How did this complex embryo develop from a single fertilized egg? Figure 47.1 How did this complex embryo form from a single cell? 1 mm

The acrosomal and cortical reactions during sea urchin fertilization Sperm plasma membrane Sperm nucleus Fertilization envelope Acrosomal process Basal body (centriole) Actin filament Sperm head Cortical granule Fused plasma membranes Figure 47.3 The acrosomal and cortical reactions during sea urchin fertilization Perivitelline space Acrosome Hydrolytic enzymes Jelly coat Vitelline layer Sperm-binding receptors Egg plasma membrane EGG CYTOPLASM

Fertilization in mammals Zona pellucida Follicle cell Figure 47.5 Fertilization in mammals Sperm nucleus Cortical granules Sperm basal body

Cleavage in an echinoderm embryo (a) Fertilized egg Figure 47.6 Cleavage in an echinoderm embryo (b) Four-cell stage (c) Early blastula (d) Later blastula

The body axes and their establishment in an amphibian Dorsal The body axes and their establishment in an amphibian Right Anterior Posterior (a) The three axes of the fully developed embryo Left Ventral Animal pole Pigmented cortex First cleavage Animal hemisphere Point of sperm nucleus entry Figure 47.7 The body axes and their establishment in an amphibian Future dorsal side Vegetal hemisphere Gray crescent Vegetal pole - yolk (b) Establishing the axes

Cleavage in a frog embryo 0.25 mm 0.25 mm Animal pole Blastocoel Figure 47.8 Cleavage in a frog embryo Vegetal pole: yolk Zygote 2-cell stage forming 4-cell stage forming 8-cell stage Blastula (cross section)

Gastrulation in a sea urchin embryo Key Future ectoderm Future mesoderm Future endoderm Vegetal Pole Invagination Blastocoel Filopodia pulling archenteron tip Animal pole Archenteron - cavity Blastocoel Blastocoel Blastopore Mesenchyme cells Ectoderm Vegetal plate Vegetal pole Mouth Figure 47.9 Gastrulation in a sea urchin embryo Mesenchyme cells Mesenchyme (mesoderm forms future skeleton) Digestive tube (endoderm) Blastopore 50 µm Anus (from blastopore)

Gastrulation in a frog embryo SURFACE VIEW CROSS SECTION Animal pole Blastocoel Dorsal lip of blasto- pore Dorsal lip of blastopore Blastopore Early gastrula Vegetal pole Blastocoel shrinking Archenteron Figure 47.10 Gastrulation in a frog embryo Ectoderm Mesoderm Blastocoel remnant Endoderm Archenteron Key Blastopore Future ectoderm Future mesoderm Late gastrula Blastopore Yolk plug Future endoderm

Gastrulation in a chick embryo Dorsal Fertilized egg Primitive streak Anterior Embryo Left Right Yolk Posterior Ventral Primitive streak Epiblast Future ectoderm Figure 47.11 Gastrulation in a chick embryo Blastocoel Endoderm Migrating cells (mesoderm) Hypoblast YOLK

Early organogenesis in a frog embryo Neural folds Eye Somites Tail bud Neural fold Neural plate SEM 1 mm 1 mm Neural tube Neural crest cells Neural fold Neural plate Notochord Neural crest cells Coelom Somite Notochord Ectoderm Figure 47.12 Early organogenesis in a frog embryo Archenteron (digestive cavity) Mesoderm Outer layer of ectoderm Endoderm Neural crest cells (c) Somites Archenteron (a) Neural plate formation Neural tube (b) Neural tube formation

Organogenesis in a chick embryo is similar to that in a frog Eye Neural tube Notochord Forebrain Somite Coelom Heart Archenteron Endoderm Lateral fold Mesoderm Blood vessels Ectoderm Somites Yolk stalk Yolk sac These layers form extraembryonic membranes Figure 47.13 Organogenesis in a chick embryo Neural tube YOLK (a) Early organogenesis (b) Late organogenesis

Adult derivatives of the three embryonic germ layers in vertebrates ECTODERM MESODERM ENDODERM Epidermis of skin and its derivatives (including sweat glands, hair follicles) Epithelial lining of mouth and anus Cornea and lens of eye Nervous system Sensory receptors in epidermis Adrenal medulla Tooth enamel Epithelium of pineal and pituitary glands Notochord Skeletal system Muscular system Muscular layer of stomach and intestine Excretory system Circulatory and lymphatic systems Reproductive system (except germ cells) Dermis of skin Lining of body cavity Adrenal cortex Epithelial lining of digestive tract Epithelial lining of respiratory system Lining of urethra, urinary bladder, and reproductive system Liver Pancreas Thymus Thyroid and parathyroid glands Figure 47.14 Adult derivatives of the three embryonic germ layers in vertebrates

