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Macronutrients
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Sweat or sebum. Sweat is secreted by sebaceous glands in humans. Sebaceous glands are holocrine glands found over the entire surface of the body except the palms, soles, and dorsum of the feet. They are abundant in the face and scalp where they are the sites of acne. The normal function of sebaceous glands is to produce and secrete sebum, a group of complex oils including triglycerides and fatty acid breakdown products, wax esters, squalene, cholesterol esters, and cholesterol (139).
Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Sebaceous glands contain cells in various stages of differentiation. Morphologically, the gland consists of a group of lobes or acini. Three types of acinar cells have been described ultrastructurally. The structure of these cells changes progressively from the periphery to the center of each gland. The peripheral cell lies on the basement membrane that surrounds the acinus of the sebaceous gland. The second cell type is the partially differentiated cell which is actively synthesizing lipid. The third cell type is the fully differentiated cell which is large and full of lipid droplets. It is at this stage that the cell will rupture and release its entire secretion (lipid) into the sebaceous duct and then onto the surface of the skin. This process is termed holocrine secretion. The function of sebum, a complex mixture of lipids, is that of acting as an antibacterial agent. Also, in hairy mammals it may act as a waterproofing agent and may prevent moisture loss from the human epidermis.217,219,229,230 As noted by Strauss et al.,230a differences can occur in sebum composition among mammals.
Hair Types and Subtypes in the Laboratory Mouse
Published in John P. Sundberg, Handbook of Mouse Mutations with Skin and Hair Abnormalities, 2020
John P. Sundberg, Margaret E. Hogan
The cilia (eyelashes) are large terminal-type hairs that are located at the mucocutaneous junction of the dorsal and ventral palpebrae (eyelids) (Figure 6). Adjacent to these large follicles are large specialized sebaceous glands known as meibomian glands. Abnormalities of the meibomian glands are observed when evaluated in mouse mutations with abnormalities of other sebaceous-type holocrine glands. This is the case with asebia (αb). rhino (hrrh), tabby (Ta), downless (dl), sleek (Dlslk), and crinkled (cr). The features of each of these mutations are described in Part Π. Lesions that commonJy occur at the mucocutaneous junction of the eyelids in specific inbred strains suggests that abnormalities at the biochemical level may be present even though no morphologic defect can be identified. The BALB/cJ, BALB/cByJ, and 129/J are strains in which there is a high incidence of ulcerative blepharitis at the lid margin.29–30 Whether this is due to abnormalities in the meibomian gland secretion, cilia, or keratinocytes at the transition point has yet to be determined.
Evaluation of Meibomian Gland Loss and Ocular Surface Changes in Patients with Mild and Moderate-to-Severe Graves’ Ophthalmopathy
Published in Seminars in Ophthalmology, 2022
Büşra Yılmaz Tuğan, Berna Özkan
Meibomian glands located in tarsal plates of eyelids are modified, holocrine, sebaceous glands.10 Meibomian glands excrete lipid that forms the lipid layer of the tear film and reduces tear evaporation.11 Meibomian gland dysfunction (MGD) causes gland loss that leads to “evaporative dry eye disease” characterized by instability of the tear film lipid layer, increased evaporation of aqueous component, and increased osmolarity of the tear film.12,13 Recently, many factors have been reported to be responsible for MGD. Age-related changes like reduced acinar cell proliferation and atrophy of the gland are the major causes of MGD.14 Some of the other factors that have been reported are smoking, incomplete blinking, diabetes, and inflammatory diseases such as rosacea.15–19
Ocular surface characteristics in acne vulgaris
Published in Clinical and Experimental Optometry, 2022
Ersin Muhafiz, Murat Öztürk, Remzi Erten
In a study evaluating tear functions in acne vulgaris, it was found that tear instability and abnormal or decreased Schirmer score were more common compared to healthy individuals. In addition, subjective eye complaints were found to be more common in patients with acne vulgaris than the healthy controls, and there was a correlation between these complaints and TBUT.27 Similarly, in our study, TBUT, which is an indicator of tear instability, was significantly shorter in patients with acne vulgaris. However, in our study, there was no significant difference between the groups in respect of the Schirmer values showing tear secretion from the lacrimal gland. These results may be related to the meibomian glands having a holocrine sebaceous structure and a close relationship with P. acnes.18,23–26 The lacrimal gland, which is mostly affected by autoimmune diseases, may not be affected in acne vulgaris because it is an exocrine gland and has no relationship with P. acnes involved in the pathogenesis of the disease.28,29
Physiology of sweat gland function: The roles of sweating and sweat composition in human health
Published in Temperature, 2019
Sebaceous glands are not a type of sweat gland but worth mentioning here since their secretions can impact the composition of sweat collected at the skin surface [25]. Sebaceous glands, first described by Eichorn in 1826 [26], are associated with hair follicles and present over much of the body surface but particularly the scalp, forehead, face, and anogenital area [26,27]. They are absent on the palms of hands and soles of the feet [26]. Sebaceous glands are holocrine glands that secrete a viscous, lipid-rich fluid consisting of triglycerides, wax esters, squalene, cholesterol, and cholesterol esters [25–27]. The rate of sebum production is related to the number and size of glands which is under hormonal (androgen) control [26]. The importance of sebaceous gland secretions is uncertain but sebum is thought to have antibacterial and antifungal properties and function as a pheromone [28].