HUBS192 – Skin Anatomy & Burns (Lecture 1)

Course Framework

• Lectures: $38$ (Mon–Wed)
• Labs: $5$ – full attendance + quiz = $2\%$
• Progress tests: $16\text{ Aug}\,(8\%)$ & $4\text{ Oct}\,(12\%)$
• Final exam: $70\%$ (≈ $30\text{ Oct}$)
• Re-streaming: $15$–$16\text{ Jul}$, $11\text{ am–}1\text{ pm}$
• Resources: slides, recordings, modules, drop-ins, discussion board
• Expectations: build on HUBS$191$ knowledge, lecture etiquette, academic integrity, seek help early

Skin Functions (Integumentary System)

• Physical + chemical protection
• Excretion of salts/water/wastes via glands
• Thermoregulation: insulation vs evaporative cooling
• Melanin → UV shielding
• Keratin → abrasion barrier + water resistance
• Vitamin $D_3$ synthesis → $\text{calcitriol}$ → $\text{Ca}^{2+}$ homeostasis
• Lipid storage (dermal & hypodermal adipocytes)
• Sensory detection: touch, temperature, pain, pressure

Primary Skin Layers

• Epidermis – stratified squamous epithelium, avascular
• Dermis – connective tissue, vascular; anchors epidermis
• Hypodermis – adipose-rich subcutaneous layer (not true skin)

Epidermis Detail

Thin-skin strata (deep → superficial)

1. Stratum basale – stem cells, melanocytes; hemidesmosomes to BM
2. Stratum spinosum – $8$–$10$ keratinocyte layers; desmosomes; dendritic cells
3. Stratum granulosum – $3$–$5$ layers; keratin + waterproofing granules
4. Stratum corneum – $15$–$30$ dead keratinised layers; barrier, water-resistant
   • Thick-skin (palms/soles) adds stratum lucidum between granulosum & corneum
   • Cell junctions
   – Hemidesmosomes: basale → basement membrane → dermis
   – Desmosomes: keratinocyte-to-keratinocyte cohesion across all layers

Dermis Detail

• Papillary layer – loose, highly vascular CT; dermal papillae ↑ SA, strengthen epidermal bond
• Reticular layer – dense irregular CT with collagen + elastin “mesh” for tensile strength
• Vascular networks
– Cutaneous plexus (dermis/hypodermis junction)
– Subpapillary plexus (deep to papillary layer) → nourishes upper dermis & epidermis
• Contains: blood & lymph vessels, nerves, hair follicles, glands

Hypodermis

• Adipocytes → energy reserve, insulation, padding
• Site for hypodermic injections

Tattoos & Anatomy

• Ink injected into dermis → retained by macrophages; dermis not shed
• Pigment can migrate to lymph nodes → mimic melanoma on imaging
• Pain due to abundant dermal nociceptors

Burn Classification

• First-degree – epidermis only; red/dry/painful (erythema); heals $3$–$10$ days
• Second-degree
– Superficial: epidermis + superficial dermis; moist/red/blistered; heals $1$–$2$ weeks
– Deep: extends deeper dermis; waxy/white patches; follicles & glands intact; heals ≤ $1$ month; possible scarring
• Third-degree – full-thickness to hypodermis ± muscle/bone; varied colour, leathery, painless (nerves destroyed); requires grafting; prolonged healing + scarring

Quick-Check Answers

1. Epidermis
2. Hemidesmosomes
3. Papillary & Reticular
4. Adipocytes
5. d) All the above (third-degree)