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WEEK 4:
Embryology 3:
| Question | Answer |
|---|---|
| what forms the notochord | cells from rostral end of primitive streak |
| the notochord induces what | induces overlying ectoderm to form the neuroectoderm of the neural plate |
| what does the neural plate form | neural folds- which eventually fuse to form the neural tube |
| the neural tube is formed from | neural folds fusing |
| the neural tube will become what (2) | brain and spinal cord |
| NT loses contact with what | overlying ectoderm |
| neural crest is made of what | neural crest cells |
| intraembryonic coelom | space between the somatic and splanchnic mesoderm- primitive body cavity forming inside embryo which becomes pericardial cavity, pleural cavities and peritoneal cavity later on |
| where does the extraembryonic coelom form | in lateral plate mesoderm |
| lateral plate mesoderm splits into what layers (2) | somatic (parietal) mesoderm and splanchnic (visceral) mesoderm |
| somatic mesoderm + endoderm form in later development | body wall |
| splanchnic mesoderm + ectoderm form in later development | gut wall |
| clinical importance of the intraembryonic coelom | is the space between the somatic and splanchnic mesoderm which allows organs to move smoothly, expand and be separated within the body |
| lateral plate mesoderm comes from | intraembryonic mesoderm |
| the intraembryonic mesoderm form which 3 longitudinal column | lateral plate mesoderm, paraxial mesoderm, and intermediate mesoderm |
| paraxial mesoderm forms | somites, muscles, vertebrae, and dermis |
| intermediate mesoderm forms | urinary and reproductive systems |
| lateral plate mesoderm forms | body wall, heart/ blood vessels, serous membranes, and contributes to limbs |
| prochordal plate will form | future mouth/ oral region |
| clocal plate will form | future anus |
| neural plate will form | brain and spinal cord |
| primitive streak | appears on surface of epiblast during gastrulation causing epiblast cells to move inward and migrate through the primitive streak forming endoderm and mesoderm and remaining epiblast become ectoderm |
| flow of what happens to cells from primitive streak | epiblast -> primitive streak -> form notochord -> signals above ectoderm to become neural plate -> folds -> neural folds -> folds fuse together -> neural tube -> brain + spinal cord |
| epiblasts moving through the primitive streak to replace hypoblast layer become | endoderm |
| epiblasts moving through the primitive streak between layers become | mesoderm |
| remaining epiblasts moving through the primitive streak become | ectoderm |
| prechordal plate/ prochordal | made of endoderm and mesodermal cells when epiblasts move through primitive streak -> these move cranially (in front) of the notocord |
| what is the shape of the intraembryonic coelom | horseshoe shape |
| over a limited area, the intraembryonic coelom becomes continuous with | extraembryonic coelom |
| intraembryonic coelom will eventually form (3) | pericardial cavity, pleural cavity, and peritoneal cavity |
| lateral plate is continuous with what | extra embryonic mesoderm |
| what happens at the beginning of the 4th week | paraxial mesoderm begins to form paired cuboidal bodies (somites) |
| when does the paraxial mesoderm begin to form paired cuboidal bodies (somites) | 4th week |
| at the 4th week, paraxial mesoderm begins to form | paired cuboidal bodies (somites) |
| the medial part of the somite becomes | sclerotome (skeleton) |
| sclerotome = | skeleton |
| intermediate part of the somite becomes | myotome (muscle) |
| myotome = | muscle |
| lateral part of the somite becomes | dermatome (skin) |
| dermatome = | skin |
| intermediate mesoderm becomes | nephrotome -> forming the genitourinary system |
| lateral mesoderm becomes | parietal (body wall) or visceral (gut wall) |
| in the fourth week, somites form in a | cranio-caudal sequence |
| when somites form in a cranio-caudal sequence in the fourth week, this results in | 3 occipital 8 cervical 12 thoracic 5 lumbar 5 sacral 1-5 coccygeal |
| occipital -> | tongue musculature |
| each somite receives a segmental spinal nerve which follows what | follows that tissue wherever it migrates |
| somatopleuric/ somatic mesoderm is continuous with | mesoderm of amniotic cavity which will form striated (voluntary) muscle |
| splanchnopleuric mesoderm is continuous with | mesoderm of yolk sac which will form the smooth muscle of the gut |
| folding of the embryo occurs in which two directions simultaneously | median and horizontal planes |
| longitudinal folding structures | prospective heart and diaphragm lie in front of the prospective mouth and the prospective brains lies behind it |
| what causes folding cranio-caudally and cranio-laterally | differential growth of embryo |
| differential growth of embryo causes | folding cranio-caudally and cranio-laterally |
| longitudinal folding is describes as | 'reversal' folding |
| what is important in producing reversal folding in longitudinal folding | rapid growth of neural tube |
| after reversal, the amnion is only attached to | embryo over a small region (umbilicus) |
| constriction is produced where during completion of longitudinal folding | junction of the embryo and yolk sac (where part of yolk sac has become incorporated into the gut tube) |
| lateral folding is basically produced by | rapidly growing spinal cord and somites |
| during lateral folding, edges of the amnion grow where | downwards towards yolk sac |
Created by:
kablooey
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