establishment of pregnancy

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6 Terms

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3 stages of esablishing pregnancy

  • fertilisation

  • blastocyst formation: the first few mitosis divisions

  • implantation of blastocyst into the endometrium

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blastocyst formation

zygote: when sperm fertilises an egg

morula: cluster of cells formed by the zygote undergoing mitosis divisions

blastocyst: a hollow ball of cells surrounding a cavity filled with fluid. on one end there is a dense mass of pluripotent cells known as inner cell mass. 6 days after fertlisation, this will occur when the original zygotes are in the uterus.

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implantation

  • once blastocyst reaches uterus it remains free in cavity for 1-2 days.

  • it will then sink into the endometrium and be firmly attached to the uterus wall

  • blastocyst will gain nutrients needed for noursihment, development and growth from glands and blood vessels in the uterine lining

  • blastocyst secretes HCG which aids the corpus lutem in the high production of oestrogen and progesterone. this will thicken the endometrium lining and prevent it from breaking down. this ceases the menstrual cycle.

  • once placenta is formed, it will take over in the production of these hormones.

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cell differentiation

  • totipotent = zygote as it has the potential to become an embryo

  • pluripotent = inner cell mass of blastocyst as it has the potential to become many different type of cells needed for foetal development.

  • outer cell mass helps to form the placenta and some other tissues

  • multipotent = blood stem cells, skin stem cells

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germ layers

layer of stem cells formed during embyronic development

totipotent zygote becomes pluripotent blastocysts that can then form layers

  • ectoderm = outlermost layer (e.g. hair, nervous system, epididermis of skin)

  • mesoderm = middle layer (e.g. skeleton, muscles, connective tissue)

  • endoderm = innermost layer (e.g. disgestive system, lungs, thyriod)

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embryonic membranes

  • form outside the embryo for noursihment and protection

amnion

  • first membrane to form on the 8th day surrounding the embyro with amniotic fluid that acts a shock absorber, helps maintain temperatue and allows development foetus to move around freely

chorion = will be part of the placenta

yolk sac and allantios = form the outer strcutre of umbilical cord