Lecture 2 Flashcards
What properties do sea urchin eggs have
- Transparent eggs
- Holoblastic cleavage
- Rapid cell division
What is the status of cells at the late blastula stage
Blastoele is surrounded by monolayer of cuboidal cells
Where does grastulation begin
At the vegetal pole
What occurs at the vegetal pole
Apical membrane constricts. Form vegetal plate. Bottle cells lose adherance, ingress in to blasoele. Form PMC
What re the precursors for mesoderm cells
Pre mesenchyme cells
What allows the cuboidal cells to change
Lack of cadherins, the constriction of the membrane by actin/myosin
What is convergent extension
The invagination of the vegetal pole from the blastopore
What is the process of convergent extension
Cells elongate perpendicular to membrane.
Lamellipodia at each end act on each other elongating the archtenon. This narrows the cells
This is mediolateral intercarlation
How does the arrchtenon attach to the animal pole
SMC are on the tip of invagination.
SMC have filopodia which search for ventral pole of basal membrane of animal pole.
This is most likely aided by proteins in blastoele
SMC attach, pull archtenon
What is the anus and mouth
Anus: site of invagination at vegetal pole
Mouth: site of anchorrage at animal pole
What occurs at the 16-32 cell range in mamallian embryos
Increased adherance leading to compaction
Trophoblasst and internal mesenchme cells are formed
What does the trophoblast secrete
Na+ into the middle of the embryo causing water to enter and a cavity, blastoele is formed
What does the Inner cell mass form
ICM forms the tissues, organs, yolk sac epitheliem, amniotic membrane, vasculature placenta layer, umbilocal cord
What does the trophoblast form
Chorionic layer of the placenta
Where are embryonic stem cells taken from
The inner cell mas pre grastrulation
What layers are formed from the Inner Cell Mass
Hypoblast, adjacent to the blastoele
Epiblast
What does the hypoblast do
Hypoblast spreads around the blatoele. Forms the Heuser’s membrane
What does Heuser’s membranw form
The yolk sac, extraembryonic endodem, that helps trasnport nutrients from the yolk to the embryo
What happens if the Egg is in not lost
Sac is usually lost in 2% of people. If not lost: Meckel’s diverticulum, malfunction in small intestine
What will the epiblast form
The extraembryonic ectoderm. This will form the amniotic membrane
What animals have an amniotic membrane
mammals, reptiles, birds
What form is the rest of the epiblast layer
Simpple cuboidal layer
What part of the embryo allows the embryo to the implant
Trophoblast attatches to the endometrium
What processes occur at the endometrium
Trophoblast proliferates rapidly. Sycytiotrohblasts invades the wall. Whole blastoele is contained within the wall
