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Early Development Gametes. Sperm Egg Lecithal = Yolk.

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Presentation on theme: "Early Development Gametes. Sperm Egg Lecithal = Yolk."— Presentation transcript:

1 Early Development Gametes

2 Sperm

3 Egg Lecithal = Yolk

4 Microlecithal egg Small amount of yolk Amphioxus Eutherians

5 Mesolecithal egg Medium amount of yolk Amphibians

6 Macrolecithal egg Large amount of yolk Bird and reptiles Most fish

7 Isolecithal Even yolk distribution In microlecithal eggs

8 Telolecithal Uneven yolk distribution Macrolecithal and Mesolecithal eggs Vegetal Pole – yolk region Animal Pole – relatively yolk-free, high metabolic activity/embryo

9 AmnionAmnion AmnioniccavityAmnioniccavity AllantoisAllantois AllantoiccavityAllantoiccavity ChorionChorion YolkYolk Amniote eggs AlbuminAlbumin

10 Layers around egg Vitelline membrane Jelly Capsule Shell Albumin Corona Radiata Zona Pellucida

11 Oviparous

12 Viviparous

13 Ovoviviparous

14 Fertilization

15 Internal Fertilization Apodans Urodeles Amniotes

16 External Fertilization Fish Frogs

17 Zygote

18 Cleavage & Blastula Microlecithal Eggs Cleavage – Mitosis divisions Blastomeres Blastocoel

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21 Cleavage & Blastula Blastocyst in mammals Inner cell mass in mammals Trophoblast cells in mammals

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24 Cleavage & Blastula Mesolecithal eggs

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27 Cleavage & Blastula Macrolecithal Eggs Blastoderm Blastocoel

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30 Gastrulation Germ layers form from which ALL future organs form Notochord forms Bilateral symmetry established

31 Gastrulation/Microlecithal eggs Involution Blastopore Archenteron

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33 Germ layers Ectoderm –outer layer Mesoderm – middle layer – Forms notochord – Splits to form coelom Endoderm – inner layer around archenteron

34 Gastrulation Mesolecithal eggs Epiboly

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36 Ectoderm Nervous System Sensory structures Neural crest cells that become melanocytes, adrenal gland… Epidermis of skin Epithelium of mouth/nose and anus

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39 Endoderm Lungs & Swim bladders Digestive viscera

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42 Mesoderm Chordomesoderm becomes notochord

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44 Mesoderm Dorsal Mesoderm = Epimere Segmented bands called somites Divides into – Dermatome – Myotome – Sclerotome

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48 Mesoderm Lateral plate mesoderm = hypomere Splits into Somatic and Splanchnic layers Coelom between these layers

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50 Hypomere Somatic Mesoderm plus Ectoderm = Somatopleure Splanchnic Mesoderm plus Endoderm = Splanchnopleure

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52 Mesoderm Intermediate mesoderm = Mesomere Kidney tubules and associated ducts

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55 Key Points Which germ layer (ectoderm, endoderm, mesoderm) gives rise to the following structures: Heart Liver Lung Biceps muscle Notochord Brain Kidney Spinal cord Skin

56 Gastrulation in Macrolecithal eggs Delamination Blastoderm forms upper sheet of cells called Epiblast and Lower sheet of cells called Hypoblast Epiblast becomes Ectoderm Hypoblast becomes Endoderm

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59 Gastrulation in Macrolecithal eggs Mesoderm forms by Primitive Streak Cells stream inward from posterior to anterior Gives rise to notochord

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64 Gastrulation in macrolecithal eggs Some mesoderm is unorganized and migrates, called MESENCHYME

65 Gastrulation in macrolecithal eggs Body stalk Connection from body to yolk

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68 Gastrulation in mammal Blastoderm Delamination to form hypoblast & epiblast Primitive streak forms mesoderm – Notochord – Mesenchyme – Coelom from splitting of lateral plate mesoderm

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71 Neurulation Dorsal hollow nerve cord Neural crest cells branch off

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74 Organogenesis Beginning of all major organs of the body

75 Extraembryonic membranes Fish – Body stalk – Yolk sac

76 Amphibians

77 Extraembryonic membranes AMNIOTES – Yolk sac (from splanchnopleure)

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80 Amniotes Amnion From somatopleure Amniotic Fluid

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83 Amniotes Chorion From somatopleure For communication with oxygen source Helps form placenta in mammals Against shell in birds

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85 Amniotes Allantois From splanchnopleure Gas exchange in reptiles Waste receptacle in eutherians

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88 Placenta in Eutherians Excellent waste removal & nutrient uptake Moms uterus plus babys extraembryonic membrane Attaches to baby via umbilical cord Yolk sac functions as placenta in marsupials


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