Embryo ExtraEmbryonic Membranes in birds and other reptiles: Amnion Allantois Embryo Amniotic cavity with amniotic fluid Albumen Shell Figure 47.15 Extraembryonic membranes in birds and other reptiles Yolk (nutrients) Chorion Yolk sac

Four stages in early embryonic development of a human Endometrial epithelium (uterine lining) Expanding region of trophoblast Maternal blood vessel Uterus Inner cell mass Epiblast Trophoblast Hypoblast Blastocoel Trophoblast Expanding region of trophoblast Amnion Amniotic cavity Chorion Ectoderm Epiblast Mesoderm Figure 47.16 Four stages in early embryonic development of a human Hypoblast Endoderm Yolk sac (from hypoblast) Yolk sac Extraembryonic mesoderm cells (from epiblast) Extraembryonic mesoderm Chorion (from trophoblast) Allantois

Change in cell shape during morphogenesis Ectoderm Neural plate Microtubules Actin filaments Figure 47.17 Change in cell shape during morphogenesis Neural tube

Cadherin is required for development of the blastula RESULTS 0.25 mm 0.25 mm Figure 47.19 Is cadherin required for development of the blastula? For the Cell Biology Video E-cadherin Expression, go to Animation and Video Files. Control embryo Embryo without EP cadherin

Blastomeres injected with dye Fate Mapping for two chordates Epidermis Epidermis Central nervous system 64-cell embryos Notochord Blastomeres injected with dye Mesoderm Endoderm Blastula Neural tube stage (transverse section) Larvae Figure 47.21 Fate mapping for two chordates (a) Fate map of a frog embryo (b) Cell lineage analysis in a tunicate

Experimental egg (side view) How does distribution of the gray crescent affect the development potential of the two daughter cells? EXPERIMENT Control egg (dorsal view) Experimental egg (side view) Gray crescent Gray crescent Thread Figure 47.23 How does distribution of the gray crescent affect the development potential of the first two daughter cells? RESULTS Normal Belly piece Normal

Can the dorsal lip of the blastopore induce cells in another part of the amphibian embryo to change their developmental fate? EXPERIMENT RESULTS Dorsal lip of blastopore Primary embryo Secondary (induced) embryo Pigmented gastrula (donor embryo) Nonpigmented gastrula (recipient embryo) Primary structures: Neural tube Notochord Figure 47.24 Can the dorsal lip of the blastopore induce cells in another part of the amphibian embryo to change their developmental fate? Secondary structures: Notochord (pigmented cells) Neural tube (mostly nonpigmented cells)

Vertebrate limb development Anterior Limb bud AER ZPA Limb buds Posterior 50 µm Apical ectodermal ridge (AER) (a) Organizer regions 2 Figure 47.25 Vertebrate limb development Digits 3 4 Anterior Ventral Proximal Distal Dorsal Posterior (b) Wing of chick embryo

Review Sperm-egg fusion and depolarization of egg membrane (fast block to polyspermy) Cortical granule release (cortical reaction) Formation of fertilization envelope (slow block to polyspermy)

Review: Cleavage frog embryo 2-cell stage forming Animal pole 8-cell stage Vegetal pole: yolk Blastocoel Blastula

Frog Sea urchin Chick/bird Review: Gastrulation / Early Embryonic Development Frog Sea urchin Chick/bird

Review: Early Organogenesis Neural tube Neural tube Notochord Notochord Coelom Coelom

Review: Fate Map of Frog Embryo Species: Stage:

You should now be able to: Describe the acrosomal reaction. Describe the cortical reaction. Distinguish among meroblastic cleavage and holoblastic cleavage. Compare the formation of a blastula and gastrulation in a sea urchin, a frog, and a chick. List and explain the functions of the extraembryonic membranes.

Describe the role of the extracellular matrix in embryonic development. Describe two general principles that integrate our knowledge of the genetic and cellular mechanisms underlying differentiation. Explain the significance of Spemann’s organizer in amphibian development. Explain pattern formation in a developing chick limb.