Actions of Dopamine on the Skin and the Skeleton
Nira Ben-Jonathan in Dopamine, 2020
Hair serves some protective functions and plays a role in sexual attraction [45,46]. It is found everywhere on the external body except for mucus membranes, palms and soles. Hair can be categorized as vellus (fine, soft and nonpigmented) and terminal (long, coarse and pigmented). The part of hair seen on the surface of the skin is the shaft, while that below the skin surface is the root. The root, together with its epithelial and connective tissue covering, is called the hair follicle. Hair is made of a tough protein called keratin and is anchored into the skin by the hair follicle. The hair follicle is a dynamic organ which resides in the dermal layer of the skin and is made of multiple cell types, each with distinct functions. For example, terminal hair grow on the scalp and lanugo (fine, soft hair) cover the body of fetuses and some newborn babies. The hair follicle regulates hair growth via a complex interaction between hormones, neuropeptides and immune cells.
Hair Follicle Keratins
John P. Sundberg in Handbook of Mouse Mutations with Skin and Hair Abnormalities, 2020
The mature hair follicle is a derivative of the epidermis formed by the epidermal cells growing down into the underlying dermis during embryogenesis. In the mouse, the first wave of pelage hairs emerge from the follicles after birth. The histological structure of the mature follicle and the changes in the cells and their protein components during differentiation of the growing hair are described in several reviews.1–7 The hair follicle consists of several approximately cylindrical and concentric cell layers, and these layers at a low level in a mouse follicle are shown in Figure 1. Beginning from the outside is the outer root sheath (ORS) composed of several layers of cells, then the inner root sheath (IRS) of three distinct layers, the Henle, Huxley, and IRS cuticle layers, in that order. The IRS encases and grows out with the developing hair fiber that consists of at least two cell types, the surface layer of flattened overlapping cuticle cells and the central cortex of spindle-shaped cells, each cell roughly 100 μm in length. Many hairs contain a medulla and in rodent species, it consists of arrays of regularly packed cells interspersed with air spaces to form a central core along the length of the fiber.
Cicatricial alopecias: Pathogenesis, classification, clinical features, diagnosis, and management
Jerry Shapiro, Nina Otberg in Hair Loss and Restoration, 2015
A basic knowledge of follicular anatomy is important in the understanding of cicatricial alopecias, because the location of the destructive process is crucial in determining the irreversibility of alopecia. Follicular stem cells are located in the bulge area where the arrector pili muscle inserts into the follicles. These cells migrate down into the hair follicle, and subsequently differentiate into the various layers of the hair follicle. As the hair cycles through anagen, catagen, and telogen, there is a permanent upper portion of the hair follicle and a nonpermanent lower portion. When the inflammation is located deep, in the vicinity of the nonpermanent portion, a scarring alopecia is unlikely to develop. If the inflammation is located within the permanent portion, then a cicatrizing alopecia is more likely to occur.
A Child Presenting with Recurrent Corneal Ulcers: Hereditary Sensory and Autonomic Neuropathy IV (HSAN IV)
Published in Neuro-Ophthalmology, 2019
Beena Suresh, Vaishnavi Reddy, Ingo Kurth, Sujatha Jagadeesh
TM is the second child of a nonconsanguineous couple. He was brought to us at 10 months for evaluation of suspected ectodermal dysplasia. TM was a healthy boy born at term by LSCS with a birth weight of 3 kg with a good birth cry. On day three of life neonate had refusal of feeds, high temperature and lethargy. He was treated for fever and discharged on day nine of life. Subsequently his milestones and development were age appropriate. Child has recurrent respiratory infections, recurrent corneal ulcers and several febrile episodes. He was also noted to have decreased sweating and skin biopsy from scalp was done elsewhere which revealed small adnexal glands and absence of sebaceous glands. Hair follicles contained small hair shafts. Hence the diagnosis of anhidrotic ectodermal dysplasia was reported.
Eclipta prostrata promotes the induction of anagen, sustains the anagen phase through regulation of FGF-7 and FGF-5
Published in Pharmaceutical Biology, 2019
Keun-Hyeun Lee, Dabin Choi, Seung-Il Jeong, Sang-Jun Kim, Chang Hyun Lee, Hyung-Sik Seo, Han-Sol Jeong
The underlying molecular mechanisms by which hair follicles are formed, differentiated, degenerated and regenerated, are not completely understood. However, complex interactions of molecules between the hair follicular cells such as dermal papilla and follicular epithelial cell are critical for the cycling of hair follicles. Among them, FGF-7 is an important mediator in the growth of hair follicle (Danilenko et al. 1995; Guo et al. 1996). FGF-7 has been shown to increase the survival of hair follicle as well as its regeneration (Booth and Potten 2000). FGF-7 is produced by dermal papilla and its receptors are highly expressed in the overlying matrix cells during anagen (Danilenko et al. 1996). In this study, we examined whether EP increases the expression of FGF-7 in vivo or in vitro. In C57BL/6 mice, EP enhanced the expression of FGF-7 both of the protein and mRNA level. Interestingly, low dose of EP was more efficient to enhance the growth of hair follicles (Figure 4(b,c)). EP also increased the expression of FGF-7 in cultured HDPs. The amount of cytosolic FGF-7 granules was increased by treatment of EP in HDPs (Figure 5(a)). EP also increased the expression of FGF-7 in cell lysates, at both protein and mRNA level (Figure 5(b,c)).
Adnexal squamous cell carcinoma: incidence of eyelid margin involvement
Published in Orbit, 2023
Alison H. Watson, Sabah Akbani, Natalie Homer, Marie Somogyi, Vikram Durairaj
The eyelash follicle differs from other hair follicles in many ways. Notably, they are terminal hair follicles unlike the surrounding vellus follicles that are able to produce fully pigmented and medullated hair shafts.9 Unlike vellus hairs, they do not have arrector pili muscle and they are independent of sex hormones. Therefore, they are the darkest in the human body and the last to turn gray.9 There are limited identified studies of the lash follicle cycle in comparison to vellus hairs.9,13 One assessment postulated that the turnover cycle of these follicles is much longer than the vellus hairs.13 The predilection of SCC to develop along the marginal versus non-marginal eyelid may be a consequence of differences in the duration of the lash follicle life cycle, as this can influence the likelihood of malignant transformation.6,7
Related Knowledge Centers
- Hair Growth
- Neuropeptide
- White Blood Cell
- Dermis
- Skin
- Lanugo
- Cell Type
- Hormone
- Hair
- Terminal Hair