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This is the complete lecture note for DER601 Dermatology. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: DER 601 Course title: Dermatology Course credit load: 3 Units Series 1: Skin Physiology, Histochemistry, and Diagnostic Skills in Dermatology • Part 1.1: Structure and Physiology of the Skin o Sub Part 1.1.1: The epidermis: structure and function o Sub Part 1.1.2: The dermis and subcutaneous tissue o Sub Part 1.1.3: Physiological functions of the skin • Part 1.2: Skin Appendages o Sub Part 1.2.1: Hair follicle structure and the hair growth cycle o Sub Part 1.2.2: Sebaceous and sweat glands o Sub Part 1.2.3: Nail structure and function • Part 1.3: Histochemistry of the Skin o Sub Part 1.3.1: Principles of skin histochemistry o Sub Part 1.3.2: Histochemical staining techniques relevant to the skin o Sub Part 1.3.3: Diagnostic applications of skin histochemistry • Part 1.4: Skin Scraping, Staining, and Microbiological Sampling Techniques o Sub Part 1.4.1: Technique for taking a skin scraping for fungal identification o Sub Part 1.4.2: Staining and slide preparation for fungal microscopy o Sub Part 1.4.3: Planting skin scrapings and swabs for culture • Part 1.5: Skin-Snip, Genital Swabs, and Skin Biopsy Techniques o Sub Part 1.5.1: The skin-snip technique for filarial diagnosis o Sub Part 1.5.2: Taking urethral and vaginal swabs for microscopy and culture o Sub Part 1.5.3: Skin biopsy technique and preservation for histopathology Introduction
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS The skin is the body's largest organ, a structurally complex, multilayered barrier whose normal physiology must be thoroughly understood before its many disease processes can be meaningfully interpreted. Equally essential to the practice of dermatology are the practical diagnostic techniques, skin scraping, staining, biopsy, and microbiological sampling, that allow a clinical suspicion to be confirmed at the laboratory bench. This opening Series establishes both of these foundations, the structural and physiological basis of normal skin, and the core diagnostic skills required throughout the remainder of this course. The aim of this Series is to equip you with a thorough theoretical understanding of the structure, physiology, and histochemistry of the skin and its appendages, and the core practical skills required to obtain and process dermatological specimens for diagnosis. This Series begins with the structure and physiology of the skin, before examining its appendages. We then turn to histochemistry of the skin, before addressing the practical skills of skin scraping, staining, and microbiological sampling, concluding with skin-snip, genital swab, and skin biopsy techniques. Series Learning Outcomes At the end of this Series, you should be able to: • SLO 1.1: describe the structure and function of the epidermis • SLO 1.2: describe the structure and function of the dermis, subcutaneous tissue, and the physiological functions of the skin as a whole • SLO 1.3: describe the structure and growth cycle of the hair follicle • SLO 1.4: describe the structure and function of the sebaceous glands, sweat glands, and nails • SLO 1.5: describe the principles of skin histochemistry • SLO 1.6: describe histochemical staining techniques and their diagnostic applications in dermatology • SLO 1.7: demonstrate the technique for taking a skin scraping and preparing it for fungal microscopy • SLO 1.8: demonstrate the technique for planting skin scrapings and swabs for culture • SLO 1.9: demonstrate the skin-snip technique for filarial diagnosis and the correct technique for taking urethral and vaginal swabs, and • SLO 1.10: demonstrate the correct technique for taking and preserving a skin biopsy for histopathology.
