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Chapter 27

0. Chapter 27. Reproduction and Embryonic Development. 0. Baby Bonanza The increased use of fertility drugs Has caused an increase in the number of multiple births in the United States. 0. Fertility drugs Are sometimes too effective. 0. ASEXUAL AND SEXUAL REPRODUCTION.

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Chapter 27

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  1. 0 Chapter 27 Reproduction and Embryonic Development

  2. 0 Baby Bonanza The increased use of fertility drugs Has caused an increase in the number of multiple births in the United States

  3. 0 Fertility drugs Are sometimes too effective

  4. 0 ASEXUAL AND SEXUAL REPRODUCTION 27.1 Sexual and asexual reproduction are both common among animals In asexual reproduction One parent produces genetically identical offspring

  5. 0 Modes of asexual reproduction include Budding, fission, or fragmentation/regeneration LM 25 Figure 27.1A, B

  6. 0 Asexual reproduction Enables an individual to produce many offspring rapidly

  7. 0 “Head” Sexual reproduction involves the fusion of gametes from two parents Resulting in genetic variation among offspring Intestine Ovary Eggs LM 210 Figure 27.1C

  8. 0 Some animals exhibit hermaphroditism In which each individual has both female and male reproductive systems Figure 27.1D

  9. 0 Reproduction in some animals is accomplished through external fertilization In which the parents release their gametes into the environment where fertilization occurs Eggs Figure 27.1E

  10. 0 Sexual reproduction May enhance reproductive success in changing environments

  11. 0 HUMAN REPRODUCTION 27.2 Reproductive anatomy of the human female Both sexes in humans Have a set of gonads where gametes are produced Have ducts for delivery of the gonads and structures for copulation

  12. 0 Ovaries Oviduct Follicles A woman’s ovaries Contain follicles that nurture eggs and produce sex hormones Corpus luteum Wall of uterus Uterus Endometrium (lining of uterus) Cervix (“neck” of uterus) Vagina Figure 27.2A

  13. 0 Oviducts convey eggs to the uterus Where the eggs develop Egg cell Ovary LM 200 Figure 27.2B

  14. 0 The uterus opens into the vagina Which receives the penis during intercourse and forms the birth canal

  15. 0 Oviduct Ovary Uterus Other structures of the female reproductive system include Labia, the clitoris, Bartholin’s glands, and the cervix Rectum (digestive system) Urinary bladder (excretory system) Pubic bone Cervix Urethra(excretory system) Vagina Shaft Glans Clitoris Bartholin’s gland Prepuce Labia minora Anus (digestive system) Labia majora Vaginal opening Figure 27.2C

  16. 0 Rectum (digestive system) 27.3 Reproductive anatomy of the human male A man’s testes Produce sperm Urinary bladder (excretory system) Seminal vesicle Vas deferens Ejaculatory duct Pubic bone Erectile tissue of penis Prostate gland Bulbourethral gland Urethra (excretory system) Penis Vas deferens Epididymis Glans of penis Testis Prepuce Scrotum Figure 27.3A

  17. 0 Urinary bladder (excretory system) Seminal vesicle (behind bladder) Several glands Contribute to the formation of fluid that nourishes and protects sperm Prostate gland Bulbourethral gland Urethra Erectile tissue of penis Scrotum Vas deferens Epididymis Testis Glans of penis Figure 27.3B

  18. 0 Urethra region here expands and fills with semen Urinary bladder Sphincter contracts Contractions of vas deferens Contractions of seminal vesicle Contractions of prostate gland During ejaculation Sperm and the nourishing fluid, called semen, are expelled through the penis Contractions of epididymis Sphincter contracts First stage Semen expelled Sphincter remains contracted Contractions of muscles around base of penis Contractions of urethra Sphincter relaxes Figure 27.3C Second stage

  19. 0 Stimuli from other areas in the brain Hypothalamus Releasing hormone Anterior pituitary A negative feedback system of hormones Controls sperm production Negative feedback LH FSH Androgenproduction Testis Sperm production Figure 27.3D

  20. 0 27.4 The formation of sperm and ova requires meiosis Spermatogenesis, the formation of sperm cells Takes about 65–75 days in the human male

  21. 0 Epididymis Penis Testis Scrotum 2n Diploid cell Testis Seminiferous tubule Differentiation andonset of Meiosis I Cross section ofseminiferoustubule Primary spermatocytes, which are diploid, are made continuously in the testes And undergo meiosis to produce haploid sperm 2n Primary spermatocyte (in prophase of Meiosis I) Meiosis I completed Secondary spermatocyte n n (haploid; double chromatids) Meiosis II Developing sperm cells(haploid; single chromatids) n n n n Differentiation Sperm cells n n n n Center ofseminiferous tubule (haploid) Figure 27.4A

  22. 0 In embryo Diploid cell 2n Differentiation andonset of Meiosis I Each month one primary oocyte Matures to form a secondary oocyte, which can be fertilized Completes meiosis and becomes a haploid ovum Primary oocyte 2n Present at birth (arrested in prophaseof Meiosis I) Completion of Meiosis Iand onset of Meiosis II Secondary oocyte n Firstpolar body (arrested at meta-phase of Meiosis II;released from ovary) n Entry of sperm triggerscompletion of Meiosis II Ovum Secondpolar body n n (haploid) Figure 27.4B

  23. 0 Degeneratingcorpus luteum Start: Primary oocyte within follicle Corpus luteum The development of an ovarian follicle Involves many different processes Growingfollicles Mature follicle Ovary Secondaryoocyte Ruptured follicle Ovulation Figure 27.4C

  24. 0 27.5 Hormones synchronize cyclic changes in the ovary and uterus The ovarian cycle includes Changes in the ovary that occur about every 28 days The menstrual cycle Involves changes that occur in the uterus

