Human reproduction for grade 12


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Human reproduction by Thandeka M.

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Human reproduction for grade 12

  1. 1. Human reproduction
  3. 3. Sexuality in human beings.
  4. 4. Characteristics of human reproduction.  Human reproduction is… sexual.  When the… ovum and the… spermatozoid are joined it formes the zygote, which forms an… embryo.  The union of these cells is called… fertilisation.  The ovum is formed in the… ovary  And the spermatozoid in the… testicles.  Both of them are called… gametes.
  5. 5. Changes during growth  Primary sexual characteristics: Present at birth.  Female genitalia  Male genitalia.  Secondary sexual characteristics: appears in the maturity.  This changes occurs during a very specifc age which is known as puberty and are the result of the action of sexual hormons.
  6. 6. Changes during puberty • In the female: • Pubic hair and hair under the arms. • Distribution of body fats. • Development os mammary glands. • In the male: • The development of public hair. • The beard and hair over a large part of the body. • An increase in the bones and muscles, change of voice, etc.
  7. 7. Diagram of human reproduction. Female reproductive apparatus ova fertilisation Male reproductive apparatus spermatozoids New-born baby zygote embryo foetus
  8. 8. The Female Reproductive organs and cells
  9. 9. The male Reproductive organs and cells
  10. 10. The female and male reproductive cells
  11. 11. Female gonads: Ovaries  Lie in the abdominal cavity  Each ovary contains  many follicles, which consist of a partially developed egg, called an oocyte, surrounded by support cells.  Once a month, an oocyte develops into an ovum (egg) by the process of oogenesis
  12. 12.  Ovulation is the release of an egg cell from the follicle.  The remaining follicular tissue grows within the ovary, forming the corpus luteum.  The corpus luteum secretes hormones e.g. that help to maintain pregnancy.  If the egg is not fertilized, the corpus luteum degenerates.
  13. 13.  After ovulation, the egg cell travels from the ovary to the uterus via an oviduct, or fallopian tube.  Cilia in the oviduct convey the egg to the uterus, also called the womb.  The uterus lining, the endometrium, has many blood vessels  The uterus narrows at the cervix, then opens into the vagina.
  14. 14.  The vagina: is a thin-walled chamber that is the repository for sperm during copulation and serves as the birth canal  The vagina opens to the outside at the vulva, which consists of the  labia majora,  labia minora,  hymen, and  clitoris
  15. 15.  The mammary glands are not part of the reproductive system but are important to mammalian reproduction.  Within the glands, small sacs of epithelial tissue secrete milk.
  16. 16. Male Reproductive Anatomy  The male’s external reproductive organs are:  the scrotum and penis
  17. 17. Male Reproductive Anatomy  Internal organs are:  the gonads (testes), which produce sperm and hormones,  and accessory glands
  18. 18. Male gonads: Testes  Testes, consist of:  highly coiled seminiferous tubules (in which sperm form)  surrounded by connective tissue  Leydig cells produce hormones and are scattered between the tubules.
  19. 19.  Production of normal sperm cannot occur at the body temperatures .  The testes are held outside the abdominal cavity in the scrotum, where the temperature is 2ºC lower than in the abdominal cavity.
  20. 20. Ducts  From the seminiferous tubules of a testis, sperm pass into the coiled tubules of the epididymis  During ejaculation, sperm are propelled through the muscular vas deferens and the ejaculatory duct, and then exit the penis through the urethra.
  21. 21. Accessory Glands  Semen is composed of:  sperm plus  secretions from three sets of accessory glands The two seminal vesicles contribute about 60% of the total volume of semen. The prostate gland secretes its products directly into the urethra through several small ducts.
  22. 22. Accessory Glands  The bulbourethral glands secrete a clear mucus before ejaculation that neutralizes acidic urine remaining in the urethra.
  23. 23. Penis  The human penis is composed of three cylinders of spongy erectile tissue.  During sexual arousal, the erectile tissue fills with blood from the arteries, causing an erection.  The head of the penis is called the glans and is covered with a prepuce.  The rest is called the shaft.
  24. 24. Fertilisation
  26. 26. Journey of sperm into female genital tract
