Human Reproduction

Reproduction – is the formation of new individuals.  The reproductive system produces, stores, and releases specialized sex cells called gametes. These specialized cells are make it possible for the fusion of sperm and egg to form a zygote.  Puberty – is a period of rapid growth and sexual maturation during which the reproductive system becomes fully functional.

Female Reproductive System  Ovaries – two almond sized structures where the egg cell is produced.  Follicle – a cluster of cells that surround, protect, and nourish a developing egg cell.  Oviduct (fallopian tube) – narrow tube which serves as the passageway to the uterus.

Female Reproductive System  Uterus – a hollow, muscular organ with thick walls.  Cervix – connects the vagina and uterus.  Vagina – is a flexible, thin walled organ which is responsible the receiving the penis and sperm during intercourse.

Ovarian Cycle  During the ovarian cycle, an egg develops and is released from the ovary.  Ovulation – When a follicle has fully matured, its egg is released in a process called ovulation.

Ovarian Cycle  When Estrogen levels are low, the pituitary gland releases FSH which causes a follicle to mature.  A sudden rush of FSH and LH cause the follicle to release a egg.

Menstrual Cycle  The menstrual cycle is controlled by hormones that are controlled by negative feedback mechanisms.  Estrogen and progesterone are released by the ovary and cause the lining of the uterus (endometrium) to thicken.  If fertilization does not occur, less estrogen in the blood cause the lining to shed causing menstruation.

Fertilization

 Fertilization must occur within the first 48 hours of ovulation.  As soon as fertilization occurs, a zygote is formed.  As the embryo travels down the fallopian tube, it divides by the process of mitosis (cleavage).  Implantation occurs on Day 8 or 9 after fertilization.

Male Reproductive System  Testes – area in which sperm is made.  Scrotum – sac like structure that holds the testis.  Epididymis- a long thin coiled tube in which sperm complete there development and are stored.  Semen – fluids that are released with sperm that aid in its survival.  Vas Deferens – a tube that brings sperm from the epididymis out through the urethra.

Sperm Cells  A sperm cell consists of a head, which contains a nucleus. Midpiece, which contains millions of mitochondria. Tail which is used for movement.

Release of Sperm  Glands lining the reproductive tract – including the seminal vesicles, the prostate, and the bulborethral gland produce nutrient rich fluid called seminal fluid.  Approximately 2.5 million sperm are found in one drop of semen! Why so many?