  25. 0 An Overview of the Ovarian and Menstrual Cycles Events in the menstrual cycle Are synchronized with the ovarian cycle, which occurs about every 28 days

  26. 0 Uterine bleeding, called menstruation Includes the breakdown of the endometrial lining Usually persists for 3–5 days After menstruation The endometrium, the lining of the uterus, regrows

  27. 0 Five hormones Synchronize the events in the ovarian cycle Table 27.5

  28. 0 Hormonal Events Before Ovulation Approximately every 28 days The hypothalamus signals the anterior pituitary to secrete FSH and LH FSH and LH Trigger the growth of a follicle

  29. 0 As the follicle grows, it secretes estrogen Which causes a burst in FSH and LH levels, leading to ovulation

  30. 0 Hormonal Events at Ovulation and After After ovulation The follicle becomes the corpus luteum The corpus luteum secretes both estrogen and progesterone Which exert negative feedback on the hypothalamus and pituitary, causing a decline in FSH and LH levels

  31. 0 As FSH and LH levels drop The hypothalamus can once again stimulate the pituitary to secrete more FSH and LH, and a new cycle begins

  32. 0 Control of the Menstrual Cycle The menstrual cycle Is directly controlled by estrogen and progesterone

  33. 0 If fertilization of an egg occurs A hormone from the embryo maintains the uterine lining and prevents menstruation

  34. A Control by hypothalamus Inhibited by combination of estrogen and progesterone Stimulated by high levels of estrogen Hypothalamus Releasing hormone Anterior pituitary FSH LH 1 B Pituitary hormones in blood 4 LH peak triggers ovulation and corpus luteum formation 6 LH FSH FSH LH 2 Ovarian cycle C 5 Corpus luteum Degenerating corpus luteum The ovarian and menstrual cycles Growing follicle Mature follicle Ovulation Pre-ovulatory phase Post-ovulatory phase Progesterone and estrogen Estrogen D Ovarian hormones in blood 3 7 8 Estrogen Progesterone Progesterone and estrogen Estrogen Menstrual cycle E Endometrium 0 5 10 14 15 20 25 28 Days Menstruation Figure 27.5

  35. 0 27.6 The human sexual response occurs in four phases The excitement phase Prepares the sexual organs for coitus The plateau phase Is marked by increases in breathing and heart rate

  36. 0 Orgasm follows Characterized by rhythmic contractions of the reproductive structures The resolution phase Completes the cycle and reverses the previous responses

  37. 0 CONNECTION 27.7 Sexual activity can transmit disease Sexual intercourse Carries the risk of exposure to sexually transmitted diseases (STDs)

  38. 0 STDs common in the United States Table 27.7

  39. 0 CONNECTION 27.8 Contraception can prevent unwanted pregnancy Contraception Is the deliberate prevention of pregnancy Table 27.8

  40. 0 Skin patch Condom Diaphragm Contraception can be accomplished Through various methods Spermicide Birth control pills Figure 27. 8

  41. 0 PRINCIPLES OF EMBRYONIC DEVELOPMENT 27.9 Fertilization results in a zygote and triggers embryonic development Embryonic development begins with fertilization The union of sperm and egg to form a diploid zygote

  42. 0 The Properties of Sperm Cells Only one sperm Fertilizes an egg Colorized SEM 500 Figure 27.9A

  43. 0 Middlepiece Plasma membrane Neck Head Tail During fertilization A sperm releases enzymes from the acrosome that pierce the egg’s coat Mitochondrion(spiral shape) Nucleus Acrosome Figure 27.9B

  44. 0 The Process of Fertilization Sperm surface proteins bind to egg receptor proteins Sperm and egg plasma membranes fuse, and the two nuclei unite

  45. 0 Changes in the egg membrane Prevent entry of additional sperm The fertilized egg (zygote) Develops into an embryo

  46. 1 The spermapproachesthe egg The sperm’sacrosomal enzymesdigest the egg’s jellycoat 2 3 Proteins on thesperm head bind toegg receptors Sperm The plasmamembranes of spermand egg fuse 4 Nucleus Spermhead The sperm nucleusenters the eggcytoplasm 5 Acrosome Plasmamembrane Acrosomalenzymes The process of fertilization A fertilizationenvelope forms 6 Receptor proteinmolecules Plasmamembrane Spermnucleus Vitellinelayer Cytoplasm Eggnucleus Jellycoat The nuclei of sperm and egg fuse 7 Egg cell Zygote nucleus Figure 27.9C

  47. 0 Zygote 2 cells 27.10 Cleavage produces a ball of cells from the zygote Cleavage is a rapid series of cell divisions That results in a blastula, a ball of cells 4 cells 8 cells Blastocoel Many cells(solid ball) Blastula(hollow ball) Cross sectionof blastula Figure 27.10

  48. 0 27.11 Gastrulation produces a three-layered embryo In gastrulation Cells migrate inward and form a rudimentary digestive cavity The resulting gastrula Has three layers of cells

  49. Animal pole Blastocoel The blastula 1 1 Blastula Vegetal pole Gastrulation 2 Blastopore formation 2 Blastoporeforming Development of the frog gastrula Blastoporeforming Blastocoelshrinking Cell migration toform layers 3 Archenteron 3 Archenteron Ectoderm Mesoderm 4 Completion ofgastrulation Endoderm 4 Yolk plug Yolk plug Gastrula Figure 27.11

  50. 0 Neuralplate Neuralfold Notochord Ectoderm Mesoderm Endoderm Archenteron 27.12 Organs start to form after gastrulation After gastrulation The three embryonic tissue layers give rise to specific organ systems Neural folds 15 Figure 27.12A

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