Overview of Periosteal Reaction by Imaging.

The periosteum is a membrane that covers almost all bones in the body. It is a living structure but attracts little attention unless it reacts excessively. We highlight the important points in the anatomy, histology, and physiology of the periosteum, the stimuli and various aspects of periosteal reaction, and the main conditions underlying periosteal reaction.

Periosteal Pathologic Conditions: Imaging Findings and Pathophysiology.

The periosteum plays a key role in bone health and is a primary means by which the skeleton responds to a wide range of insults, both benign and malignant. Developmental and histologic features of normal periosteum explain some of the characteristic imaging findings seen in the setting of bone abnormalities. Patterns of periosteal reaction, both in morphology and distribution, are key to distinguishing benign or physiologic periosteal reaction from types of periosteal reaction that warrant further evaluation. The authors review the histologic features, distribution, and development of normal periosteum. Nonaggressive and aggressive types of periosteal reaction are presented with key associations for each. The presence of nonaggressive types of periosteal reaction implies that the underlying process affecting the bone is slow enough that the periosteum is able to heal it or contain it in an organized manner. In contrast, aggressive types of periosteal reaction are seen when the underlying bone insult outpaces the ability of the periosteum to contain it. Image-guided biopsies of lesions with periosteal reaction should be used to sample the site of the most aggressive pattern, as this approach can aid in accurate histologic grading and in detection of tumor cells and bone matrix. The distribution of periosteal abnormalities is as important as the morphology, with a diffuse periosteal reaction favoring systemic causes such as rheumatologic, metabolic, and hematologic conditions compared with a more localized periosteal reaction. Important causes of localized and diffuse periosteal reaction are discussed in a systems-based format, with an emphasis on clinically important causes. © RSNA, 2022.

Modeling of the human mandibular periosteum material properties and comparison with the calvarial periosteum.

Knowledge of mandibular periosteum mechanical properties is fundamental for understanding its role in craniofacial growth, in trauma and bone regeneration. There is a lack in the literature regarding mechanical behavior of the human periosteum, including both experimental and modeling aspects. The proposed study involves tensile tests of periosteum samples from different locations including two locations of human mandibular periosteum: lingual and vestibular, compared with samples from various locations of the calvarial periosteum. We propose to analyze the tensile response of the mandibular periosteum using a model, initially applied on the skin, and based on a structural approach involving the mechanical properties of the corrugation of the collagen. Two different approaches for the model parameters' identification are proposed: (1) identification from experimental curve fitting and (2) identification from histological study. This approach allows us to compare parameters extracted from the traction test fitting to structural parameters measured on periosteum histological slices. Concerning experimental aspects, we showed significant differences, in terms of stiffness, between calvarial and mandibular periostea. (The mean final stiffness is [Formula: see text] for the mandible versus [Formula: see text] for the calvaria.) About modeling, we succeed to capture the correct mechanical behavior for the periosteum, and the statistical analysis showed that certain parameters from the geometric data and traction data are significantly comparable (e.g., [Formula: see text] for [Formula: see text]). However, we also observed a discrepancy between these two approaches for the elongation at which the fibril has become straight ([Formula: see text]).

Releasing incisions of the buccal periosteum adjacent to the lower molar teeth can injure the facial artery: an anatomical study.

PURPOSE: Periosteal releasing incision (PRI) techniques are often used with guided bone regeneration procedures. As complications such as intra- and postoperative bleeding have been noticed, we aimed to study and clarify these as related to the PRI, especially on the mandibular buccal periosteum. METHODS: Fourteen sides from seven fresh-frozen Caucasian cadaveric heads were used in this study. The seven cadavers were derived from two females and five males. The mean age at the time of death was 75.9 ± 10.8 years. The PRI was made using a no. 15c blade using a surgical microscope. Subsequently, the fat tissue lateral to the periosteum was slightly dissected. The diameter of the facial artery (or its branch) and closest relationship between the tooth and position of the artery was recorded. Finally, the artery was traced back proximally to clarify its origin. RESULTS: On all sides, the inferior labial artery (ILA) was identified in the fat tissue lateral to and close to the periosteum. The ILA was closest to the periosteum at the midpoint of the PRI (approximately between the first and second molar teeth area or 10 mm mesial to the apex of the retromolar pad). The mean diameter of the ILA was 2.72 ± 0.26 mm. CONCLUSION: This anatomical finding should encourage dentists to make the PRI incision without invading the tissue underneath the periosteum.

It's time to recognize the perichondrium.

