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
Defective fields =
Sirenomelia
Myogenic cells
Originate in somite; resemble mesenchymal cells; restricted to muscle-forming line; mitotic
My oblasts
Derived from myogenic cells; postmitotic
Myotubes
Formed when my oblasts line up and adhere to one another; characterized by appearance of actin, myosin, troponin and tropomysoin; formation of sarcomeres***; nuclei move to periphery
Satellite cells
Located b/w sarcolemma and basal lamina; mitotic and myogenic; able to fuse w/ muscle fiber and provide for growth; note that satellite cells don’t form new muscle fibers
Where do mitosis and DNA replication occur within the neural epithelium
Mitosis occurs close to the lumen and DNA replication occurs close to the external limiting membrane
If metaphase plate is perpendicular to inner margin of nueral tube (I.e next to lumen), what is the outcome?
Two resulting daughter cells will remain proliferative
If metaphase plate is parallel to inner margin, what is the outcome?
Daughter cell closest to the lumen will remain proliferative and the one further from the lumen will become postmitotic, move to the external limiting membrane, and become a neuroblast
If the forelimb rudiment of an amphibian embryo, prior to the outgrowth of nerves, is cut out and transplanted to a position very near the original one:
The brachial nerves will deviate from their normal paths and will be deflected in the direction of the transplanted limb. If the distance of the transplanted limb from the original position is not too great, the brachial nerves will penetrate into the limb and ratify. The limb becomes fully functional.
If an additional limb is transplanted into the immediate vicinity of the host limb
The brachial nerves will develop branches running out to the additional limb and will supply it
Transplant thoracic neural crest cells to head region and vice versa
Cannot form cartilage or skeletal elements (normal for cranial neural crest)
Compare single neural crest cells grown in culture to dye-injected neural crest cells in vivo
Cells grown in culture differentiate into neuronal and pigment cell phenotypes. Dye injected cells also will give rise to two or more phenotypes
Expose rat nueral crest cells in vitro to glial growth factor
GF suppressed ability of cells to form neurons; they instead formed Schwann cells
What does the lens vesicle induce?
Overlying ectoderm to become the cornea
Optic vesicle induction event in the absence of Pax6 expression
Lens placode
1st pharyngeal arch
Mandibular Arch - CN V Trigeminal
Derivatives: Meckel’s Cartilage - lower jaw; sphenomandibular ligament; malleus; quadrate cartilage –> incus
Derived from rhombomeres 1 and 2 and midbrain. Differentiation associated w/ Otx-2
2nd Pharyngeal Arch
Hyoid Arch - CN VII Facial N.
Derivatives: Reichert’s cartilage - body and lesser horn of hyoid; stapes; styloid process and stylohyoid ligament; muscles of facial expression
Development: induced by Hoxa2
Caudally, each mesonephric duct forms and evagination called the?
Ureteric bud (Diverticulum) or metanephric Diverticulum
Ureteric Bud (Diverticulum) or Metanephric Diverticulum
Pocket-like expansion grows into the surrounding mesenchymal of the mesonephric ridge during week 5 of gestation. Will give rise to the adult ureter, renal pelvis, and collecting tubules.
As the metanephric diverticula expand, they induce the surrounding mesenchymal to condense into the what?
Metanephrogenic blastema - will form the renal tubules of adult kidney; have a reverse inductive effect on the ureteric diverticula; neither can continue to develop in the absence of their other
In a genetic male, the product of the SRY gene causes what?
The developing Sertoli cells in the sex cords to secrete Mullerian inhibitory factor
What does the secretion of Mullerian inhibitory factor cause?
Regression of the Müllerian ducts. Testosterone produced by the interstitial cells of the rete cords causes retention of the mesonephric ducts
In a genetic female, nothing is produced to repress the Müllerian ducts or retain the mesonephric ducts so . . ?
Müllerian ducts will be retained and the mesonephric ducts will eventually regress
Which aortic arches form and later degenerate?
First and second pairs
Third pair of aortic arches
Form internal carotids
What forms the right subclavian artery?
Right 4th aortic arch
The left 4th aortic arch forms what?
The aortic arch
6th pair of aortic arches become associated with what?
Pulmonary system
Primary heart field forms the what?
Left ventricle and the atria
What is phylogenetically the most primitive component of the mammalian heart?
Primary heart field aka heart crescent
Secondary heart field forms what?
Right ventricle and outflow tract. Cells here express Hand-2
Inter atrial septum primum
Downward growth from cephalic wall of single atrium to endocardial cushion. Separates the atrium into left and right chambers
Inter atrial septum secundum
Forms to the right of the sputum primum and grows form dorsal to the ventral part of the atrium
Inter atrial foramen primum
Space b/w the leading edge of the septum primum and the endocardial cushion. Right to left atrial shunt
Inter atrial foramen secundum
Forms at cephalic end of septum primum through apoptosis. Continues the right to left atrial shunt after foramen primum closes w/ the fusion of the suptum primum w/ the endocardial cushion
Foramen ovale
Space formed w/I the septum secundum; right to left atrial shunt
