embrology of neuroanatomy

8/9/2019 Embrology of Neuroanatomy

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Neural Plate

Thickened Ectoderm

(+ )Rapid proliferation & stratification

Leads to Neural Groove formation

Primitive streak

Neural tube

Neural crest


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Cranio caudal fusion of Neural Folds

Anterior Neuropore

Posterior Neuropore


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Neural tube is completed by

24th day: Anterior neuropore

26th day: Posterior neuropore

The Cephalic end becomes enlargedindicating the formation of the PrimaryBrain vesicles

The Caudal end forms the Spinal cor

Vascular system now formed


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3 Primary bulges: Procencephalon

Mesencephalon

Rhombencephalon

Secondary Bulges: Optic vesicles

Cephalic flexure

Cervical flexure

Cavities


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Division of forebrain

Posterior: Diencephalon and diocele

Anterior: Telencephalon

-Telencephalic vesicles

(lateral teloceles)

-Median telocele

- Mesocele


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Differentiation of the Hindbrain

Metencephalon and metacele

Myelencephalon and myocele


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Differentiation of the Telencephalon

2 Olfactory lobes (Rhinencephalon)

Pontine flexure


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Smooth Telencephalon has overgrown

the diencephalon

Spinal cord extended to the coccygealtip of the vertebral column

Formed foramens of the ventricular

system


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Diffferentiation of the Telencephalon

- 2 hemispheres

- 3 parts of each hemisphere

Rhinencephalon

Basal / Striatal

Suprastriatal


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Rhinencephalon (Limbic lobe)

- Hippocampus ( Archipallium)- olfactory bulbs

- Bilateral Piriform lobes

- Septum Pellucidum

- Fornix

- Stria terminalis

- Amygdaloid body

- Olfactory gyri

- Parahippocampal gyrus

- Cingulate gyrus


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Striatal Area

- Corpus Striatum- Thalamus


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Suprastriatal Region

- Convoluted cerebral cortex

1.5 to 4mm thick

2,300 cm3

Differentiation of ventricular system with the choroid ..


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Thinned lateral margin of the Neural

plate

Neural Crest Cells


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Neural Crest cells of Occipital and

Spinal areas give rise to:

1. Primary sensory neurons in the

Dorsal root Ganglia 2. Sensory Neurons of Cranial nerves

( V, VII, VIII, IX, X )

3. All sensory cells and fibers of PNS 4. Most Peripheral Cells of ANS


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5. Neurolemmal sheath of allperipheral nerves

6. Capsule cells of the ganglia

7. Sympathetic ganglia 8. Chromaffin Cells of Adrenal gland

9. Pigment cells


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Neural Crest of the Cephalic Neural

Tube give rise to

xMany Diverse structures of the

Head and Neck


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Modern Concept

Neuroepithelial cells

a. Neuroblasts

Mantle Layer

Marginal layer

b. Glioblasts

Glial cells


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MargMan

Ger


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Neuroblasts

- Primitive nerve cell

- Once formed, they lose their abilityto divide

- APOLAR

BIPOLARMUTIPOLAR


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Glioblasts

- Primitive supporting cells

- formed after Neuroblast

production has ceased- Transforms into

a. Ependymal cells

b. Astrocytesc. Oligodendrocytes


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Arise from mesoderm

Appear once blood vessels are present

Derived from blood histiocytes

Phagocytic functions


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The Mantle

2 thickenings:

a. Anterior-----Basal Platesforms the Anterior Gray Horn

b. Posterior--- Alar Plates

forms the Posterior Gray Horn


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Efferent Peripheral neurons arise from

Neuroblasts of the Basal plates

Alar Plate axons remain within the CNS


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The Marginal layer

Contains ascending and descending axons

( white matter )


