Skin is the first line of defense and encounters a variety of microbes. Some pathogenic strains are often the cause of a broad range of infections of the skin and other body systems. These conditions can affect people of all ages and may have different causes, including genetic factors, infections, autoimmune reactions, environmental factors, and lifestyle choices.
Gram-positive Staphylococcus spp. and Streptococcus spp. are responsible for many of the most common skin infections. However, many...

Acne is a multifactorial skin condition primarily affecting adolescents and young adults, with a global prevalence estimated to exceed 75% in this demographic. The condition is characterized by the formation of comedones (blackheads and whiteheads), papules, pustules, nodules, and, in severe cases, cysts, particularly in areas rich in sebaceous glands such as the face, neck, chest, and back. The pathogenesis involves increased sebum production, follicular hyperkeratinization, colonization by...

The human skin serves as a complex ecosystem inhabited by a diverse community of microorganisms, including bacteria, fungi, and viruses. This microbiome plays a critical role in maintaining skin health and defending against pathogenic invaders. The composition of microbial communities varies significantly across different regions of the body, influenced primarily by the local levels of moisture and sebum.Regional Variation in Skin MicrobiotaCutibacterium acnes predominantly colonizes sebaceous...

The epidermis is made of four or five layers of epithelial cells, depending on its location in the body. From deep to superficial, these layers are the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
The cells in all these layers except the stratum basale are called keratinocytes, a type of cell that manufactures and stores the protein keratin. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from...

Staphylococcus aureus is a Gram-positive coccus that resides harmlessly on the skin and mucous membranes of healthy individuals. When the skin barrier is breached, it can shift from a commensal to an opportunistic pathogen. This transition is facilitated by surface adhesins, such as clumping factor B and S. aureus surface protein G (SasG), which bind to structural proteins, including loricrin and cytokeratin, in the damaged epidermis. Protein A, another key factor, binds the Fc region of...

Dermis
The dermis might be considered the "core" of the integumentary system, as distinct from the epidermis and hypodermis. It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis is made of two layers of connective tissue that comprise an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts.
Papillary Layer
The papillary layer is made of loose, areolar connective tissue, which means the collagen and...