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Fertilization

Fertilization. Spermatozoa maturation steps. The maturation and activation of the spermatozoa occur in the following four steps: Storage in the epididymis  Maturation Ejaculation  Activation Ascension to the ovary  Capacitation Near the oocyte  Acrosome reaction. Human. COW.

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Fertilization

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  1. Fertilization

  2. Spermatozoa maturation steps

  3. The maturation and activation of the spermatozoa occur in the following four steps: • Storage in the epididymis  Maturation • Ejaculation Activation • Ascension to the ovary Capacitation • Near the oocyte Acrosome reaction

  4. Human

  5. COW

  6. MARE SOW

  7. Maturation of the oocyte in the dominant follicle shortly before ovulation

  8. Termination of the first meiosis

  9. The secondary oocyte

  10. The follicle that is about to rupture

  11. Secondary oocyte in metaphase 2

  12. The acquisition of the oocyte by the fallopian tube

  13. Consequences of multiple ovulation • Twin pregnancy • from one mating male • Superfecundation: from two males, after synchrone ovulation • Superfoetation: from two males, after asynchrone ovulation

  14. Formation of a bilaminar germ disk • In the bilaminar primordium of the embryo (hypoblast or primary endoderm and epiblast) one recognizes in the epithelium of the epiblast a fluid-filled space, the first primordium of the amniotic cavity. • Ventrally, the roof of the still incompletely uncovered primary umbilical vesicle (previously the blastocyst cavity) is formed by the hypoblast.

  15. Develomental differences in early embriogenesis • A: Folding (Carnivores, Rodents, Ungulate (hoofed animal) • B: Exocoel formation (Primates, Human, Insectivores)

  16. 1. Extra-embryonic mesoblast 2. Extra-embryonic reticulum 3. Primary umbilical vesicle 4. Cytotrophoblast 5. Lacunae in the reticulum 6. Hypoblast 7. Heuser´s membrane between hypoblast and mesoblast cells

  17. Formation of the ‘Trilaminar germ disc’AKA epithelio-mesenchymal transition • Immigrated cells form a third germinal layer: the intraembryonic mesoblast • The mesoblast cells wander in all directions: laterally, cranially and caudally. • This middle germinal layer lies between the definitive endoblast and epiblast. • Exceptions are the cloacal membrane as well as the pharyngeal membrane, where the ectoderm and endoderm lie directly opposite each other!

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