Madison Kuhn

-First week after conception
-Joining of ovum and sperm forms fertilized egg or zygote
-Both chromosomes of the ovum and sperm are involved
-first period of three distinct successive periods of prenatal development
(If any disturbances occur in meiosis during fertilization, major congenital malformations result from the chromosomal abnormality in around 10% of cases)

This is the second period of prenatal development., and it extends to the end of week eight.
Certain physiologic processes or spatial and temporal events called patterning occur during this period, which are considered key to further development.
These physiologic processes include induction, proliferation, differentiation, morphogenesis, and maturation.
These processes cause the structure of the implanted blastocyst to become, with further development, an embryo.
These physiologic processes also allow the teeth and associated orofacial structures, as well as other organ structures, to develop in the embryo.

-Ectoderm gives rise to the CNS, mesoderm gives rise to connective tissue.
-Endoderm gives rise to respiratory epithelium
** The embryonic disc forms a cephalic end(mouth) and a caudal end(anus)

The primitive streak forms within the bilaminar disc.

Trilaminar embryonic disc has folded into the embryo. Disc now has undergone embryonic folding as a result of extensive growth of the ectoderm, and there is development of the brain with spinal cord, heart, and digestive tract. The digestive tract is divided into regions, these regions include the foregut, midgut, and hindgut.

The Yolk sac is replaced by the umbilical cord and the brain, spinal cord, and heart begin development; this includes the heart beginning to beat.

-The maxillary process fuses creating the upper lip, the nasal process, and the remaining facial structures (If the fusion of the maxillary process and median nasal processes fails, a cleft lip can occur
-Kidneys, lungs, and liver start to develop

Week 7: Arms and legs start to bud, brain develops.
Week 8: Fingers and toes are formed.
*External genitalia begin to form. Lymphatic system forms.

-Takes place from ninth week to the ninth month
-embryo enlarges to become the fetus
-Includes proliferation, differentiation, and morphogenesis
-development changes during this period allow the new tissue types and organs to function