Flashcards in Early Embryology Deck (45):
Where does fertilization take place?
Ampulla of the uterine tube
What processes must sperm undergo to be able to fertilize the egg?
Capacitation and acrosome
Formed after sperm has entered the egg via meiosis II of the oocyte's nucleus
Formed by enlargement of the sperm's nucleus
When and what is cleavage?
Occurs about 30 hrs post-fertilization, and is the cell division to form the blastocyst
when the cell have reached about 16-32 cells from division
What layers does the blastocyst separate into?
Embryo proper (inner cell mass) and Trophoblast (outer cell mass)
What portion of the trophoblast penetrates into the endothelium?
Where is the extraembryonic mesoderm and what is it derived from?
Forms between the inner surface of the cytotrophoblast and outer surface of the amnion/exocoelomic membrane, and is derived from the umbilical vesicle
How is the chorionic cavity (extraembryonic cavity) formed?
Large cavities form in the extraembryonic mesoderm to form the cavity
What 2 layers does the extraembryonic mesoderm form?
Extraembryonic somatic mesoderm and extraembryonic splanchnic mesoderm
Trophoblast forms placenta membranes, but no embryonic development. Secretes high levels of hCG and may become malignant. Most arise from fertilization of an oocyte with no nucleus
Placenta forms over the cervix, causing severe and possibly life-threatening bleeding later in pregnancy
Chorionic villi penetrate the myometrium all the way to the perimetrium
Abnormal adherence of placenta to the myometrium
Implantation of blastocyst outside of the uterus
Process of establishing trilaminar germ disc. Cells slip underneath the epiblast forming the primitive streak
3 primary germ layers
ectoderm, mesoderm, endoderm
Forms the paraxial/lateral/intermediate mesoderms
Forms the neuroectoderm and neural crest cells
Cephalic end of primitive streak surrounding the primitive pit
establishes the primitive streak, which is the body axis
Fate map: Cranial region cells
Turn into notochord
Fate map: Intraembryonic mesoderm
turns into Paraxial mesoderm
Fate map: Intermediate mesoderm
Turns into lateral plate of mesoderm
Fate Map: Extraembryonic mesoderm
Continuous with the lateral mesoderm
Growth of embryonic disc
w3: cephalic region broadens and differentiates
w4: caudal region differentiates, primitive streak regresses
w3-8: Organogenesis, cranio/caudal/lateral folding, vasculogenesis
CNS, PNS, eyes, epithelial skin, neural plate
Derivatives: Paraxial Mesoderm
Bones, tendons, cartilage, muscles, dermis of skin
Derivative: Intermediate mesoderm
Derivates: lateral mesoderm
Parietal: serous membrane that lines the body cavity
Visceral: membranes around the organs
GI and epithelium of the organs
When do most large structural defects occur?
aka fetal alcohol syndrome– high doses of EtOH kill the anterior midline, creating craniofacial structure deficiencies
Caudal region has insufficient mesoderm, impacting lower limb/vertebral/urogential development
Left and right organ positions are switched
Remnants of the primitive streak proliferate, forming a teratoma on the new borns coccygeal region. Is the most common type of tumor in new borns
Weeks 9-12 of fetal development
External genitalia is formed, liver is main site of erythropoiesis
Weeks 13-16 of fetal development
Rapid growth, limb movement, face forms, ovaries have oogonia
Weeks 17-20 of fetal development
Movements can be felt by mom, CRL size increases another about 50mm
Weeks 21-25 of fetal development
Sucking movements begin, fetus reacts to sound, surfactant is beginning to be secreted at 24w
Weeks 25-29 of fetal development
Higher survival rate, erythropoiesis switches to the bone marrow
Weeks 30-34 of fetal development
Pupillary light reflex, 32+w usually survive