Human Reproduction

Leydig cells are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH). Leydig cells are polyhedral in shape, display a large prominent nucleus, an eosinophilic cytoplasm and numerous lipid-filled vesicles.

A Testis is one of a pair of organs and part of the male reproductive system. They are the site of sperm production and are also the major producer of the male hormone Testosterone. These are male gonads.

After a female egg is fertilized, it becomes known as a zygote. Once the egg is fertilized, the zygote begins a two-week period of rapid cell division and will eventually become an embryo. The zygote divides through a process known as mitosis, in which each cell doubles by dividing into two cells.

The scrotum is a sac that hangs under the penis and holds the testes in males. It is divided internally into two halves by a membrane each half containing a testis.

The vagina is a muscular passage which forms a part of the female sex organs and which connects the neck of the uterus (called the cervix) with the external genitals. The vagina, which is approximately two and one-half to four inches long, has muscular walls which are supplied with numerous blood vessels.

The bulbourethral are also known as Cowper's glands.These are two small structures about the size of peas, which are located below the prostate gland. They are composed of many tubes whose linings secrete a fluid that is released in response to sexual stimulation to provide some lubrication to the end of the penis in preparation for sexual intercourse.

The two labia minora meet at the clitoris, a small, sensitive protrusion in females that is comparable to the penis in males. The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect.

The uterus or womb is a hollow, muscular organ in which a fertilized egg, called the zygote, becomes embedded and in which the egg is nourished and allowed to develop until birth. It lies in the pelvic cavity behind the bladder and in front of the bowel.

All of these are the main external structures of the female reproductive system .

Spermatogenesis is the process by which male primary germ cells undergo division, and produce a number of cells termed spermatogonia, from which the primary spermatocytes are derived. Each primary spermatocyte divides into two secondary spermatocytes, and each secondary spermatocyte into two spermatids or young spermatozoa.

A thick white opaque fluid that is secreted by seminal vesicals, glands that open into the urethra is called semen.. The function of semen is to protect the sperm cells in the vagina, provide energy for weakened sperm cells, and help contract the uterine muscle to move the sperm cells into the uterus faster.

This tubular female sex organ serves many functions. It is the place where menstrual discharges pass out of the body. It also stretches to function as a birth canal when it is time for the fetus to be expelled from the uterus. It is the channel through which the sperm in the semen travel up toward the fallopian tube to fertilize an egg.

The clitoris is covered by a fold of skin, called the prepuce, which is similar to the foreskin at the end of the penis. Like the penis, the clitoris is very sensitive to stimulation and can become erect. These are the external structures of the female reproductive system.

Menarche is the first menstrual cycle, or first menstrual bleeding, in female human beings. From both social and medical perspectives it is often considered the central event of female puberty, as it signals the possibility of fertility.

A small walnut-shaped wrinkled bag of skin holds the testicles and is called the scrotum. Muscle fibers in the scrotum contract to help hold the sperm producing testicles closer to the body when warmth is needed and relax to allow the testicles to move farther away when it is too warm.

After the ovum (egg) is released from the ovary, a small temporary gland called Corpus Luteum, forms in the ovary and begins to produce the hormone progesterone.

All of these are the phases of menstruation cycle.

The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are analogous to testes in males, in that they are both gonads and endocrine glands.

During the leutal phase the empty follicle develops into a new structure called the corpus luteum. The corpus luteum secretes the hormones estrogen and progesterone. Progesterone prepares the uterus for a fertilized egg to implant.

The entire external genitalia of the female is called the vulva. This includes the labia majora, labia minora and clitoris.

During the leuteal phase of menstruation cycle if the egg is not fertilized, it passes through the uterus. Not needed to support a pregnancy, the lining of the uterus breaks down and sheds, and the next menstrual period begins.

Testosterone is a steroid hormone from the androgen group . In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid.

Estrogen is a hormone that comprises a group of compounds, including estrone, estradiol and estriol. It is the main sex hormone in women and is essential to the menstrual cycle. Although estrogen exists in men as well as women, it is found in higher amounts in women, especially those capable of reproducing.

The hormone human chorionic gonadotropin (better known as HCG) is produced during pregnancy. It is made by cells that form the placenta, which nourishes the egg after it has been fertilized and becomes attached to the uterine wall.

Progesterone is a steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. Progesterone belongs to a class of hormones called progestogens, and is the major naturally occurring human progestogen.