Biology XII:3 Human Reproduction(1 Male and Female Reproductive Sys

Male and Female Reproductive Systems Human beings reproduce sexually and are viviparous. In humans, the reproductive phase starts after puberty. It involves: Gametogenesis Insemination Fertilisation Implantation Gestation Parturition The Male Reproductive System It is located in the pelvic region. It consists of: A pair of testes Accessory glands and ducts External genitalia Testes Situated within the scrotum, which protects the testes and also helps in maintaining the temperature. Each testis is 4 to 5 cm in length, and 2 to 3 cm in width, and has about 250 compartments called testicular lobules. Testicular lobules have seminiferous tubules which are the sites of sperm formation. Seminiferous tubules are lined by two types of cells: Male germ cells − They undergo meiosis to form sperms. Sertoli cells − They provide nourishment to the germ cells. Region outside the seminiferous tubules is called the interstitial space, which contains Leydig cells (interstitial cells). The Leydig cells produce androgens. Accessory Ducts and Glands Accessory ducts include: Rete testis Vasa efferentia Epididymis Vas deferens The seminiferous tubules open into the vasa efferentia through the rete testis. The vasa efferentia open into the epididymis, which leads to the vas deferens. The vas deferens opens into the urethra along with a duct from the seminal vesicle called the ejaculatory duct. The ejaculatory duct stores the sperms and transports them to the outside The urethra starts from the urinary bladder, extends through the penis and opens via the urethral meatus. Accessory glands include: A pair of seminal vesicles Prostate gland A pair of bulbourethral glands The secretions of these glands make up the seminal plasma, and provide nutrition and a medium of motility to the sperms. The Female Reproductive System It is located in the pelvic region: It includes: A pair of ovaries A pair of oviducts Uterus Cervix Vagina External genitalia Mammary glands (not part of the reproductive system, but aids in child care) Ovaries They are the primary female sex organs. They produce the ovum and other ovarian hormones. They are located in the lower abdomen, and are 2 to 4 cm in length. They are connected by ligaments to the pelvic walls and to the uterus. Each ovary is covered by epithelium, and contains the ovarian stroma. The ovarian stroma is made up of: Peripheral cortex Inner medulla Oviducts They are also called fallopian tubes. They are 10 to 12 cm long, and extend from the ovary to the uterus. The part of each oviduct lying towards the ovary is funnel shaped, and is called infundibulum. It has finger-like projections called fimbriae. The infundibulum leads to the ampulla, and then to the isthmus, which has a narrow lumen opening into the uterus. Uterus It is also called womb, and is pear shaped. It is connected to the pelvic walls by ligaments. The uterine wall consists of: External perimetrium Middle myometrium Internal endometrium, which lines the uterine cavity The endometrium undergoes changes during the menstrual cycle. Cervix and Vagina The cervix connects the uterus to the vagina. The cervix and the vagina constitute the birth canal. External Genitalia Consists of: Mons pubis − Fatty tissue covered by skin and pubic hair Labia majora − Extends from mons pubis and surrounds the vaginal opening Labia minora − Fold of skin beneath the labia majora Hymen − Partially covers the vaginal opening Clitoris − Lies at the junction of labia minora Mammary Glands Present in all female mammals It is paired and is glandular. Each breast contains 15 to 20 mammary lobes with alveoli which secrete milk. The alveoli open into the mammary tubules, which unite to form a mammary duct. Many mammary ducts constitute the mammary ampulla, which is connected to the lactiferous duct.