The perichondrium is a complex structure centered at the chondro-osseous junction of growing bones. It plays an important role in both normal skeletal development and in pathological conditions. This review illustrates the normal anatomy, function and imaging appearance of the perichondrium from fetal development to older childhood. The radiologic appearance of the perichondrium in skeletal trauma, infection and tumors in which it plays a role also are reviewed.

Error in the estimation of periosteal and endosteal contours from micro-CT scans for nonadult tibiae and humeri.

OBJECTIVES: This article summarized errors obtained by diverse techniques used for the derivation of cross-sectional contours in nonadult humeri and tibiae. MATERIALS AND METHODS: We analyzed cross-sectional contours in a total sample of 62 humeral and 75 tibial diaphyses in the age between birth and 12 years divided into three age groups. Long bone 35% (humeri) and midshaft (tibiae) cross-sections were taken on micro-CT images and analyzed by EPJMacro in FIJI. Properties were extracted from contours derived by manual, automatic, spline, and ellipse techniques. Agreement between techniques was assessed using manually extracted properties such as the true value using percent prediction error (%PE), reduced major axis regression, and ±95% limits of agreement. RESULTS: The lowest measurement errors were obtained for total areas, moderate errors for cortical areas and section moduli, and the highest errors for medullary areas for both bones. Derivation of humeral nonadult cross-sectional properties is less sensitive to the technique used for derivation of periosteal and endosteal contours, reaching mean %PEs below 5%. In contrast, tibial nonadult cross-sectional properties are more sensitive to the technique used and exceed 5% for some combinations. DISCUSSION: Automatic techniques provide reasonably high agreement with manually extracted contours for nonadult humeri but low agreement for tibiae. Semiautomatic approaches-spline and ellipse techniques-may reduce the error for all studied properties in tibiae, especially when combined with manually traced periosteal contours. The positive effect of the semiautomatic technique on measurement error is low for humeri.

The macroscopic and histomorphological properties of periosteal rib lesions and its relation with disease duration: evidence from the Luis Lopes Skeletal Collection (Lisbon, Portugal).

Periosteal new bone formation (PNBF) is a common finding in a large spectrum of diseases. In clinical practice, the morphology and location of periosteal lesions are frequently used to assist in the differential diagnosis of distinct bone conditions. Less commonly reported is the presence of PNBF on the ribs. This contrasts with the data retrieved from the study of skeletonized human remains that shows a high frequency of cases and a strong, albeit not specific, association between periosteal rib lesions and pulmonary conditions (e.g. tuberculosis). Despite that, an overall disagreement regarding the specificity and non-specificity of periosteal reactions exists in the study of dry bone remains. The insufficient number of clinical models exploring the morphology and the pathophysiology of PNBF's and the lack of systematic studies of pathological samples with a known diagnosis are claimed as major reasons for the disagreements. This study aimed to describe and compare the macroscopic and the histomorphologic appearance of periosteal rib lesions and to discuss their usefulness as diagnostic indicators. To pursue this goal, an assemblage of 13 rib samples (males = 11, females = 2, mean age-at-death = 36.6 years old) was collected from the Luis Lopes Skeletal Collection (Museu Nacional de História Natural e da Ciência, Universidade de Lisboa, Portugal). The assemblage belongs to individuals who died from pulmonary-TB (group 1), non-TB pulmonary infections (group 2) and other conditions (group 3). Prior to sample preparation, the ribs were visually inspected and the PNBF described according to its thickness, the degree of cortical integration and the type of new bone formed (e.g. woven, lamellar or both). After sampling, each bone sample was prepared for histological analysis under plane and polarized light microscopy. Macroscopically, the results showed no differences in the new bone composition between cause-of-death groups. Only slight differences in the degree of cortical integration, which was most frequently classified as mild to high in the pulmonary-TB group, were observed. Histologically, no distinguishing features were identified by pathological group. However, new bone microarchitectures were observed compatible with (1) acute, fast-growing processes (e.g. spiculated reactions), (2) long-standing processes with a rapid bone formation (e.g. appositional layering of bone) and/or (3) chronic, slow-growing processes (e.g. layers of compact lamellae). To some extent, these distinct rates of disease progression resonate with the cause-of-death listed for some individuals. Despite the small sample size, the results of this investigation are in agreement with previous studies, according to which the macroscopic and histological appearance of periosteal formations are not specific for a particular pathological conditions. Nevertheless, the results support the conclusion that the morphology of periosteal lesions is a good biological indicator for inferring the rate of progression and duration of pathological processes. This study provides important reference data regarding the histomorphology of periosteal lesions that can be used for comparative purposes, as well as to narrow down the differential diagnosis in unidentified skeletal remains.

