Embryogenesis Flashcards
Week 1 Events (2)
Fertilization
Blastocyst Implantation
Week 2 Events (3)
Embryoblast Differentiation
Trophoblast Differentiations
Placenta
Week 3 Events (2)
Gastrulation
Primitive Streak Invagination
Pre-fertilization in Females
Ovulation to prep the ovary and uterine endometrium
Pre-fertilization in Males
Capacitation of sperm (ripening process)
Primes it to penetrate the oocyte
Glycoproteins removed from sperm head
Oocyte shell layers (3)
Corona radiata
Zona pellucida
Plasma membrane
Corona Radiata
Outermost shell
Chemoattractants for sperm
Protection, Energy, Support for oocyte
Zona pellucida
Thick glycoproteins layer
Made of zona proteins (ZP)
Plasma Membrane
Last layer the sperm has to penetrate
Fertilization steps (3)
- Capacitated sperm penetrate corona radiata
- Sperm head binds ZP3 receptor, releases acrosomal enzymes to dissolve and penetrate zona pellucida
- Oocyte and sperm plasma membrane fuse
Oocyte blocks polyspermy (2)
- Quick block = plasma membrane depolarizers
2. Slow block = inc. intracellular Ca to release cortical enzymes so the zona pellucida becomes impenetrable
Cells are totipotent until
8 cell stage
Cleavage divisions occur _________ apart and lead to _________
20 hours
Blastomeres
Blastomeres
Daughter cells that get smaller with each division (totipotent until 8 cells)
Morula
32 cell stage
Develops polarity as developing into ICM and OCM
Inner cell mass (ICM)
Also known as embryoblast
Gives rise to embryo proper and some extra embryonic tissue
Outer cell mass (OCM)
Also known as trophoblasts
Gives rise to fetal part of placenta
Blastocyst cavity formation
Uterine cavity fluid penetrates zona pellucida and surrounds cells
Blastocyst
4.5 day early embryo
Embryoblast cells are pluripotent
Trophoblasts forms rim of cells and fetal part of placenta
Blastocysts implant where?
Endometrium
What happens to the uterine endometrium after blastocyst implantation?
Thickens and increases glandular activity
Secretes hCG that will continue secreting progesterone to help nourish and support implantation
Embryoblast differentiate into
Epiblast layer (dorsal) Hypoblast layer (ventral)
Forms bilaminar embryonic disk
Epiblasts
Form all cells of embryonic body proper and extra embryonic amnioblasts
Amniotic cavity
Epiblasts
On dorsal side until it surrounds embryo
Amniotic fluid is
Fetal urine (mainly water)
Hypoblast migrate
Along inner surface of trophoblast-lined blastocyst cavity
Yolk sac
Hypoblasts
Degenerates during embryonic period
Waste-nutrient exchange, early hematopoietic, migrate and become gonads
Connecting stack
Hypoblasts
Connects embryo to trophoblasts
Becomes umbilical cord
Placenta
Nutrient waste exchange at fetal-maternal barrier
Modifies during gestation
Fetal part of placenta
Chorion frondosum
Maternal part of placenta
Decidua Basalis
Fetal arteries and veins carry:
Arteries = deoxygenated blood Veins = oxygenated blood
Gastrulation
Occurs with primitive streak formation
Bilaminar disk becomes trilaminar (3 layered)
Invagination
Epiblast migrate to primitive streak and dive down centrally
Endoderm
Structures for digestion, breathing, secreting
Ex: epithelial of urinary bladder, GI, gland
Epiblast cells displace and replace hypoblast cells
Mesoderm
Structures that provide support
Ex: skeletal, muscular, CV systems
Epiblast cells settle between endoderm & epiblast
Ectoderm
Structures that communicate with external environment
Ex: NS, epidermis, sensory receptors
Epiblast cells remain in epiblast
Buccopharyngeal Membrane
Cranial end
Future location of oral cavity
Cloacal Membrane
Caudal end
Future location of anus
Notochord
Formed by mesoderm
Release factors to induce development of NS and axial skeleton
Teratomas form when
Primitive streak doesn’t completely regress
