Germ layer

cell lineage specification

allocation of stem cells into lineages that have a more restricted and less plasticity in developmental potential. the ability of the cell to undergo self renewal becomes limited as cell becomes more restricted

hypoblast

cell contribute to placenta and support the embryo

differentiation

cells will develop from an uncommitted stem cell type to a differentiated cell with specific functions

plasticity

develomental versatility of cell to form other structures. Influenced by cell signal and adult Stem cells are less plastic thatn embryonic stem cells

three germ layers

ectoderm - layer of cell in contact with the outside world mesoderm - bone, cartilage, connective tissue of body, skeletal muscle, smooth muscle, cardiovascular, genitourinary endoderm - internal lining of hollow organs like stomach, lung, bladder

two cell layers in embryo

epiblast and hypoblast

two main outcomes from gastrulation

establishment of body axes and formation of three germ layers by the end of third week

what is germ layer

layer of cells which may differentiate into any cell in adult body

gastrulation

migration of epiblast cells through the primitive streak

migration

movement of cells based on interactions with surrounding cells and environment. Interactions is juxtacrine. E.g: mature ooccyte migrates as it becomes the embryo

Induction

one cell tissue acts on another cell tissue to alter its developmental outcome. Eg: cellular pure pressure = inductive response. Teeth formation

Development of an embryo in2 weeks

the embryo or inner cell mass has differentiated into two layers and the amniotic cavity has developed

prochordal plate

thickening of cell

Lineage specification and differentiation

totipotent, pluripotent, multipotent, restricted cell lineage, committed cell type differentiated or mature functional cell

Four division of mesoderm

axial or notochord, paraxial, intermediate and later plate

epiblast

cell that give rise to three main tissues layers of the embryo cells that have the most control because it forms all the cells of the embryo the epiblast is above the hypoblast.

route of epiblast migration

1. ventrally to form endoderm 2. through streak and move cranial but stay in the middle to form axial mesoderm or notochord. Notochord is important because it induces formation of brain and spinal chord 3. through streak and laterally to form middle layer called mesoderm 4. remain on dorsal outer surface to form ectoderm