BIOSCI 107 Special topic 1

Stages of embryonic development

fertilisation, cleavage, formation of morula and blastocyst, implantation, gastrulation, embryonic folding

Cleavage

Rapid mitotic divisions of the zygote into smaller and smaller blastomeres

Blastomere

cells formed during cleavage

Morula

Solid mass of blastomeres

Blastocyst

A hollow ball of cells including the trophoblast and embryoblast/inner cell mass

Trophoblast and it’s purpose

Outer layer of blastocyst, nourish embryo

Implantation

process in which the blastocyst attaches to the wall of the uterus

Syncytiotrophoblast

Outer layer of the trophoblast which grows into the endometrium

Bilaminar embryonic disc

Embryoblast/inner cell mass divided into two sheets: epiblast and hypoblast

Gastrulation

the process in which germ layers develop by the inward migration of cells

primative streak

Groove that forms down the epiblast, allowing it to separate into three germ layers.

What forms from the ectoderm?

Nervous system, epidermis, hair, nails, sensory organs

What forms from the mesoderm?

Muscles, skeleton, Cardiovascular system, Lymphatic system, connective tissue, kidneys, gonads

What forms from the endoderm?

Respiratory and gastrointestinal tracts, internal organs such as bladder, liver, pancreas, lungs

What are stem cells?

Unspecialized cells from which differentiated cells develop

totipotent stem cells

(Zygote) cells that give rise to all body cells and extraembryonic cells

Pluripotent stem cells

Stem cells that give rise to all body cells

Multipotent stem cells

Stem cells that give rise to all cell types of a particular tissue or organ

IPSC (induced pluripotent stem cells)

An adult cell that has been genetically reprogrammed to mimic the pluripotent behavior of embryonic stem cells

Nullipotent cell

Not capable of giving rise to other cell types

IPSC medicinal purpose

Regenerative medicine

Embryonic folding

Flat dish folds into a 3D tube structure with ectoderm on the outside, endoderm on the inside

What causes embryonic folding

Different growth rate of tissue, cell shape changes, cell movement

zona pellucida

A thick, transparent coating rich in glycoproteins that surrounds the oocyte, zygote and morula