Neural - Hippocampus Development

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Introduction

Stage10 sem6.jpg
Adult hippocampus structure

Neural development is one of the earliest systems to begin and the last to be completed after birth. This development generates the most complex structure within the embryo and the long time period of development means in utero insult during pregnancy may have consequences to development of the nervous system.

The early central nervous system begins as a simple neural plate that folds to form a groove then tube, open initially at each end. Failure of these opening to close contributes a major class of neural abnormalities (neural tube defects).

Within the neural tube stem cells generate the 2 major classes of cells that make the majority of the nervous system : neurons and glia. Both these classes of cells differentiate into many different types generated with highly specialized functions and shapes. This section covers the establishment of neural populations, the inductive influences of surrounding tissues and the sequential generation of neurons establishing the layered structure seen in the brain and spinal cord.

  • Neural development beginnings quite early, therefore also look at notes covering Week 3- neural tube and Week 4-early nervous system.
  • Development of the neural crest and sensory systems (hearing/vision/smell) are only introduced in these notes and are covered in other notes sections.


Neural Links: ectoderm | neural | neural crest | ventricular | sensory | Stage 22 | gliogenesis | neural fetal | Medicine Lecture - Neural | Lecture - Ectoderm | Lecture - Neural Crest | Lab - Early Neural | neural abnormalities | folic acid | iodine deficiency | Fetal Alcohol Syndrome | neural postnatal | neural examination | Histology | Historic Neural | Category:Neural
Neural Parts: neural | prosencephalon | telencephalon cerebrum | amygdala | hippocampus | basal ganglia | diencephalon | epithalamus | thalamus | hypothalamus‎ | pituitary | pineal | mesencephalon | tectum | rhombencephalon | metencephalon | pons | cerebellum | myelencephalon | medulla oblongata | spinal cord | neural vascular | ventricular | lateral ventricles | third ventricle | cerebral aqueduct | fourth ventricle | central canal | meninges | Category:Ventricular System | Category:Neural

Some Recent Findings

  • Development of laminar organization of the fetal cerebrum[1] "Heads of 131 fetal specimens of 14-40 weeks gestational age (GA) were scanned by 3.0T MRI. Eleven fetal specimens of 14-27 weeks GA were scanned by 7.0T MRI. On T(1)-weighted 3.0T MRI, layers could be visualized at 14 weeks GA and appeared clearer after 18 weeks GA. On 7.0T MRI, four zones could be recognized at 14 weeks GA. During 15-22 weeks GA, when laminar organization appeared typical, seven layers including the periventricular zone and external capsule fibers could be differentiated, which corresponded to seven zones in histological stained sections. At 23-28 weeks GA, laminar organization appeared less typical, and borderlines among them appeared obscured. After 30 weeks GA, it disappeared and turned into mature-like structures. The developing lamination appeared the most distinguishable at the parieto-occipital part of brain and peripheral regions of the hippocampus. The migrating thalamocortical afferents were probably delineated as a high signal layer located at the lower, middle, and upper part of the subplate zone at 16-28 weeks GA on T(1)-weighted 3.0T MRI."

Development Overview

Neuralation begins at the trilaminar embryo with formation of the notochord and somites, both of which underly the ectoderm and do not contribute to the nervous system, but are involved with patterning its initial formation. The central portion of the ectoderm then forms the neural plate that folds to form the neural tube, that will eventually form the entire central nervous system.

Early developmental sequence: Epiblast - Ectoderm - Neural Plate - Neural groove and Neural Crest - Neural Tube and Neural Crest


Neural Tube Development
Neural Tube Primary Vesicles Secondary Vesicles Adult Structures
week 3 week 4 week 5 adult
neural plate
neural groove
neural tube

Brain
prosencephalon (forebrain) telencephalon Rhinencephalon, Amygdala, hippocampus, cerebrum (cortex), hypothalamus‎, pituitary | Basal Ganglia, lateral ventricles
diencephalon epithalamus, thalamus, Subthalamus, pineal, posterior commissure, pretectum, third ventricle
mesencephalon (midbrain) mesencephalon tectum, Cerebral peduncle, cerebral aqueduct, pons
rhombencephalon (hindbrain) metencephalon cerebellum
myelencephalon medulla oblongata, isthmus
spinal cord, pyramidal decussation, central canal

