11b; reproduction

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  • 11b; reproduction

    1. 1. Lecture 11b;Reproduction and Development
    2. 2. IntroductionNot all animals have sexualreproduction, but most doGametes are produced in the gonads-sperm produced in testes and eggsproduced in ovariesZygote- the fertilized egg
    3. 3. IntroductionMany animals have externalfertilization- where each parent depositsegg and sperm in same place,fertilization occurs outside the bodyInternal fertilization- when sperm isintroduced to female by copulation,fertilization occurs within the body
    4. 4. Ways of ReproductionOviparous- lays eggs, either in water orlandOvoviviparous- eggs retained in bodyuntil they hatch- give birth to livingyoungViviparous- produce living young- thereis no membrane bound egg
    5. 5. Human ReproductionEssentially two groups of parts: 1. Gonads (testes or ovaries) that produce the gametes and the sex hormones 2. Accessory organs that conduct gametes and in females house the embryo and fetus during development
    6. 6. Male System
    7. 7. Male SystemTestes produce sperm, are suspended inthe scrotum Sperm production must occur at a lower temperature than the body- that is why they are located thereEpididymis - a coiled tube just outsideeach testis, where sperm mature
    8. 8. Male SystemVas deferens- sperm move into these ducts when theyare mature, wait to move into the ejaculatory duct hereSperm is mixed with secretions from 3 glands toproduce semen 1. Seminal vesicles- just below bladder, secrete nutrients for the sperm 2. Prostate gland- alkaline fluid believed to increase motility 3. Bulbourethral gland- lubricating secretions
    9. 9. Male SystemAfter combining with seminal fluids fromvarious glands in the ejaculatory duct, semenis expelled from the penis through the urethra(which carries urine as well as semen)During ejaculation in the male orgasm, spermenter the ejaculatory duct from the vasdeferentia, then muscle contractions from theurethra and muscle at the base of the peniseject the semen
    10. 10. Male SystemTestes produce spermEach sperm has aflagellum whichallows it to swimNormal ejaculate~40 million sperm/mL
    11. 11. Male SystemThe hypothalamus controls the productionof the testes by secreting gonadotropicsecreting hormone, which triggers 1. folicle stimulating hormone- promotes spermatogenesis 2. Leutenizing hormone- controls production of testosterone
    12. 12. Male SystemTestosterone main sex hormone in males 1. Essential for normal development and function of sex organs 2. Necessary for maturation of sperm 3. Initiates and maintains development of secondary sex characteristics
    13. 13. Female System
    14. 14. Female SystemOvaries contain eggsOvum exit the ovaries and are picked up by theoviducts/ fallopian tubesFertilization occurs in the first 1/3 of thefallopian tube, then cilia and musclecontractions move fertilized egg to the uterusThe uterus is about the size of a pear when idle.The narrow end that meets the vagina is the cervix
    15. 15. Female SystemFertilized embryo will imbed itself in the liningof the uterus, the endometriumExternal female sexual organs are collectivelycalled vulva Mons pubis, labia minora and majora, and clitoris- homologous to penis hymen- thin membrane which covers vaginal opening, broken by activities of many sorts
    16. 16. Female SystemFemales are born with eggs, they do not makethem throughout life as males make spermHowever, development occurs: Born with Primary oocytes (2n) Some of these will develop into secondary oocytes (n) These are then released from the ovary during ovulation
    17. 17. Female SystemEstrogen- one main female sex hormone Essential for development and function of female sex organs Responsible for secondary sex characteristicsProgesterone- other main female sex hormone Works with estrogen to control different parts of the cycle
    18. 18. Female SystemMenstrual cycle Caused by female sex hormones cycling to cause oocyte development and ovulation Days 1-5- hormone levels low, menstruation occurs as endometrium disintigrates Days 6-13- Increased estrogen causes endometrium to thicken Day 14- ovulation Days 15-28- increased progesterone causes endometrium to double in size- it is ready to receive embryo
    19. 19. Human DevelopmentFertilization- when sperm and egg fuse toform a zygoteEmbryonic period- first two monthsFirst, embryo becomes multicellularCleavage- lots of cell division without growth- forms morulaMorula becomes hallow, then called blastocyst
    20. 20. Human DevelopmentGastrulation- 3rd week- the movementof cells to establish the three germ layers:endoderm, mesoderm, and ectodermNeurulation- formation of the centralnervous system Form notochord from mesoderm Form CNS from part of ectoderm
    21. 21. Human DevelopmentAt 5 weeks, limb buds appear- this willdevelop into limbs Sense organs begin to form6-8 weeks- begins to look very human At 8 weeks, is only 1.5 inches long, but has all organ systems
    22. 22. Human Development3-9 months is basically growthHeartbeat heard around week 10 Weight increases 600 times Length increases as wellFetus is able to move starting around 3rdmonthOrgans also continue to develop and grow
    23. 23. PlacentaThe ‘sack’ that the fetus is in- has a fetal sideand a maternal sideMaternal and fetal blood do not mix;exchange occurs across the placenta There are chorionic villi where the exchange occurs- lots of capillaries around them The umbilical cord goes from the fetus to the placenta, is part of the fetal circulation
    24. 24. BirthProbably initiated by the fetal brainbecoming mature enough- brain thenreleases hormones which are used by theplacenta to create three more hormones estrogen, oxytoin, prostaglandin These three hormones cause the uterus to contract
    25. 25. BirthBirth occurs in three basic stages: 1. Dilation of cervix, amnion breaks (Water breaks) 2. Birth of baby 3. Delivery of placenta (afterbirth)

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