Brittany Black

-Takes place during the first week after conception.
-Sperm fertilizes the egg and forms a zygote.
-During fertilization, final stages of meiosis that occurs in the ovum.
-Zygote later becomes a blastocyst because of the ongoing mitosis.
-By the end of the first week, the blastocyst stops traveling and undergoes implantation.

-Patterning occurs
-Five physiologic processes occur:
Induction: action of one group of cells on another that leads to the
establishment of the developmental pathway in the
responding tissue.
proliferation: controlled cellular growth and accumulation of
byproducts.
differentiation: change in identical embryonic cells to become distinct
structurally and functionally.
morphogenesis: development of specific tissue structure or differing
form due to embryonic cell migration or proliferation
and inductive interactions.
maturation: attainment of adult function and size due to proliferation,
differentiation, and morphogenesis.

-Implanted blastocyst grows by increased proliferation of the embryonic cells.
-Differentiation also occurs resulting in changes in cellular morphogenesis.
-This increased number of embryonic cells creates the embryonic cell layers within the blastocyst.
-Bilaminar embryonic disc is eventually developed from the blastocyst and appears as a three-dimensional but flattened, essentially circular plate of bilayered cells.
-The placenta forms.

-Primitive streak form within the bilaminar disc, results from an increased proliferation of cells in the midline area.
-Some cells from the epiblast layer move or migrate toward the hypoblast layer only in the area of the primitive streak. These become the mesoderm.
-With the three layers present, the bilaminar embryonic disc has thickened into trilaminar embryonic disc, and the epiblast is now considered the ectoderm.
-In areas without the mesoderm, both the ectoderm and endoderm fuse together and prevent the migration of the mesoderm.
-The disc now has a cephalic, or head, end.
-The beginning of the mouth and digestive tract are formed.
-The CNS begins to form in the latter part of the third week.
-The ectoderm is now considered the neuroectoderm localized on the neural plate. Further growth transforms this into the neural groove. Further deepens by the neural folds and turns into the neural tube.
-Neural crest cells develop from neuroectoderm. Join mesoderm to form mesenchyme.
-Formation of the pulp, dentin, cementum, alveolar process, and PDL.
-Mesoderm additionally differentiates and divideds into 38 paired somities.

-Trilaminar embryonic disc undergoes anterior and lateral embryonic folding. Folding results from extensive proliferation of ectoderm and differentiation of basic tissue and occurs mainly at cephalic end where brain will form. Grows beyond oropharyngeal membrane to overhand developing heart.
-Future digestive tract is formed.
-Face and neck begin to develop with the primitive eyes, ears, nose, oral cavity, and jaw areas.
-Two mandibular processes appear, will fuse at the mid line to form the mandibular arch.

-Primitive muscle cells from the mesoderm in the mandibular arch begins to differentiate.
-Upper lip begins formation when each maxalliary process fuses with each medial nasal process on both sides of the stomodeum
-Primary palate formation.
-Intermaxillary segment from fused medial nasal processes.
-Secondary palate starts formation in the sixth week.
-Palatal shelves begin fusing

-Tooth induction
-Mandibular muscle mass has enlarged, and cells have begun to migrate into areas where they will begin to differentiate.
-Secondary palate is formed.
-Paired medial nasal processes also fuse internally and grow inferiorly on the inside of the stomodeum forming the intermaxillary segment by the end of the seventh week.
-By the end of the seventh week, the last four branchial grooves are obliterated as a result of a sudden spurt of growth experienced by the pair of hyoid arches.

-Tongue finishes developing.
-All facial structures are completed.
-Hands and feet are forming fingers and toes.
-Eyes development pigment.
-Genitals are forming too

-Maturation of individual tissues to form specialized organs.
-By twelfth week the final palate is formed, all three processes are fused.
-Heartbeat detected by the fourth month.
-Proliferation, differentiation, morpheogenesis
-Birth occurs at the end of the 9 months. Happy birthday!