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1 Structure and Physiology of the Skin 1.1.1 the epidermis: structure and function A stratified, continuously renewing epithelial barrier The epidermis is a stratified squamous epithelium composed principally of keratinocytes, organised into four distinct layers in most skin, the stratum basale, stratum spinosum, stratum granulosum, and stratum corneum, with a fifth layer, the stratum lucidum, present only in the thick skin of the palms and soles. Keratinocytes arise from mitotically active cells within the stratum basale and progressively differentiate as they migrate toward the skin surface, ultimately forming the fully keratinised, anucleate corneocytes of the stratum corneum, a process termed keratinisation that typically takes approximately 28 days to complete under normal physiological conditions. Beyond keratinocytes, the epidermis additionally contains melanocytes, located within the stratum basale and responsible for melanin production, discussed further in a later Series of this course, Langerhans cells, dendritic antigen-presenting cells contributing to cutaneous immune surveillance, and Merkel cells, involved in light touch sensation. Fill in the blank: Keratinocytes progressively differentiate as they migrate from the stratum basale toward the skin surface in a process termed ________, typically taking approximately 28 days. 1.1.2 the dermis and subcutaneous tissue The dermis lies beneath the epidermis and is divided into a superficial papillary dermis, composed of loosely arranged collagen and elastic fibres interdigitating with the epidermis via dermal papillae, and a deeper reticular dermis, composed of densely packed, thicker collagen bundles providing the skin's principal tensile strength. The dermis houses the skin's vasculature, including the superficial and deep vascular plexuses supplying nutrition and enabling thermoregulation, sensory nerve endings, and the skin appendages discussed in the next Part of this Series, all embedded within an extracellular matrix produced principally by dermal fibroblasts. The subcutaneous tissue, or hypodermis, lies beneath the dermis and consists principally of adipocytes organised into fat lobules separated by fibrous septa, functioning as an energy reserve, thermal insulator, and mechanical cushion protecting underlying structures from external trauma.
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: The reticular dermis is composed of densely packed, thicker collagen bundles providing the skin's principal tensile ________. 1.1.3 physiological functions of the skin The skin performs several essential physiological functions, foremost among them barrier protection, preventing excessive transepidermal water loss and restricting entry of pathogens, allergens, and chemical irritants, a function attributable principally to the stratum corneum discussed earlier in this Part. Further essential functions include thermoregulation, achieved through cutaneous vasodilation and vasoconstriction together with eccrine sweat gland activity, discussed further in the next Part of this Series, sensation, mediated by specialised cutaneous nerve endings, and vitamin D synthesis, initiated by ultraviolet-induced photoconversion of 7-dehydrocholesterol within the epidermis. Fill in the blank: Vitamin D synthesis is initiated by ultraviolet-induced photoconversion of 7-dehydrocholesterol within the ________. Figure 1.1: Cross-sectional diagram of skin showing the epidermis, dermis, and subcutaneous layers. Pilot questions 1.1
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1. Name the four layers of the epidermis found in thin skin, in order from deepest to most superficial. (Linked to SLO 1.1) 2. Define keratinisation and state the approximate time it takes to complete. (Linked to SLO 1.1) 3. Name the three specialised cell types found within the epidermis in addition to keratinocytes. (Linked to SLO 1.1) 4. Distinguish the papillary dermis from the reticular dermis. (Linked to SLO 1.2) 5. List three physiological functions of the skin. (Linked to SLO 1.2) 1.2 Skin Appendages 1.2.1 hair follicle structure and the hair growth cycle A cyclical mini-organ embedded within the dermis The hair follicle is a complex epithelial and mesenchymal structure extending from the epidermal surface into the dermis, or, for terminal scalp hair, into the subcutaneous tissue, comprising the hair bulb, containing the mitotically active matrix cells, and the dermal papilla, a specialised mesenchymal structure regulating follicular activity. Hair growth follows a cyclical pattern comprising three phases, anagen, the active growth phase, generally lasting two to six years on the scalp, catagen, a brief involutional phase, and telogen, a resting phase preceding eventual shedding, with the relative proportion of follicles in each phase at any given time determining overall hair density. Fill in the blank: Hair growth follows a cyclical pattern comprising anagen, catagen, and ________ phases. 1.2.2 sebaceous and sweat glands Sebaceous glands are holocrine glands generally associated with hair follicles, forming the pilosebaceous unit, and secreting sebum, a lipid-rich substance contributing to skin surface lubrication and barrier function, with particular density on the face, scalp, and upper trunk. Eccrine sweat glands, distributed across nearly the entire body surface, produce a hypotonic, watery secretion central to thermoregulation, discussed earlier in this Series, while apocrine sweat glands, confined principally to the axillae and anogenital region, produce a more viscous secretion that becomes odoriferous following bacterial decomposition on the skin surface.
la-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: Sebaceous glands are holocrine glands generally associated with hair follicles, together forming the ________ unit. 1.2.3 nail structure and function The nail unit comprises the nail plate, a hardened keratinised structure produced by the nail matrix, the nail bed, upon which the plate rests, and the surrounding nail folds, including the cuticle, which seals the proximal nail fold against the plate. Nails protect the distal digits from mechanical trauma, enhance fine tactile discrimination by providing counter-pressure to the fingertip pulp, and
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