Embryology Flashcards
What does embryogenesis achieve?
Patterning: cells acquire identity in space and time
Major axis defined: anterior/posterior, dorsal/ventral
Three germ layers are defined
Rudiments of the major organs
Gastrulation generates which three layers?
Ecto (outside): e.g skin, tissue, nervous system
Meso (between): in between tissue e/g skeleton and muscle
Endo (inside): e.g gut
What is fertilisation
When male and female gamete fuse together to form a diploid gamete
Fertilisation - corona radiata
- somatic cells are released (when egg released from ovary)
- sperm fights through C.R cells, and releases barrier into zona pellucida
Fertilisation - Zona Pellucida
- fibrous matte surrounding egg
- sperm interacton
- ZP releases enzymes that allow sperm through
- fuse with membrane of secondary ocyte
Fertilisation - PM secondary ocyte
- fused to get through cytoplasm
What is cleavage?
When the zygote undergoes a series of relatively rapid mitotic cell divisions in a process referred to as cleavage
What happens in cleavage
When the zygote divides, the mass of the embryo does not increase, so cells become progressively smaller. After 5 days, the cells that were previously loosely associated become tightly packed and an internal cavity is formed called the blastocyst cavity.
What is implantation
When the blastocyst hatches as the embryo, it invades the female uterine wall
What happens in the development of the trophoblast?
The two subtypes give rise to the chorionic villi, which includes the female placenta, where nutrient and gas exchange occurs with the mother. enzymes are secreted which allows the embryo to burrow in the uterine wall.
Development of the bilaminar embryonic disc
The hypoblast gives rise to endodermal tissues, and the epiblast gives rise to ectodermal tissues. 2 different tissues are visible in the cell mass.
What is gastrulation
Where three ‘germ layers’ are established
What happens in gastrulation
Cells from inner mass divides, change shape and become motile. They rearrange to form a flat disc with three distinct layers, so can say cellular differentiation has begun.
What happens after gastrulation
Organogenesis, where a mass of cells transforms into a complete organ in developing embryo.
Connecting stalk
connects bi-lamina disc to tropho/ectoderm cels
Yolk sac
Provides nutrients to embryo
Amnion and yolk sac
provides extra embryonic tissues
Embryonic folding
The embryo (previously a flat disc) now folds to give rise to a three-dimensional structure - the head and tail form a comma-like structure. At the same time, the ectoderm folds down and surrounds the mesodermal layer with the endoderm forming a hollow tube inside the embryo.
What are stem cells
Cells divide to form one daughter that goes on to differentiate, and one daughter cell that retains its stem-cell properties.
What can stem cells do
Replace themselves and generate differentiated daughter cells
We need stem cells for…
Growth (embryogenesis), renewal (e.g tissues and skin) and repair (e.g blood)
What is decreasing developmental potential
As development happens, there is decreased developmental potential.
Totipotent cell
Capable of giving rise to all cell-types of body, including extra embryonic tissues
Pluripotent cell
Capable of giving rise to all cell types of the body, but not including embryonic tissue
Multi-potent cell
Capable of giving rise to all cell types of a particular tissue or organ
Uni/Nullipotent cell
Not capable of giving rise to other cell types (only one - kerantinicite)
Clinical utility of stem cells?
Long-lasting skin grafts (gene edited)
