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Anatomy SDL 6

When does Implantation begin? on the 6th day when the blastocyst settles onto the uterine lining, and continues to the 10th day when the blastocyst is completely embedded in the endometrium.
How are syncytiotrophoblast cells made and what do they cover? As trophoblast cells contact the endometrium they differentiate into syncytiotrophoblast cells and cover the blastocyst.
What do Syncytiotorphoblast cells eventually make? They continue dividing and invading the endometrium. They form a multinucleated mass of cells with no cell boundaries (a syncytium).
What does the the syncytiotrophoblast produces? hCG (human chorionic gonadotropin) which diffuses into maternal blood and acts on the corpus luteum in the ovary to maintain the pregnancy.
What’s used in rapid pregnancy detection tests? Sufficient hGC is produced by the second week to be detected and is the basis for most rapid pregnancy tests.
What are lacunae? Isolated cavities that appear in the syncytiotrophoblast by day 10. The lacunae fill with maternal blood and eroded endometrial tissue. By day 12 the lacunae fuse, forming lacunar networks.
Cytotrophoblast cells do what and form what? proliferate on day 13 forming extensions into the syncytiotrophoblast called primary chorionic villi.
What do the primary chorionic villi make? the chorion, the foundation for the future placenta, and establish early maternal fetal nutrient exchange.
What regulates Syncytiotrophoblast invasion? its regulated by prostoglandins, growth factors, nitric oxide, and uterine natural killer cells.
What is insufficient or overly aggressive invasion is thought to lead to? obstetrical complications including early pregnancy loss and preeclampsia.
Where does Implantation usually occurs? on the superior anterior or superior posterior endometrial surface in the body of the uterus.
What are ectopic pregnancies? implantation outside the uterus.
Where do Ectopic pregnancies occur? Ectopic implantations mainly occur in the uterine tube (95%).
When can Ectopic pregnancies occur? They can occur if the zygote does not fully traverse the uterine tube. This often occurs with blockage or scarring of the uterine tube.
Are Ectopic pregnancies of serious concern? yes, can result in death of mother and fetus
What types of Ectopic pregnancies are there and can any work? Most won't: tubal, cervix, ovararian implantation. Sometimes abdominal pregnancies will work
How is the bilaminar embryonic disc formed? At the beginning of the second week, the embryoblast consists of the epiblast and the hypoblast together forming a flat bilaminar embryonic disk.
What events occur in the second week? amniotic cavity formation; amniotic membrane is made
How is the amniotic cavity former? It forms within the epiblast and will enlarge to become the amniotic cavity.
What does the amniotic membrane do? Encloses the amniotic cavity
How is the exocoelomic membrane made? Cells from the marginal edge of the hypoblast grow over the cells of the cytotrophoblast. This layer forms the exocoelomic membrane, which lines the blastocystic cavity; the cavity is then called the exocoelomic cavity (or primary umbilical vesicle or pr
Where is the extraembryonic mesoderm made? What is it derived from? A new layer of cells form between the exocoelomic membrane and the cytotrophoblast. This layer is the extraembryonic mesoderm and it is derived from the exocoelomic membrane. It grows around the exocoelomic cavity, the epiblast, and amniotic cavity.
How is the chorionic or extraembryonic coelomic cavity made? Spaces begin to form in the extraembryonic mesoderm. These coalesse to form the chorionic or extraembryonic coelomic cavity. The cavity enlarges to surround the amnion and yolk sac leaving a connecting stalk attaching the disk to the chorion.
What does the connecting stalk become? It will eventually develop blood vessels and become the umbilicus.
What are the three embryonic germ layers? endoderm, mesoderm, ectoderm
What does endoderm give rise to? epithelium lining the respiratory and alimentary tracts including glands and associated organs (liver, pancreas).
Mesoderm gives rise to what? muscle, cartilage, bone, connective tissue, blood elements, and the cardiovascular, reproductive and excretory systems.
Ectoderm gives rise to the what? skin, nervous system, neural crest tissue and many structures of the head and face.
How does gastrulation begin? Gastrulation begins with formation of the primitive streak. The primitive streak is clearly seen on the epiblast as a groove. The cephalic end is slightly enlarged to form the primitive node.
What happens at the primitive streak from here? cells begin proliferating; they separate from the epiblast and migrate inward (invaginate) between the epiblast and hypoblast.
Cells migrated through the primitive streak and form what two layers? –Lower layer: replaces the hypoblast cells forming the endoderm layer. –The middle layer, forming between the new endoderm and the epiblast, is mesoderm. – The cells remaining in the epiblast forms the ectoderm.
Gastrulation lasts how long? begins in the 3rd week and tapers off in the 4th.
What major entities control development? signaling molecules that cause induction and differentiation of adjacent cells and secreted growth factors that allow for cell growth and differentiation
What are the major families of growth factors? Fibroblast growth factor (FGF) Hedgehog, wingless, transforming growth factor
Describe Hedgehog? neural tube, somite, gut and limb regional sequence patterning.
Describe WNT (Wingless ):? limb patterning, midbrain and urogenital differentiation.
Describe Transforming growth factor B (TGFB) ?: cell division and migration, cell death.
What and how does the oropharyngeal membrane form? Early in gastrulation, some of the newly formed endoderm cells migrate to the cranial end of the embryonic disk and fuse with the ectoderm to form the prechordal plate. This will become the oropharyngeal membrane and later the mouth).
How does that cloacal membrane form? Caudal to the primitive streak, endodermal cells fuse with the ectoderm to form the cloacal membrane (will become the anus).
How is the notochord made? Mesoderm cells at the primitive node begin to form a cord in the midline. The cells grow cranially toward the prechordal plate and become the notochord.
What does The notochord do? induces tissues around it to differentiate:
What does the notochord induce The overlying ectoderm to differentiate into? to form the neural plate which will become the nervous system.
What does the notochord induce the Mesoderm on either side of the notochord to differentiates into? The paraxial mesoderm (close to the notochord), intermediate mesoderm (further from the notochord), and lateral mesoderm (continuous with the extraembryonic mesoderm).
What do Mesoderm that migrate on either side of the notochord do? fuse cranial to the prechordal plate forming the cardiogenic area (will become the heart).
Describe Fibroblast growth factor (FGF)? angiogenesis, limb, brain and axon growth
Created by: VCOM2013