Biology today

• major secondary sex characters of human females are
development of breasts, broader pelvis, rounded body
contours, fat deposition in thighs, buttocks and face, high
pitched voice, etc.

• Puberty is defined as the state at which the gonads come
to maturity relative to their endocrine and gametogenic
potential. These changes occur in response to rising levels
of gonadal hormones. It occurs sometime between 10 and
15 years.

• Adolescence is the period between puberty and complete
sexual maturity. Generally, it is considered to start with the
development of secondary sexual characteristics and to end
when physical growth of body slows down. In humans, age
11 to 20 years for boys and 10 to 18 years for girls is the
adolescence period.
Precocious puberty and delayed puberty
Precocious puberty is defined as the premature appearance of
secondary sex characteristics and is usually caused by an early
increase in gonadal steroid production. This leads to an early
onset of puberty growth spurt, maturation of skeleton, breast
development (in girls) and enlargement of genitalia (in boys).
Onset of puberty is considered delayed if menstruation fails to
occur by the age of 17 or testicular development by the age of

20. It may arise due to absence of pituitary hormones or due
    to defect at the level of hypothalamus.

male reProductive system

• male reproductive system consists of scrotum, a pair
of testes, vasa efferentia, epididymides, vasa deferentia,
ejaculatory ducts, urethra, penis and certain glands.

Ureter

Seminal vesicle

Prostate gland

Ejaculatory duct

Cowper's gland

Epididymis

Scrotum

Sperm duct

(vas deferens)

Erectile tissue corpus

cavernosa containing

blood sinuses

Corpus spongiosum

Penis

Urethra

(penile urethra)

Prepuce (foreskin)

Orifice of urethra

(urogenital aperture)

Bladder

Testis

Fig.:The male reproductive system

scrotum

• It is a sac consisting of loose pouch of skin, muscles and
connective tissue that hangs from the root i.e., attached
portion of the penis.
• a septum divides the scrotum into two sacs. Each of these
sacs contains one testis.

•    The scrotum remains connected with the abdomen or pelvic

cavity by two inguinal canals on each side of the scrotal

septum. The spermatic cord, formed from the spermatic

artery, vein and nerve bound together with connective tissue

passes into the testis through inguinal canal.

scrotum as thermoregulator

The scrotum acts as a thermoregulator and maintains testes

at a temperature 2°c lower than the body. This temperature

is required for normal sperm production. It is maintained and

regulated by two mechanisms:

(i) Location of scrotum outside the pelvic body.

(ii) contraction of the smooth involuntary dartos muscle

which brings the testes closer to the pelvic cavity to get

the warmth when the body is chilled.

testes

•    There is a pair of testes that are suspended in the scrotum

by the spermatic cords. During early foetal life the testes

develop in the abdominal cavity just below the kidneys and

then they descend into the scrotum.

•    a fibrous cord that extends from the caudal end of the testis

to the scrotal wall is called gubernaculum.

Layers surrounding testis

Tunica vaginalis

Tunica albuginea

Tunica vasculosa

Serous covering of testis.

Actual covering, made of fibrous

or collagenous connective tissue.

Delicate, loose, lines testicular

lobules, has rich supply of blood

capillaries.

•    Tunica albuginea divides the major part of the testis into

about 250 testicular lobules by forming a vertical partition

called mediastinum and a number of transverse septa.

•    Each testicular lobule contains several intricately sperm

producing coiled tubules called seminiferous tubules.

•    The lining of seminiferous tubules is formed of a single

layered germinal epithelium which has two types of cells,

spermatogenic cells and supporting cells.

•    In between the seminiferous tubules, in the connective

tissue, there are present small groups of rounded endocrine

cells, called interstitial or Leydig’s cells.

•    Spermatogenic cells by mitotic division produce

spermatogonia. Spermatogonia grows into primary

spermatocyte which undergo meiosis to form secondary

spermatocyte and then spermatids.

•    The process of formation of spermatozoa (mature sperms) from

the spermatogenic cells is called spermatogenesis which

occurs in seminiferous tubules.