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Mesoderm forms the bones and

cartilages around cord

Until the beginning of the 3rd month

spinal cord extends the entire length

of the vertebral canal


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At birth

Conus Medullaris: level of L3

Adult

Conus Medullaris: between L1-L2

Spinal cord occupies the upper 2/3

of vertebral canal


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Anterior Neuropore

Posterior neuropore

Neural crest cells Neural tube


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3rd week post fertilization

Anterior neuropore closes

3 Vesicles/ Dilatations appear at thecephalic end

Prosencephalon - forebrain

Mesencephalon - midbrainRhombencephalon- hindbrain


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Brain Flexures

1- Cervical FlexureBetween Rhombencephalon andspinal cord

2- Cephalic Flexure

Between Mesencephalon andRhombenceephalon

3- Pontine flexure

Between Metencephalon andMyelencephalon


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Week 4


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Week 5


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Brainstem

- consist of the Mesencephalon

Metencephalon

Myelencephalon

- also with Basal and Alar plates

- Cerebellum forms from the

dorsomedial rhombencephalic alarplate over the roof of the 4th ventricle


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V

entr

icu

lar

system

Telencephalon- contains the

primitive lateral ventricles

Diencephalon- 3rd ventricle

Mesencephalon- Cerebral aqueduct

Rhombencephalon 4th ventricle


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Cranial Nerves

Appear in the 4th-5th wks

Motor nuclei

- basal columns

- ventromedial

Sensory nuclei

- alar columns- Dorsolateral


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Telencephalon

Diencephalon


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Diencephalon

4th wk: pituitary gland( anterior lobe)formation

5th wk: Thalamus and hypothalamusformation (floor)

6th wk: Epithalamus formation (roof)

-- later becomes

Pineal gland

HabenulaPosterior commisure


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Optic vesicles are attached to thediencephalon at early embryonicperiod

3rd ventricle situated within

Boundaries:

caudal: Posterior commissure

Cephalic: interventricular foramen


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Telencephalon-Endbrain

-4th to 5th wk: bubble like, lateral

diverticula divided by the

Lamina terminalis

-Sulci- gyri complexes form at the4th month

- expands caudally to coverdiencephalon


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Contain the lateral ventricles and

Interventricular foramen of Monro Hippocampal formation ( archipallium)

Striatal Portion-Corpus striatum formation

- thickened basal portion

Supras

tria

tal po

rtion

- primordium of the cerebral cortex


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Supratriatal portion

1. Germinal/ Matrix zone

-surrounds lateral ventrcle

2. Intermediate zone

- pale; white matter

3. Cortical zone

- represents the prospectiveNeopallium

- Layers: Marginal LayerDeep Pyramidal layer


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Most primitive vesicle

Smallest, least differentiated part of

brainstem

Contains :

Cerebral aqueduct

3rd and 4th cranial nerves

Superior and inferiorColliculus

Midbrain Reticular formation


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PONS

-2 parts :

Dorsal ( pontine Tegmentum)

Ventral

- contains :

5th,6th,7th,8th CN

Solitary nuclei

Pontine reticular formation


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CEREBELLUM

from the dorsolateral portions of the

alar plates that form the rhombic lips


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Most caudal brain segment

Extends from 1st spinal nerve to

pontine flexure

Expanded by the 4th ventricle


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Contains:

Motor nuclei of CN 9th,10th, 11th, 12th

Sensory nuclei of 5th and 8th CNNuclei Gracilis and Cuneatus

Inferior Olivary complex

Foramina of LuschkaForamen of Magendie


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Fibers connecting the cerebral

hemispheres

Anterior commissureconnects the olfactory and bulb and

parts of the temporal lobe with the

opposite side


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Commissure of the Fornix

connects the hippocampal formation

with each other

Corpus Callosum

largest, most importantconnects nonolfactory cortical areas

Subdivisions of the brain


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Neural tube

(2 weeks)

3 primary vesicles

(4 weeks)

5 secondary vesicles

(5 weeks)Mature structures

Prosencephalon

(forebrain)

Telencephalon

Cerebral cortex

Caudate nucleus

Putamen

Amygdala

Diencephalon

Thalamus

Hypothalamus

Epithalamus

Subthalamus

Retina

Mesencephalon

(midbrain)

Tectum

Tegmentum

Cerebral peduncles

Rhombencephalon

(hindbrain)

MetencephalonPons

Cerebellum

Myelencephalon Medulla

Spinal cord


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Neuronal migration defect


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Organization of

dendrites and axon


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Monday

Neural tube formation

Neural Crest

Histogenesis of the Neural Tube

Neurons

Glial Cells

Spinal Cord


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Friday

Brain

Myelencephalon

Metencephalon

Mesencephalon

Diencephalon

Telencephalon

embrology of neuroanatomy

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