II. Physiology: Day 1 - Conception

  1. Ovulation
  2. Fertilization

III. Physiology: Day 2-3 - Zygote develops into Morula

  1. Morula: round mass of cells
  2. Morula passes through fallopian tube

IV. Physiology: Day 4 - Morula develops into blastocyst

  1. Blastocyst: hollow sphere
    1. Inner Cell mass: mound on inner surface
    2. Primitive trophoblast: outer shell of sphere
      1. Together with mesoderm will form Chorion
  2. Blastocyst floats free in Uterus

V. Physiology: Day 7-14

  1. Embryo Embeds into wall of Uterus

VI. Physiology: Day 8 - Bilaminar Germ Disk develops

  1. Ectoderm (Epiblast) lines amniotic sac
    1. Skin and appendages
    2. Nervous system
      1. Adrenal Medulla
      2. Anterior pituitary
      3. Salivary Glands
  2. Mesoderm forms between Ectoderm and Entoderm
    1. Bone, Muscle, Cartilage, and connective tissue
    2. Serous linings
    3. Cardiovascular System
    4. Kidneys
    5. Genitalia
  3. Entoderm (Hypoblast) lines Yolk Sac
    1. Gastrointestinal tract
    2. Liver
    3. Gall Bladder and biliary tract
    4. Pancreas
    5. Respiratory tract
    6. Gonadal germ cells

VII. Physiology: Day 9-13 - Placenta develops

  1. Trophoblast forms with lacunae
  2. Maternal and Trophoblast Vessels develop
  3. Uteroplacental circulation begins

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