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Anatomy of the Midface
Published in Neil S. Sadick, Illustrated Manual of Injectable Fillers, 2020
Stephen A. Goldstein, Evan Ransom
The dermis lies between the epidermis and subcutaneous fat, forming the greatest bulk of the skin in youth and progressively thinning with age. The papillary dermis is most superficial and interdigitates with the undulating epidermis. Below this lies the thicker reticular dermis, where the bulk of the sebaceous glands and apocrine sweat glands reside. Hair follicles sit at the deep margin of the dermis where it meets the subcutaneous fat and project through the dermis and epidermis to emerge at the skin surface. Along the way, the apocrine sweat glands and erector pili muscles attach to the follicles. Eccrine sweat glands also reside at the deep margin of the reticular dermis. The dermis provides the strength and distensibility of the skin, and is composed of an extracellular matrix of collagen, elastin, and ground substance. The cellular component of this layer is largely fibroblasts, which are more prevalent in the papillary dermis. These cells synthesize the extracellular connective tissue matrix and have a significant role in wound healing and scar formation. Dermal and subdermal fillers add volume and may promote collagen deposition within this layer. Together, these effects aid in creating a youthful appearance.
Skin Perforation and Solid Microneedles
Published in Boris Stoeber, Raja K Sivamani, Howard I. Maibach, Microneedling in Clinical Practice, 2020
Michael L Crichton, Mark Kendall
Below the epidermis sits the dermis—a rich mesh of collagen, blood capillaries, cells, hair/sebum follicles, and nerve endings, embedded in a proteoglycan and hyaluronic acid gel (5). This layer can be further split into the papillary dermis (the upper dermis around the base of the epidermis) and the reticular dermis (the lower dermis). The papillary dermis has a finer mesh of collagen than the reticular dermis and contains smaller capillary ends; the reticular dermis has larger collagen bundles forming its structure and large capillaries (6). This composition means that the tissue has a range of properties that can challenge the engineer looking to deliver drugs or vaccine within. The collagen fibers in particular give an overall structural strength to the skin that enables it to be flexible but hard to puncture.
Biology of the Hair and Skin
Published in Randy Schueller, Perry Romanowski, Conditioning Agents for Hair and Skin, 2020
The dermis is divided into two parts: the papillary dermis and the reticular dermis (13). The papillary dermis contains smaller collagen and elastic fibers than the reticular dermis, but encloses the extensive circulatory, lymphatic, and nervous system of the skin. It also contains fibronectins, which function as adhesive proteins to attach fibroblasts to collagen, and abundant glycosaminoglycans, also known as ground substance, which are anionic polysaccharides. The major glycosaminoglycans are hyaluronic acid, chondroitin sulfate, dermatan sulfate, and heparin sulfate. They function to maintain adequate water homeostasis within the skin and influence flow resistance to solutes. In essence they are the natural moisturizing substances of the skin, necessary to prevent cutaneous dehydration. They comprise only 0.2% of the dry weight of the skin, but are capable of binding water in volumes up to 1000 times their own.
Comparison of the effectiveness of local anesthesia for the digital block between single-volar subcutaneous and double-dorsal finger injections: a systematic review and meta-analysis of randomized control trials
Published in Journal of Plastic Surgery and Hand Surgery, 2023
Che-Hsiung Lee, Mo-Han Lin, Yu-Te Lin, Chung-Chen Hsu, Cheng-Hung Lin, Shih-Heng Chen, Ren-Wen Huang
The classic double-dorsal injection, first proposed by Braun and Harris [14], involves an injection on each side of the digit, and it has been used for a long time. In this review, the general approach was to inject 1-3 ml of local anesthesia into the base of the proximal phalanx on each side of the finger from the dorsal side. The reason for injecting the dorsal skin of the finger is because volar skin is considered to be more sensitive than dorsal skin [37]. The pooled meta-analysis of the 9 RCTs in the present study showed a statistically significantly higher painful sensation with a dorsal injection (p = 0.041), which contrasts with the previous hypothesis. The reason may result from two puncture sites of the double-dorsal injection and the more extended pathway from dorsal injection than the volar injection. The other method to evaluate the pain sensation of the skin is by assessing the intraepidermal nerve fiber density (IENFD). The previous study showed that IENFD is higher in hairy skin than glabrous skin at the wrist level, but no study evaluated at the palm level yet [38]. Also, the other study found that the fingertip skin has more than twice the nerve fiber density in the papillary dermis than the volar skin of the palm [39]. These results may explain that volar injection has less pain than dorsal skin at the palm level, but further anatomical and histological studies were needed to verify it.
Skin proteomics – analysis of the extracellular matrix in health and disease
Published in Expert Review of Proteomics, 2020
Jörn Dengjel, Leena Bruckner-Tuderman, Alexander Nyström
The second important skin layer is the dermis (Figure 1). It provides tensile strength, elasticity, and resilience to the skin. Histologically the dermis can be divided into a thin superficial layer, the papillary dermis, and a thicker deeper layer, the reticular dermis. Although adnexal, vascular, lymphatic and neural structures traverse the dermis, fibroblasts constitute the major cell population embedded in the dermal connective tissue. These are ECM producing mesenchymal cells responsible for maintenance, repair, and regeneration of the dermis. Recent research data indicate that the superficial, middle, and deeper dermal layers harbor distinct fibroblast subpopulations [62], nevertheless definitive cell markers still remain elusive and functional characteristics that distinguish them are not fully understood. Quantitatively minor and changing cell populations in the dermis encompass immune cells. Upon need, they migrate into the skin and exert decisive functions in immune response, inflammation, and regenerative processes [63].
Impairment of wound healing by reactive skin decontamination lotion (RSDL®) in a Göttingen minipig® model
Published in Cutaneous and Ocular Toxicology, 2020
Jessica M. Connolly, Robert S. Stevenson, Roy F. Railer, Offie E. Clark, Kimberly A. Whitten, Robyn B. Lee-Stubbs, Dana R. Anderson
The naïve control sites from the 21- and 56-day cohorts appeared histologically similar in the majority of pigs (Figures 9 and 10). In both cohorts the overlying epidermis showed normal thickness and epidermal maturation with no cytological atypia. All layers of the dermis, particularly the papillary dermis, were arranged normally with no evidence of an increased dermal inflammatory infiltrate, proliferation of fibroblast-like stromal cells, loss/reduction in dermal elastic fibres, abnormal dermal collagen orientation, loss of adnexal structures, epidermal/dermal separation, epidermal degeneration/necrosis/apoptosis/ulceration, edoema, and/or haemorrhage. In the 56-day cohort there was no evidence of RSDL remaining on the hair or epidermis in the NC_RSDL where all animals had no skin damage.