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Home > Reproductive Anatomy
Reproductive Anatomy in Preganancy
Male Sexual and Reproduc.. Female Sexual and Reprod.. Conception
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Reproduction is the hallmark of life and living organisms and forms the basis of cycle of life. The ability to reproduce is a unique capability of all living things. Sexual reproduction produces offspring that are genetically different from their parents.

In human beings, reproduction is much the same as for other mammals. Specialized reproduction organs are located in the lower abdomen. The male has glands called testes that make microscopic, tadpole-shaped sperm cells. The female has glands called ovaries that make pinpoint-sized eggs cells. Together they result in a fertilized egg cell and the beginning of new life. Fetal and embryonic development is the life before birth, while pregnancy focuses on labor and delivery of the baby.

In sexual reproduction new life is formed by the fusion of gametes to form a zygote. Sperm are male gametes while, ova are female gametes. Meiosis produces cells that are genetically distinct from each other; fertilization is the fusion of two such distinctive cells that produces a unique new combination thus increasing variation on which natural selection can operate.

Sexual reproduction has the advantage of generating genetic variation among offspring, thereby increasing the chance of the population`s survival. The process needs two individuals to mate.

Human reproduction involves internal fertilization based on the integrated action of hormones, the nervous system, and the reproductive system. Gonads are sex organs that produce gametes. Male gonads are the testes, which produce sperm and male sex hormones. Female gonads are the ovaries, which produce eggs (ova) and female sex hormones.

The male reproductive system includes the testes suspended outside the abdominal cavity in the scrotum. The scrotum is a pouch of skin that keeps the testes either close or far from the body to maintain an optimal temperature for sperm development. Seminiferous tubules are inside each testis where sperms are produced. About 250 meters (850 feet) of tubules are packed into each testis. Spermatocytes inside the tubules produce spermatids that in turn develop into mature sperm.

Sperm production begins at puberty and continues throughout life, with several hundred million sperm being produced each day. Once sperm form they move into the epididymis, where they mature and are stored.

The anterior pituitary produces follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Action of LH is controlled by the gonadotropin-releasing hormone (GnRH). LH stimulates cells in the seminiferous tubules to secrete testosterone, which has a role in sperm production and developing male secondary sex characteristics. FSH acts on cells to help in sperm maturation.

Sperms pass through the vas deferens and connect to a short ejaculatory duct that connects to the urethra. The urethra passes through the penis and opens to the outside. Secretions from the seminal vesicles add fructose and prostaglandins to sperms as they pass. The prostate gland secretes a milky alkaline fluid. The bulbourethral gland secretes a mucus-like fluid that provides lubrication for intercourse. Sperms and secretions make up semen.

The Female Reproductive System consists of the female gonads, ovaries located within the lower abdominal cavity. The ovary contains many follicles composed of a developing egg surrounded by an outer layer of follicle cells. A developing egg (oocyte) is released each month from puberty until menopause.

After puberty, the ovarian cycle starts and continues until menopause when reproductive capability ends. These cyclic phases are interrupted only by pregnancy. The ovarian cycle lasts usually 28 days. During the first phase, the oocyte matures within a follicle. At midpoint of the cycle, the oocyte is released from the ovary in a process known as ovulation. Following ovulation the follicle forms a corpus luteum which synthesizes and prepares hormones to prepare the uterus for pregnancy.

The oocyte passes into the oviduct (fallopian tube or uterine tube). The oviduct is connected to the uterus. The uterus has an inner layer, the endometrium, in which a fertilized egg implants. At the lower end of the uterus the cervix connects the uterus to the vagina. The vagina receives the penis during intercourse and serves as the birth canal.

The female external genitals are collectively known as the vulva. The labia minora is a thin membrane of folded skin just outside the vaginal opening. The labia majora cover and protect the genital area. A clitoris, important in arousal, is a short shaft with a sensitive tip covered by a fold of skin.

The ovarian cycle is hormonally regulated in two phases. The follicle secretes estrogen before ovulation; the corpus luteum secretes both estrogen and progesterone after ovulation. Hormones from the hypothalamus and anterior pituitary control the ovarian cycle. The ovarian cycle covers events in the ovary; the menstrual cycle occurs in the uterus.

Menstrual cycles vary from between 15 and 31 days. The first day of the cycle is the first day of blood flow (day 0) known as menstruation. During menstruation the uterine lining is broken down and shed as menstrual flow. FSH and LH are secreted on day 0, beginning both the menstrual cycle and the ovarian cycle. Both FSH and LH stimulate the maturation of a single follicle in one of the ovaries and the secretion of estrogen. Rising levels of estrogen in the blood trigger secretion of LH, which stimulates follicle maturation and ovulation (day 14, or mid-cycle). LH stimulates the remaining follicle cells to form the corpus luteum, which produces both estrogen and progesterone. Estrogen and progesterone stimulate the development of the endometrium and preparation of the uterine inner lining for implantation of a zygote. If pregnancy does not occur, the drop in FSH and LH cause the corpus luteum to disintegrate. The drop in hormones also causes the sloughing off of the inner lining of the uterus by a series of muscle contractions of the uterus.

Humans do not have a mating season. Females are sexually receptive to the male at all times of the year. During male arousal, blood flows into the three shafts of spongy erectile tissue inside the penis, causing it to become elongated and erect. The female arousal has the swelling of the areas around the vagina, erection of the clitoris and nipples, and secretion of lubricating fluids in the vagina. After insertion of the penis into the vagina, pelvic thrusts by both partners stimulate sensory receptors in the penis, vaginal walls, and clitoris. The sperm leave the epididymis and secretions of glands form the semen. Orgasm involves contractions of muscles of the penis (male) or vagina (female) and waves of pleasurable sensations. | Home | Sitemap | Contact Us