Ultrasound Features of the Normal and Pathologic Periosteum.

Thickening and elevation of the periosteum from the underlying bone cortex, defined as a periosteal reaction, can be associated with several bone disorders. Although ultrasound (US) has limited possibilities in assessing bones, it can depict a periosteal reaction earlier than plain radiography, thus indicating underlying bone disorders. This pictorial essay aims to illustrate the normal and pathologic US appearances of the periosteum in both children and adults. Several disorders are discussed, such as pediatric bone trauma, infections and tumors, as well as trauma, overuse, including medial tibial stress syndrome, and finally certain seronegative spondyloarthropathies in adults. Whenever US depicts a periosteal reaction, a correlation with clinical and laboratory data is mandatory to differentiate different bone disorders. Computed tomography or magnetic resonance imaging must be performed when an infection or a tumor is suspected based on both US and the clinical presentation.

Micro-anatomical structure of the first spine of the dorsal fin of Atlantic bluefin tuna, Thunnus thynnus (Osteichthyes: Scombridae).

The first spine of the first dorsal fin (FS) of the Atlantic bluefin tuna (ABFT), Thunnus thynnus, is customarily used in age determination research because its transverse sections display well-defined growth marks. In this paper the FS structure was studied to explain its known dramatic age- and season-related morphological modifications, which are evidently caused by bone remodeling. Cross sections of samples from six adult ABFT were in part decalcified to be stained with histological, histochemical and immunohistochemical methods, and in part embedded in methyl-methacrylate to be either observed under a linear polarized light or microradiographed. FS showed an external compact bone zone and an inner trabecular bone zone. The compact bone zone consisted of an outer non-osteonic primary bone layer (C1) and an inner osteonic bone layer (C2). C1 was in turn characterized by alternate translucent and opaque bands. Evidence of spine bone remodeling was shown by the presence of osteoclasts and osteoblasts as well as by tartrate-resistant acid phosphatase (TRAP) positive bands at the boundary between old and newly formed bone. The examination of plain, i.e. not-fixed and not-decalcified, FS from 28 ABFT showed that the average thickness of C1 remained fairly constant during fish growth, whereas C2 increased significantly, indicating that the periosteal primary bone apposition is counterbalanced by the parallel bone remodeling occurring inside the compact bone zone. The present study revealed the structure of the ABFT FS and the pattern of its bone remodeling. Both of them underlay phenomena, never examined in detail before, such as the appearance followed by the progressive disappearance of growth bands.

Epinephrine auto-injector needle lengths: Can both subcutaneous and periosteal/intraosseous injection be avoided?

BACKGROUND: Epinephrine should be administered intramuscularly in the anterolateral aspect of the thigh. The length of the epinephrine auto-injector (EAI) needle should ensure intramuscular injection. OBJECTIVE: To discuss suitable EAI needle lengths based on ultrasound measurements related to weight. METHODS: The skin-to-muscle distance (STMD) and skin-to-bone distance (STBD) were measured by ultrasound in the mid-third of the anterolateral area of the right thigh when applying high pressure (8 lb; high-pressure EAI [HPEAI]) or low pressure (low-pressure EAI [LPEAI]) on the ultrasound probe. The study included 302 children and adolescents and 99 adults. The maximum and minimum STMD and the maximum and minimum STBD were estimated. RESULTS: Using HPEAIs, the risk of periosteal or intraosseous penetration was 32% in children weighing less than 15 kg. The risk of subcutaneous injection was 12% in adolescents and 33% in adults. With LPEAIs, there was no risk of periosteal or intraosseous injection and the risk of subcutaneous injections in adolescents and adults was lower at 2% and 10%, respectively. A new EAI for injection in small children would have no risk of periosteal or intraosseous injection but would have 71% chance of subcutaneous deposit of epinephrine. CONCLUSION: Common HPEAIs have a high risk of periosteal or intraosseous penetration in children and subcutaneous injections in overweight and obese adults. LPEAIs have some risk of subcutaneous injection in adults. HPEAIs with 0.1 mg of epinephrine and shorter needles have no risk of periosteal or intraosseous injection but have a high risk of subcutaneous deposit. For adult or overweight or obese patients, HPEAIs and LPEAIs should have longer needles. Future studies should focus on triggering pressures and variations in needle length.

Histological Changes in the Periosteum Following Subperiosteal Expansion in Rabbit Scalp.

