HUMAN REPRODUCTIVE SYSTEM
Man is unisexual. There is a distinct sexual dimorphism. Males can be easily distinguished from female by many character, such as physical standerds, externals genetial organs and accessory sex characters. Human reproduction is highly evolved. Structures associated with reproduction are different in male and female. In humans, reproduction system becomes functional after attaining a definite age called puberty. Puberty in male is generally attained at the age of 13 to 14 years. But in female puberty is attained at the age of 10 to 12 years.
Reproductive system of each sex consist of many organs. The latter are distinguished into primary and secondary sex organs. Primary sex organ called gonads. Gonads produce gamets and secret sex harmones. Growth and functions of gonads are regulated by harmones ,the FSH and LH from pituitary. Gonads of male are called testes and females are called ovaries. Testes produce sperms and male sex harmones testosterone. Ovaries produce ova or eggs and female sex harmones estrogen. These harmones play an important role in process of reproduction.
1. They regulate the process of gametogenesis ( formation of sperm and ovum)
2. Maintain structure and function os accessory sex organs and
3. Regulate development of secondary sex character like facial, axial and pubic hair, pitch of the voice and development of mammary gland, etc.
Organs which nither produce gamets nor secrete sex harmons but perform important function in reproduction, are called secondary sex organs. They include prostate gland, seminal vesicles, vasa deferentia and penis in male. In female they include fallopian tube, uterus, vagina and mammary glands.
MALE REPRODUCTIVE SYSTEM
Human male reproductive system consist of a pair of testes, apair of epididymis, a pair of vasa deferentia, a pair of ejaculatory ducts, penis and certain gands.
I. Testes (singular testes) : Testes are primary male reproductive organs. They are soft, smooth, pinkish, oval organs, about 4-5 cm long, 2.5 cm wide and 3 cm thick. They lie in small scale like muscular structure out side the abdominal cavity called scrotum. Scrotum is a pauch of skin arising from the lower abdominal wall and hanging between the legs. Testes originate in the abdominal cavity but later, during the seventh month of development , descend into scrotum. Scrotum acts as thermoregulator and provides an optional temperature for the formation of sperms. This temperature is 1-3 degree Celsius lower the temperature of the body. Failure of testes to descend into scrotum causes sterility. Because formation of sperms does not occur at abdominal temperature.
Each testis is formed of several highly coiled tubules called seminiferous tubules. Seminiferous tubules are heald by connecting tissues, in which are present interstitial cells or Leyding cells. Seminiferous tubules produce sperms. Interstitial cell secrete male sex hormons, the testosterone. This hormons regulate primary and secondary sex character in man. Testes form sperms throughout the reproductive life of man.
II. Epididymis: Each epididymis consist of a long, high coiled tube and remains attached to the side of the testis. It receives sperms from testes and store them temporarily till ejaculation. It leads into a sperm duct called ducts deferens or vas deferens.
III. Vas defentia : Each vas deferens is a tube with a thick muscular wall. It enters the abdominal cavity through inguinal canal. In abdominal cavity it passes over the urinary bladder and joins the duct of seminal vesicle to from ejaculatory duct.
IV. Ejaculatory ducts: Each duct is small thin walled tube which passes through prostate gland and opens into urethra. Urethra carries both sperms and urine and passes through the penis. Urethra opens to the outside at the tip of penis through a male genital aperture. There is one opening for urine and sperm.
V. Penis : It is a male copulatory organ. It is a cylindrical, spongy, muscular and highly vascular organ. It is used for passing out urine, sexual act and for depositing sperms in the female genital tract.
VI. Accessory sex gland : In man a pair of seminal vesicles, a prostate gland and a pair of cowper’s gland are associated with male reproductive system. Secretions of these gland protect sperms from acidity of male and female reproduction tracts. Secretions also increases sperm motility.
Secretion of these various glands and sperms collectively form semen.
FEMALE REPRODUCTIVE SYSTEM
Human female reproductive system is more complex than that of male. This complexity in structure and function ensure the union of sperm and ovum inside the body of female. Female reproductive system consist of a pair ovaries, a pair of fallopian tubes, uterus, vagina, external genitalia and mammary gland.
I. Ovaries : Ovaries are the primary sex organ of a female. They are almond shaped bodies, about 3 cm long , 1.5 cm wide and 1 cm thick. They are located in the abdominal cavity near the kidney. They are suspended from the dorsal body wall near the kidney by a section of peritoneum, the mesovarium.
Each ovary perform a dual function of :
a. Production of female gamete and,
b. Secretion of female sex harmones.
Each ovary is composed of ovarian follicles. At puberty, these follicles undergo maturation to produce ova. The process of formation of eggs in the ovary is known as oogenesis. It is controlled by hormones from anterior pituitary.
Release of mature ovum from a mature ovarian follicle is called ovulation. Ovulation controlled by LH from pituitary.
II. Fallopian tube (oviducts) : Each fallopian tube or oviduct is about 12 cm long muscular tube . it conveys eggs from ovary to the uterus. It also provides site from fusion of ovum and sperm. Funnel shaped proximal part of oviduct is called infundibulum. Margin of infundibulum bears finger like process called fimbrae. It opens into the abdominal cavoty by an aperture called ostium. Ostium recives eggs released from ovary. While eggs is moving down the oviduct it is fertilized by the sperm in the terminal part of the oviduct.
III. Uterus : Uterus is also called womb. It is large highly elastic sac apecialized for the development of the embryo. Two oviduct open into it. Lower narrow part of the uterus is called cervix which opens into the vagina. Wall of the uterus is formed three coats: innermost endometrium, middle myometrium and outside perimtrium. Endometrium provide site for implantation of embrayo.
IV. Vagina : Vagina is a tubular structure and is called birth canal. It also act as a female copulatory organ. It is about 7.5 cm long. It is called birth canal because through this canal the young is born after completion of development inside the uterus. It is called copulary organ because it receives penis during copulation.
V. External genitalia : There is a depression, the vestibule in front of anus. Urethera and vegina open by separate apertures into the vestibule. A pair of vestibular or bartholin gland occur on each side of vaginal opening into the vestibule.
VI. Mammary glands ( Brestes) : because enlarge considerasly in adult female. They contain mammary glands. Mammary glands becomes functions after the birh of a child.