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41 Cards in this Set
- Front
- Back
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oocyte
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-female gamete
-stored in the ovaries, one released ~once/month -will become zygote/embryo if fertilized by sperm |
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sperm
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-male gamete
-stored in testes -if introduced into female, may fertilize an ovum to become a zygote/embryo |
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fertilization
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24 hour process of complex molecular steps following the contact of a sperm and oocyte that ends with the mixing of maternal/paternal DNA during metaphase of the first mitotic division of the zygote
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Function of fertilization
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-restores diploid number of chromosomes
-determination of genetic sex -initiates cleavage |
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cleavage
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first mitotic divisions of the zygote
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zygote
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initial single cell formed after fusion of male and female gametes
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Location of fertilization
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ampulla of uterine tube (fallopian tube)
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blastomere
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-intial cells formed by cleavage
-created during the first two-three days after fertilization |
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morula
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-solid ball of cells formed by end of day three of cell division after fertilization
-consists of zona pellucida, outer cell mass (trophoblasts), and inner cell mass (embryoblasts) -morula located near the end of the uterine tube |
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Destiny of layers of morula
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-outer cell mass/trophoblasts: placenta
-inner cell mass/embryoblasts: embryo -morula-->blastocyst |
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Development of blastocyst
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-inner cell mass/embryoblasts gather at the embryonic pole
-trophoblasts remain along the outside, helping to form the blastocoel, which includes the blastocystic cavity |
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blastocoel
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area formed by blastocystic cavity and layer of trophoblast cells
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Location/timing of blastocyst development
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-Day 5
-Uterus |
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endometrium
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-lining of the uterus
-location of implantation of blastocyst -becomes blood vessel filled/increased during points of menstrual cycle and post-implantation |
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implantation
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-trophoblast cells invade endometrium
-process of the embryo embedding itself in the endometrium -begins at the end of week 1 |
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ectopic pregnancy
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-implantation of the embryo somewhere besides the endometrium
-usually in the uterine tube, but may also end up in the abdominal cavity -does not support development of the embryo and very dangerous to mother |
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Week 1 of embryonic development
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-fertilization (ampulla of uterine tube)
-cleavage: blastomeres-->morula (end of uterine tube) -morula-->blastocyst (enters uterus) -blastocyst implants in uterine wall (endometrium) |
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Development of blastocyst after attachment (Day 7)
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-embryoblasts differentiate into hypoblast and epiblast layers
-epiblasts are directly adjacent to the trophoblast layer; longer, more column-like cells -hypoblasts remain next to the blastocele (now yoke sac) |
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Trophoblast differentiation
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-synciotrophoblasts (invade maternal blood supply)
-cytotrophoblasts maintain layer around embryoblasts |
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Epiblasts during D8
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-begin to gather/grow as lining to form a cavity
-form the amniotic cavity -differentiate into amnioblasts to form amnion/amniotic membrane/extraembryonic ectoderm |
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hypoblasts during D8
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-grow so as to line the cytotrophoblasts and form the membrane of exocoelimic cavity (yolk sac), aka extraembryonic endoderm
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uteroplacental circulation
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-synciotrophoblasts invade maternal blood supply between D12-D13 to gain nutrients for growing embryo
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Bilaminar embryonic disc
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layer of cells that develops between the amniotic cavity and the ecoceolimic cavity and includes one layer derived from hypoblasts and one layer derived from amnioblasts
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Formation of the chorionic cavity
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-mesoderm form from hypoblast cells to fill space between two main cavities and cytotrophoblasts
-cavities form within mesoderm; cavities fuse/grow together to form chorionic cavity -D12-D14 |
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Week II Embryonic development
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-blastocyst becomes completely implanted (w/in endometrium)
-establishment of uteroplacental circulation -formation of bilaminar disc -formation of extraembryonic mesoderm -formation of amniotic and chorionic cavities -formation of extraembryonic ectoderm, mesoderm, and endoderm |
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Gastrulation
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-formative process by which the 3 embryonic germ layers and axial orientation are established in the embryo
-bilaminar germ disc (2 layers) --> 3 layers |
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Main steps of gastrulation
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-D14/15 brings formation of the primitive streak which arises from cell division in the epiblast at the edge of the bilaminar germ disc
-primitive streak begins migrate from cloacal membrane towards the prechordal plate/buccopharyngeal membrane -while migrating, primitive streak forms the primitive groove and is being led by the primitive node, which contains the primitive pit -these dividing cells are responsible for forming the three germ layers (endoderm, mesoderm, and ectoderm) and for establishing the axes of the body (caudal/cranial and ventral/dorsal) |
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3 germ layers and origin
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-ectoderm
-mesoderm -endoderm -all derived from epiblast cells |
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notochord
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-derives from prenotochordal cells of the primitive node
-forms in the mesoderm layer, cranial to the primitive node -forms the backbone of the embryo |
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mesenchyme
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-cells that derive from the mesoderm
-undifferentiated loose connective tissue |
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paraxial mesoderm
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-runs directly alongside/around notochord
-destined to become "tomes": -sclerotome=bone -myotome=muscle -dermatome=skin |
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intermediate mesoderm
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-surrounding paraxial mesoderm
-destined to become kidneys, ureters, and gonads |
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lateral plate mesoderm
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-splits into two layers: somatic/parietal and splanchnic/visceral
-intraembryonic coelom formed between the two layers -both layers are continuous with the extraembryonic lateral plate mesoderm layers -intraembryonic coelom is continuous with extraembryonic coelom at midline of embryo |
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Fate of lateral plate mesodermal layers/intraembryonic coelom
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-somatic=anterior body wall
-visceral/splanchnic=GI tract -intraec=body cavities |
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Week III Embryonic Development
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-gastrulation forms trilaminar disc
-formation of primitive streak/node -establishment of body axes -epithelial to mesenchymal transition -formation of 3 germ layers -formation of notochord -beginnings of neuraltion -migration of mesoderm -growth of embryo |
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neurulation
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-process by which the brain/spinal cord form
-begins in week III; ends in week IV |
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Process of neurulation
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-ectoderm layer outside of the notochord thickens and forms the neural groove/neural folds
-neural folds eventually come together to form neural tube with a neural canal inside -by about D22/23 the neural tube as completely formed with two open ends: cranial neuropore and caudal neuropore -this is the precursor to the brain and spinal |
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neural crest cells
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-cells that form during the folding/formation of the neural tube
-give rise to dorsal root ganglia/primary sensory neurons -also migrate and insert other places to form different structures |
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Problems resulting from improper neural tube formation
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-abnormal closure of neural folds can lead to congenital abnormalities
-meronenchephaly/anencephlay: partial/nearly complete absence of brain when the anterior neural tube does not completely close -spina bifida cystica results when posterior neuropore does not properly close |
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embryonic folding
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-occurs in a cranial/caudal direction and a lateral direction
-head fold occurs to bring forebrain to most cranial position and form foregut -tail fold occurs to form hindgut -midgut is between -lateral folding helps close off gut/separate from yolk sac |
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Purpose of embryonic folding
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-move cells/layers structure to the correct 3D anatomical locations
-after folding, embryo is a comma-shaped, ectoderm-covered tbue containing an endoderm lined gut tube |