PURPOSE: In intraoral bone grafting, tension-free coverage of the recipient site with periosteal flap results in optimal wound closure. Tissue expansion could be a suitable modality to obtain soft tissue in the oral cavity. The aim of this study was to assess the histology of the periosteum after subperiosteal expansion in the rabbit scalp. MATERIALS AND METHODS: In this animal study, 6 rectangular tissue expanders were placed in the skulls of 6 male white New Zealand rabbits; in 6 control rabbits, an incision was made to the periosteum but no expansion was performed. Three months after the surgeries, the rabbits were sacrificed and tissue samples were stained with hematoxylin and eosin and Masson trichrome. RESULTS: The number of osteoblasts, fibroblasts, and blood vessels and the density of collagen fibers were significantly increased in the experimental group compared with the control group (P < .001). CONCLUSIONS: Subperiosteal tissue expansion in the rabbit scalp markedly increased the histologic components of the periosteum involved in bone regeneration.

Functional anatomy of the nasal bones and adjacent structures. Consequences for nasal surgery.

The periosteum of the nasal bones, the periosteal-perichondrial nasal envelope, and the cartilaginous support of the bony vault were studied in serial coronal sections of four human cadaver noses. To differentiate between the various tissue components, the sections were stained according to Mallory-Cason and Verhoeff-Van Gieson stain. The results demonstrated: 1. the presence of clearly distinguishable layers of the periosteum covering the nasal bones; 2. the presence of a continuous periosteal-perichondrial covering of the bony and cartilaginous nasal vaults; 3. the way the cartilaginous support of the bony vault is constructed. The findings described in the present study may have clinical relevance in nasal surgery.

The interperiosteodural concept applied to the jugular foramen and its compartmentalization.

OBJECTIVE The dura mater is made of 2 layers: the endosteal layer (outer layer), which is firmly attached to the bone, and the meningeal layer (inner layer), which directly covers the brain and spinal cord. These 2 dural layers join together in most parts of the skull base and cranial convexity, and separate into the orbital and perisellar compartments or into the spinal epidural space to form the extradural neural axis compartment (EDNAC). The EDNAC contains fat and/or venous blood. The aim of this dissection study was to anatomically verify the concept of the EDNAC by focusing on the dural layers surrounding the jugular foramen area. METHODS The authors injected 10 cadaveric heads (20 jugular foramina) with colored latex and fixed them in formalin. The brainstem and cerebellum of 7 specimens were cautiously removed to allow a superior approach to the jugular foramen. Special attention was paid to the meningeal architecture of the jugular foramen, the petrosal inferior sinus and its venous confluence with the sigmoid sinus, and the glossopharyngeal, vagus, and accessory nerves. The 3 remaining heads were bleached with a 20% hydrogen peroxide solution. This procedure produced softening of the bone without modifying the fixed soft tissues, thus permitting coronal and axial dissections. RESULTS The EDNAC of the jugular foramen was limited by the endosteal and meningeal layers and contained venous blood. These 2 dural layers joined together at the level of the petrous and occipital bones and separated at the inferior petrosal sinus and the sigmoid sinus, and around the lower cranial nerves, to form the EDNAC. Study of the dural sheaths allowed the authors to describe an original compartmentalization of the jugular foramen in 3 parts: 2 neural compartments-glossopharyngeal and vagal-and the interperiosteodural compartment. CONCLUSIONS In this dissection study, the existence of the EDNAC concept in the jugular foramen was demonstrated, leading to the proposal of a novel 3-part compartmentalization, challenging the classical 2-part compartmentalization, of the jugular foramen.

Vascularized ulnar periosteal pedicled flap for forearm reconstruction: Anatomical study and a case report.

PURPOSE: Through an anatomical review, the aim of this study is to define the ulnar periosteal branches of the posterior interosseous vessels (PIV). In addition, we report the clinical utility of a vascularized ulnar periosteal pedicled flap (VUPPF), supplied by the investigated PIV, in a complex case of radial nonunion. METHODS: Ten upper limbs latex colored from fresh human cadavers were used. Branches of the PIV were dissected under 2.5× loupe magnification, noting the periosteal, muscular, and cutaneous branches arising distal to the interosseous recurrent artery. The VUPPF was measured in length (cm) and width (cm). RESULTS: The PIV provided a mean 12.8 periosteal branches to the ulna distributed along the most distal 15 cm, with a mean distance between branches of 1 cm, allowing for the design of a VUPPF which measured a mean 12 cm in length and 1.7 cm in width. We used a VUPPF of 7.8 cm in length and 2 cm in width to treat extensive nonvascularized bone graft nonunion with a defect of 2 cm of the left radius in a 6-year-old girl, secondary to previous Ewing's Sarcoma reconstruction. Successfully consolidation was achieved 6-months after surgery. The patient did not present postoperative complications. At 2-years of follow-up after surgery, active supination was 80° and pronation 0° (due an incomplete interosseous ossification); grip strength was 80% that of the opposite hand. The patient had resumed all her daily activities. CONCLUSIONS: VUPPF may be considered a valuable and reliable surgical option for forearm reconstruction in complex clinical scenarios.

