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Cleavage and Morphogenesis

Cleavage and Morphogenesis. Chapter I. Development- The series of changes from a fertilized egg to an adult of a species The fertilized egg is initially unicellular The adult is multicellular Cell division must occur to go from one cell to many cells

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Cleavage and Morphogenesis

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  1. Cleavage and Morphogenesis Chapter I

  2. Development- The series of changes from a fertilized egg to an adult of a species • The fertilized egg is initially unicellular • The adult is multicellular • Cell division must occur to go from one cell to many cells • Cleavage- Early divisions of the fertilized egg

  3. During cleavage egg undergoes mitosis and cytokinesis • End result of cleavage is a multicellular mass of cells • Decrease in the amount of yolk and cytoplasm and yolk during cleavage • Increase in the amount of nuclear material

  4. Development-when fertilized egg changes into an adult • 1st event of development is cleavage (mitosis and cytokinesis) • Morphogenesis-2nd major event of development • During morphogenesis mass of cells acquires a definite form or structure

  5. Injected dyes into mass of cells. Location of dyes change during development. Only way is for the cells to change position • Movement of cells is characteristic of morphogenesis • After cell mass acquires a definite form and structure its called an embryo

  6. Germinal Layers • Ectoderm develops into the skin • Endoderm and mesoderm develop into other structures in the body • Germinal layers are specific masses or layers of cells • Gastrulation-phase of morphogenesis where germinal layers are produced • Gastrulation leads to formation of gastrula which has three germinal layers

  7. All other cell movements like thickening , folding, separation of layers fall under the morphogenesis phase of development • Know examples of morphogenesis, cleavage, gastrulation

  8. Differentiation & Growth Chapter II

  9. Differentiation-After cells find a location, they change into a specific type of cell in the adult organism • Result of differentiation is a specific structure and function of cells • Morphogenesis results in movement of cells so that differentiation can take place • After differentiation, cells are able to perform specialized functions

  10. Tissues-group of closely associated cells that are differentiated in a similar way and have similar structure and function. • Types-muscle, epithelial, nervous, connective tissues • Tissues are specialized • All develop from ectoderm, mesoderm and endoderm

  11. Organ-Development continues and several tissues combine to perform a specific function • System-group of organs together

  12. Growth-4th major developmental process • increase in the total mass of a living thing • Factors of growth • 1. Increase in the number of cells (mitosis, cytokinesis) • 2. Increase in the size of the cells (After mitotic division the cells get bigger)

  13. Growth vs.. Time forms S shaped curve

  14. Spermatozoon Morphology Chapter III

  15. Parts of the mature spermatozoa are • 1. Head 8. Distal Centriole • 2. Neck 9. Mitochondrial Spiral • 3. Middle piece 10. Axial Filament • 4. Tail • 5. Acrosome • 6. Nucleus • 7. Proximal Centriole

  16. Head of the sperm contains the nucleus and the acrosome • The neck contains the distal and proximal centrioles • The middle piece contains the mitochondrial spiral • The tail contains the axial filament

  17. Sperm Functions • Head-carries the genetic information in the nucleus. Also acrosome has a part in the penetration of the egg and in the activation of egg in further development • Neck-Distal centriole forms and attaches the axial filament. Proximal centriole plays a role in the first cleavage division of the egg • Middle Piece-mitochondria for energy • Tail-Axial filament uses energy to move

  18. Egg Types and Morphology Chapter IV

  19. Egg-Also called Ova or Ovum are specialized cells contributed by the female • Have a cell membrane, nucleus, cytoplasm, mitochondria and centriole • Also surrounded by one or more secondary membranes produced by ovary or oviduct • Secondary membranes lie outside cell membrane

  20. Jelly coating on frog eggs is secondary. • Shell and egg white are secondary on chicken and quail eggs • Eggs also require ATP from mitochondria for energy • Also may have food reserves in the form of the yolk located in the cytoplasm

  21. Yolk has varying chemical substances in it. • Compounds may not all be the same. Varying amounts of carbos, lipids, proteins • Human egg has small amount of yolk • Frog egg has medium amount of yolk • Chicken has high amount of yolk • Bird egg has cytoplasm in cap on top of yolk

  22. Yolk is also distributed differently in different animals • Human has even distribution, frog and chicken have uneven distribution • Due to uneven yolk distribution most animals eggs show polarity. Some materials are distributed more to one side of egg. Call these sides poles

  23. Animal pole is the side where the nucleus is at. • Opposite side is the Vegetal pole. • In frogs the animal pole is dark and the vegetal pole is light • In chickens the cytoplasmic cap is the animal pole • To ID poles look at distribution of materials in egg and location of nucleus • Humans are distributed evenly-look for nucleus to find animal pole

  24. Initiation of Development Chapter V

  25. Fertilization-When a sperm fuses with the egg • Development begins with fertilized egg and ends with adult • Most conditions to develop an adult, egg and sperm must fuse • Egg is mass of chemical systems primed to go

  26. Activation-chemical systems of egg are turned on when fused with sperm • Final process of fertilization • Fertilization process involves 4 steps • Encounter • penetration of egg membranes • Activation of chemical systems in egg • Fusion of nuclei

  27. Encounter-the meeting of sperm with the egg.Pure chance in most • Large numbers of sperm to fertilize the egg • Large size of egg to be target • Surface of egg usually causes sperm to clump and stick to surface

  28. Penetration-when sperm penetrates the membranes of the egg • Partially a chemical process • Lysin-chemical of sperm helps dissolve egg membranes like jelly coat • Mammals-Hyaluronidase-dissolves substance cementing ovarian cells to egg

  29. Lysins are produced by the acrosome • When first contact with egg is made the acrosome ruptures and the lysins are released to head of sperm • Lysins dissolve path through membrane of egg. • Fertilization cone forms from egg cytoplasm rising to meet sperm nucleus • Egg cytoplasm envelops sperm nucleus

  30. Chemical systems are primed to function and when sperm is in egg they are turned on • Activation-chemical reactions induced by penetration of sperm

  31. Fusion-sperm and egg nuclei approach each other and fuse. • Results in nucleus with genetic instructions from both parents

  32. Parthenogenesis- development of unfertilized eggs into a normal adult • Some species this is natural • Egg is the system ready to go it just needs a stimulus. Usually the sperm

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