Embryology Flashcards
What are the Stages of Fertilization?
ZCMBGO Zygote Cleavage Morula Blastocyst Gastrulation Organogenesis
What is a Zygote?
Fertilized egg - has unequal distribution of some cellular products i.e leptin
What happens during Cleavage?
The cell divides into blastomeres and becomes 2 cells, this is a rotational cleavage resulting in 8 cells
How is the Morula formed?
Flattening of blastomeres maximises cell contracts and forms tight junctions, at this point it is a 16-cell
What Happens to the cell on day 5?
This becomes a blastocyst which is 32+ cells
What happens to the Cell on day 7?
The Zona Pallucida sheds, trophoblasts are cells gathering on the edge of cell to create cavity
What happens to external polarised cells?
Trophectoderm formed
What happens to Internal non-polar cells?
Inner Cell Mass created
What does the formation of Blastocoel lead to?
Hatching
What does the Trophectoderm lead to?
Syncytiotrophoblast which spreads around blastocyst
What does the Inner cell Mass divide into?
Epiblast and Hypoblast
What does Epiblast create?
Leads to embryo Amniocytes which secrete fluid leading to Amnion
What does Hypoblast create?
Lines the Blastocoel which forms the Yolk sac
What does the Ectoderm help form?
Epidermis, Nervous system and pigment cells
What does the Mesoderm help form?
Kidney, Gonads, Bones, Muscle, Heart and Blood Cells
What does the Endoderm help to form?
Lines the Gut, Respiratory System
What is meant by Pattern Formation?
Process by which a spatial and temporal pattern of cell activites is organised within the embryo i.e Axis Specification
Co-ordinations variety of cellular mechanisms
What is meant by Induction?
Production of signals that bring about response in target cells
What is Morphogenesis?
Achievement of developmental diversity by formation of different structures from the same initial structure i.e gastrulation
What does Juxtacrine/Paracrine signalling lead to?
Yes/no response, can be variable by modulation
What is Morphogen?
Signalling molecule that forms an extracellular concentration gradient
What must responding cells do?
Be competent to respond
detect inducing agent
quantify level of inducing agent
