Embryo Flashcards
How many germ cells are present at embryonic midterm?
7 million
How many germ cells remain at birth?
2 million
How many germ cells survive to puberty?
400,000
The germ cells that survive to puberty will be arrested in what stage?
Diplotene stage of meiotic prophase 1
When to oocytes resume meiosis?
After puberty at the beginning of each menstrual cycle - until second metaphase
When does ovulation in most mammalian species occur?
Metaphase II
Proliferative phase is due to?
Increase in levels of estradiol secreted by granulosa cells
Secretory phase is controlled by?
Rising levels of progesterone, secreted by granulosa and the cal cells
Ovulation occurs around day 14 of the cycle and is precede by a sharp spike in ?
LH - occur about 24 hrs prior to ovulation
What is one of the major enzymes in the acrosome and what is its function?
Hyaluronidase - helps breakdown the HA component of the intercellular matrix b/w the corona radiata cells
What is acrosin
Serine proteinase that is the most important enzyme involved in the penetration of the ZP
The notochord is important in the formation of many axial structures through what signal?
Shh
What is the principal inductor in primary neural induction?
The notochord
The notochord induces overlying ectoderm to convert to what?
Nueral ectoderm - using Foxa2 and Goosecoid as TFs and noggin and Chordin as signals
Where is the isthmic organizer located?
B/w the mesencephalon and metenchephalon
The isthmic organizer is a signaling center which the principal signaling molecule is what?
FGF-8
Isthmic organizer organizes and polarizes what?
Midbrain and cerebellum - induced by FGF-8/Wnt-1
Anterior neural ridge
Important in organizing telencephalon, parts of diencephalon, olfactory area, and pituitary gland - using Shh and FGF-8
Zona Limitans
Organizes border b/w dorsal and ventral thalamus - using Shh
Extraembryonic tissues and their derivatives
Amnion (ICM: epiblast derivative) - ecto + meso Yolk Sac (ICM: hypoblast) - endo + meso Chorion (fetal maternal interface) - ecto + meso Allantois (ICM; interfaces w/ placenta) - endo + meso
What directly interfaces w/ the maternal uterine connective tissue?
Cytotrophoblast
Absence of normal cells death =
Syndactyly
Failure of migration =
Pelvic kidneys
Failure to fuse/merge =
Cleft palate