Week 1 Flashcards
What occurs with fertilization? (3)
- pronuclei
- zona pellucida
zona pellucida
hick extracellular coat that surrounds all mammalian eggs and preimplantation embryos. The zona pellucida supports communication between oocytes and follicle cells during oogenesis; protects oocytes, eggs, and embryos during development, and regulates interactions between ovulated eggs and free-swimming sperm during and following fertilization.
pro-nuclei
pair of gametic nuclei, in the stage following meiosis but before their fusion which will lead to the formation of the nucleus of the zygote.
polar body
small haploid cell that is formed concomitantly as an egg cell during oogenesis, but which generally does not have the ability to be fertilized; byproducts of meiosis and have no biological role in fertilization or in embryo development.
blastomere
cell formed from cleavage of initial cell formed from fertilization
Day 1-5 of zygote formation
- 1: fertilization
- 2: cleavage-blastomeres formed
- 3: compaction- blastomeres form tight cell junctions, allows for passage of mRNA and proteins by individual cells
- 4: differentiation- some blastomeres move to inner part of cell while others stay on outside
- 5: cavitation: blastomeres on outside of cells now trophoblasts, inner cells become a mass, and a blastocoelic cavity created
trophoblast
outer cells in blastula; supplies the embryo with nourishment and later forming the major part of the placenta.
inner cell mass
will become the fetus
morula
- solid ball of 10-30 cells resulting from division of a fertilized ovum, and from which a blastula is formed
- final stage prior to formation of a fluid filled cavity called the blastocoel cavity.
hydatdiform mole
- molar pregnancy
- rare complication of pregnancy characterized by the abnormal growth of trophoblasts
- complete molar pregnancy: placental tissue is abnormal and swollen and appears to form fluid-filled cysts, no formation of fetal tissue.
- partial molar pregnancy: may be normal placental tissue along with abnormally forming placental tissue;may also be formation of a fetus, but the fetus is not able to survive
Day 6
zona hatching- zona pellucida is shed
Day 7
implantation- embryo implants into the uterus
Day 9
cell mass differentiation- inner cell mast differentiates into hypoblast and epiblast
Hypoblast
inner layer composed of cuboidal cells
Epiblast
outer layer that consists of columnar cells
Cause of hydatdiform mole
-result of fertilization between an enucleate egg and multiple sperm
What forms the bilaminar disc?
Epiblast and Hypoblast
Gastrulation
-process in which bilaminar disc forms trilaminar disc
Primitive streak
- develops on day 15 of pregnancy
- thickened structure in epiblast near caudal end
- defines major axes of embryos body
Primitive node
-develops from the primitive streak
Primitive pit
-Circular depression in the primitive node that elongates toward the caudal end of the primitive streak
Primitive pit
-Circular depression in the primitive node that elongates toward the caudal end of the primitive streak forming primitive groove
Invagination
cells from the epiblast going through the primitive pit and invading space of hypoblast displacing and replacing its cells and creating the definitive endoderm
Ectoderm
- Cells of the epiblast that did not invade space of hypoblast and are therefore on the outside of the definitive endoderm
- gives rise to nervous system and skin
Mesoderm
- cells from epiblast that remain between the ectoderm and definitive endoderm
- gives rise to connective tissue
Endoderm
- comes from cells of epiblast that replaced hypoblast during invagination through the primitive pit
- gives rise to lining of the airways and gastro intestinal tract
Notochord
- comes from
- will form
- importance, secretion
- part of mesoderm
- will become nucleus pulposus of IV discs
- induces neurulation, secretes sonic hedgehog
Neurulation
- Lateral edges of ectoderm will fold in forming two neural folds with a neural groove in the middle– the folds will continue until they meet and pinch the groove off into a closed off tube (neural tube); the open ends of the ectoderm will then begin to move around the mesoderm and endoderm until they meet on the other side and envelop the other two layers
- Reorganization of germ layers, outter to inner is ecto, meso, endo–with endo being smallest
Neural plate
-neural folds and groove
Neural tube
-formed from the neural folds growing towards each other and pinching off, making the neural groove a closed off tube
Neural crest
-pieces of the ectoderm from neural tube that migrate and give rise to PNS and cranial nerves
What factor induces neural crest formation?
-transcriptor factor
- WNT pathway
- Gbx2
Chordoma
-Vestigial remanence of notochord; tumor derived from notochord
Somatogenesis
- formation of somites
- Dermatome: becomes skin (dermis)
- Myotome: becomes skeletal muscle
- Syndotome: becomes tendons
- Sclerotome: becomes vertebral column