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Describe the process of neurulation.
Cells invaginate through primitive pit and migrate towards buccopharyngeal membrane.
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What do notochrodal cell migrating forward forming a shild shape overlying structure give rise do?
Neurectoderm
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What does neuroectoderm give rise to?
CNS and retina
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How does the neural tube form?
Neural folds come together in midline over neural groove and fuse. Neuropore then zips up cranially and caudally.
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What does the neuropore communicate with?
amnion cavity
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As neural folds differentiate into as they approach midline, differentiate, and detach laterally?
neural crest cells
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What does the neural crest give rise to?
- 1) Melanocytes
- 2) Cartilage of bones in head from pharyngeal arches
- 3) C cells of thyroid
- 4) Aorticopulmonary septum
- 5) Odontoblasts
- 6) Adrenal Medulla
- 7) Sensory and Motor Ganglia
- 8) Schwann Cells
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What does the mangle layer of the spinal cord form from?
Neuroepithelial cells that differentiate into neuroblasts
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What does the marginal layer of the spinal cord come from?
Neuroblasts that differentiate into neurons and processes that extend into marginal layer
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What forms the ventricular layer of the spinal cord?
Neuropithelial cells that do not differentiate
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What divides the mantle zone of the spinal cord into two latyers? What does this separate?
- Sulcus limitans (Alar and Basal plate)
- Alar = sensory
- Basao = motor
- Separates snesory and motor functions
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What layers in spinal cord are between white matter? Grey matter?
- White - Marginal layer
- Grey - Mantle layer
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What forms the wall of the thrird ventricle in the brain?
Thalamus and hypothalamus
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Describe the flow of CSF.
CSF is produces in lateral ventricle (choroid plexus) --> third ventricle --> fourth ventricle --> subarachnoid space --> reabsorbed through acahnoid villi
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What are the three primary vesicles the nerual tube dilates into?
- Forebrain (proscencesphalon)
- Midbrain (mesencephalon)
- Hindbrain (rhombencephalon)
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What does the forebrain (prosencesphalon) give rise to?
Telencephalon and Diencephalon
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What does telencephalon give rise to?
Cerebral hemispheres
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What does diencephalon give rise to?
Thalamus, hypothalamus
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What is the lateral wall of the third ventricle?
Thalamus (dienchepalon)
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What dilation gives rise to midbrain?
Mesencephalon
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What dilation gives rise to pons and cerebellum?
Metenchephalon
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What dilation gives rise to medulla?
Myelenchephalon
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What is the arrangement of the alar and basal plate in the floor of the 4th ventricle ?
- Alar is lateral to basal
- (Remember - alar is sensory and basal is motor)
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What does neurectoderm give rise to?
- 1) CNS, retina, CN II
- 2) Neurohypophysis
- 3) Astrocytes, Oligodendrocytes
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What does the musculoskeletal system derive from mainly?
Mesoderm
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What does proliferation of mesoderm near the notochord produce?
- Paraxial mesoderm.
- The remaining mesoderm is called lateral plate.
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What is between lateral plate and paraxial mesoderm?
Intermediate mesoderm
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What does paraxial mesoderm form?
somites
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What three regions does each somite have?
- Sclerotome
- Dermatome
- Myotome
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What are less well organized regions of paraxial mesoderm cranially called?
Somiteomeres
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What is a sclerotome made of?
Medial and ventral cells that migrate away and head toward notochord that becomes bone and cartilage of vertebral column.
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How many sclerotomes make up a vertebral body?
- 2
- Caudal and cranial portion of different sclerotomes fuse to form v. bodies.
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What does the remnant of the notochord form?
Nucleus pulposus in intervertebral disk
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What germ layer do the bones of the face form from?
Neural crest forms sphenoid bone, squamos portion of temporal bone, frontal, madible, etc.
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What does the rest of the cranial vault form from?
Paraxial mesoderm
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What does a dermatome form?
Dermis of skin
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What does a myotome form?
muscles of the region and retain segmental innervation
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What are some clinical signs of spina bifida?
- Tuft of hair covering lesion
- Increased AFB and AchEsterase
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What happens when the neural tube fails to close caudally?
- Spina bifida (can be spina bifida occulta - no fusion of vertebra)
- Spina bifida meningocele (with meninges protruding)
- Spina bifida meningomyelocele (with spinal cord and meninges)
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What can meningomyelocele lead to?
Arnold Chiaria malformation
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What is Rachiscisis?
failure of spinal cord to form
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What happens when the neuropore fails to close cranially?
anencephaly
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What causes clinical presentation of anencephaly?
- Exposes brain to amniotic fluid which destroys brain
- Increased amnion fluid
- Increased AFB
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What vies rise to the intrinsic muscles of the back?
Epimere
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What does hypomere give rise to?
muscle with thoracic, lateral and medial abdominal wall (muscles of trunk), some of hypomere forms limb muscles
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What vies rise to limb bones?
Parietal mesoderm
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What sends messages into underlying mesenchyme for limb differentiation?
Ectodermal ridge
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What are the first bones of the limb to develop?
Forearm, then hands, them humerus
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Where did parietal mesoderm come from?
lateral plate mesoderm
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What forms the digits of the hand? What does a failure of this process cause?
- Apoptosis (programmed cell death)
- Syndactyly
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What is it called when there is a complete abscence of limbs? Partial?
- Complete - amelia
- Partial - melomelia
- (thalidomide caused this)
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What does parietal lateral plate mesoderm give rise to?
serous lining of peritoneal, pericardial, and pleural membranes
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What does visceral lateral plate mesoderm give rise to?
cardiac and smooth muscle
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Describe the formation of the skeletal system.
- Skeletal system is ALL from mesoderm
- Sclerotome, Somite = bones of axial skeleton, cranial vault
- Somatic layer of lateral plate mesoderm = bones of shoulder, pelvic girdle, and limbs
- Neural crest = bones of face
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* The posterior neuropore provides a communication between what two spaces?
The developing neural tube and the amnion
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* Cells of the adrenal medulla are derived from what?
neural crest cells
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* The vertebrae are derived from segmental _______.
sclerotomes
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* What part of the brain's ventricular system is derived from the diencephalon?
third ventricle
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* The membrane lining the abdominal cavity is derived from what division of mesoderm?
lateral plate
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* The sulcus limitans divides the developing central nervous system into what two major functional area?
sensory and motor
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