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Caucasus International University
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# FIGURE 18-17 Sebaceous glands ## Sebaceous Glands Sebaceous glands secrete a complex, oily mixture of lipids called sebum, which is released into hair follicles. This is an example of holocrine secretion, where the entire cell dies and contributes to the secretory product. **(a)** A section of...
# FIGURE 18-17 Sebaceous glands ## Sebaceous Glands Sebaceous glands secrete a complex, oily mixture of lipids called sebum, which is released into hair follicles. This is an example of holocrine secretion, where the entire cell dies and contributes to the secretory product. **(a)** A section of a pilosebaceous unit shows acini composed of large sebocytes (S), which undergo terminal differentiation by filling with small lipid droplets and then disintegrating near the ducts (D) opening into hair follicles. **(b)** A micrograph shows the gland's capsule (C) and differentiates sebocytes (S) at a higher magnification. Proliferation of small progenitor cells forces sebum into the ducts. Myoepithelial cells are not present. ## Apocrine Sweat Glands Apocrine sweat glands are mainly found in the axillary and perineal regions. Their development is dependent on sex hormones and isn't fully functional until after puberty. These glands have larger lumens than eccrine glands, and the secretory components consist of simple cuboidal, eosinophilic cells with numerous granules. These cells exhibit merocrine, not apocrine, secretion. The ducts are similar to eccrine gland ducts but typically open into hair follicles. The secretion is initially odorless but may acquire an odor due to bacterial activity. The production of pheromones is also likely in humans, though perhaps in a reduced capacity, similar to many other mammals. These glands are innervated by adrenergic nerve endings. ## Eccrine Sweat Glands Eccrine sweat glands also function as auxiliary excretory organs, removing nitrogenous waste and excess salts. ## Medical Application Sweat in infants with cystic fibrosis (CF) is often salty, which is an indicator of the disease. CF patients often have defects in a transmembrane conductance regulator (CFTR) which leads to disruptions such as thick mucus accumulation in respiratory and digestive tracts. Failure to remove salt from sweat is related to this same genetic defect. ## Skin Repair Skin has a good capacity for repair, which is crucial for this exposed organ. The process of cutaneous wound healing involves several overlapping stages, depending on wound size. The initial stages include blood coagulation, the release of growth factors and chemokines from platelets. Neutrophils and macrophages then remove bacteria and debris.