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Anatomy (Fach) / Lectures (Lektion)
- What happens during the 3 stages of fertilisation? 1. The sperm cells (180m ejaculated, 300 reach the female gamete) swim towards the Oocyte 2. One of the sperm cells crosses the zona pellicuda and the oocyte membrane and sperm cell membrane (inner acrosomal membrane) start to fuse (facilitated by enzymes) 3. Fusion of oocyte and sperm cell membranes
- Hydatidiform Mole formation of a cystic structure which may become malignant when little or no embryonic tissue is present --> no chromosomes in oocyte
- Which steps does ART include? 1. Hormonal stimulation - egg maturation 2. Removal of oocytes by laporoscopy 3. In vitro fertilisation or ICSI (intro-cytoplasmic sperm injection) 4. Growth in culture for 2-6 days and transferation into the uterus
- Stages of Embryogenesis 1. First cell divisions - Zygote divides by mitosis --> blastomeres get smaller with every division --> Two-cell stage - Four-cell stage - Morula - Differentiation into Inner cells (embryoblast) and outer cells (trophoblast) 2. Blastocyst formation - Blastocyst = fluid filled cavity formed after 5 days, comprising the trophoblast (OCM) and the embryoblast (ICM) - The trophoblast implants into the uterine epithelium (endothelium) after 5-6 days --> abnormal implantation (ectopic pregnancy) - the embryo implants outside of the uterus and causes haemorrhage 3. Bilaminar disk (Week 2) - Trophoblast differentiates and becomes placenta - Embryoblast develops into bilaminar disk --> hypoblast, epiblast - 2 cavities form: amniotic and yolk sac 4. Trilaminar disk (Week 3) - Cells of epiblast migrate towards the primitive streak and slip beneath (invagination), resulting in the formation of 3 germ layers: Ectoderm, Mesoderm, Endoderm - Folding of the trilaminar disc in lateral and longitudinal direction to form the main organ systems of the embryo (organogeneis)
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