Direct medial approach in surgical fixation of fractures in the posterior aspect of the medial malleolus.

Fractures in the posterior aspect of the medial malleolus form an important subset of ankle fractures and the indications for fixation include involvement of > 25% of the articular surface or an articular step off by > 2 mm. Several approaches have been described but there has been no recent study on the direct medial approach. Five fresh frozen cadaveric ankles were dissected using the direct medial approach. A longitudinal incision of 10 cm was centered directly over the medial malleolus and deepened straight down to the bone. The periosteum was identified over the distal tibia and careful subperiosteal dissection yielded access to the posterior aspect of the medial malleolus. We investigated the relationship of the neurovascular bundle to the incision by measuring the distance from the center of the medial malleolus to the closest aspect of the bundle. The mean distance from the center of the medial malleolus to the neurovascular bundle was only 2.64 cm (95% CI: 2.06 to 3.22 cm). We found that the neurovascular bundle could be avoided if a periosteal sheath was developed during the dissection and elevated off the posterior aspect of the medial malleolus. The direct medial approach can be performed safely by creating a periosteal sheath through subperiosteal dissection, and the distance of the neurovascular bundle from the incision allows for a good margin of safety during surgery. This approach can be extended proximally and distally and the medial malleolus can be fixed concurrently. Clin. Anat. 31:605-607, 2018. © 2017 Wiley Periodicals, Inc.

Anatomic characterization of the humeral nutrient artery: Application to fracture and surgery of the humerus.

Anatomic characterization of the humeral nutrient artery varies among the several textbooks on human anatomy. To clarify the anatomic characteristics of the humeral nutrient artery, we reexamined its origin and course by cadaveric dissection. In typical cases, one prominent nutrient foramen was situated on the anteromedial surface of the humeral shaft, and the nutrient canal distally penetrated the cortical bone layer. The humeral nutrient artery originated from the brachial artery below the level of the nutrient foramen as a short ascending branch. On reaching near the nutrient foramen, the humeral nutrient artery formed a hairpin loop on the periosteum to enter into the nutrient foramen. In some cases, an accessory nutrient foramen was also found near the groove for the radial nerve on the posterior surface of the humerus. This accessory nutrient foramen received an accessory humeral nutrient artery that originated from the radial collateral artery. The present findings corresponded well with the descriptions in the anatomy textbooks published in English-speaking countries. However, textbooks published in German-speaking countries describe only one type of humeral nutrient artery, the branch of the profunda brachii artery. Terminologia Anatomica, the international standard in human anatomic terminology, most likely adopted the description in the German anatomy textbooks, and thus, it is necessary to correct the position of the humeral nutrient artery in the hierarchy of Terminologia Anatomica for accurate morphological description. Clin. Anat. 30:978-987, 2017. © 2017 Wiley Periodicals, Inc.

Custom-built tools for the study of deer antler biology.

Deer antlers can be developed into multiple novel models to study growth and development of tissues for biomedical research. To facilitate this process, we have invented and further refined five custom-built tools through three decades of antler research. These are: 1. Pedicle growth detector to pinpoint the timing when pedicle growth is initiated, thus stimuli for pedicle and first antler formation can be investigated and identified. 2. Thin periosteum slice cutter to thinly slice (0.2mm or 0.7 mm thick) a whole piece of antlerogenic periosteum (AP) or pedicle periosteum (PP), which facilitates gene delivery into cells resident in these tissues, thus making transgenic antlers possible. 3. The porous periosteum multi-needle punch to effectively loosen the dense AP or PP tissue. This allows most cells of the periosteum to come into direct contact with treating solutions, thus making artificial manipulation of antler development possible. 4. The intra-dermal pocket maker to cut the thin dermal tissue (less than 2 mm in thickness) of a male deer calf horizontally into two layers to make an intra-dermal pocket. This allows loading of AP tissue intra-dermally to test the theory of "antler stem cell niche" in vivo. 5. The sterile periosteum sampling system to allow aseptic collection of the AP, PP or the antler growth centre tissue on farm, thus allowing antler generation, regeneration or rapid growth to be investigated in vitro. Overall, we believe the application of contemporary cellular and molecular biological techniques coupled with these custom-built tools would greatly promote the establishment of this unique and novel model for the benefits of biomedical research, and hence human health.

