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Arachnoid trabeculae
Arachnoid trabeculae
	The arachnoid trabeculae connecting the arachnoid and pial layers of the meninges
Identifiers
TA98	A14.1.01.206
TA2	5390
FMA	77761
	Anatomical terminology [edit on Wikidata]

The arachnoid trabeculae (AT) are delicate strands of connective tissue that loosely connect the two innermost layers of the meninges – the arachnoid mater and the pia mater.^[1]^[2] They are found within the subarachnoid space where cerebrospinal fluid is also found. Arachnoid trabeculae are also known as subarachnoid trabeculae (SAT) or leptomeningeal trabeculae.^[3]

Structure

Human cranial arachnoid trabeculae are made mostly of type I collagen.^[4]^[5] A study of 7 post-mortem human brains found that average trabecula fiber width was 30μm, and the average volume fraction was 26%.^[6]

Arachnoid trabeculae are surrounded by fibroblast cells.^[4] There are five principal architectures of arachnoid trabeculae structures, whose shapes may be described as single strands, branched strands, tree-like shapes, sheets, and trabecular networks.^[7] Some authors describe the structures in the subarachnoid space as having three forms, namely "trabeculae", "septa" and "pillars".^[8]^[9]^[10]^[11]

The arachnoid trabeculae structures of humans and rats have been shown to have similar morphology. Therefore many studies of AT use rats instead of humans.^[12] Also AT embryology is similar in humans and mice.^[13]

Function

The arachnoid trabeculae help limit displacement of the brain relative to the skull. The region-dependence of trabeculae volume fraction has a strong influence on the magnitude and distribution of brain deformation in the event of head impact.^[14]

Development

Embryologically, the arachnoid trabeculae are the remnants of the common precursor that forms both the arachnoid and pial layers of the meninges. The initial development of the subarachnoid space occurs in two phases:^[13]

A mesenchymal layer "invades" between the embryonic epithelium and the developing neuroepithelium of the telencephalon. The extracellular space is filled with GAG (glycosaminoglycan) gel.
The trabecular structure arises from withdrawal of the GAG gel. This results in fluid-filled cavities with random spacing and size. The mesenchymal material between these cavities is the origin of the arachnoid trabeculae. The upper and lower surfaces of the layer become the arachnoid and pia mater membranes, to which the trabecular structure remains attached.

Above the subarachnoid space, collagen fibers from the trabeculae are attached to the arachnoid mater, reinforcing it with collagen to withstand fairly strong forces. Below the subarachnoid space, trabecular collagen passes through the pia mater and sub-pial space, and is attached to the basement membrane, beneath which it embeds itself in a layer of astrocytes and oligodendrocytes.^[15]

Notes

^ "Arachnoid trabeculae." Encyclopædia Britannica. 2010. Encyclopædia Britannica Online. 09 Sep. 2010.
^ Diamond, Scheibel & Elson 1985, p. 9–10.
^ Mortazavi et al. 2018, p. 279.
^ ^a ^b Saboori & Sadegh 2015, p. 1.
^ Mortazavi et al. 2018, p. 283.
^ Benko et al. 2020, pp. 277, 280.
^ Saboori 2021, p. 40.
^ Killer et al. 2003, p. 777.
^ Lu, Brusic & Gaillard 2022, p. 167.
^ Mortazavi et al. 2018, pp. 281–282.
^ Saboori 2021, p. 41.
^ Saboori & Sadegh 2015, p. 3.
^ ^a ^b Mortazavi et al. 2018, p. 280.
^ Benko et al. 2020, p. 275.
^ Mortazavi et al. 2018, p. 281.

References

Benko, Nikolaus; Luke, Emma; Alsanea, Yousef; Coats, Brittany (2020). "Spatial distribution of human arachnoid trabeculae". Journal of Anatomy. 237 (2): 275–284. doi:10.1111/joa.13186. PMC 7369197. PMID 32202332.
Diamond, Marian Cleaves; Scheibel, Arnold Bernard; Elson, Lawrence M. (1985). The Human Brain Coloring Book. New York: Barnes & Noble. ISBN 978-0-06-460306-5.
Killer, H E; Laeng, H R; Flammer, J; Groscurth, P (2003). "Architecture of arachnoid trabeculae, pillars, and septa in the subarachnoid space of the human optic nerve: anatomy and clinical considerations". British Journal of Ophthalmology. 87 (6): 777–781. doi:10.1136/bjo.87.6.777. PMC 1771732. PMID 12770980.
Lu, S.; Brusic, A.; Gaillard, F. (2022). "Arachnoid Membranes: Crawling Back into Radiologic Consciousness". American Journal of Neuroradiology. 43 (2): 167–175. doi:10.3174/ajnr.A7309. PMC 8985673. PMID 34711549.
Mortazavi, Martin M.; Quadri, Syed A.; Khan, Muhammad A.; Gustin, Aaron; Suriya, Sajid S.; Hassanzadeh, Tania; Fahimdanesh, Kian M.; Adl, Farzad H.; Fard, Salman A.; Taqi, M. Asif; Armstrong, Ian; Martin, Bryn A.; Tubbs, R. Shane (2018). "Subarachnoid Trabeculae: A Comprehensive Review of Their Embryology, Histology, Morphology, and Surgical Significance". World Neurosurgery. 111: 279–290. doi:10.1016/j.wneu.2017.12.041. PMID 29269062.
Saboori, Parisa; Sadegh, Ali (2015). "Histology and Morphology of the Brain Subarachnoid Trabeculae". Anatomy Research International. 2015: 1–9. doi:10.1155/2015/279814. PMC 4458278. PMID 26090230.
Saboori, Parisa (2021). "Subarachnoid space trabeculae architecture". Clinical Anatomy. 34 (1): 40–50. doi:10.1002/ca.23635. PMID 32519396.