L13 - Early Human Development Flashcards
What does embryogenesis achieve
Patterning - cells acquire identity in space and time
The major axes are defined
Three germ layers are defined
Rudiments of the major organs
What are the major axes of the developing embryo
Anterior (head) and posterior (bottom)
Dorsal (back) and ventral (stomach)
What are the 3 germ layers
Ectoderm, Mesoderm, Endoderm
What is the path of the sperm cell
Corona radiata, Zona pellucida, plasma membrane of secondary oocyte, cytoplasm of secondary oocyte
Why is egg much larger than sperm?
The egg contains nutrients and proteins required for early development
What happens when male and female pronuclei fuse
Fertilisation, forms a zygote
What is cleavage
A series of rapid cell division to form a blastocyst
What is a morula
A ‘ball of cells’ formed through rapid cell division that occurs after fertilisation but before the blastocyst formation
What does the embryoblast and trophoblast give rise to
Embryoblast - gives rise to embryo itself
Trophoblast - gives rise to extra embryonic tissue e.g placenta
What does a blastocyst contain
Embryoblast (inner cell mass) and trophoblast
Where does fertilisation occur
In the fallopian tube 12-24 hours after ovulation
Where does implantation occur
In the uterus ~6 days after fertilisation
What are the types of trophoblast cells
Syncytiotrophoblast and cytotrophoblast
What is the enzyme we test for in a pregnancy test
Chorionic gonadotropin
What is the chorionic villi
Projections of foetal placental tissue
What is the bilaminar embryonic disc
Two layered structure formed by the the inner cell mass consisting of hypoblast and epiblast cells
What germ layer do hypoblast and epiblast cells form
Hypoblast cells - endoderm
Epiblast cells - ectoderm
What occurs during invagination in gastrulation
Formation of the mesoderm germ layer
What is the step after gastrulation
Organogenesis
What side of the embryo is the primitive streak on
Posterior side (bottom)
What 2 parts form the future umbillical cord
Yolk sac and connecting stalk
What is lateral folding in organogenesis
Ectoderm layer folds downwards to surround the embryo (forms skin)
Endoderm folds to form a tube (gut)
What is the function of stem cells
Growth, renewal, repair
What is an example of a tissue that is constantly renewing
Blood
What is a stem cell
A cell that divides to form one daugther that goes on to differentiate and one daugther that retains its stem-cell properties
What are the types of stem cells (from most to least potent)
Totipotent, pluripotent, multipotent, nullipotent
(TPMN)
What are totipotent cells
Cells capable of giving rise to all cell types of the body and extra-embryonic tissues (ZYGOTE)
What are pluripotent cells
Cells capable of giving rise to all cell types of body (blastocyst)
What are multipotent cells
Cells capable of giving rise to all cell types of a particular tissue or organ (e.g cells in gut)
What are nullipotent cells
Cells not capable of giving rise to other cell types (e.g keratinocytes, RBCs)
What are keratinocytes
Unipotent stem cells in the skin that allow for constant renewal
What is epidermolysis bullosa (EB)
A mutation in a gene for collagen 7 that causes fragile, blistering skin
What is a clinical utility of stem cells
Long lasting skin grafts (using CRISPR and gene editing) e.g for epidermolysis bullosa (EB)
