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Anatomy L2 Embryo 1
Embro
| Question | Answer |
|---|---|
| What is fertilization | sperm entering Secondary Oocyte to form zygote |
| Where does normal fertilization occur | Ampulla of fallopian tube |
| What are the genetic consequences of fertilization | Restoration of diploid number of chromosome; Determination of genetic sex of embryo; initation of cleavage |
| What has to occur before can penetrate the ovum | Capacitation |
| What is capacitation | A series of functional changes that cause sperm's tail to beat faster and the release of cholesterol, glycoproteins and proteins from the head. |
| What causes capicitation | The release of secretion from the female urinary tract |
| What two layers must the sperm penetrate in order for fertilization to occur | Corona radiata and zona pelucida |
| T/F? Only the head of sperm enters the ovum | False: Only genetic material from the head and the tail enter the ovum |
| What happens when the sperm enters the oocyte | Head forms the male pronucleus, tail degenerates; fuses with female pronucleus |
| How does sperm penetrate the corona radiata | The acrosomal releases of enzymes and fast sperm tail movements. |
| What is the sperm receptor on the ZP | ZP3 |
| What is the fast block to polyspermy | Depolarization of the oocyte |
| What is the slow block to polyspermy | Depolarization causes the release of intracellular calcium. The release of calcium stimulate exocytosis of molecules which inactivate ZP3 and harden the ZP |
| What is a Morula | Morula: a solid ball of cells/blastomeres consisting of 32 cells |
| What two structures fuse to form the zygote | The male and female pronuclei |
| What structure surrounds the Morula | Zona Pellucida |
| Name the three layers of the uterus | Perimetrium (external lining); Myometrium (middle layer, thick wall of muscle); Endometrium (inner most lining; layer lost during menstration) |
| What is cleavage | Rapid mitotic division of zygote into blastomeres (small cells) |
| When and How is the morula transformed into the blastocyst | On 5th day - morula moves thru fallopian tube into uterine cavity (UC); secretions from UC pass thru zona pellucida and collect b/w blastomeres, reorganizes them around fluid-filled cavity (blastocyst cavity). Hollow fluid-filled mass = blastocyst |
| What is the main event that occurs in week 1 | Implantation |
| How are the cells rearragned during the formation of the blastocyst | into 2 diff cell types: inner cell mass AKA embryoblast and Trophoblast (outer superficial layer of cells that form wall of blastcyst |
| T/F? Zona pellucida is not present around the blastocyst. | Trick question! T & F. ZP is present when blastocyst is formed (Early blastocyst); after it degenerates mass is called Later blastocyst. |
| T/F? Implantation cannot occur if zona pellucida is present. | True. Shedding of zona pellucida is necessary for implantation |
| Where is the normal site of implantation | Posterior wall of body of uterus, close to the fundus (in endometrium) |
| How does the blastocyst orient itself when it attaches to the endometrium | Inner cell mass is adjacent to the endometrium; faces the endometrium |
| What is the endometrium called after implantation | Decidua |
| Describe the differentiation of the trophoblast | upon loose attachment of blastocyst to endometrium, trophoblast divides into Cytotrophoblast (inner layer of well defined cells, located b/c icm & syncytiotrophoblast) and syncytiotrophoblast (multinucleated cell mass, no distinct cell boundaries) |
| Describe the process of implantation | Syncytiotrophob. (SCT) secretes proteolytic enzymes th erode endomet., allowing blastocyst to enter. Endomet. becs. vascularized & glands enlarge. SCT secretes hCG to maintain corpus lut. (produces progesterone & estrogen to maintain uterine lining) |
| Describe ectopic pregnancy and its different forms | Implantation at abnormal sites: Abdominal cavity, various parts of fallopian tube, uterine cervix, the ovaries |
