Exam #1: Development--Self Study Flashcards Preview

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Flashcards in Exam #1: Development--Self Study Deck (33):

What is neurulation?

Process by which the trilaminar embryo internalizes its developing nervous system (ectoderm)


Describe the process of neurulation.

Gastrulation= formation of the trilaminar disc

1) Mesoderm forms the notochord
2) Notochord induces the overlying ectoderm to proliferate & become the neural plate
3) Induction causes the neural plate to fold & become a central neural groove/ lateral & raised neural folds
4) Neural folds approximate & fuse, forming the neural tube


What is the embryological defect that causes spina bifida?

Incomplete fusion of the neural tube (opening into the ectoderm)


What are the three sources of nervous tissue in the body?

1) Neural tube
2) Neural crest cells
3) Ectodermal placodes


What tissue & cell types are derived from the neural tube?

Somatic motoneurons
Preganglionic ANS neurons


Where do most neural crest cell migrate?

Pharyngeal arches of the developing head & neck


What tissue & cell types are derived from ectodermal placodes?

Lens of the eye
Inner ear
Pituitary gland
Some somatic sensory ganglia of cranial nerves


What are neural crest cells?

- A narrow strip of cells at either edge of the neural plate
- Do NOT fuse with the neural tube; instead, lie ontop of it forming "neural crest"


What are the derivatives of neural crest cells? Specifically, what are the neural crest derivates of the head/ neck & body?

Head & Neck
- Bones, cartilage, & muscles in the head / neck
- Neurons of sensory ganglia in CN: V, VII, VIII, IX, X
- Odontoblasts
- Parafollicular cells of the thyroid gland
- Cells of aortic & carotid bodies
- PNS ganglia of CN

- Ganglia (ANS & DRG)
- Schwann cells
- Adrenal medulla
- Melanocytes)


During early development, what are the three divisions of the neural tube?

1) Prosencephalon (forebrain)
2) Mesencephalon (midbrain & cerebral aqueduct of Sylvius)
3) Rhombencephalon (hindbrain)


When in gestation are the three major division of the neural tube further divided?

Week 5


Which of the three major divisions further divide?



What does the prosencephalon divide into?

Telencephalon-->cerebral hemispheres & lateral ventricles
Diencephalon-->thalami & 3rd ventricle


What does the Rhombencephalon divide into?

Metencephalon= pons & cerebellum/ upper 4th ventricle
Mylencephalon= medulla oblongata/ lower 4th ventricle


What are the three flexures in the brain?

1) Cephalic flexure
2) Cervical flexure
3) Pontine flexure


What is the Cephalic Flexure?

Bend in the region of the mesencephalon


What is the Cervical Flexure?

Bend between the Rhombencephalon & future spinal cord


What is the Pontine Flexure?

Bend in the Rhombencephalon that forms the two distinct:
- Metencephalon (pons & cerebellum)
- Myelencephalon (medulla oblongata)


What are CNS neurons & neuroglia derived from?

Neuroepithelium of the neural tube


What is the neuroepithelium?

Cells of the neural tube that form three distinct layers:
1) Ventricular
2) Intermediate/ Mantle
3) Marginal


Describe the formation of neurons in the CNS.

During weeks 4-20:
1) G1 ventricular
2) Migration to marginal & S-phase
3) Return to ventricular G2
4) Mitosis in ventricular
5) Migration to mantle & differentiation into neurons
6) Axon growth into the marginal layer

*****Migratory neurons that establish synaptic contacts remain; those that don't undergo apoptosis


Describe the formation of neuroglia in the CNS.

Following the same general process as neuroblasts, glioblasts migrate into the marginal layer


How do the three zones of the neural tube translate into the mature spinal cord?

Ventricular= ependymal cells that line the ventricles
Mantle= gray matter
Marginal= white matter


How do microglia differ from other glial cells in the CNS?

Derived from bone marrow i.e. hematopoietic stem cells that migrate to the CNS; these are the macrophages of the CNS


How does the development of the PNS differ from the CNS?

All PNS cells are derived from neural crest cells i.e. neurons & neuroglia of the PNS are neural crest in origin


How do the meninges differ in their development?

Pia & arachnoid mater= neural crest
Dura= mesoderm


Describe the process of myelination. Specifically address: start & end/ cell types.

- Myelination begins at 16 weeks gestation
- Ends 3 years, except frontal lobes that continue till 20s
- CNS= oligodendrocytes
- PNS= Schwann cells


What is Spina Bifida Occulta?

- Incomplete closure of the neural tube in 1st month of gestation
- Overlying bone (L5/ S1) will have subtle defects
- Mildest form that is typically asymptomatic--maybe tuft of hair on skin in lumbar region


What is Spina Bifida Cystica?

- Incomplete closure of the neural tube in 1st month of gestation
- Herniate of nervous tissue through the bony defect causes a visible cyst-like structure in the individuals back i.e. "cystica"
- Two subtypes:
1) Meningocele
2) Meningomyelocele


What is Spina Bifida Meningocele?

- Herniation of meninges through body defect
- Spinal cord intact in spinal canal


What is Spina Bifida Meningomyelocele?

Herniation of meninges & spinal cord through defect


What is Spina Bifida Myeloschisis?

This is the most severe form of Spina Bifida that involves an externally open & flattened spinal cord


What supplement in early pregnancy can reduce the risk of Spina Bifida?

Folic acid