Presentation on theme: "Chapter 16: The reproductive system"— Presentation transcript:
1 Chapter 16: The reproductive system (Slides by Jennifer Wade, modified by Paul Nagami)
2 The reproductive system The main organs of the reproductive system are the gonads: ovaries and testiclesThe gonads make gametes: eggs & spermMost human cells have 46 chromosomes (two sets of 23 chromosomes each, one set from each parent).Gametes only have one set of 23 chromosomes, which are passed down to offspringMeiosis is a special term for the cell division that gives rise to gametes
3 Sexual reproduction in diploid organisms Cells that give rise to gametes are called germline cellsThe letter n is used to indicate the number of copies of each chromosome a cell in an organism has. n = 23 in humans.use the terminology n and 2n for the number of chromosomes
4 Testes are the male gonads Housed in the scrotumSeminiferous tubules are where meiosis actually occurs to make spermThey travel to the epididymis where they mature (takes about 20 days)Mature sperm leave the testis through the vas deferensThe spermatic cord attaches the testis to the body, as well as housing the vas deferens & blood vessels and nerves
5 Vas deferens empties into the ejaculatory duct, surrounded by smooth muscle The seminal vesicles, prostate, and bulbourethral glands make fluids that help the sperm move and survive. Semen is sperm + seminal fluid.The urethra delivers semen, as well as urine, to the outside of the body
6 Signals from the anterior pituitary, controlled by the hypothalamus, trigger sperm development In males, FSH and LH trigger testosterone release and sperm production. Too much testosterone blocks FSH/LH production!
7 Female reproductive anatomy Ovaries are the female gonads, where eggs (ova) develop. They then travel through the fallopian tubesFertilization usually occurs in the fallopian tubes; the ovum migrates to the uterus, where it implants in the endometrium
8 Female reproductive anatomy talk about ovarian & cervical cancerThe cervix separates the uterus from the vaginaFemales also have a urethra, but unlike in males, it plays no reproductive function
9 Oogenesis: Making Eggs Oo = eggGenesis = makingOogenesis = making eggsOogenesis begins before birth; women make their supply of primary oocytes early. One matures per month (usually) and women run out at menopause.
10 The monthly cycle & menstruation Fertile women undergo a series of hormonal changes each month; these changes help prepare the body for pregnancy if the ovum is fertilized after ovulation.Main hormones: FSH and LH from anterior pituitary, and estrogen and progesterone from the gonads.
11 Hormones from the anterior pituitary control the cycle FSH triggers maturation of the follicle and egg.FSH + LH spike triggers ovulation (release of the egg)
12 Maturation of the ovumAfter meiosis produces the egg and the follicle ruptures, the remains of the follicle become the corpus luteum, which releases hormones.
13 Estrogen and progesterone are made in the ovaries Rising estrogen triggers FSH + LH releaseProgesterone + estrogen prepare the body for pregnancyFall in progesterone triggers menstruation
14 Changes in the endometrium The buildup of the endometrium provides a safe “landing zone” for the fertilized zygote to implant and grow. Blood vessels give nutrients to the growing embryo. In absence of pregnancy, this lining breaks down.
15 Fertilization usually happens in the fallopian tube, and leads to a series of rapid divisions, of cleavage, in the developing zygote. The resulting hollow ball of cells that implants in the uterus is called a blastocyst.