-
Child's Nervous System : ChNS :... Oct 2013The pia mater has received less attention in the literature compared to the dura and arachnoid maters. However, its presence as a direct covering of the nervous system... (Review)
Review
INTRODUCTION
The pia mater has received less attention in the literature compared to the dura and arachnoid maters. However, its presence as a direct covering of the nervous system and direct relation to the blood vessels gives it a special importance in neurosurgery.
METHOD
A comprehensive review of the literature was conducted to study all that we could find relating to the pia mater, including history, macro- and microanatomy, embryology, and a full description of the related structures.
CONCLUSION
The pia mater has an important anatomic position, rich history, complicated histology and embryology, and a significant contribution to a number of other structures that may stabilize and protect the nervous system.
Topics: Humans; Pia Mater
PubMed: 23381008
DOI: 10.1007/s00381-013-2044-5 -
Genesis (New York, N.Y. : 2000) May 2019The meninges are membranous layers surrounding the central nervous system. In the head, the meninges lie between the brain and the skull, and interact closely with both... (Review)
Review
The meninges are membranous layers surrounding the central nervous system. In the head, the meninges lie between the brain and the skull, and interact closely with both during development. The cranial meninges originate from a mesenchymal sheath on the surface of the developing brain, called primary meninx, and undergo differentiation into three layers with distinct histological characteristics: the dura mater, the arachnoid mater, and the pia mater. While genetic regulation of meningeal development is still poorly understood, mouse mutants and other models with meningeal defects have demonstrated the importance of the meninges to normal development of the calvaria and the brain. For the calvaria, the interactions with the meninges are necessary for the progression of calvarial osteogenesis during early development. In later stages, the meninges control the patterning of the skull and the fate of the sutures. For the brain, the meninges regulate diverse processes including cell survival, cell migration, generation of neurons from progenitors, and vascularization. Also, the meninges serve as a stem cell niche for the brain in the postnatal life. Given these important roles of the meninges, further investigation into the molecular mechanisms underlying meningeal development can provide novel insights into the coordinated development of the head.
Topics: Animals; Arachnoid; Brain; Cell Differentiation; Developmental Biology; Dura Mater; Humans; Meninges; Pia Mater; Skull
PubMed: 30801905
DOI: 10.1002/dvg.23288 -
Clinical Biomechanics (Bristol, Avon) Dec 2020Cranial pia mater, the innermost layer of the meninges, protects the central nervous system by tightly wrapping the brain and damping the external impact force to the...
BACKGROUND
Cranial pia mater, the innermost layer of the meninges, protects the central nervous system by tightly wrapping the brain and damping the external impact force to the brain. Accurate experimental data of the mechanical property of the cranial pia mater can enhance the theoretical prediction of traumatic brain injury or the scientific surgery design for brain disease. The aim of this study is to characterize the mechanical behavior of the cranial pia mater.
METHODS
In vitro tensile and stress-relaxation experiments of ovine cranial pia mater specimens were conducted at eight strain rates to characterize the rate-dependent viscoelastic property. The tensile and stress-relaxation experimental data were fitted by an Ogden hyper-viscoelastic model with a strain rate function to describe the mechanical behavior of the cranial pia mater.
FINDINGS
The elastic modulus and the ultimate stress are significantly increased from 5.545 MPa and 0.535 MPa at 0.00167 s to 18.345 MPa and 2.547 MPa at 0.83 s (p < .0001), respectively. The initial stress and the long-term stress (300 s) are also increased significantly with the increasing strain rates (p < .0001). A good fit of the experimental data with the Ogden hyper-viscoelastic model incorporated with a strain rate function was achieved (R > 0.93).
INTERPRETATION
The cranial pia mater exhibits as a rate-dependent hyper-viscoelastic material in the tensile and stress-relaxation experiments. Compared with the brain, the stiffer nature of the cranial pia mater indicates its essential role in brain protection. The rate-dependent constitutive model provides a proper description of the hyper-viscoelastic characteristics of the cranial pia mater in tension and may provide a basic constitutive relationship for numerical simulations of traumatic brain injury.
