Human Reproductive System ( Male)

 

Male Reproductive System-

1)     Scrotum- It is a Pouch of deeply pigmented skin divided into two separate sac. Each sac contains one testis. The normal temperature of the testis in scrotum is about 2 to 2.5-degree Celsius lower than the internal body temperature. this temperature difference is ideal temperature for developing sperm when the body is chilled the smooth muscles contract and bring the testis close to the pelvic cavity. When the temperature drops movement towards pelvic cavity allows the testis to absorb heat from rest of the body so that the sperm cells do not become chilled. Scrotum remains connected with abdomen or pelvic cavity by inguinal canal.

2)     Epididymis- it is a mass of long narrow closely coiled tube which lies along the inner side of each testis. At anterior end of testis it is called caput epididymis. At middle part of epididymis is known as caudal epididymis. At posterior part of epididymis is known as caudal epididymis epididymis stores the sperm and also nourishes the sperm.

3)     Vas deferentia- A vas deferentia arises from caudal epididymis on each side and leaves the scrotal sac and enters the abdominal cavity through inguinal canal. Vas deferentia loops over the urinary bladder where it is joined by duct from the seminal vesicle to form ejaculatory duct.

4)     Ejaculatory duct- the ejaculatory duct is two short tube formed by union of the ducts from a seminal vesicle and a vas deference. They pass through the prostrate gland and joins prosthetic part of urethra.

5)     Urethra- it comprises of three parts:

a.      First part is surrounded by prostrated gland and is called prostatic urethra which arises from urinary bladder and carries urine only.

b.      Second part is the membranous urethra which is situated behind the lower part of pubic symphasis. The membranous urethra is the smallest urethra.

c.      Third part is penil urethra which is situated in penis.

6)     Penis- penis is the male genital (male copulatory organ) at the tip of glance penis is the slit like opening called the urogenital aperture.

7)     Male accessory gland-

a.      Seminal vesicle- these are one pair of sac like structure near the base of the bladder. Their ducts join the vas deference to form the ejaculatory duct.they produce and alkaline secretion which forms 60% of the volume of semen. Secretion of seminal vesicle contains protein. Fructose is a source of energy for sperm. Prostaglandin stimulates urine contraction and thus may help the sperm to be moved towards the female oviduct. Alkaline nature of seminal fluid help to neutralise the acidity of urethra.

b.      Prostrate gland- it is a single large gland that surrounds the urethra. It produces a milky slightly alkaline secretion which forms 25% of the volume of semen. This secretion contains citric acid (a sperm nutrient) and enzyme and prostaglandin.

c.      Bulbourethral gland or Cowper’s gland- they are present on either side of the membranous urethra. These ducts open into the membranous urethra carrying the fluids that neutralize acidity of urethra. They also secret the mucus that lubricates the end of the penis and lining of urethra.

8)     Testese- they are the primary sex organ in man. During early foetal life the testes develop in the abdominal cavity just below the kidney then they descend into scrotum. There is a pair of testes that are suspended in the scrotum by the spematic chords. A fiberous chords that extends from caudal end of testis to the scrotal wall is called gubernaculum. Each testes is oval in shape with a length of about 4 to 5 cm and a width of about 2 to 3 cm.

a.      Proctective covering- testes are surrounded by three layers-

                                                    i.     Tunica vaginalis is the outer covering of testis.

                                                   ii.     Tunica albuginea is the fibrous covering surrounding the testis situated under tunica vaginalis.

                                                  iii.     Tunica vasculosa consist of a network of capillaries supported by delicate connecting tissue which lines the tunica albuginea.

b.      Teticular lobule- each testicular lobule has one to three highly coiled seminiferous tubules. Each testis has about 250 compartments called testicular lobules.

c.      Seminiferous tubules- each testicular lobule of testis contain one to three highly coiled seminiferous tubules. Walls of each seminiferous tubules is formed of a single layered germinal epithelium. Majority of cells in this epithelium are cuboidal called male germ cells.at certain places there are present tall Sertoli or sustancular cells. Sertoli cell secret androgen binding protein (ABP) that concentrates estrogen in the seminiferous tubules. Sertoli cells also secretes another protein called inhibin which supresses FSH synthesis. The cuboidal cells undergo mitosis to produce spermatogonia. Spermatogonia grows into primary spermatocyte. Which undergoes meiosis, producing haploid cells, first secondary spermatocyte and then spermatids and then they get converted into spermatozoa (sperm) Sertoli cell produces nutrition to the developing sperm.

