PLB 115 1st EditionExam # 3 Study Guide Lectures: 12-15Lecture 12(Thursday March 19th- Human Reproduction)Embryonic Sexual DevelopmentGonad development begins at 5 weeksMales- 5-7 weeks testes begin to form from SRY gene (on X chromosome)- 8 weeks testosterone is made by testes- Testosterone creates differentiation: biological male’s physical sexual characteristics: penis- 7 months testes move thru inguinal canal to scrotumFemales- 12 weeks ovaries develop b/c of lack of TDF- Absence of testosterone creates biological female’s physical sexual anatomy: vaginaX & Y - X chromosome carries info for blood clotting, color vision, etc.- Y carries less info & is most important for determining sexo Has SRY gene coding for testes Sex Determination- Female eggs= 22 autosomes & X - Sperm= 22 autosomes & X or Y to create a female or male Sexual Maturation- Puberty= main developmental period- Body begins to change to adult form- becoming sexually mature & able to reproduceMales: 11-14 yrs old hypothalamus begins release of gonadotropin-releasing hormone (GnRH)- GnRH stimulates pituitary gland to release luteinizing hormone (LH or interstitial cell-stimulating hormone (ICSH) in males) & follicle stimulation hormone (FSH)- LH stimulates more testosterone production by testes- FSH stimulates sperm cell productiono Testosterone stimulates semen production (sperm & other secretions-from seminal vesicles, prostate gland, and bulbo-urethral glands- released in ejaculate)o Seminal vessels produce alkaline fluid containing fructose & hormones Alkaline fluid neutralizes acidic nature of vagina Fructose is fuel for spermo Prostate gland produces a thin milky fluid containing sperm-activating enzymesMale Reproductive System- Seminiferous tubules : Where meiosis takes place - Epididymis:Receives sperm from seminiferous tubules- Sperm stored in epididymis & matures prior to ejaculation- Vas deferens (sperm duct) receives sperm from epididymis- Vas deferens empties into the urethra- Urethra takes sperm out of the body through penisSpermatogenesisAfter puberty, seminiferous tubules’ cells begin meiosis1. Diploid cells in wall of seminiferous tubules enlarge and prepare for meiosis2. Meiosis I produces two haploid cells3. Meiosis II produces four spermatids4. Spermatids lose most of their cytoplasm & develop long tails and mature into spermSperm- Live to 72 hours (outside body)- Can be frozen for later use (artificial insemination)- Produced all throughout male life cycle- 150 million sperm/ml of semenFemale Sexual MaturationPuberty= beginning of ovulation (release of egg from ovary) & menstrual cycle (cycle where there is a periodic buildup & subsequent shedding of uterus lining (endometrium) when womandoes not become pregnant) - Cycles start off irregular but become more regular over timeFemale Reproductive System- Ovary: Where meiosis occurs that results in formation of eggs- Oviduct: Carries egg cell from where it is produced to the uterus- Uterus: Where embryo develops into a fetusOogenesis: The production of egg cells in females occurring via meiosis in ovaryo *Begins during prenatal development of ovaries1. Special cells in the ovary stop dividing by mitosis and enlarge to make future eggs or primary oocytes2. Oocytes go through early stages of 1st meiotic division & stopa. FSH stimulates a primary oocyte in a follicle to resume meiosis3. Meiosis I generates two cells, but only one receives most of the cytoplasma. Smaller cell = polar bodyb. Bigger cell will become the eggOvulation1. When follicle is mature, LH stimulates it to rupture & release egg (ovulation)2. Egg is swept into fallopian tube (oviduct) 3. The egg travels through fallopian tube to uterus4. The egg completes meiosis in uterus after it is fertilized5. Once ruptured, follicle becomes corpus luteum6. The corpus luteum produces hormone progesterone that prevents release of more eggs7. If an egg is not fertilized, it is released from the body through the vagina during menstruationHormonesControl changes in breasts, ovaries, uterusEstrogen & progesterone stimulate changes that will support a pregnancy- Growth of uterine lining to support the developing embryo- Prepare breasts to make milkIf fertilization does not occur, menstruation resultsLining of uterus breaks down and is released (menses)The cycle of changes continues on a monthly basis if pregnancy does not occurHormonal Cycle- FSH from pituitary gland causes the follicle to growo Follicle releases estrogen Causing uterine lining (endometrium) to become thicker- After ovulation, LH stimulates the ruptured follicle to become a corpus luteumo Corpus luteum releases the hormone progesterone. Causing growth in # of blood vessels in the uterine lining- If the egg is not fertilized, the corpus luteum will break down, reducing amount of progesterone released- Without progesterone, uterine lining breaks down & is shed in menstruationFertility- Drugs (hormones) given to women to stimulate ovulationo Increase likelihood of egg being shed at right time to achieve fertilization Often results in release & fertilization of 1+ egg 7 multiple embryos implanted in uterus (Twins/triplets!!, etc.)Contraception- Estrogen and progesterone inhibits ovulation (female)- Testosterone & progesterone can temporarily turn off the production of spermFertilizationEgg is released 14th day of the menstrual cycle.o About 2 weeks before next menstrual periodo Once released, the egg is moved into the oviduct toward the uterus The egg is fertilized in the oviduct Sperm swarm around the egg, but only one penetrates the egg.- Other sperm contribute an enzyme that digests away the mucus barrier around the eggo Once fertilized, the egg completes meiosiso The second polar body is pinched offo The true ovum is formed The chromosomes from the ovum and the sperm pair up, forming a diploid zygotePregnancy- The zygote begins to divide by mitosis to form an embryoo 1st cell divisions = cleavage stageo Produces a ball of cells called a morula- The morula continues to divide to form a blastocyst- The blastocyst travels down the oviduct & enters uteruso In the uterus, the blastocyst implants into the uterine lining- The blastocyst continues to divide and the cells migrate and differentiate to form specific portions of the embryoEmbryonic DevelopmentAs the embryonic cells divide, they become differentiated into specialized cell types.- Molecules from the mother provide nourishment for this process.o