Professor Dr. Akram Yousif Yasear, PhD(Ireland) Implantation

Implantation is an event that occurs early in pregnancy in which the embryo adheres to the wall of uterus.embryoadheresuterus At this stage, the embryo is a blastocyst.blastocyst It is by this adhesion that the fetus receives the oxygen and the nutrients from the mother to be able to grow.

Implantation(day 6-7)

Implantation

Six day old human embryo implanting

Implantation Human chorionic gonadotropin(HCG) Human chorionic gonadotropin Functions of HCGH: Acts as an immunosuppressive helping with other factors not to consider the embryo as allograft. Sustaining the function of the luteum. That will notifies" the mother's body that she is pregnant.pregnant

Abnormal implantation: Extra-uterine gravidity. Placenta praevia

GASTRULATION Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar ("three-layered") structure known as the gastrula. These three germ layers are known as the ectoderm,mesoderm and endoderm.animals Gastrulation is followed by organogenesisorganogenesis

Beginning of gastrulation 2 nd week of embryonic life

Gastrulation (3 rd week of pregnancy)

Derivatives of germ layers MesodermEndodermEctoderm Muscles Connective tissues in the body Gastrointestinal tract & associated glands Nervous system Sensory epithelium Epidermis, hair, nails Mammary & cutaneous glands Sinuses epithelium, enamel

The notochord induces the overlying neuroectoderm cell layer to invaginate to form the neural tube Represents paracrine signals Neural tube closure begins near the rostral end of the embryo and progresses caudally

Neural Crest Cells Neural crest: “a transient band of cells that joins the neural tube to the epidermis.” migrate long distances give rise to a variety of cell types Sensory neurons, autonomic neurons, glial cells, pigment cells, endocrine cells, and connective and supportive

Connective tissue of head and neck Mesoderm =mesenchyme Neural crest=ectomesenchyme All tooth structures are derived from neural crest except enamel

Child with mandibulofacial dysostosis(Treacher’s Collin’s syndrome),results from failure of neural crest migration to facial region.

Treachear Collin’s syndrom