Skin Structure and Function (2026) - AQA Past Paper PDF

Module 1: Skin Structure and Function Lisa Long, PA-C UNM PA Program Skin is our largest organ, weighing approximately 4 kg and covering 2m.2  Barrier to physical agents Protects against mechanical injury Prevents dehydr...

Module 1: Skin Structure and Function Lisa Long, PA-C UNM PA Program Skin is our largest organ, weighing approximately 4 kg and covering 2m.2  Barrier to physical agents Protects against mechanical injury Prevents dehydration of body through fluid loss Reduces the penetration of UV Radiation Functions of Helps regulate body temperature the skin Provides a surface for grip Acts as a sensory organ Acts as an outpost for immune surveillance Plays a role in Vitamin D production Skin Components 1. Epidermis 2. Dermis 3. Skin appendages (Adnexa) 4. Subcutaneous fat Epidermis: Layers Ohio State University Epidermis: Stratum basale Cell division starts Keratinocytes Melanocytes Merkel cells Epidermis: Stratum spinosum Differentiation begins Undifferentiated cells become keratinocytes Desmosomes, or spines, hold keratinocytes together Yale.edu Epidermis: Stratum granulosum Differentiation continues, cells develop more keratin Cell destruction begins Waterproofing Cement Lablogatory Epidermis: Stratum corneum Corneocytes Cell death Physical barrier Microbiome- outer most layer? The major physical barrier; stacked “bricks & mortar” Differentiation continues; more keratin formed; visible granules; cement made Epidermis Recap Differentiating; forming keratin Undifferentiated; constantly dividing Other structures of the Epidermis Langerhans cells 1st line of skin’s immunologic defense Derived from bone marrow Melanocytes Pigment producing cells Protect from UV radiation Merkel cells Mechanoreceptors, more on palms and soles Merkel cell carcinoma rare, but deadly Dermal Epidermal Junction Basement Membrane Zone (BMZ) Serves as the “glue” between dermis and epidermis Site of blister formation in many diseases 4 regions: Hemidesmosomes attach to keratin filaments Lamina lucida Lamina densa Anchoring fibrils Dermis: Composition and Components Provides structural integrity Regulates functions of cells Composed of: Collagen Elastin Extrafibrillar matrix Components include: Blood vessels Nerves Appendages Wikipedia Dermis: Nerves Touch sensation Hot & cold Pain Free nerve endings Dermatomes Dr. Michael A Castillo Dermis: Blood vessels Superficial plexus Deep plexus Functions: Supply nutrition Regulate temperature Dermis: Skin appendages Eccrine sweat glands Apocrine sweat glands Hair follicles Sebaceous glands Nails TeachMeAnatomy Dermis: Eccrine sweat glands Important for cooling! Emotions and thermal stimuli Cholinergic innervation Botox blocks acetylcholine Research Gate  Dermis: Apocrine sweat glands Androgen dependent Axillary & anogenital areas Also a coiled tubule deep in dermis Drains into the midportion of hair follicles Dermis: Sebaceous glands Androgen dependent Puberty Produces sebum Part of pilosebaceous unit Face, scalp, upper trunk Mucous membranes Not on palms or soles Dermis: Hair Protective; decorative Entire body except palms and soles Basal cells at the bottom (bulb) of the matrix Keratinous hair shaft pushes thru epidermis Color by melanin Follicle attached to arrector pili muscles r/oddlysatisfying Dermis: Hair types (3!) Lanugo hairs (“baby fur”) Normally shed before birth, may remain on premature babies. Vellus hairs (“peach fuzz”) Short and fine Covers most of the body Terminal hairs: Longer, darker, thicker hairs Eyebrows, eyelashes, scalp, pubic and axillary regions Lanugo: Birth Fort Worth Vellus: Dermacore Terminal: Curly Nikki Dermis: Hair Growth Phases istock Hair Growth Phases: Anagen Growth phase ~ 1 cm per month Duration depends on location Eyebrow hair: 4 months Scalp hair: ~3 years 80-90% of scalp hairs are in anagen Hair Growth Phases: Catagen Transitional phase Lasts 3-4 weeks for scalp hair