secrete an alkaline fluid which acts as a lubricant and also neutralize the acidity of urethra.

Semen:

Semen or seminal fluid is a white colored fluid. It is composed of sperms (10%) and the secretions from accessory glands- seminal vesicles (60%), prostate glands (30%),and a small amount from cowper’s glands. It’s pH is 7.35 to 7.5 (alkaline). It’s alkalinity protects sperms from acidity of urethra and vagina. Semen also helps to transfer ,nourish and activate the sperms.

Hormonal control of male reproduction system:-

The growth, maintenance and functions of the male reproductive system are under the control of Hormones. Gnrh (Gonadotropin releasing hormone) is secreted by the hypothalamus. It stimulates anterior lobe of pituitary gland. It secretes and releases two hormones  -- LH (luteinizing hormone) and FSH (follicle stimulating hormone). In males LH is k/as ICSH(interstial cell stiulating hormone). It stimulates Leydig cells to secrete a male hormone called testosterone. This hormone controlls growth, maintenance and functions of sec. sex organs.

FSH stimulates sertoli cells to secrete ABP(androgen binding protein) which concentrates testosterone in the seminiferous tubules.