Early Brain Vesicles

Primary Vesicles

CNS primary vesicles.jpg

Secondary Vesicles

CNS secondary vesicles.jpg

Human Hippocampus Development

Neural - Human hippocampus marker expression.jpg

Human and rodent hippocampus developmental markers.[2]

Fetal

The following data (weeks gestation) is from an imaging study of the human fetal hippocampus.[3]

  • 13 to 14 weeks - unfolded hippocampus, on the medial surface of the temporal lobe, surrounds a widely open hippocampal sulcus (hippocampal fissure)
  • 15 to 16 weeks - dentate gyrus and cornu ammonis have started to infold. The hippocampal sulcus remains open. The parahippocampal gyrus is larger and more medially positioned. The CA1, CA2, and CA3 fields of the cornu ammonis are arranged linearly. The dentate gyrus has a narrow U shape.
  • 18 to 20 weeks - fetal hippocampus begins to resemble the adult hippocampus. The dentate gyrus and cornu ammonis have folded into the temporal lobe. The hippocampus and subiculum approximate each other across a narrow hippocampal sulcus. The CA1-3 fields form an arc and the CA4 field has increased in size within the widened arch of the dentate gyrus.

Childhood

The following data is from a postnatal magnetic resonance imaging study.[4]

  • 3 months - a longitudinal fasciculus of high signal intensity was seen in the white matter beneath the subiculum
  • birth to 2 years - volume increases rapidly
  • after 2 years - volume increases slowly thereafter
  • hippocampal formations on the right side were larger than those on the left in 38 cases (91%)
  • anterior temporal lobes on the right were larger than those on the left in 32 cases (76%)
  • right-left asymmetry of the hippocampal formations and anterior temporal lobes was observed from early infancy

Adult

The following data is from an magnetic resonance imaging study of adult Chinese aged 6 to 82 years.[5] Other studies have described a reduction in the hippocampal volume during ageing.

  • volume of right hippocampus was larger than that of the left side (p<0.001)
  • right side volume of hippocampus - 2.204 to 2.944 cm3
  • left side volume of hippocampus - 2.068 to 2.700 cm3
  • no statistically significant differences among different age and gender groups (p>0.05)

Neuronal Development

The following data is from a histological study of postmortem hippocampi neurons.[6]

  • Bilateral coronal sections from postmortem hippocampus, 24 to 76 weeks postmenstrual age (gestational age plus postnatal age), were studied.
  • Cell body (soma) size correlated positively and significantly with age in CA2 and CA3, bilaterally.
  • CA2 somata were significantly larger (left, 34%; right, 32%) than adjacent CA3 somata.
  • Variability in soma form or size increased appreciably with age, in both subfields, bilaterally
  • Variability in soma orientation was weakly correlated with brain growth.

Mouse Hippocampus

Mouse- hippocampus dentate granule cells.jpg

The developmental changes of GFP+ newborn mouse dentate granule cells.[7]


Brain histology 02.jpg

References

  1. <pubmed>20981415</pubmed>
  2. <pubmed>20126454</pubmed>| PLoS One.
  3. <pubmed>9090416</pubmed>
  4. <pubmed>10319988</pubmed>
  5. <pubmed>17601367</pubmed>
  6. <pubmed>9892421</pubmed>
  7. <pubmed>20824075</pubmed>| PLoS One.

Reviews

<pubmed>19206138</pubmed> <pubmed>19427519</pubmed> <pubmed>19021538</pubmed> <pubmed>17148945</pubmed> <pubmed>10675917</pubmed> <pubmed>9100228</pubmed>

Articles

<pubmed>15597062</pubmed> <pubmed>2748838</pubmed> <pubmed>8413958</pubmed>

Search PubMed

November 2010 search "Hippocampus Embryology" - All (3051) Review (208) Free Full Text (739)

Search Pubmed: Hippocampus Embryology | Hippocampus Development | Limbic Development


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Cite this page: Hill, M.A. (2024, March 28) Embryology Neural - Hippocampus Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_-_Hippocampus_Development

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G