Embryology Flashcards
Nondisjunction
Uneven splitting in anaphase - leading cause of death
Fertilization
The process of fusing a sperm and egg
Capacitation
When the sperm has the ability to have direction, motility, and energy
Barriers of egg the sperm must cross
Corona radiata (outer) Zona pellucida (middle) Egg plasma membrane
2 reactions for fertilization
Acrosome - sperm getting through the barriers
Cortical - egg closing the gate
Cleavage
When zygote undergoes mitosis inside the plasma membrane, reducing cell size
Compaction
Outer cells flatten and inner cells differentiate forming morula (solid ball of cells)
Blastogenesis
Blastocyst (hollowed morula) cell walls begin to differentiate
First week
Cleavage, compaction, morula formation, implantation
Second week
Week of twos
Trophoblast - cytotrophoblast, syncytial trophoblast = placenta
Inner cell mass - epiblast (amniotic cavity), hypoblast (yolk sac)
Third week
Gastrulation - form 3 germ layers by mesenchymal epiblast cells flowing through the primitive streak
Primitive streak components
Pit, groove, node
Where are there no mesenchymal cells?
Buccopharyngeal membrane and cloacal membrane
Fourth week
Nerulation- neural plate folds to form the neural tube
Where is the notochord found and what does it do?
Mesoderm and it’s a SIGNALING MACHINE
Three types of mesoderm
Paraxial (somites) - muscle, bone, and CT of most of body
Intermediate - urogenital system
Lateral - muscle of body wall, digestive tract, proximal part of limbs
Two sets of body folding in planning
Lateral/transverse - endorsed and mesoderm closing both sides, forms placenta
Cephalocaudal - ectoderm closing neural tube (zipper)
What is the order in which the neural tube closes?
Begins midway along neural plate
Cranial end closes first
Caudal end second (primitive streak at caudal end)
Placodes
Thickening of ectodermal tissue that make CNS segmentation
Makes lens plac, otic plac, olfactory epithelium, ant pit, sens ganglion of CN
Folding in week 3 and 4
Purse string constriction
Endoderm derivatives
Digestive glands, endocrine glands, respiratory sys, liver, ant pit
Pregenesis
- Make primordial germ cells (sperm/egg)
- Find a place to sequester cells and develop gonads (ovary/testes)
- Increase number of cells (mitosis)
- Gametogenesis (meiosis)