d.      Interstinal cells or Leydig’s cells- in between the seminiferous tubule in the connecting tissue there are present small group of round interstitial or Leydig’s cell which secrets androgen in male sex hormone.

e.      Rete testis and vas efferenta- seminiferous tubules are closed at one end but on the other end they join to a network the rete testis where fine ciliated ductless vas efferentia arises.

Hormonal control in male reproductive system-

GnRH is secreted by the hypothalamus. It stimulates the anterior lobe of the pituitary gland to secret LH and FSH. In males LH is called interstitial cell stimulating hormone (ICSH) because it stipulates interstitial cells ( Leydig’s cell) to secret androgen.

Testosterone is the principal androgen. FSH stimulates Sertoli cells of the testis to secret and androgen binding protein (ABP) that concentrates testosterone in the seminiferous tubules. Sertoli cells secrate a protein hormone called inhibin which supresses FSH synthesis. FSH acts directly on spermatogonia to stipulate sperm production.

Semen-

Semen is a collection of secretion from the seminal vesicle, prostrate gland and Cowper’s gland along with sperm from testis. A single ejaculation may contain 200- 300 spermatogonia of them at least 60 % must have normal shape and rest 40 % must show vigorous mortality for normal fertilization. Semen has alkaline pH of 7.35 to 7.50.

Spermatogenesis-

The process of formation of sperm is called spermatogenesis it is done in two steps-

1)     Formation of spermatids- it is done in three steps-

a)      Multiplicative phase- at sexual maturity the undifferentiated primoidal germ cell divides several times by mitosis to produce a large number spermatogonia. Type A spermatogonia serves as the stem cell which divide for additional spermatogonia. Type B spermatogonia are the precursor of sperm

b)     Growth phase- Each type B spermatogonia actively grows to a large primary spermatocyte by obtaining a nourishment from the nursing cell

c)      Maturational phase- each primary spermatocyte undergoes two successive division called maturation division. The first maturation division is reduction or meiotic. Hence the primary spermatocyte divides into two haploid daughter cells called secondary spermatocyte. Both secondary spermatocytes undergo second maturational division (mitotic division) to form four spermatids by each spermatocyte.

2)     Formation of spermatozoa from spermatid-(spermiogenesis)- The spermatozoa after nourishment are later known as sperm. Thus, four sperm are formed from one spermatogenesis. After spermiation sperm head become embedded in the Sertoli cell and are finally released from the seminiferous tubules by the process called as spermiation.

 

Spermatozoon:

1)     Head- It is the enlarged end of a sperm, containing the large nucleus. It forms the acrosome. Acrosome contains hydrolytic enzyme which are used to contact and penetrate the egg at the time of fertilization.

2)     Neck- it is the shortest part and is present between the head and middle piece. It contains

a.      Proximal centriole towards the nucleus which plays a role in first cleavage of zygote.

b.     Distal centriole which gives rise to axial filament of the sperm.

3)     Middle pice- the middle piece of human sperm contains the mitochondria coiled round the axial filament called mitochondria spiral (lnebenkern). They provide energy for movement. Posterior half of nucleus, neck and middle piece of sperm is covered by manchette.

4)     Tail- it is the longest part of sperm in its most part the axial filament is surrounded by a thin layer of cytoplasm.

Disorder of male reproductive system-

Benign Prostatic Hypertrophy- this is the enlargement of the prostrate gland it compresses the urethra causing frequent night urination.

Inguinal hernia- tearing of inguinal tissue by any means may result in bulging out of a loop of intestinal into scrotum.

ADAM (androgen deficiency in aging males) it is due to reduced production of testosterone. It normally occurs in men above the age of 40.

Cryptorchidism- it is the failure of descent of testis into the scrotum. It is caused by deficiency in secretion of testosterone by foetal testes.

Hydrocoel-it is the collection of fluids usually in the tunica vaginalis of the testis.