  27. 27. 1ST PHASE: Passage of a sperm through the corona radiata. Dispersal of the follicular cells of the corona radiata surrounding the oocyte and zona pellucida enzyme hyaluronidase released from the acrosome of the sperm, tubal mucosal enzymes and movements of the tail of the sperm are important in its penetration of the corona radiata.
  28. 28.  2ND PHASE:  Penetration of the zona pellucida. Passage of a sperm through the zona pellucida.  The enzymes esterases, acrosin, and neuraminidase appear to cause lysis of the zona pellucida, thereby forming a path for the sperm to follow to the oocyte.  Once the sperm penetrates the zona pellucida, a zona reaction-a change in the properties of the zona pellucida- occurs making it impermeable to other sperms. The zona reaction is believed to result from the action of lysosomal enzymes released by cortical granules near the plasma membrane of the oocyte.
  29. 29.  3RD PHASE:  Fusion of plasma membranes of the oocyte and sperm.  The plasma or cell membranes of the oocyte and sperm fuse and break down at the area of fusion.  The head and tail of the sperm enter the cytoplasm of the oocyte, but the sperm's plasma membrane remains behind
  30. 30.  4th PHASE:  Completion of the second meiotic division of oocyte and formation of female pronucleus. Penetration of the oocyte by a sperm activates the oocyte into completing the second meiotic division and forming a mature oocyte and a second polar body  Following decondensation of the maternal chromosomes, the nucleus of the mature oocyte becomes the female pronucleus.
  31. 31.  5TH PHASE:  Formation of the male pronucleus. Within the cytoplasm of the oocyte, the nucleus of the sperm enlarges to form the male pronucleus and the tail of the sperm degenerates  Morphologically, the male and female pronuclei are indistinguishable. During growth of the pronuclei, they replicate their DNA-1 n (haploid), 2 c (two chromatids). The oocyte containing two haploid pronuclei is called an ootid.
  32. 32.  6TH PHASE  As the pronuclei fuse into a single diploid aggregation of chromosomes, the ootid becomes a zygote. The chromosomes in the zygote become arranged on a cleavage spindle in preparation for cleavage of the zygote
  33. 33.  7TH PHASE:  As the pronuclei fuse into a single diploid aggregation of chromosomes, the ootid becomes a zygote. The chromosomes in the zygote become arranged on a cleavage spindle in preparation for cleavage of the zygote
  34. 34. 1. Restoration of the diploid number of chromosomes. 2. Determination of the sex of the new individual. 3. Initiation of cleavage. 4. Trasportation of gentic features of parentes. Results of Fertilization
  35. 35. Embryo development  Human embryo development is viviparous because it is carried in the mother's womb.
  36. 36.  The zygote leaves the fallopian tube and goes to the uterus. It gets stuck to the wall and starts growing there.  It is now called embryo.  The embryo remains in the mother's womb for about nine months.
  37. 37. Gestation  It is the time the embryo remains in the mothers womb for nine months.  We divide this period into three trimesters.
  38. 38. First trimester. ● The embryo is surrounded and protected by a sack full of liquid, the amnion. ● The embrio produces and organ called placenta. This placenta extracts nutrients and oxygen from the mother's blood. ● These oxygen and nutrients reach the embryo through a conduct: the umbilical cord.
  39. 39. First trimester.
  40. 40. Second trimester. ● The embryo is called now a foetus. ● The skelleton, musculature and organs develope.
  41. 41. Third trimester. ● At the end of the seventh month, all the foetus' organs are already sufficiently developed for it to survive outside the mother. ● From this moment until the ninth month it gains weigh and fits the head into the neck of the uterus. It is ready to be born.
  42. 42. Childbirth  When the baby is ready, the muscles of the uterus produce contractions.  The amnion breaks and the baby comes out of the vagina  The remains of the cord leave a scar on the abdomen of the baby: the navel.
  43. 43. References  Human Reproduction. Human reproduction; anatomy, cells, hormones, pregnancy. Paqelena. 20.04.2009  Human reproduction. Female and Male Reproductive anatomy. DarealThandeka. 04.06.2013  Human reproductionPresentación sobre la reproducción humana para alumnos de 6º de primaria. Damarbe.  Fertilization. Including all stages and events of fertilization and formation of embryo. Reda Cheema. 23.11.2012  Fertilization. Rashid Ahmed. 30.01.2012