Topics: Animals; Biomechanical Phenomena; Elastic Modulus; Humans; Pia Mater; Sheep; Stress, Mechanical; Viscosity
PubMed: 32736277
DOI: 10.1016/j.clinbiomech.2020.105108 -
Progress in Neurobiology Feb 1997In addition to motor axons and preganglionic axons, ventral roots contain unmyelinated or thin myelinated sensory axons and postganglionic sympathetic axons. It has been... (Review)
Review
In addition to motor axons and preganglionic axons, ventral roots contain unmyelinated or thin myelinated sensory axons and postganglionic sympathetic axons. It has been said that ventral roots channel sensory axons to the CNS. However, it now seems that these axons end blindly, shift to the pia or loop and return towards the periphery and that these units reach the CNS via dorsal roots. Sensory ventral root axons project from a variety of somatic or visceral receptors; some of them are third branches of dorsal root afferents and some seem to lack a CNS projection. Many ventral root afferents contain substance P (SP) and/or calcitonin gene-related peptide (CGRP). These fibres are not affected by neonatal capsaicin treatment and they cannot induce radicular or pial extravasation. Some thin ventral root axons are sympathetic and relate to blood vessels. Afferents containing SP and/or CGRP and sympathetic axons also occur in the spinal pia mater. The sensory axons mediate pain. They might also have vasomotor, tissue-regulatory and/or mechanoreceptive functions. The motor roots of cranial nerves IV, VI and XI contain unmyelinated axons arranged like in ventral roots outside the autonomic outflow. However, the motor root of cranial nerve V channels some unmyelinated axons into the CNS. The occurrence of thin axons in ventral roots and pia mater changes during development and ageing. After peripheral nerve injury, ipsilateral ventral roots and pia are invaded by new sensory and postganglionic sympathetic axons.
Topics: Animals; Axons; Ganglia; Humans; Motor Neurons; Pia Mater
PubMed: 9247961
DOI: 10.1016/s0301-0082(96)00052-4 -
Spine May 2016Intraparenchymal pressure (IPP) measurements in an in vitro cadaveric model of CNS edema.
STUDY DESIGN
Intraparenchymal pressure (IPP) measurements in an in vitro cadaveric model of CNS edema.
OBJECTIVE
To assess the contribution of pia mater to IPP and the effect of piotomy.
SUMMARY OF BACKGROUND DATA
Multicenter randomized control trials have shown that decompression with durotomy/duroplasty significantly decreases intracranial pressure (ICP). There is a paucity of evidence regarding the effectiveness of decompression of the spinal cord by piotomy.
METHODS
The supratentorial brain and spinal cord were removed from six fresh cadavers. Dura and arachnoid mater were removed. ICP monitors were placed bilaterally in the frontal and parietal lobes, and centrally in the cervical and thoracic spinal cord. To simulate edema, specimens were submerged in hypotonic solution. IPP was recorded for 5 days. A complete dorsal midline piotomy was performed on the spinal cord and resulting IPP was recorded.
RESULTS
Brain and spinal cord both increased in weight. IPP significantly increased in both brain and spinal cord. The IPP increase within the spinal cord was substantially greater (averages: all four lobes = 4.0 mm Hg; cervical = 73.7 mm Hg; thoracic = 49.3 mm Hg). After piotomy, cervical and thoracic spinal cord IPP decreased immediately (avg. postpiotomy IPP = 9.7 and 10.3, respectively).
CONCLUSION
There were differential effects on brain and spinal cord IPP. Brain IPP increased only slightly, possibly because of the absence of the cranium and dura mater. In contrast, spinal cord IPP increased substantially even in the absence of the laminae, dura, and arachnoid mater. Piotomy immediately and dramatically reduced spinal cord IPP. These data are consistent with the hypothesis that spinal cord IPP is primarily dependent on constraints imposed by the pia mater. Conversely, in the absence of the cranium and dura mater, the sulci may permit the pia-invested brain to better accommodate edema without significant increases in IPP.
