Living Environment Dr. Golub The Male Reproductive System Key Terms Epididymis Penis Testes Prostate gland Scrotum Semen Seminiferous tubules Urethra Urinary bladder Vas deferens Hormones • Chemical substances produced by endocrine glands that act on target cells • Regulate processes in the body • Works like a thermostat • Travel through the body. • Are very specific for receptor sites. Male Reproductive System • Testes o Testis (singular) o The male reproductive glands o Paired organs (2 of them) o Located outside the body cavity in a pouch called the scrotum o Sperm is developed here, and needs a temperature lower than normal body temperature. o Oval shaped glands where sperm is manufactured; inside are the seminiferous tubules • Epididymis: coiled tubes where sperm matures • Vas deferens: tube that goes from each testis and join together and enter the urethra • Urethra: the tube that carries urine and semen outside the body • Scrotum o Has two sets of muscles to bring testes closer to the body or allow them to descend further from body, depending on temperature. § Maintains constant temperature = homeostasis • Testicle o Testes plus other supportive structures § Epididymis, vas deferens Acrosome: contains enzymes to breakdown outer covering of egg Nucleus: contains ½ the number of chromosomes. Mid section contains mitochondria for energy to “swim” to the egg. Flagellum: acts like a whip to propel sperm to egg. Sperm Cells • Produced in testes in the seminiferous tubules • 100-­‐200 million produced each day Sperm travels this route: • Sperm develop in the seminiferous tubules in the testes • Next, sperm travel to the epididymis, where they mature and are stored • When sperm are released from the body, they travel through the vas deferens • The two vas deferens join together and enter the urethra, which in the male, carries both urine and semen outside of the body through the penis Sperm cells are alive, so they need nourishing fluid to survive long enough to make it to the egg to fertilize it. Semen • The fluid that contains: o Sperm o Nourishing fluid o Other fluids Sperm must be protected from acidic environments. Where do you think sperm may encounter acidic environments? • Urethra • Vagina Sperm Delivery • Ejaculation o Ejection of semen out of the penis through the urethra o During ejaculation, muscles around each vas deferens contract, moving sperm into the urethra. o About 3.5 ml of semen, containing 300-­‐500 million sperm, are expelled during ejaculation. Seminal Vesicle • Produces about ½ of the semen, and secretes sugar into the semen used for energy. Prostate Gland • Produces a clear, alkaline solution to neutralize the acidic environment in the female reproductive system. Cowper’s Gland • Below prostate • Coats urethra Male Hormones • Testosterone o Made in the testes o Steroid hormone necessary for sperm production o Influences development of male secondary sex characteristics that begin to appear at puberty. What is puberty? o = sexual maturity o In males: § Facial and chest hair § Broad shoulders § Muscular development § Deeper voice Penis • Main parts o Glans o Shaft • Composed of spongy, erectile tissues • During an erection, arteries open allowing blood to fill the tissue, and veins close, preventing blood from exiting. Living Environment Dr. Golub The Female Reproductive System • Each month, the female reproductive system prepares for a possible pregnancy by producing a mature egg cell…the female gamete. • This mature egg cell is called an ovum. • If the ovum is fertilized by a sperm cell, and if it implants in the uterus, a pregnancy will begin. Female Reproductive System • Specialized to produce egg cells, receive sperm, and provide an environment that is right for fertilization of an egg, and the development of an embryo. Egg cells • The female reproductive cells • Produced in the ovaries o Two ovaries are found within the female’s abdomen o Ovaries produce egg cells and secrete estrogen and progesterone (female sex hormones) o Female Reproductive System Ovaries § Contain oocytes § Oocytes are immature eggs § About once every 28 days oocyte development is stimulated and an egg called an ovum is formed. § The ovum is surrounded by follicle cells that provide protection and nourishment. • After the egg is released from the ovary, it travels through an oviduct § Oviduct = a tube that connects the ovary to the uterus. § Also known as the fallopian tube The Uterus § Also called the womb § About the size of a fist § Where the baby develops before birth The Cervix § At the lower end of the uterus § Has a narrow opening into the vagina § Cervix comes from the Latin word meaning neck. The Vagina § Also called the birth canal § Opens to the outside Female Hormones § Estrogen and Progesterone o Steroid hormones produced in ovaries § In the brain is a gland called the pituitary gland § The pituitary gland produces the hormones LH (leutinizing hormone) and FSH (follicle stimulating hormone). § LH and FSH influence estrogen and progesterone production. § During puberty, an increase in estrogen levels cause: o Breast development o Hips widen o Increase in fat tissue o Menstruation Gamete Production § As we have already learned, during meiosis, one germ cell gives rise to four sex cells (gametes). § In males, sperm are produced daily, beginning at puberty and continuing throughout life. Egg Cell Production § In females, it’s different. § A female is born with all of her eggs already beginning to develop. § About 2 million immature egg cells develop, although only 300-­‐400 will mature throughout a lifetime. § Primary oocytes replicate before birth, and meiosis stops before the first meiotic division is complete (in prophase I). § At puberty, sex hormones cause meiosis to resume. § Each menstrual cycle, one oocyte from one ovary continues with meiosis. § By the end of meiosis I, we have two cells of unequal size; the smaller one is the first polar body, which disintegrates. § During meiosis II, a similar process occurs. o Metaphase II > an egg ruptures through the ovary wall = ovulation § Meiosis II is completed only if fertilization occurs. o Then, the zygote (fertilized egg) and the second polar body are produced. The second polar body also disintegrates. The Egg’s Path § An ovum (a mature egg cell) is about 75,000 times larger than a sperm cell. § An ovum is released from the ovary, as cilia sweep it into a fallopian tube. § Rhythmic contractions of muscles that line the fallopian tubes move the ovum down the tube towards the uterus. 1. Egg is released from an ovary and swept into a fallopian tube 2. If sperm are present in fallopian tube during this journey, fertilization may occur. 3. The fertilized egg passes into the uterus and implants on the walls in the upper portion of the uterus, where it will develop and grow. 4. If the egg is not fertilized, it will pass into and through uterus without implanting, and will be eliminated during menstruation. Female Reproductive System The external structures are collectively called the vulva. Labia § Folds of skin and mucous membranes that cover and protect the opening of the vagina. Vagina § Muscular tube that leads from the vulva to the entrance to the uterus, the cervix. Cervix § A muscle in the cervix controls the opening to the uterus. Uterus § A muscular, triangle-­‐shaped organ that is about the size of a small fist. § During sexual intercourse, sperm are deposited inside the vagina, and if fertilization occurs, the zygote develops into a baby inside the uterus. Childbirth During childbirth, a baby passes through the cervix, and leaves the mother’s body through the vagina.