Reproductive structures in human beings
Male Reproductive System
It is located in the pelvic region of the body. It involves a pair of testes along with the accessory ducts, external genitalia, and glands. A pouch-like structure called scrotum is located outside the abdominal cavity. It helps in the maintenance of the optimal low temperatures (2-2.5 degree lower than the normal body temperature. In adults, the size of each testis is about 4 to 5 cm in length and 2 to 3 cm in width and is oval.
There are about 250 compartments in each testis which are called testicular lobules. Highly coiled seminiferous tubules are present in each lobule. Seminiferous tubules are lined on its inner side by two types of cells namely spermatogonia and Sertoli cells. The spermatogonia (male germ cells) undergo meiotic divisions and lead to the formation of sperm while Sertoli cells are capable of providing nutrition to the spermatogonia. Seminiferous tubules are surrounded by interstitial spaces and Leydig cells on the outside. Leydig cells are responsible for the synthesis and secretion of testicular hormones known as androgens. Some immunologically competent cells are also found in this region.
The male sex accessory duct is formed with rete testis, epididymis, vasa efferentia, and vas deferens. Vasa efferentia is connected to seminiferous tubules through rete testis. Further, the vasa efferentia end in the testis and open into epididymis that is situated along the posterior surface of each testis. The epididymis opens to vas deferens that move up to the abdomen and coil over the urinary bladder. It connects to a duct from the seminal vesicle and opens into the urethra as the ejaculatory duct. The function of these ducts is to store and transport the sperms from testis to the outside through urethra. The urethra starts from the urinary bladder and extends through the penis to its external opening called urethral meatus. The penis is a male external genitalia. It is formed by special tissue that aids in the erection of the penis to facilitate insemination. The enlarged terminal of the penis is called glans penis which is covered by a loose fold of skin called foreskin. The male accessory glands involve a pair of seminal vesicles, a pair of bulbourethral glands and prostate. Secretions of these glands comprise the seminal plasma which is rich in calcium, enzymes, and fructose. Bulbourethral glands release some secretions which help in the lubrication of the penis.
Female reproductive system
The female reproductive system includes of a pair of ovaries along with a uterus, vagina, cervix and a pair of oviducts are present in the pelvic region. The whole system integrated with a pair of mammary glands works together structurally and functionally to support the processes of fertilization, ovulation, pregnancy, birth, and care of the child.
Ovaries are the prime female sex organs that produce the ovum and many ovarian (steroid) hormones. The ovaries are located on each side of the lower abdomen. Each ovary is around 2 to 4 centimeters in length and is attached to the pelvic wall and uterus by ligaments. Each ovary is enveloped by a thin epithelium which encases the ovarian stroma. The stroma is further divided into two zones – an inner medulla and a peripheral cortex.
The oviducts (fallopian tubes), vagina and uterus, comprise the female accessory ducts. Each fallopian tube is around 10-12 cm long and extends from the sides of each ovary to the uterus. A small funnel-shaped portion closer to the ovary is called infundibulum. The edges of the infundibulum consist of finger-like small projections called fimbriae, which help in the collection of ovum after ovulation. The infundibulum is further extended to the wider part of the oviduct called ampulla. The last portion of the oviduct, isthmus has a narrow lumen, and it connects to the uterus.
The uterus is also termed as the womb. The configuration of the uterus is like an inverted pear. It is aided by ligaments that are attached to the pelvic wall. The uterus opens into the vagina through the narrow cervix. The pit of the cervix is called cervical canal which forms the birth canal with the vagina. There are three layers of tissue in the wall of the uterus.
Perimetrium – External thin membrane
Myometrium – Middle dense layer of smooth muscles. It is the layer that is responsible for contractions during delivery.
Endometrium – inner glandular layer. It lines the cavity of the uterus. It experiences cyclical changes during the menstrual cycle.
The female external genitalia consists of parts like mon pubis, labia minora, labia majora, clitoris, and hymen.
Mons pubis – it is a cushion like fatty tissue that is covered by skin and public hair.
Labia majora – These are the fleshy folds of tissue that surrounds the vaginal opening.
Labia minora – There are paired folds of tissue under the labia majora.
Hymen – It is a membrane-like structure partially covering the opening of the vagina. The hymen is often destroyed during the first intercourse (coitus). However, it can also break by a sudden jolt or fall, insertion of a tampon, active participation in some sports like cycling, horse riding, etc. In some women, the hymen can still be present after coitus. Thus, the presence or absence of it is not a reliable indicator of virginity or sexual experience.
Clitoris – It is a tiny finger-like structure that lies at the upper joint of the two labia minora and just above the urethral opening.
A mammary gland is a feature of all female mammals. Mammary glands are found in pairs that contain gland tissues and a variable amount of fat. The tissue of glands of each breast is divided into 15 to 20 mammary loves containing clusters of cells called alveoli.
Milk is secreted through these alveoli cells which are stored in the cavities of alveoli. It further opens into mammary tubules which joins to develop a mammary duct. Numerous mammary ducts join to form a wider mammary ampulla which is connected to lactiferous duct through which milk is sucked out.