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Reproduction & Development

Reproduction & Development. Chp 21. GAMETE FORMATION. Meiotic division produces Haploid Gametes Egg Sperm. Anatomy Of A Sperm Cell. Arcosome head Midpiece tail. Anatomy Of Egg Cell. Jelly coat Membrane Organelles. Fertilization.

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Reproduction & Development

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  1. Reproduction & Development Chp 21

  2. GAMETE FORMATION Meiotic division produces Haploid Gametes • Egg • Sperm

  3. Anatomy Of A Sperm Cell • Arcosome • head • Midpiece • tail

  4. Anatomy Of Egg Cell • Jelly coat • Membrane • Organelles

  5. Fertilization • Sperm and egg unite: 6-24 hours after intercourse, sperm survives days • One sperm fertilizes one egg • Acrosome: rich in digestive enzymes • Sperm penetrates corona radiata and zona pellucida • Sperm proteins lock with egg membrane receptors • Zona pellucida made impermeable to other sperm

  6. Arcosomal Reaction • Arcosome opens & releases digestive enzyme • Fertilization tube forms • DNA moves into egg & joins w/Egg DNA

  7. Prevention of Polyspermy • Wave of depolarization - Fast block to polyspermy • Cortical reaction - fertilization membrane

  8. Twins • Fraternal: more than one oocyte fertilized by different sperm, may be different sex • Identical: one oocyte fertilized, split before 16 cell stage, same sex • Conjoined twins: separation not complete

  9. Developmental Processes • Cell division or mitosis - cell division without cell growth • Differentiation - individual cells take on specialized forms and functions • Morphogenesis - physical development of organism, ongoing • Growth - at implantation, growth in size

  10. Summary Early Developmental Events • Cleavage - • Blastulation - • Gastrulation - • Organogenesis/Nerulation -

  11. Pre-embryonic Development:The First Two Weeks Process • Travels through oviduct • Implantation into uterine lining • Growth, differentiation, and morphogenesis begins • Morula to blastocyst to embryonic disk • Ectopic pregnancy possible

  12. Embryonic Development: Weeks Three to Eight, Embryo Tissues and organs: derived from three germ layers • Ectoderm: body covering & neural structures -brain, spinal cord, & nerves. • Mesoderm: skeleton, muscles, blood vessels, heart, kidneys, gonads, & dermis. • Endoderm: primitive gut, lungs, liver & pancreas [+ most organs]

  13. Placenta and Umbilical Cord Figure 21.8

  14. Placenta • Development • Chorion digests into endometrium, creating pool of blood • Placenta seals off the pool and projects chorionic villi into blood • Villi contain blood capillaries connected through the umbilical vessels to the fetus

  15. Placenta (cont.) • Functions • Filters nutrients, waste, and antibodies for fetus without mixing mother or fetal circulations • Some toxins or viruses may pass through • Hormonal: produce estrogen and progesterone

  16. Embryo Development: Third and Early Fourth Week Figure 21.9

  17. Rapid Embryo Development • Day 15 • Primitive streak: appears in embryonic disk, elongates along one axis • Day 19-24 • Neural groove: brain and spinal cord • Somites: bone, muscle, skin • Pharyngeal arches: part of face, neck, and mouth • Limb buds: arms and legs

  18. Fetal Development: Eight Weeks to Birth • Months three and four: organ development, beginnings of organ function • Months five and six: fetal movement begins, responds to external sounds, survival possible outside mother • Months seven through nine (third trimester): growth and maturation

  19. Stages of Birth Figure 21.13A

  20. Stages of Birth (cont.) Figure 21.13B, C

  21. Birth Labor & delivery • Stages of labor: • Stage 1: dilation • Stage 2: expulsion • Stage 3: afterbirth • Cesarean delivery: surgical delivery of baby

  22. Early Postnatal Period • Transition from fetus to newborn • Taking the first breath: pulmonary surfactants necessary • Changes in cardiovascular system • Umbilical circulation cut off • Ductus venosus regresses to connective tissue • Foramen ovale and ductus arteriosus close in days/weeks • All blood from the digestive tract goes to liver • Lactation: colostrum to milk

  23. Birth to Adulthood • Neonatal period: helpless period, movement by reflex • Infancy; rapid development and maturation of organ systems • Childhood: continued development and growth • Adolescence: transition to adulthood

  24. Aging: Change Over Time • Causes of aging: theories • Internal cellular program that counts finite number of cell divisions, thus determining cell death • Cell DNA damaged beyond repair • Aging a whole body process; all systems interdependent

  25. Aging: Change Over Time (cont.) • Body systems: age at different rates; musculoskeletal, skin, cardiovascular, respiratory, immune, nervous, sensory, reproductive, endocrine, digestion and nutrition, urinary • Aging well: life style, exercise, diet

  26. Death: Final Transition • Legal and medical criteria • Irreversible cessation of circulatory and respiratory functions • Irreversible cessation of all functions of the entire brain, including the brain stem

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