1. Chapter 47 Animal Development

2. From eggs to organisms

3. Figure 47.1 A “homunculus” inside the head of a human sperm
Preformation: a series of successively smaller embryos within embryos
Epigenesis: the form of animal emerges gradually from a formless eggs( Aristotle)

4. Fertilization activate the egg and brings together the nuclei of sperm and eggs

5. The Acrosomal reaction
release of enzyme from acrosomal vesicle
 elongation of acrosomal process and penetration
through jelly coat
 binding of acrosomal process to specific
receptors on eggs
 fusion of sperm and egg plasma causes influx of
sodium and membrane depolarization
 fast block to polyspermy

6. 2. The Cortical reaction
 release of Ca+2 from the site of sperm entry
 2nd messenger ( IP and DAG) induced by Ca+2
release opens Ca+2 channel on egg's’s ER
 cortical granule release content into periventilline
layer
 formation of fertilization envelope) slow block to
poly spermy

7. Figure 47.2 The acrosomal and cortical reactions during sea urchin fertilization

8. Figure 47.3 A wave of Ca2+ release during the cortical reaction

9. 3. Activation of eggs
 DAG activate H+ channel , causes pH change
and induce metabolic rate
 fusion of sperm and egg nucleus
 DNA synthesis begin
 cell division begins in 90 minutes

10. Figure 47.4 Timeline for the fertilization of sea urchin eggs

11. Fertilization of mammals
Migration of sperm through follicle cells
2. Binding induces acrosomal reaction
3. Binding of sperm cells to ZP3 receptor in coat of
zona pellucida
4. Nucleus of both eggs and sperm did not fuse until the 1st division of the zygote

12. Figure 47.5 Fertilization in mammals

13. Cleavage partitions the zygote into many smaller cells
Three stages after fertilization
Cell division 細胞分裂期
 cell undergo S and M phase of cell cycle but skip
G1 and G2 phase
 partition cytoplasm of zygote into many smaller
cells called blastomere ( distribution of different
cytoplasmic content in the different regions)
 polarity defined by substances that are
heterogeneously distributed in the cytoplasm of
the eggs

14. Figure 47.6 Cleavage in an echinoderm (sea urchin) embryo
45-90 min after fertilization

15. Figure 47.7 The establishment of the body axes and the first cleavage plane in an amphibian
(More concentrate yolk)
灰月區

16. Figure 47.8x Cleavage in a frog embryo
Animal pole
Vegetal pole

17. 2. Gastrulation 原腸期
 rearrangement of cells of blastula
 transformation of blastula into three layer embryonic germ layer
ectoderm: nervous system and outer layer of skin
endoderm: digestive tract and associated organs
mesoderm: dermis, kidney, hearts, muscles…

18. Figure 47.9 Sea urchin gastrulation (Layer 1)

19. Figure 47.9 Sea urchin gastrulation (Layer 2)

20. Figure 47.9 Sea urchin gastrulation (Layer 3)

21. Figure 47.10 Gastrulation in a frog embryo

22. Table 47.1 Derivatives of the Three Embryonic Germ Layers in Vertebrates
外胚層
內胚層
中胚層

23. 3. Organogenesis器官形成
 folds, splits and dense clustering( condensation)
of cells
 notochord ( dorsal mesoderm)neuroplate(
dorsal ectoderm)
 somite ( mesoderm)  backbone of animals axial
skeleton
 morphogenesis and differentiation continue to
refine organs as they formed

24. Figure 47.11 Organogenesis in a frog embryo

25. Amniote embryos develop in a fluid filled sac with shell or uterus
Amniotes: within the shells or uterus, embryos
surrounded by fluid within a sac formed by
membrane called amnion

26. Avian development
 meroblastic cleavage : cell division occurs only in
a small yolk-free cytoplasm atop of the large mass
of yolk
 The tissue layer out side the embryo develop into
four extra embryonic membrane( yolk sac, amnion,
chorion, and allantois)

27. Figure 47.12 Cleavage, gastrulation, and early organogenesis in a chick embryo

28. Figure 47.13 Organogenesis in a chick embryo

29. Figure 47.14 The development of extra embryonic membranes in a chick
( filled with amnionic fluid for protection)
(Waste storage)

30. 7 days, 100 cells implantation
Figure Early development of a human embryo and its extraembryonic membranes
7 days, 100 cells
implantation
Inward movement of epiblast starts the gatrulation
Development of extraembryonic membrane

31. The cellular and molecular basis of morphogenesis and differentiation in Animals
Morphogenesis: cell movement , shape and position
change of developing cells
 invagination and evagination

32. Figure 47.16 Change in cellular shape during morphogenesis

33. Figure 47.17 Convergent extension of a sheet of cells
 cells of tissue layer rearrange to become narrower
and longer
Possible guide by ECM( Ecm act as a track to guide
the movement of the cells)

34. Figure 47.18 The extracellular matrix and cell migration

35. Figure 47.19 The role of a cadherin in frog blastula formation
CAM: cell adhesion molecule
cadhesrin
Experimental: inject with antisense cadhedrin
control

36. The developmental fate of cells depends on the cytoplasmic determinants and cell-cell induction
The heterogeneous distribution of cytoplasmic
determinants in the unfertilized eggs lead to
regional differentiation in the early embryo
2. Induction, interaction among the embryo cells
themselves induces gene experssion

37. Figure 47.20 Fate maps for two chordates

38. Figure 47.21 Experimental demonstration of the importance of cytoplasmic determinants in amphibians

39. Figure 47.22 The “organizer” of Spemann and Mangold
Primary organizer of embryo

40. BMP-4( bone morphogenic proteins)
Locate at ventral side of gastrula
Organizer produce proteins to inhibit the BMP-4
activity

41. Figure 47.23 Organizer regions in vertebrate limb development
AER

42. AER( Apical Ectodermal Ridge)
required for proximal-distal axis and patterning of
this axis
EGF: epidermal growth factor is responsible for the
growth signal

43. ZPA (Zone of Polarizing Area)
Responsible for pattern formation along anterior-
posterior axis
secret sonic hedgehog, which is important for the
growth of limb bud growth

44. Figure 47.24 The experimental manipulation of positional information

45. Figure 47.6x Sea urchin development, from single cell to larva

46. Figure 47.8d Cross section of a frog blastula

47. 課程網頁:
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