Neural - Hippocampus Development: Difference between revisions
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The following data is from an magnetic resonance imaging study of adult Chinese aged 6 to 82 years.<ref><pubmed>17601367</pubmed></ref> | The following data is from an magnetic resonance imaging study of adult Chinese aged 6 to 82 years.<ref><pubmed>17601367</pubmed></ref> 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) | * 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 cm<sup>3</sup> | * right side volume of hippocampus - 2.204 to 2.944 cm<sup>3</sup> |
Revision as of 18:02, 4 November 2010
Introduction
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.
Some Recent Findings
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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 | Primary Vesicles | Secondary Vesicles | Adult Structures |
---|---|---|---|
week 3 | week 4 | week 5 | adult |
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
Secondary Vesicles
Human Hippocampus Development
Fetal
The following data (weeks gestation) is from an imaging study of the human fetal hippocampus.[2]
- 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.[3]
- 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.[4] 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.[5]
- 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.
References
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
Glossary Links
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Cite this page: Hill, M.A. (2024, May 19) Embryology Neural - Hippocampus Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Neural_-_Hippocampus_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G