Anatomy of the human orbital muscle (OM): Features of its detailed topography, syntopy and morphology.

The human orbital muscle (OM) is not readily accessible during ordinary anatomical teaching because of insufficient time and difficulties encountered in the preparation. Accordingly, its few anatomical descriptions are supported only by drawings, but not by photographs. The aim of this study was to present OM in dissected anatomic specimens in more detail. Following microscope-assisted dissection, its location, syntopy and morphology were analyzed in 88 orbits of 51 cadavers. Together with the periorbital connective tissue OM filled the infraorbital fissure (IOF) and extended back to the cavernous sinus. As a new finding, we here report that in 34% of the orbits we observed OM-fibers, which proceeded from IOF caudally to the facies infratemporalis of the maxilla. OM had a mean width of 4±1mm, a mean length of 22±5mm and its mean mass was 0.22±0.19g. The subsequent histological analysis of all specimens showed features of smooth muscle tissue: long, spindle-like cells with a centrally located cell nucleus (hematoxylin-eosin staining) which were innervated by tyrosine-hydroxylase immunopositive adrenergic fibers. We conclude that precise knowledge on OM might be very helpful not only to students in medicine and dentistry during anatomical dissection courses, but also to head and neck surgeons, ear-nose-throat specialists and neurosurgeons working in this field.

Scale-up of nature's tissue weaving algorithms to engineer advanced functional materials.

We are literally the stuff from which our tissue fabrics and their fibers are woven and spun. The arrangement of collagen, elastin and other structural proteins in space and time embodies our tissues and organs with amazing resilience and multifunctional smart properties. For example, the periosteum, a soft tissue sleeve that envelops all nonarticular bony surfaces of the body, comprises an inherently "smart" material that gives hard bones added strength under high impact loads. Yet a paucity of scalable bottom-up approaches stymies the harnessing of smart tissues' biological, mechanical and organizational detail to create advanced functional materials. Here, a novel approach is established to scale up the multidimensional fiber patterns of natural soft tissue weaves for rapid prototyping of advanced functional materials. First second harmonic generation and two-photon excitation microscopy is used to map the microscopic three-dimensional (3D) alignment, composition and distribution of the collagen and elastin fibers of periosteum, the soft tissue sheath bounding all nonarticular bone surfaces in our bodies. Then, using engineering rendering software to scale up this natural tissue fabric, as well as multidimensional weaving algorithms, macroscopic tissue prototypes are created using a computer-controlled jacquard loom. The capacity to prototype scaled up architectures of natural fabrics provides a new avenue to create advanced functional materials.

The Periosteum of the Zygomatic Arch: Vascularization and Growth.

In addition to conveying the forces of attaching muscles and ligaments to the zygomatic and temporal bones, the arch periosteum is responsible for lateral apposition and medial resorption during the growth period. In this contribution, we describe the vasculature of the zygomatic arch in young pigs (Sus scrofa dom.) in order to understand the relationship of osseous and periosteal vessels to each other, to surrounding tissues, and to patterns of modeling. Subjects 2-6 weeks of age were perfused with vascular fill; some also received the vital bone label calcein. Whole mounts were prepared of the decalcified bony arch and of its lateral periosteum. Undecalcified arches were plastic-embedded and thick-sectioned. Additional observations on cell replication were made using material from a previous study. The osseous and periosteal vascular supplies were largely independent, joined only by a fine network at the tissue interface. Osseous vessels entered the medial side of the arch through clusters of nutrient foramina. The intraosseous branching pattern resembled the direction of appositional growth, which in turn describes the disposition of bony trabeculae in older pigs. In contrast, vessels arrived at the periosteum via muscles and ligaments and thus its perfusion may partially depend on functional activity. The open weave of periosteal vessels bore little similarity to bone architecture, especially for the temporal bone, but the appositional lateral periosteum showed indications of angiogenesis, whereas the thinner, resorptive periosteum on the medial side featured composite, possibly fusing vessels at the bone surface. Anat Rec, 299:1661-1670, 2016. © 2016 Wiley Periodicals, Inc.