The reproductive system is the biological system composed of all the anatomical organs involved in sexual reproduction. Reproduction is the process by which living organisms produce young ones of their own species. It is of 2 types:
- Asexual Reproduction: It is the type of reproduction in which new individuals are produced from a single parent without the formation and fusion of gametes.
- Sexual Reproduction: It is the type of reproduction in which new offspring are produced through the formation and fusion of gametes.
The reproductive system of human being includes:
- Male Reproductive System
- Female Reproductive System
A. Male Reproductive System
Organs associated with the male reproductive system are –
- Vas deferens
- Accessory glands.
- Testes are paired, pinkish and oval bodies measuring 4.5 cm by 2.3 cm in size and are situated inside a sac called scrotal sac or scrotum.
- They are situated outside the abdominal cavity, the temperature of testes remains 2-3°C below the body temperature which is essential for the optimum production of sperms.
- Each testis is surrounded by 3 layers, outer tunica vaginalis layer, middle tunica albuginea and inner tunica vasculosa.
- Tunica albuginea projects inwards forming numerous interlobular septa which divide testis into a number of lobules and each lobule consists of 1-4 long and coiled seminiferous tubules.
- The seminiferous tubules are lined with germinal epithelium that produces sperms by the process called spermatogenesis.
- Sertoli cells are present between germinal epithelium that supply nourishment to sperms.
- Leydig or interstitial cells between the tubules produce the male sex hormones testosterone which promotes the development of accessory glands and control male secondary sexual characters like the change of voice, development of moustache etc.
- All the seminiferous tubules of each testis unite and open into the epididymis by vasa efferentia and sperm produced by testis are transferred through vasa efferentia into the epididymis.
- It is a highly coiled tube of about 6 m long that leads into the vas deferens. It is divided into 3 parts:
- Caput epididymis: broad anterior part.
- Corpus epididymis: a middle part, narrower than caput epididymis.
- Cauda epididymis: posterior part of epididymis.
- The epididymis concentrates sperms and nourishes the sperms until they are mature and capable of being motile.
c. Vasa deferentia:
- 2 vasa deferentia are present in males having 40 cm long tube emerges from cauda epididymis.
- It ascends into the abdominal cavity and joins by a duct from seminal vesicles to form the ejaculatory duct.
- The ejaculatory duct is about 2 cm long that transports semen to the urethra.
- It stores sperms and carries sperms from the testis to the urethra.
- It is a long tube arising from the urinary bladder and common passage for both urine and semen.
- It is a cylindrical, muscular and erectile male copulatory organ that hangs in front of the scrotum.
- It contains 3 cylindrical masses of erectile tissues: 2 dorsal Corpora cavernosa and one ventral Corpus spongiosum.
- The tip of the penis is expanded into a triangular structure known as the glans penis and covered by a fold of skin called prepuce or foreskin.
- It deposits semen into the vagina of the female during sexual intercourse.
f. Accessory glands:
- These are the glands associated with the reproductive organs. These are:
- Seminal vesicles: These are two small fibro-muscular sacs situated below the urinary bladder. Each seminal vesicle opens into a short ejaculatory duct and secrets viscous fluid, containing fructose mucus, etc which helps to keep sperms alive.
- Prostate gland: large gland present below the urinary. It secretes mucus and slightly alkaline milky prostatic fluid which is released during ejaculation. Prostatic fluid helps to neutralize the acidity of the vagina, making the sperms more active.
- Cowper’s glands: Situated below the prostate gland and their secretions serve as lubricant for the semen.
B. Female Reproductive system
Organs associated with the female reproductive system are –
- Fallopian tubes (oviducts)
- Accessory glands
- They are paired, greyish-pink, almond-shaped and about 3-5 cm x 2-3 cm in size.
- They are attached to the dorsal body wall of the abdominal cavity, behind the kidney, by a fold of the peritoneum called mesovarium.
- Histologically, each ovary shows the outer layer of germinal epithelium and inner stroma; surrounded by germinal epithelium which gives rise to the follicles and ova.
- Developing follicles produce a female sex hormone called oestrogen.
- A fully mature ovarian follicle is called Graafian follicle and at every menstrual cycle, a single Graafian follicle bursts and release the ovum inside the body cavity called ovulation.
- After ovulation follicular cells filled with blood clots called corpus luteum that secretes another female sex hormone called progesterone.
- The sex hormones produced by the ovaries activate the uterus and mammary glands for their development and maintain the secondary sexual characters.
b. Oviducts or fallopian tubes.
- These are about 12 cm long, ciliated and muscular tubes at the ends of the uterus.
- They carry eggs from the ovaries to the uterus and is differentiated into 4 parts:
- Infundibulum: These are funnel-shaped which lie near the ovary. Each end has feathery processes called fimbriae. They move closer to the ovaries to draw eggs during ovulation.
- Ampulla: widest and curved part behind infundibulum where fertilization takes place.
- Isthmus: narrow and straight part of the fallopian tube.
- Uterine part: It is the part very close to the uterus.
- It is a hollow, thick-walled, muscular and pear-shaped organ.
- It is 7.5 cm long and 5 cm wide.
- The foetus grows for 9 months during pregnancy in the uterus.
- The Wall of the uterus is composed of 3 layers: outer peri-metrium, middle myometrium and inner endometrium where the endometrium is richly supplied with blood vessels.
- It is differentiated into 3 parts:
- Fundus: Upper dome-shaped, found above the opening of the fallopian tube.
- Body: the main part which is broader above and narrower towards the lower side.
- Cervix: the lower part, connected with the body of uterus above and with the vagina below.
- It is a muscular, folded and tubular female copulatory organ which is about 8-10 cm long extending from the cervix to the outside of the body.
- It provides passage for the menstrual flow, receives sperms during sexual intercourse and acts as a birth canal.
- In virgins, the vaginal orifice is partly covered by a centrally perforated membrane, called the hymen.
- The external genitalia is collectively called a vulva which consists of the following parts:
- Mons pubis: anterior part containing pubic hair in adult females.
- Clitoris: small, cylindrical, erectile organ which is analogous to the penis of a male. It has no reproductive significance but increases sexual excitement in females.
iii. Labia majora: These are 2 large thick folds of skin on the boundary of the vulva. These are partly covered with pubic hairs on their lateral surface and contain a large number of sebaceous glands.
iv. Labia minora: These are 2 smaller pink folds of skin inner to labia Majora and have many sebaceous glands.
f. Accessory glands
- Bartholin’s glands: These are 2 bean-shaped glands. These glands secrete a viscid fluid that lubricates the vulva during sexual excitement.
- Mammary glands: These are paired and each consists of 15-25 lobules, each with its own duct called lactiferous duct that emerges in the nipple. The lobules contain mammary alveoli lined with milk-producing cells.