Reproductive System

Reproduction is one of the features of living beings and produces offspring to continue the race. Human reproduction is sexual and fertilization is internal.

In humans, male and female are different and distinct with sexual dimorphism. The organs taking part in reproduction are reproductive organs which remain interconnected and form the reproductive system.

Male Reproductive System:

• It is involved in production of gametes and transportation of it to appropriate region of female reproductive part to ensure fertilization.
• Male reproductive system includes the following organs:

[Diagram: Frontal view of male reproductive system]
Labels: Urinary bladder, Vas deferens, Bulbourethral (Cowper's) gland, Epididymis, Right testis, Scrotum, Seminal vesicle, Ejaculatory duct, Prostate gland, Prostatic urethra, Membranous urethra, Penile urethra, Penis, Glans Penis.

1) Testis:

• One pair of oval whitish testes is located in a skin pouch called Scrotum which has darker pigmentation & thin hairs.
• The testes are located out of body cavity in scrotum to maintain the temperature of 35°C, which is required for production & maturation of sperm.
• Each testis is 4cm long and 2.5cm in thickness and weight about 10-14gm.
• The left testis is slightly lower than right testis to avoid collision between the thighs.
• The testes at interior surface remains attached with muscles called Cremaster muscle which at another end remains attached with body wall. These muscles regulates movement of testes and bring them near to body wall to provide warmth during winter seasons.

Histology of testes:

[Diagram: T.S. of Testis]
Labels: Tunica Vaginalis, Hydrocoel, Tunica albuginea, Spermatogenic cell, Sertoli cell, Sperm, Seminiferous tubule, Interstitial cell (Leydig cell).

• Each testis has 2 layers: Outer tunica vaginalis and inner tunica albuginea. In between them is a fluid called Hydrocoelwhich absorb mechanical shocks.
• Internally, Testis contains 200 - 250 lobes called seminiferous tubule. Each seminiferous tubule has 2 kinds of cell: Spermatogenic cell & Sertolic cell.
• The Spermatogenic cell produces sperm by the process called spermatogenesis.
• Among the spermatogenic cells are irregular cells called Sertoli cell which nourishes sperm.
• In between seminiferous tubules is Interstitial cell or Leydig cell which synthesis male sex hormone like testosterone & androgen.

2) Duct System:

It include tubes of different sizes that transports sperms from testis to the appropriate region of female reproductive part. It including following duct:

• a) Epididymis: It lies on posterior surface of each testes and is clove shaped having head, body and tail. It reaches sperms from testis for the sperms are mature there. It is about 6m in length but is highly coiled.
• b) Vas deferens: Posterior surface of Epididymis continuous as narrow tube called vas deferens which is about 45cm in length. Vas deferens run upward to Pelvic Cavity, make a loop around Ureter of its sides. It transport sperms during sexual arousal.
• c) Ejaculatory duct: Vas deferens receives Seminal vesicle at its side & forms a duct called Ejaculatory duct which is 2 cm in length. Two ejaculatory duct, one on either side of Urethra eject sperm to Urethra.
• d) Urethra: Below to Urinary bladder is a tube called Urethra which is about 20cm in length and is a common passage to both Urine and Semen. Based on location, Urethra is classified as Prostatic Urethra, membranous Urethra & Penile Urethra.
  • The part of Urethra below to Urinary bladder is prostate urethra which remains grounded with prostate gland & is about 4-5 cm in length.
  • The prostate urethra is followed by 2cm long urethra called membranous urethra.
  • The terminal path of Urethra is called Penile Urethra which opens out through an opening called Urethral Orifice. It is about 10 to 14cm in length.

3) Copulatory Organ:

• The organ which help in discharge in semen to appropriate region of female reproductive system is called copulatory organ which is penis in male.
• Structurally, Penis is composed of free erectile muscle. Out of them the median is called Corpus spongiosum which on either side contain Corpus cavernosa. These sets of muscles are externally covered with loose skin which allows extension of the muscles during sexual arousal.
• The terminal end of penis is called Glance Penis which is sensitive to touch & has opening called Urethral orifice. The glance penis is partly covered with skin which is called fore-skin (Prepuce).

4) Accessory Gland:

• a) Seminal Vesicle: Below to Urinary bladder one on either side of Urethra is a whitish fibro-muscular organ is available & is called Seminal Vesicle. It is about 5cm in length & produces fructose which nourishes sperm.
• b) Prostate gland: Below to Urinary bladder around Urethra is whitish structure called Prostate gland. It is about 4cm in length & produces an alkaline fluid which provides median to sperm for swimming. The fluid with sperm is called semen.
• c) Bulbourethral Gland: It is also called Cowper's gland & is about oval in shaped. It is located at the base of penis & produces an alkaline fluid which passes out before discharge of semen. It neutralize acidic nature of penile urethra & lubricate glans penis. It assist in penetration of vagina & protect glans penis from friction with vaginal wall.

Female Reproductive System:

Female Reproductive System is well developed. It has following function:

1. To produce ova.
2. To transport ova at appropriate region.
3. To receive penis during coitus & collects semen.
4. To ensure fertilization, development of embryo & parturition.
5. To feed to the baby.

Female reproductive system has following parts:

[Diagram: Internal Part of female reproductive system]
Labels: Isthmus, Ampulla, Infundibulum, Fimbriae (Uterine tube / fallopian tube), Ovary, Ligaments, Fundus, Body, Cervix (Uterus), Perimetrium, Myometrium, Endometrium, Vagina, Vaginal rugae.