LEVEL OF EVIDENCE
N/A.
Topics: Aged; Edema; Female; Humans; Male; Models, Neurological; Organ Size; Parenchymal Tissue; Pia Mater; Pressure; Spinal Cord
PubMed: 27128257
DOI: 10.1097/BRS.0000000000001306 -
Brain : a Journal of Neurology Sep 1961
Topics: Humans; Pia Mater
PubMed: 14473930
DOI: 10.1093/brain/84.3.514 -
Journal of Neurosurgery Sep 1986Using scanning and transmission electron microscopy and light microscopy, the authors studied the human pia mater and its relationship to the entry of blood vessels into...
Using scanning and transmission electron microscopy and light microscopy, the authors studied the human pia mater and its relationship to the entry of blood vessels into the normal cerebral cortex. The purpose of this investigation was to examine the long-established concept that the subarachnoid space communicates directly with the perivascular spaces of the cerebral cortex. Brains obtained post mortem from subjects with recent subarachnoid hemorrhage (SAH) and purulent leptomeningitis were studied by light microscopy to determine the permeability of the pia mater to red blood cells and inflammatory cells. Scanning electron microscopy showed that the normal pia mater is a flat sheet of cells that is reflected from the surface of the brain to form the outer coating of the meningeal vessels in the subarachnoid space. Transmission electron microscopy confirmed that the cells of the pia mater are joined by junctional complexes and form a continuous sheet that separates the subarachnoid space on one side from the subpial and perivascular spaces on the other. Thus, neither the pia mater nor the subarachnoid space extends into the brain beside blood vessels as they enter the cerebral cortex. The perivascular spaces were, in fact, found to be confluent with the subpial space and not with the subarachnoid space. In cases of recent SAH, red blood cells did not enter the perivascular spaces from the subarachnoid space; neither did India ink injected post mortem into the subarachnoid space pass into the perivascular spaces. The results of these crude tracer studies suggest that the pia mater is an effective barrier to the passage of particulate matter. Histological examination of brains of patients who had died with purulent leptomeningitis showed that inflammatory cells were present in the cortical perivascular spaces and in the contiguous subpial spaces. The presence of a large number of inflammatory cells in the subarachnoid space suggests that inflammatory cells readily penetrate the pia mater that separates the perivascular spaces from the subarachnoid space. The permeability of the pia mater to small molecular weight substances is briefly discussed.
Topics: Adult; Aged; Brain; Humans; Meningitis; Microscopy, Electron, Scanning; Middle Aged; Pia Mater; Subarachnoid Hemorrhage
PubMed: 3734882
DOI: 10.3171/jns.1986.65.3.0316 -
Neuropathology and Applied Neurobiology 1988The objects of the present study were: (1) to define the relationships of the arachnoid mater to blood vessels in the subarachnoid space; (2) to establish the structure...
The objects of the present study were: (1) to define the relationships of the arachnoid mater to blood vessels in the subarachnoid space; (2) to establish the structure of leptomeningeal trabeculae and their relationships to the pia mater; and (3) to investigate the fine structure of the human pia mater. Intracranial portions of vertebral artery were taken at post mortem, and normal cerebral cortex and overlying leptomeninges were obtained from surgical lobectomies. Tissue from these specimens was examined by scanning and transmission electron microscopy, by light microscopy and by immunocytochemistry for the presence of basement membrane, desmosomal proteins and vimentin. Results of the study showed that as the vertebral artery pierced the posterior atlanto-occipital membrane and entered the subarachnoid space, it acquired a leptomeningeal coat as the arachnoid was reflected on to it. It has been demonstrated previously that as vessels enter the brain, the leptomeningeal coat is reflected on to the surface of the cortex as the pia mater. The arachnoid mater was seen to consist of a subdural mesothelial layer and a compact central layer as previously reported. From the inner layer of the arachnoid, collagen bundles coated by leptomeningeal cells extended as trabeculae across the subarachnoid space to fuse with the pia mater. The pia itself was composed of a delicate but apparently continuous layer of cells joined by desmosomes and gap junctions but no tight junctions were observed. It was possible to detect pia mater cells in the perivascular spaces of the brain by immunocytochemical techniques using light microscopy. The significance of the observed anatomical arrangement for cerebrospinal fluid physiology is discussed.
