It is a pouch of deeply pigmented skin divided into two separate sacs.Each sac contains one testis.The normal temperature of the testes in the scrotum is about \({ 2 }^{ \circ }C\)lower than the internal body temperature the ideal temperature for developing sperms.

(a) It is a blastocyst.
 'a' - Inner cell mass.
  'b' -Trophoblast
(b) Inner cell mass

Follicular phase.
The primary follicles in the ovary grow and become a fully mature Graafian follicle.
The endometrium of the uterus is regenerated by proliferation of the cells.
These changes are due to an increased level of pituitary hormones,FSH and LH and ovarian hormone,estrogen.
FSH controls the follicular phasa; it stimulates the growth of follicles and secretion of estrogen by the follicular cells.
Both FSH and LH reach their peak level in the middle of the cycle.

1.Hymen is the membrane that partially covers the vaginal opening.
2.The hymen gets torn during the first coitus.
3. But it can also be torn by active participation in sports like horse-riding,cycling,or by a sudden fall or jolt and insertion of vaginal tampon;so its presence or absence cannot indicate virginity.

The process of formation of a mature female ganete is called oogenesis. This process starts during embryonal stages where millions of gamete mother cells, oogonia are formed in foetal ovary.
Oogonia starts division and enters prophase-I and gets temporarily arrested at this stage to forn primary oocytes. Each primary oocyte gets surrounded by a layer of granulosa cells forming primary follicle. From birth to puberty, large number of follicles degenerate (follicular atresia) and at puberty 60,000-80,000 follicles are left in each ovary.
Primary follicles form secondary follicles, surrounded by more layers of granulosa cells.
Secondary follicle transforms into tertiary follicle with a fluid-filled cavity called antrum, having theca externa and theca interna. The primary oocyte completes Ist meiotic division (grows in size) forming two unequal haploid cells, large haploid secondary oocyte and a tiny first polar body.
Tertiary follicle transforms into mature Graafian follicle, which bursts to release ovum/secondary oocyte (ovulation). The hormones involved are FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone) secreted by anterior pituitary in response to production of GnRH (Gonadotropin Releasing Hormone). FSH stimulates follicular growth and maturation of oocyte.Granulosa cells of follicles produce oestrogen. In the presence of both LH and oestrogen, ovulation Occurs.

(i) (a) Sertoli cells
(b) Seminiferous tubule
(c) Spermatozoa
(d) Spermatogonia
(e) Interstitial cells.
(ii) Function of parts:
(a) Sertoli cells provide nutrition to developing spermatozoa.
(b) Spermatozoa are formed in the seminiferous tubules from spermatogonia that arise from germinal epithelial cells.
(c) These are male gametes which fertilize the ovum.
(d) The spermatogenic cells of germinal epithelium lining the seminiferous tubules by mitotic divisions produce spermatogonia. The latter undergo meiotic division to form spermatozoa.
(e) Interstitial cells secrete male sex hormones (Testosterone).

Each fallopian tube extends from the periphery of each ovary to the uterus.
The part of the fallopian tube closer to the ovary is the funnel-shaped infundibulum.
The edges of the infundibulum possess finger like projections,called fimbriae.
The infundibulum leads to the wider part of the fallopian tube,called ampulla.
The last part of the oviduct with a narrow lumen;is called isthmus;it joins the uterus.

Duct System of male Reproductive System.
The intratesticular duct system starts with tubuli recti,which are the short,straight end segments of the seminiferous tubules ;these tubules connect the seminiferous tubules to the cuboidal epithelium-lined channels,called rete testis.
Form the rete testis arise 10-20 fine tubules,called vasa efferentia that leave the testis and open into the epididymis.
Epididymis is a single convoluted tubule that is located along the posterior surface of the testis.
The epididymis continues as the vas-deferens,that ascends into the abdominal cavity through inguinal canal.
It loops over the urinary bladder and receives a duct from the seminal vesicle of its side to form ejaculatory duct that runs through the prostate and opens into the prostatic urethra,just after its emergence from the urinary bladder.
The urethra receives the ducts of prostate gland and bulbourethral glands,a little ahead and runs through the penis to its openning called urethral meatus,to the outside.

The target cells for luteinising hormone in males are the Leydig cells and in females are the mature follicles.

LH in males stimulates the Leydig cells of testes to secrete androgens (testosterone) which controls spermatogenesis.

LH in females stimulates ovulation formation of corpus luteumfrom the reptured follicle and secretion of progesterone by corpus luteum.

(i) Use of alcohol, drugs, smoking and stress may cause decrease in sperm counts.
(ii) If a man is unable to erect his penis properly, he is unable to perform intercouse and semen containing sperms cannot be introduced into the vagina in required amount.
(iii) Treatment depends on the cause, In this case cessation of alcohol, drugs, etc., may lead to significant improvement.
(iv) Pari is sensible, intelligent and has power of logical reasoning.

Structures derived from ectoderm