-
1000
Preimplantation Period: Week One: Fertilization
**Conception --> Fertilization **Conception: Ovum + Sperm = Zygote (Fertilized Egg) **During Fertilization: Final Stages of Meiosis in Ovum = Diploid 46 Chromosomes = Haploid 23 Chromosomes = Karyotype **After Fertilization: Zygote undergoes Mitosis (tissue growth/regeneration) = Initial Cleavage = Morula --> Zygote becomes a Blastocyst -
1000
Preimplantation Period: End of Week One: Implantation
***Blastocyst (Former Zygote) has Stopped Traveling for Implantation ***Blastocyst is Embedded in the Prepared Endometrium (Uterus's Innermost Lining on Back Wall) ***At the moment, Blastocyst Layers are: Peripheral Cells, Trophoblast, Small Number of Embryonic/Embryoblast Cells **Trophoblast Layer ---> Important Tissue (Prenatal)
**Embryoblast Layer --> Embryo during Prenatal Period then Embryonic Period -
Embryonic Period: More on the Second Week
***Certain Physiologic Process = Patterning = Key to the Further Developmental Processes ***Physiologic/Developmental Process: Induction, Proliferation, Differentiation, Morphogenesis, and Maturation = Implanted Blastocyst = Embryo -
Embryonic Period: Second Week
**Proliferation: Blastocyst grows (Increased Embryonic Cells)
**Differentiation: Changes in Cellular Morphogenesis (Every Bump, Ridge, and Recess) **Increased Embryonic Cells = Embryonic Cell Layers (Germ Layers)
*Bilaminar Embryonic Disc = A Flattened Three-Dimensional - Circular Plate of Bilayerd Cells
*Bilaminar Embryonic Disc contains: Superior Epiblast Layer (High Columnar Cells) and Inferior Hypoblast Layer (Small Cuboidal Cells)
**Placenta Forms -
Embryonic Period: Third Week
Beginning of Third Week:
Primitive Streak forms within Bilaminar Disc
Migratory Cells = Mesoderm (Embryonic CT) and Endoderm = Epiblast Layer now is considered Ectoderm
**Bilaminar Embryonic Disc = Trilaminar Embryonic Disc = Cephalic End (head) and Caudal (tail) [Neural Plate is a central band between]
*Middle of Third Week:
CNS develops
*Ectoderm = Neuroectoderm =
Neural Plate thickens = Neural Groove
**Near the End of Third Week:
Neural Groove deepens and Neural Folds surround -
Embryonic Period: Fourth Week
**Trilaminar Embryonic Disc undergoes Embryonic Folding -Anterior/Cephalic and Lateral (Proper Placement of Forming Tissue Types)
*Movement of Embryonic Layers from Oropharyngeal Membrane to Cloacal Membrane - Future Digestive Tract Foregut, Midgut, and Hindegut)
*Anterior = Foregut = Primitive Pharynx
*Posterior = Midgut and Hindegut = Mature Pharynx
**Face/Neck Form = Primitive Eyes, Ears, Nose, Oral Cavity, and Jaw -
Embryonic Period: Forth Week: Facial Developments
**Disintegration of Oropharyngeal Membrane of Stomodeum --> Primitive Pharynx Access to Primitive Mouth
*Mandibular Processes Fuse --> Mandibular Arch --> Mandibular and Lower Lip --> Labial Commissures
*Frontonasal Process Forms --> Nasal: Pits, Placodes, Medial/Lateral Processes, and Intermaxillary Segments --> Nose and Primary Plate
*Maxillary Processes Fuse with Medial Nasal Process --> Upper Lip
**The Stomodeum's each side of Mandibular Arch's --> Maxillary Process Forms -
Embryonic Period: Fifth Week
***Intermaxially Segment Forms --> Primary Palate ***Differentiate = Mesoderm = Primitive Muscle Cells in Mandibular Arch -
Embryonic Period: Sixth Week
***Beginning of Sixth Week:
Bilateral Maxillary Processes --> Two Palatal Shelves - Vertical Growth --> Shelves Flip Up - Horizontal Position --> Secondary Palate ***Upper Lip Formation = Maxillary Processes Fuse with Medial Nasal Processes -
Embryonic Period: Seventh Week
**Differentiate --> Mesoderm Muscle Cells from the Hyoid Arches --> Mandibular Arches
**Completion --> Upper Lip Formation --> Fusion of Medial Nasal and Maxillary Processes Complete -
Embryonic Period: Eighth Week
**Completed: Nasolacrima Groove, Phitrum, Upper Lip, and Lower Jaw
*Pigment in Eyes Develop
**Flex in Wrist and Elbows -
Fetal Period
Third Month through Ninth Month
