Actions of Dopamine on the Skin and the Skeleton
Nira Ben-Jonathan in Dopamine, 2020
The epidermis has a 5- to100-μm thickness, depending upon its location, and is composed of stratified squamous epithelium devoid of blood or nerve supplies. Keratinocytes are the major cell type, constituting 95% of the epidermis, which also contains melanocytes. The deepest section of the epidermis, the stratum basale (basal layer or BL), is the reproductive layer of the epidermis. Its cells constantly divide and provide a continuous supply of new cells to the upper strata. This layer also contains neuroendocrine mechanoreceptors (Merkel cells). The proliferating keratinocytes are pushed upward to form the stratum spinosum (spinous layer or SL). The SL consists of about 10 rows of cells that fit closely together and are connected by desmosomes, or specialized structures for cell-to-cell adhesion. Also found in the SL are bone marrow-derived sentinel cells of the immune system called Langerhans’ cells, which are the antigen-presenting cells of the skin and play a role in immunological reactions such as allergic contact dermatitis. As they move upward toward the skin surface, keratinocytes gradually flatten and become part of the stratum granulosum, where the nondividing keratinocytes produce of a protein called keratinohyalin. The next layer, stratum lucidum, is present only in the thick skin of palms and soles.
Structure and function of skin
Roger L. McMullen in Antioxidants and the Skin, 2018
The stratum basale (or stratum germinativum) is the lowest layer in the epidermis and consists of a single layer of cells, which are predominantly keratinocytes. In this part of the epidermis, the keratinocytes are undifferentiated and contain all of the usual organelles that are present in viable cells, such as mitochondrion, Golgi apparatus, ribosome, endoplasmic reticulum, lysosome, and nucleus. The stratum basale is germinative and contains several populations of keratinocytes: stem cells, transient amplifying cells, and postmitotic cells. Stem cells divide rather infrequently and give rise to daughter cells known as transient amplifying cells. In turn, transient amplifying cells divide much more frequently than stem cells, producing postmitotic cells—the cells that actually undergo differentiation.
Adverse Effects to the Skin and Subcutaneous Tissue
Tiziana Rancati, Claudio Fiorino in Modelling Radiotherapy Side Effects, 2019
The two main layers of the skin are the epidermis, which is the outer shell, and the dermis, the inner one. The epidemis is 30 to 300 µm thick, the deepest layer is the stratum basale, a proliferative basal cell monolayer whose cells divide to form the keratinocytes of the epidermal cells. The outermost layer of the epidermis is the stratum corneum, made of flattened dead cells. The epidermal shell is bonded through the basement membrane to the dermal shell, which is 1–3 mm thick. The upper portion is the papillary layer, which contains the microvessels supplying the epidermis. The remaining dermis, the rete dermis, consisting of collagen bundles, scattered fibroblasts, and single microvessels, is bonded to the subcutaneous fat layer, which may be several centimeters thick. The subcutaneous tissue contains predominantly fat cells, but also a network of arteries, veins, and lymphatics (Archambeau et al. 1995).
IL-1β strengthens the physical barrier in gingival epithelial cells
Published in Tissue Barriers, 2020
Kim Natalie Stolte, Carsten Pelz, Cynthia V. Yapto, Jan-Dirk Raguse, Henrik Dommisch, Kerstin Danker
TJs are part of the physical barrier, and the existence of TJs and the expression of tight junction proteins in gingival epithelial cells have been described.33,39,40 Nevertheless, the exact distribution of the numerous different tight junction proteins in the healthy human gingiva is unknown. Thus, we initially studied the localization of claudin-1 (CLDN1), zonula occludens-1 (ZO-1), and occludin (OCLN) in healthy gingiva using indirect immunofluorescence analysis (Figure 4). This study revealed that all three proteins were expressed in mature human gingiva. For CLDN1 and ZO-1, distinct staining of intercellular contacts in the stratum granulosum was observed. Additional signals in lower layers appeared more diffuse. Both proteins were excluded from the stratum corneum and the stratum basale. OCLN was mainly expressed in the stratum granulosum (Figure 4). Costaining with antibodies directed against OCLN and ZO-1 revealed signs of colocalization only in superficial parts of the stratum granulosum (Figure A3).
Maternal long-term inhalation exposure to perchloroethylene and prenatal teratogenicity: morphometric, hormonal, and histological study
Published in Toxicology Mechanisms and Methods, 2023
Naser Mirazi, Elham Amini, Abdolkarim Hosseini, Zahra Izadi, Alireza Nourian
Histopathological examinations of embryos from pregnant rats affected by PCE are shown in Figures 1–4. Skin tissue from the normal control group shows it is normally developed. The epidermis contains all typical layers from the stratum basale toward the cornified layer of stratum corneum. The underneath layer of dermis has normal structure with growing hair follicles (Figure 1(a)). Skin tissue from G(I) and G(II) groups shows the skin layers of the epidermis and dermis are slightly thinner than normal, along with fewer number of developing hair follicles (Figure 1(b,c)). Skin tissues from G(III) group showed that the epidermal and dermal layers of the skin are thinner than normal with underdeveloped hair follicles (Figure 1(d)).
Anti-ageing peptides and proteins for topical applications: a review
Published in Pharmaceutical Development and Technology, 2022
Mengyang Liu, Shuo Chen, Zhiwen Zhang, Hongyu Li, Guiju Sun, Naibo Yin, Jingyuan Wen
The stratum basale acts as the epidermal-dermal junction consisting of the papilla and forms the most critical linkage to the dermis (Xie et al. 2019). Stratum basale is the deepest layer of the epidermis (Castellano-Pellicena et al. 2021). It consists of the basal layer and the basal lamina, as well as some dendritic cells, dividing keratinocytes and tactile cells. Keratinocytes are produced through cell division from the stem cells. While, tactile cells are linked with the sensory nerve endings, which differentiate them from other epidermal layers. The basal lamina forms the boundary between the epidermis and dermis.