1) Ovary:

• A pair of almond shape ovary lies one on either side of uterus. It is female gonad, lies in pelvic cavity & is held in position with the help of several ligament like mesovarium.
• Each ovary is 3.5cm long, 2cm width & 1cm thick. It is pinkish at early age & becomes darker at later age.
• Histological: Each ovary has outer germinal epithelium & inner tunica vaginalis. The space occupied by inner to tunica albuginea is called stroma. The stroma is differentiate into peripheral cortex & central medulla.
• The cortex contains many small cell called as Graffian follicle. Few Graffian follicle mature at each menstrual cycle & become primary oocyte. Out of many primary oocyte few become secondary oocyte. The secondary oocyte which mature enough is called Ovum & others are ruptured to form yellowish fluid called Corpus luteum.
• The ovum ejects out of ovary by the process called ovulation which occurs at 14 day of menstrual cycle.

2) Duct System:

• The duct system in female is represented by uterine tube or fallopian tube which has 3 parts: Infundibulum, Ampulla, Isthmus.
• The terminal end of uterine tube which lies over the ovary is called Infundibulum which is encircled with finger like projection called Fimbriae. They capture the ovum.
• The wider path of uterine tube is called Ampulla where fertilization take place. The ampulla posterior narrows & is called Isthmus which open into uterus.

3) Uterus:

• The hollow muscular & inverted pear shaped structure is called uterus. It is also called womb where fetus grows. It is about 7cm long, 5cm width & 2.5cm thick but it is extended many time at pregnancy.
• Structurally Uterus has 3 parts: fundus, body and cervix. The part above to the opening of isthmus is called fundus. The middle widest part is called body & lower narrow part is called cervix which has a canal called Cervical canal.
• Histological: Uterus has 3 layers: The outer is called Perimetrium, middle is called myometrium and inner is called endometrium. The endometrium is eroded as vaginal fluid during menstruation.

4) Vagina:

• It is a female copulatory organ and is tubular in shape it measure 8-10cm in length and has ridges on dorsal surface. These ridges are called vaginal rugae and helps in distension during coitus (sexual).
• The inner wall of vagina has Bartholin's glands which secrets alkaline fluid that keeps vagina lubricative.
• The opening of vaginal orifice which at early stage remains covered with thin membrane called hymen. Hymen is later rupture.

The External Genitalia (Vulva):

The external visible female genitalia are collectively called vulva which includes following parts:

• Mons Pubis: Below to abdominal wall is a thick hump called mons pubis which is densely covered with pubis hair.
• Labia majorum: Inferior to mons pubis is a pair of thick folds labia majora which are laterally covered with pubis hair.
• Labia minorum: Inner to each labia majorum is a thin folds called labia minorum. The labia minora is uncovered with pubic hairs and contains sebaceous & sweat gland that keep the vulvar region moist.
• Vestibule: Labia minora inclose a space called vestibule. At anterior end a stimulating rod shaped structure called clitoris is available. It is homologus to penis in male. Below to clitoris is an opening called Urethral orifice which allows release of urine. Below to urethral orifice is another opening called Vaginal orifice which leads inwards into vagina.

Breast (Mammary Gland):

[Diagram of Breast]
Labels: Adipose, Areolar tissue, Nipple, Fluid, Lobule, Duct.

• A pair of globular mammary gland is located at chest and is accessory reproductive organ.
• Each breast has a terminal rod shaped part called nipple which is followed by a coloured region called areolar. The colour is pinkish at early stage and then gradually becomes dark.
• Posterior to areolar is a mass of adipose covered with skin. This adipose contains 15-25 chamber and each chamber contains lobules which contains the cells that eject milk.
• Each lobule give out a duct called lactiferous duct which unite with others and forms a common duct which opens at the surface of nipple. The cells of lobule eject milk under the influence of Prolactin after the birth of baby. When the baby suckles the nipple the lobule eject the milk.

MENSTRUAL CYCLE

• Menarche: The first menstruation.
• Menopause: Stoppage of menstruation (usually around 50 - 59 years).

Phases summary:

1. Menstrual phase: Bleeding phase (1 - 5 days). "Weeping of uterus" or "Funeral of ovum".
2. Follicular phase: (6th - 13th days). Pituitary gland releases FSH → Stimulate follicles → Ovary releases Estrogen hormone. Also LH is secreted.
3. Ovulation: 14th day.
4. Luteal phase: (15th - 28th days).

Details:

In human female cyclic change occurs in reproductive parts. This biological phenomenon is called menstrual cycle which is of 28 days in an average. All the phase in menstrual cycle are controlled and regulated by several hormone.

The first menstruation is called menarche which starts at the age of 12 yrs or beyond on heredity, climate, diet etc. It is continued up to the age of 52-55 years and then stoppage of menstruation is called menopause.

1. Menstrual Phase: This phase lasts for 3-5 days and is characterized with bleeding. The fluid discharged has mucus and unfertilized ovum. This phase is therefore also called as weeping of uterus or funeral of un-fertilized ovum.
2. Follicular Phase: It extends between 6th and 13th days of menstrual cycle. The pituitary gland secrets FSH which stimulate follicles in ovary. These follicles secret estrogen which is increased in concentration at 12th day. Simultaneously LH is secreted. Stimulated follicles becomes primary oocyte when estrogen and LH are at peak level. Eocyte ejects out of ovary at 14th day. This phenomenon is called ovulation.
3. Luteal Phase: Once secondary oocytes (ovum) is ejects the remaining primary oocytes are disintegrated and forms progesterone which prepares uterus for anchorage of fertilizes zygote. The hormone adds a mucus layer on the surface of endometrium and remains maximum in blood for 1 week. The fate of progesterone depend upon whether the ovum is fertilizes.
   • If ovum is fertilize the progesterone continuously remain in maximum in blood until parturition.
   • When ovum is not fertilizes the level of progesterone continuously decline checks the supply of blood to the overgrown tissues. Overgrown endometrium at 28th day is separated and discharged out through vagina starting another menstrual cycle.