Topics: Adult; Arachnoid; Female; Humans; Immunohistochemistry; Male; Microscopy, Electron, Scanning; Middle Aged; Pia Mater; Vertebral Artery; Vimentin
PubMed: 3374751
DOI: 10.1111/j.1365-2990.1988.tb00862.x -
Journal of Anatomy Jun 1990Biopsies of histologically normal adult human cerebral cortex, underlying white matter and overlying leptomeninges were taken from frontal and temporal lobectomy...
Biopsies of histologically normal adult human cerebral cortex, underlying white matter and overlying leptomeninges were taken from frontal and temporal lobectomy specimens excised during the removal of cerebral tumours. Multiple blocks from 6 patients (aged 18-53 years) were examined by light and transmission electron microscopy. A thin sheath of pia mater cells was found to surround completely arterioles and arteries in the brain, in the subpial space and in the subarachnoid space. Pia mater cells, forming the perivascular sheath, were identified by the presence of desmosomes or small nexus junctions and by continuity with the pia mater itself. The presence of the pial sheath suggests that the perivascular spaces around intracerebral arteries are in direct continuity with the perivascular spaces around subarachnoid arteries. No similar pial sheath was observed around intracerebral or subpial venules. The role of the periarterial spaces, enclosed by the pial sheath, is discussed in relation to the results of physiological experiments suggesting drainage of interstitial fluid from brain tissue into the perivascular pathways along major cerebral arteries in the subarachnoid space. As arterioles in the brain become smaller and lose their smooth muscle coats, the pial sheath becomes incomplete. The anatomical relationships between the pia mater and blood vessels in the human cerebrum is summarised diagrammatically, and a possible role for pial cells as an enzymic barrier protecting the brain from exogenous catecholamines is discussed.
Topics: Adolescent; Adult; Arterioles; Brain; Cerebral Cortex; Female; Humans; Male; Microscopy, Electron; Middle Aged; Pia Mater; Regional Blood Flow; Subarachnoid Space; Venules
PubMed: 2254158
DOI: No ID Found -
Surgical Neurology Dec 1992In 18 cats the omentum was mobilized, transposed, and placed directly upon the pia mater of the spinal cord. Within 2 months, vascular anastomoses developed at the...
In 18 cats the omentum was mobilized, transposed, and placed directly upon the pia mater of the spinal cord. Within 2 months, vascular anastomoses developed at the omento-spinal cord interface and, as demonstrated by India ink perfusion, communicated widely with the cord's intramedullary vessels. Light and scanning electron microscopy (SEM) of the interface revealed the development of a "fibrous coat" of Goldsmith in continuity with the edges of the dura mater. It consisted mainly of a matrix of collagen fiber and fibroblasts, well vascularized with sinusoids, capillaries, arterioles and venules. The sinusoids, as identified by SEM, were present in both the fibrous coat and adjacent omentum, were lined with attenuated endothelium, and had multiple communications. The possible significance of the sinusoidal formation is discussed in this report.
Topics: Animals; Carbon; Cats; Coloring Agents; Female; Male; Microscopy, Electron, Scanning; Omentum; Pia Mater; Spinal Cord; Staining and Labeling
PubMed: 1284320
DOI: 10.1016/0090-3019(92)90108-y