| What are possible cause of ectopic pregnancy | scarring in fallopian tube (prevents zygote from traveling out of tube); STDs; Nicotine (paralyzes cilia in uterine lining); Pelvic inflammatory disease due to previous surgery |
| How are ectopic pregnancies treated | Terminate pregnancy, surgery to remove zygote; surgery to remove tube is they've ruptured (lining in tubes too thin to support growth) |
| Name the 3 ways pregnancy can we detected and their time frame of effectiveness. | detection of Early pregnancy factor (immunosuppressant protein in maternal serum) 24 to 48 hrs; Assay of hCG in maternal urine (end of 2nd week); Ultrasound to confirm heartbeat (end of 5th week). |
| What the signs of an ectopic pregnancy | Missed period w/ abdominal pain and hCG levels lower than expected |
| What is the penetration defect and how is it fixed | PD is the hole in the endometrium due to its erosion by secretions of syncytiotrophoblast to allow implantation. Closed by fibrin coagulum to complete implantation |
| During what time frame does implantation begin and end | Starts 5th/6th day and completed 10 -12 day after fertilization |
| Describe the differentiation of the inner cell mass (ICM) and when it occurs and how it is oriented | ~8th day, 2nd week: ICM differentiates into bilaminar embryonic disc (hyboblast/primitive endoderm & epiblast/primitive ectoderm). Hypo is located @ bottom-side of embroyoblast, facing blastocyst cavity; Epi cells are over Hypo, facing SCT |
| What is the handy Mnemonic used to remember the orientation of Hypoblast and Epiblast | HypO = yOlk side (yolk sac); EPi = AMNi side (amnion) |
| How is the amnion formed and when | During 2nd week, a small cavity (amniotic cavity) appears b/w epiblast and trophoblast, cells from epiblast migrate and line the inner wall of trophoblast to surround the amniotic cavity, enclosure around amniotic cavity is the amnion |
| What is the function of the amniotic cavity | provide nutrition to cells and acts as shock-absorber |
| How is the yolk sac formed and when | During 2nd week, a layer of cells from the hypoblast migrate and line the trophoblast to enclose a cavity. Enclosure called Yolk sac, cavity called exocoelomic cavity. |
| What is the exocoelomic membrane | Layer of cells that line the yolk sac. Originated from epiblast |
| What structure is formed after formation of the yolk sac? How | Extraembryonic mesoderm (EEM): cells from yolk sac migrate outward to surround the yolk sac and amnion; cytotrophoblast forms its outer border. |
| Describe the formation of the extraembryonic coelom (EEC)/choronic cavity | Clefts appear in the extraembryonic mesoderm fuse together to form extraembryonic coelom/chorionic cavity |
| Describe the function of the chorionic cavity | Splits the EEM into somatic & splanchnic layers. |
| Where are somatopleuric and splanchnopleuric layers located in relation to yolk and amnion | Splnchnpleur layer cvrs yolk sac & bcoms meets somatpleuric layer @ bilam disc. Somatpleur layr lines outer surf. of amnion (begnng @ bilam disc) & inr side of cytotrophoblast. EEC dosn't extnd 2 amnion side of embryoblast; it doesn't go all wy around |
| What is the chorion | the syncytiotrophoblast + cytotrophoblast + somatopleuric layer |
| During week 2, Where will the future connecting stalk located? Connects bilaminar disc to the trophoblast. Future umbilical cord. | the syncytiotrophoblast + cytotrophoblast + somatopleuric layer |
| What does the epiblast and hypoblast constitute | the bilaminar disc |
| What are lacunae and where do they develop | Lacunae are channels that develop in the synctiotrophoblast. They form lacunar networks for cirultory exchange between mother and fetus |
| What is the fluid the enters the lacunar networks | maternal blood |
| Where does the primary chorionic villus form | Between the central core of the cytotrophoblast and the synctiotrophblast |
| T/F The prechordal plate is formed from the hypoblast cells | True. |
| What does the prechordal plate define | The cranial-caudal axis |
| What does the prechordal plate define | The cranial-caudal axis |
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