9/18 Neurulation - Dennis (Completed) Flashcards
What happens during week 1? 4
Blastocyst begins to implant in uterus
What happens by week 3? 4
Chorion, yoke sac, umbilical vesicle forms
Where are all three germ layers derived from?
The epiblast
Where are GI glands and glandular cells of the liver and pancreas derived from? 6
Endoderm
Where are skeletal muscles, RBCs, and lining of the BVs derived from?
Mesoderm
Where is the notochord and most of the cardiovascular system derived from? 6
Mesoderm
Where is the epidermis of the skin derived from? 6
Ectoderm
Where is the CNS/PNS, eyes, and internal ears derived from? 6
Ectoderm
Where is the dermis derived from? 6
Mesoderm
What induces neurulation? 8
The notochord
What is induction? 8
Notochord instruction growth of the rest of the neural plate (neural ectoderm) and neural crest
What is the progression into a functional neural tube? 10
Neural plate –> neural folds –> neural tube
What is the neural plate?
A region of the ectoderm that has been specified to be a part of the nervous system
Prior to neural fold formation what must happen? 10
Neural groove must be in place (think of it as a hinge point)
What is the notochord’s orientation to the neural tube? 11
Notochord is inferior/ventral to the neural tube
After the neural tube has formed what lies superior/dorsal to it? 11
Epidermis
Where are neural crest cells found? Where are they after the neural tube has been formed? 11
The dorsal edge of the neural folds
Once the neural tube has been formed the neural crest cells are released and become free floating
Where does secondary neurulation take place? What tissue are these secondary neurulation sites derived from? 12
Derived from mesenchyme
Takes place at the sacral vertebrae
How are the neural crest cells released from the neural tube? 13
Neural crest at the most dorsal aspect of the neural tube pinch off and migrate away at the very end of neural tube closure, but some leave earlier
What pharyngeal arch produces the laryngeal cartilage? 15
Arch 4
What pharyngeal arch produces malleus, incus, and meckel’s cartilage? 15
Arch 1
Which pharyngeal arch produces the stapes, styloid, and hyoid cartilage?
Arch 2
What is the defect in Micrognathia? 17
Neural crest failure to form the lower jaw
What are the meninges derived from? 19
From neural crest cells and mesenchyme
What do the primitive meninges differentiate into? 19
Ectomeninx –> becomes compact, forms spaces for future venous sinuses
Endomeninx –> becomes reticulate, subarachnoid space/cisterns appear
How does the neural tube actually close? 20
Not a uniform closure along the entire length
Closing begins at the thoracic region and spreads away from the middle in both directions
What do we call the last portions of the neural tube to close (prior to their actual closing)? 21
Neuropore
Cranial neuropore and Caudal neuropore
What may arise from lack of closure 5 (5th site)? 22
Various forms of spina bifida
What clinical manifestation may you see with lack of closure 2 (2nd site)? 22
Anencephaly
Define Anencephaly. 23
Lack of brain, not compatible with life
What are the types of Anencephaly? 23
Meroencephaly - some brain tissue
Holoencephaly - single brain structure forms
Craniorachischisis - cranial and other regions of neural tube open
What happens in spina bifida occult? 24
Unfused neural arch (two sides) of vertebrae open
What’s happening in meningocele? 24
Meninges protrude past the body wall
What’s happening in meningomyelocele?
Both spinal cord tissue and meninges prodtrudes past body wall
What’s happening in myeloschisis? 24
Failure for closure of the neural tube
What is the first fold that occurs in the developing brain? 27
The developing brain folds forward resulting in the forebrain
Folding pushes the hear and mouth more Caudal LH
What does the connecting stalk eventually become? 29
The umbilical cord
What happens in Omphalocele? 32
Bowel w/ membranous sac outside of body wall
What happens in Gastroschisis? 32
Exposed bowel protruding from body wall
What’s happening in Ectopia cordis? 32
Heart located beyond the body wall
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