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17 Cards in this Set
- Front
- Back
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When does gastrulation begin?
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7th day
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What is the main aim of gastrulation?
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Converts the bilayered blastula composed of epiblast (ectoderm) and hypoblast (endoderm) into an embryo with 3 layers of ectoderm, endoderm and mesoderm
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What does it bring into contact?
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Previously separated cell types allowing inductive signals for differentiation and determination (body axes)
Establishes the rudimentary body plan |
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What determines the type of cell it differentiates into?
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the proteins it synthesises
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The synthesis of functional proteins is regulated. What are the regulation steps? (5)
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1. Transcriptional control (Regulatory and response)
2. Processing (RNA can be capped/ splice out intron) 3. Transport (dependent on extent of processing) 4. Translation (tRNA synthetases/ initiation and elongation factors)/ antisense RNA 5. Modification (protein folding- methonine removal, disulphide bonds, glycosylation, protease activities) |
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How is differentiation maintained?
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Cells retain a memory of previous developmental decisions
Transcription factors influence gene expression- regulation of transcription factor activity maintains the expression of a particular set of genes |
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How do transcription factors influence gene expression?
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1. Interacting at promotor region with initiation factors
2. Binding to DNA/ chromatin and altering structure 3. Affecting activity of 2nd transcription factor |
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Name 2 types of modification of gene expression
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Chromatin structure (euchromatin or heterochromatin)
DNA methylation (of cytosine residues) |
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Other than transcription factors, how else is differentiation maintained?
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Inherited cytoplasmic determinants
External signals (Growth factors) |
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What is the first sign of gastrulation?
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Formation of the primitive streak
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What is gastrulation facilitated by?
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Cell - cell recognition
Cell signaling Cellular migration Selective adhesion |
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Describe the movement of cells at the primitive streak
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Movement of surface cells towards the primitive streak and node results in migration of cells between the hypoblast and the epiblast
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How is the mesoderm created?
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By invagination and lateral migration of the epiblast along a spatio- temporal axis
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How long is the lifespan of the notochord?
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Short, often breaks down before completion
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Name the ectodermal derivatives
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CNS
Retina Pineal body Posterior pituitary gland Cranial sensory ganglia and nerves Medulla of adrenal glands Melanocytes Epidermis Hair Nails Cutaneous and mammary glands Anterior pituitary gland Enamel of the teeth Inner ear Lens |
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Name the mesodermal derivatives
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Cranium
CT of head Dentine Muscles of head Dermis of skin CT Urogenital system and accessory glands CT and muscle of viscera Serous membranes of pleura Pericardium and peritoneum Adrenal cortex Primordial heart, blood and lymphatic cells |
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What are the endodermal derivatives?
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Epithelial parts pf trachea/ bronchi/ lungs
Epithelium of GIT/ liver/ pancreas/ urinary bladder Epithelial parts of the pharynx/ thyroid/ tympanic cavity/ tonsils/ parathyroid gland |
