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 Fertilization 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?