FORM & FUNCTION (Neurulation, Coelomic Cavities, etc.) Flashcards
Pear-shaped gastrula:
-continues to change where the three germ layers and the associated structures undergoes various changes
>assisted by gene regulatory networks and cellular processes
Cellular processes:
-cell proliferation
-migration/movement of cells
-formation of tubes and spaces within the embryo
Ectoderm gives rise to:
-neuroectoderm
-surface ectoderm
Mesoderm transforms into:
-paraxial mesoderm
-intermediate mesoderm
-lateral plate mesoderm
Endoderm develops into:
-gut tube
-respiratory tract
Formation of the primitive streak to neurulation:
- Ectoderm proliferates to form the neural plate/neuroectoderm
- Neural plate to neural grove
- Neural grove to neural tube: gives rise to brain and spinal cord
- Induction leads to thickening of the surface ectoderm cells to form placodes
Neural tube gives rise to:
-brain
-spinal cord
Peripheral NS comes from:
-neural tubes
-neural crest cells: migrated neuroectoderm cells)
Placodes give rise to:
-nasal chambers
-lens of eye
-inner ear
-cranial nerves
-etc.
Neurulation: example of roles of genes
-dorsal ventral patterning of neural tube requires 2 primary signaling centers
1. Surface ectodermal cells
2. Notochord
Surface ectodermal cells:
-secrete bone morphogenetic protein (BMP) 4 and 7 so some ectodermal cells become roof plate of tube
Notochord:
-sonic hedgehog (Shh) signaling from notochord produces floor plate of tube
Neurulation:
-folding of the neural plate into the neural tube
-embryo at this stage=neurula
Mesoderm types:
-paraxial
-intermediate
-lateral
*all connective tissue components are mesodermal in origin
Paraxial mesoderm:
-gives rise to aggregation of cells:
>somitomeres near the neural plate (head region)
>somites in caudal region
Somitomeres:
-gives rise to structures in the head region
Somites:
-form the axial skeleton
Intermediate mesoderm:
-forms the reproductive and urinary systems
Lateral mesoderm:
-clefts: spaces that appear and fuse together and creates a cavity=intra-embryonic coelom
-forms the somatopleure (somatic mesoderm and ectodermal cells) and splanchnopleure (splanchnic mesoderm and endoderm cells)
>eventually line the space in between (later turn into body cavities): mesodermal lining=mesothelium
Mesothelium:
-simple squamous epithelial cells
-forms the serous membranes that line the body cavities (pluera, peritonium, pericardium)
Endoderm gives rise to:
-epithelium of the gut and respiratory tract and their glands
-urinary bladder
-middle ear and auditory tube
-liver
-pancreas
-thyroid and parathyroid glands
Process of formation: coelomic cavities:
-cleft develops within the right and left lateral mesoderm
-cleft later coalesce, forming a cavity that splits the lateral mesoderm into an outer layer of somatic mesoderm and an inner layer of splanchnic mesoderm
*cavities between the 2 layers of mesoderm on L and R sides are called the COELOMIC cavities
*lateral folding of coelomic cavities give rise to pericardial, pleural and peritoneal cavities
Pleural-pericardial cavity:
-first formation of pleural and pericardial cavities
-covers the embryonic/developing lungs and heart
*further development and folding of mesoderm leads to the formation of pleural and pericardial cavities (pericardial fold)
Pleural and pericardial cavities:
-both lined by mesothelium
-mediastinum
-all these structures are found within the thoracic cavity
Mediastinum:
-mesenchymal tissue that forms a septum separating the pleural cavities
Function of pleural and pericardial cavities:
-protect the lungs (pleura) and the heart (pericardium)
Diaphragm arises by the fusion of 3 embryonic structures:
-pleuroperitoneal folds
-mesothelial folds
-septum transversum (aggregation of mesoderm)
Mesodermal structures: diaphragm
-develop into the muscular structure of the diaphragm
Diaphragm:
-allows structures (ex. blood vessels, nerves) to pass through at three different sites of the diaphragm
Improper formation of diaphragm:
-cause developmental defects
Function of diaphragm:
-structural partition of the thoracic and abdominal cavities
Peritoneal cavity/peritonium:
-mesothelium lining the abdominal cavity
-intra- and retro-peritoneal
-omentum
Intra-peritoneal:
-organs enclosed by a fold of the peritoneum
Retro-peritoneal:
-organs partly covered by peritoneum
Omentum:
-fold of the peritoneum that attaches an organ to the stomach
