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44 Cards in this Set
- Front
- Back
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Please define gastrulation
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epiblast cells near primitive streak begin to proliferate and migrate through the streak to the space between epiblast and hypoblast and form the three germ layers
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define primitive streak
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primitive streak is a midline structure on the caudal end of the epiblast layer
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what is important about the primitive streak and the axis of the embryo
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establishes the longitudinal axis of the embryo
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where is the primitive pit and node
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small depression on the superior end of the primitive streak
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where is the positioning of the primitive pit relative to the primitive node?
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the node is surronding the pit
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where will the future head of the embryo form?
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germ disc near the primitive pit
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what will form the dorsal surface of the embryo
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surface of epiblast adjacent to the midline
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When are left/right, ventral/dorsal axes of the body established?
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early in the third week
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When does the primitive streak appear?
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day 16
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What is the notochord?
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1)mesoderm cells migrate cranially to form notochord process
2) notochord process hollows out to form the notochord |
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What does the notochord differentiate to form?
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axial skeleton
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What are the somites?
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somitomeres 7+
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what do the somites give rise to?
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axial skeleton and voluntary muscles of neck, body wall, limbs
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what is the neural tube?
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surface ectoderm has nueral folds around neural groove
they fuse to form a tube called the neural tube |
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what does neurulation form?
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neural tube
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What tissue is derived from the ectoderm? (mnuemonic)
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5 EPI
GAP GURT |
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What is the tissue derived from the ectoderm?
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Epithelium for the following five categories:
G- GI and associated glands Anterior Pituitary Urinary system -bladder/ureter R- Respiratory passages T - Tonsils, thyroid, parathyroid, tympanic cavity, thymus |
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What is the tissue derived from the mesoderm? mneumonic
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DUCCCS
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What is the tissue derived from the meso derm?
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Dermis of skin
U - Urogenital system C - Cardio vascular cell system C- Connective tissue and vessels associated with organs C - Cells of lymphatic system, spleen, adrenal cortex S - Skeletal, straited and smooth muscle coats |
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What is the tissue derived from ectoderm (mneumonic)?
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RENS PP
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What is the tissue derived from the ectoderm?
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R - Retina and lens of eye
E - Epidermis NS - Central and peripheral NS P - Pupillary muscle of iris P - Pineal body, nerve cells, adrenal medulla, melanocytes, odontoblasts |
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What are the common malformations arising a result of disrupted gastrulation
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-Sirenomelia
-Spina bifida -Sarcococcygeal teratoma |
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What is sarcococcygeal teratoma and what causes it?
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remnants of primitive streak persist
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What is the cause of spina bifida?
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defects of neural tube closure so vertebral arches remain underdeveloped and fail to close
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what is the cause of sirenomelia?
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fusion of lower extremity limb buds during development leading to "mermaidlike" appearance of fetus
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What is the time course of neurulation?
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starts in 4th week
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What is the difference between primary neurulation and secondary neurulation?
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1 ° neural plate comes together to form the neural tube
2 &# 176; solid tube hollows out to form hollow tube |
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What cell type/tissue derivatives forms from the neural crest cells?
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cranial neural crest - diverse structures of head and neck
-spinal nueral crest cells - major components of central peripheral ns |
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What are the common malformations of neural tube closure?
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spina bifida occulta
spina bifida with meningocele spina bifida with meningomyelocele |
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What is spina bifida occulta
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unfused vertebral arch and tuft of hair
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what is spina bifida with meningocele
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subarachnoid space and cerebrospinal fluid pushes out back muscles
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what is spina bifida with meningomyelocele
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spinal cord is displaced there is essentially no vertebral arch
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What are the three functions of gastrulation?
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1) bringing cell populations close together so they can induce each other
2) establishing the axis of the body 3) forming 3 germ layers from 2 |
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what is the definitive endoderm made up of?
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former epiblast cells (it kicked out the hypoblast cells)
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what forms the mesoderm?
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epiblast cells that got between the new endoderm and the epiblast
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What are the steps of gastrulation (general)
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1) go through the primitive streak and make the endoderm, meso derm and ectoderm
2)form the notochord 3) three types of mesoderm form around the notochord 4) the paraaxial mesoderm forms the somites 5) somites differentiate into body tissues etc |
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What are the general steps of neurulation?
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1) neural plate forms
2)nueral plate begins to crease along neural groove 3) two nueral folds form 4)they fold and pinch away from ectoderm forming the neural tube 5) cranial neuropore closes and cranial neuropore closes |
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what does the paraaxial mesoderm form? (3)
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axial skeleton
voluntary muscles part of dermis |
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What does the intermediate mesoderm form?
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urinary system
portion of genital system |
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What does lateral plate mesoderm form?
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epithelial covering of viscera
parts of limb most of dermis inner lining of body wall |
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what are the two subdivisions of the lateral plate mesoderm?
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somatoplueric mesoderm
splanchonoplueric mesoderm |
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which way does the neural tube zip up?
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cranially
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What is going on with the embryo during the third week? (3)
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1) Gastrulation - formation of trilaminar disk
2) Initial Development of Somites 3) Initial development of neural tube |
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What is going on during the fourth week of embryogenesis?
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Differentiation of somites and nervous system
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