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Nail anatomy and physiology
Published in Archana Singal, Shekhar Neema, Piyush Kumar, Nail Disorders, 2019
Nail bed closely resembles the Henle layer of the internal root sheath of the epidermis as the transitional zone from living keratinocyte to dead ventral nail plate cell is abrupt, occurring in the space of one horizontal cell layer.1–4
How to diagnose the patient with hair loss
Published in Jerry Shapiro, Nina Otberg, Hair Loss and Restoration, 2015
Cells of the hair matrix differentiate into six different types of cells, each of which keratinizes at a different level. The outer layer, Henle’s layer, of the IRS keratinizes first, establishing a firm coat around the soft central portion of the follicle. The two opposed cuticles covering the hair shaft and the inside portion of the IRS keratinize next, followed by the Huxley’s layer. The hair cortex then follows, and the medulla is last.
Structure and function of skin
Published in Roger L. McMullen, Antioxidants and the Skin, 2018
The base of the hair follicle is circumfused with nerve fiber endings and capillaries, providing sensation and nourishment. As shown in Figure 1.8, the hair follicle is the base of the pilosebaceous unit and is an invagination of the epidermis into the dermis. The base of the hair follicle is known as the hair bulb, which is the metabolically active portion of the hair fiber (Figure 1.10).26 At the very bottom of the hair bulb, the dermal papilla protrudes inward into the hair bulb and is lined with matrix cells, which are responsible for the synthesis of the cells that constitute the mature hair shaft. Melanocytes are also located in this region and deposit melanin granules into differentiating cortical cells, which will become part of the mature hair shaft. The portion of the hair follicle in contact with the invaginated epidermis is known as the outer root sheath. It provides a protective coating for most of the hair shaft with the exception of dermal papilla where the matrix cells reside. The outer root sheath is composed of a stratified epithelial layer. The inner root sheath consists of three concentric layers; beginning from the outside going in, they are: Henle, Huxley, and cuticle layer. The Henle layer is a single layer of cuboidal epithelial cells. The Huxley layer—named after the nineteenth century English biologist, Thomas Henry Huxley—contains flattened keratinized cells. The cuticle—not to be confused with the cuticle of the mature hair shaft—borders the outer root sheath (Figure 1.10). Differentiation, or keratinization, takes place in the hair follicle region and results in the production of the mature hair shaft, producing cuticle and cortical cells filled with lipids and keratins and void of metabolically active organelles.
Risk Factors for Presence of Cystoid Macular Edema following Rhegmatogenous Retinal Detachment Surgery
Published in Current Eye Research, 2021
Matthew R. Starr, Louis Cai, Anthony Obeid, Edwin H. Ryan, Dean Eliott, Claire Ryan, Nora J. Forbes, Michael Ammar, Luv G. Patel, Antonio Capone, Geoffrey G. Emerson, Daniel P. Joseph, Omesh P. Gupta, Carl D. Regillo, Jason Hsu, Yoshihiro Yonekawa
Post-operative cystoid macular edema is thought to occur from the breakdown of the retinal vascular endothelial cells tight junctions.10 This leads to accumulation and exudation of extracellular fluid within the macula secondary to increased vascular impermeability. The macula is thought to be predisposed to edema formation due to lax interconnecting fibers in Henle’s layer as well as the relative lack of Muller cells.11 The specific etiology regarding CME following RRD is debated. Immediate cell apoptosis following RRD has been demonstrated in a study by Berglin et al which may lead to postoperative CME with loss of cellular function.12 Additionally, iatrogenic damage to vascular tight junctions has been proposed as a mechanism.13 The predominant mechanism in most cases is likely the postsurgical pro-inflammatory state, where numerous cytokines lead to tight junction dysfunction, permeability, and thus CME.14
Differentiation of Underlying Pathologies of Macular Edema Using Spectral Domain Optical Coherence Tomography (SD-OCT)
Published in Ocular Immunology and Inflammation, 2019
Muriel Dysli, René Rückert, Marion R. Munk
Patients with diabetic retinopathy (DR) or previous DME have a significantly increased risk of developing a PCME after cataract surgery (16.3% in DR vs 0.1–2.3% in non-DR).6,7 For these cases, it is often particularly challenging to identify the main underlying cause of ME after cataract surgery. A detailed analysis using machine learning has shown that a higher central retinal thickness/retinal volume ratio, a thicker foveal ONL/Henle’s layer (HL), the absence of an ERM, and solely INL cysts are evidence for PCME. In contrast, a higher ONL/INL thickness ratio parafoveally, presence of microaneurysms, HE, HRF, additional GCL cysts and/or RNFL cysts, and the absence of SRF strongly suggest DME. Based on these factors, DME can be differentiated from PCME with an accuracy ranging from 86%-96%. With these parameters, masked graders are also able to differentiate disease entities correctly 93% of cases.7 Based on this initial classifier, which included 42 parameters, a simpler classifier was established which only required 3–6 parameters (SRF, HE, HRF, ME pattern, and location of cysts within retinal layers) to rule out or confirm an underlying diabetic etiology with an excellent area under the curve (AUC) ranging from 0.94 to 0.99 depending on the machine learning algorithm used. A simple decision flowchart used by masked graders, which was developed based on these findings, achieved an AUC of 0.94 (see Figure 2).6
Macular Pigment Optical Density Measured by a Single Wavelength Reflection Photometry with and without Mydriasis
Published in Current Eye Research, 2019
Haifan Huang, Chaoqiang Guan, Danny Shiu-chun Ng, Xinyu Liu, Haoyu Chen
Macular pigment is composed of three carotenoids, lutein, zeaxanthin and meso-zeaxanthin, which have photoprotective, antioxidant and anti-inflammatory properties.1,2 Such macular pigment has been found throughout the visual pathway and have the highest concentration in the retina.3 Zeaxanthin and lutein are found within the 7° eccentricity from the fovea and reach negligible levels outside this region.4 Majority of retinal xanthophylls are located in the Henle’s layer and the inner plexiform layer of the retina.5 These carotenoids cannot be synthesized de novo in the human body and must be acquired from the diet, such as fruits, vegetables and egg yolks. Supplementation of xanthophylls was found to decrease the risk of age-related macular degeneration.6 Measurement of macular pigment optical density (MPOD) allows quantification of the level of carotenoids in the eye during clinical assessment. Further studies also found changes of MPOD in other diseases including diabetic retinopathy7, primary open angle glaucoma8,9 and Alzheimer’s disease.10