AN4.1-5 | General features of skin and fascia — Gate Quiz

Correct! The epidermis is composed of stratified squamous keratinized epithelium. The multiple layers provide barrier protection and resistance to abrasion. Keratinocytes move from the basal layer to the surface, undergoing keratinization and desquamation.

Epidermis layers (mnemonic 'Californians Like Girls in String Bikinis'): Basale, Spinosum, Granulosum, Lucidum (only thick skin), Corneum. Cell types: Keratinocytes (90%), Melanocytes (UV protection), Langerhans cells (immunity), Merkel cells (touch).

Incorrect. Epidermis = stratified squamous keratinized epithelium. The layers from deep to superficial are: Stratum basale, spinosum, granulosum, lucidum (thick skin only), corneum.

Correct! Melanocytes are found in the epidermis (stratum basale), not the dermis. The dermis contains collagen and elastic fibres, blood vessels, nerve endings, sweat glands, sebaceous glands, and hair follicles.

Dermis layers: Papillary dermis (superficial, loose collagen, capillaries, tactile corpuscles) and Reticular dermis (dense irregular collagen, larger vessels, hair follicles, glands). Melanocytes: basal layer of epidermis; produce melanin (transferred to keratinocytes via melanosomes). Dermis is richly vascularized (epidermis is avascular).

Incorrect. Melanocytes are in the epidermis (basal layer), not the dermis. Dermis contains collagen, vessels, glands, follicles, and nerve endings.

Correct! Langer's lines (cleavage lines) represent the predominant orientation of collagen fibres in the dermis. Incisions made parallel to these lines disrupt fewer collagen fibres, resulting in less tension, better wound healing, and minimal scarring.

Langer's lines (cleavage lines): Lines of dermis collagen fibre orientation. Incisions parallel = minimal wound tension = fine linear scar. Incisions across = collagen disruption = wider, hypertrophic scar. Important in cosmetic and reconstructive surgery. Also mark the direction of natural skin tension (RSTL — relaxed skin tension lines).

Incorrect. Langer's lines represent collagen fibre orientation in the dermis. Incisions along them → less collagen disruption → better healing → minimal scarring.

Correct! The deep fascia (investing fascia) forms osteofascial compartments by sending intermuscular septa to the bone. These compartments separate functional muscle groups (e.g., anterior = dorsiflexors, posterior = plantarflexors in the leg) and contain them.

Deep fascia (investing fascia): envelops muscle groups, forms compartments with intermuscular septa and bone. Compartment syndrome: increased pressure → ischaemia → 5 P's (Pain, Pallor, Pulselessness, Paraesthesia, Paralysis). Treatment: emergency fasciotomy. The leg has 4 compartments; the forearm has 2 (anterior + posterior).

Incorrect. Deep fascia forms compartments that separate and contain muscle groups. The clinical significance: compartment syndrome occurs when pressure within these rigid compartments rises, compressing vessels and nerves.

Correct! Acute compartment syndrome presents with pain out of proportion to the injury, pain on passive stretch of muscles in the compartment, and a tense swollen compartment. Pulses may be present early. Definitive treatment is emergency fasciotomy — delay leads to irreversible muscle necrosis (Volkmann's contracture).

Compartment syndrome 5 P's: Pain (disproportionate), Pressure (tense), Paralysis, Paraesthesia, Pallor/Pulselessness (late). Pain on PASSIVE stretch is the most sensitive early sign. Common causes: tibial fracture, crush injury, burns, tight casts. Treatment: fasciotomy within 6 hours to prevent permanent damage.

Incorrect. Pain out of proportion + pain on passive stretch + tense compartment = acute compartment syndrome. This is a surgical emergency requiring fasciotomy. Pulses can be present early.

Correct! The superficial fascia (hypodermis, subcutis) consists of loose areolar connective tissue and adipose tissue (fat). It provides thermal insulation, energy storage, mechanical cushioning, and allows skin mobility over deeper structures.

Superficial fascia (hypodermis): Loose areolar + adipose tissue. Functions: Insulation, energy storage, cushioning, skin mobility. Contains cutaneous nerves and vessels. In palms and soles, it is dense and anchored (prevents excess skin movement). In some areas, it contains muscle (platysma in neck).

Incorrect. Superficial fascia = loose areolar tissue + adipose tissue. Dense irregular collagen = deep fascia. Retinacula cutis are fibrous bands that connect skin to deep fascia through the superficial fascia.

Correct! Stage III pressure ulcer shows full-thickness tissue loss with subcutaneous tissue visible but no exposed bone, tendon, or muscle. The wound base may have slough. It extends through the full thickness of the dermis into the subcutaneous tissue but not into deeper structures.

Pressure ulcer staging (NPUAP): Stage I: Intact skin, non-blanchable erythema. Stage II: Partial thickness — blistering/shallow open wound, pink wound bed. Stage III: Full thickness — subcutaneous fat visible, no bone/tendon. Stage IV: Full thickness — exposed bone/tendon/muscle. Unstageable: depth unknown. Prevention: regular turning, pressure-relieving mattresses.

Incorrect. Yellow slough without visible muscle = Stage III (full thickness, subcutaneous fat may be visible, no exposed bone/tendon). Stage IV: bone or tendon visible. Stage II: partial dermis loss (blister or shallow open wound).

Correct! Eccrine sweat glands are most concentrated on the palms, soles, and forehead (also the axillae). They play the primary role in thermoregulation through evaporative cooling. They open directly onto the skin surface (not into hair follicles).

Eccrine glands: All over body, highest density at palms/soles/forehead. Secretion: watery, hypotonic, thermoregulatory. Apocrine glands: Axillae, groin, areola, perianal; secretion is odourless initially; bacterial breakdown causes body odour. Open into hair follicles. Become active at puberty.

Incorrect. Eccrine sweat glands are most concentrated on the palms, soles, and forehead. They are found all over the body but in highest density at these sites.

Correct! Fascial spaces are potential spaces between fascial layers that can allow rapid spread of infection. In Ludwig's angina, infection spreads through the submandibular, sublingual, and submental fascial spaces, which communicate with each other and with the retropharyngeal and parapharyngeal spaces.

Fascial spaces: Potential spaces along fascial planes that can allow rapid infection spread. Ludwig's angina: Submandibular/sublingual space infection → airway compromise (major risk). Retropharyngeal space infection → 'danger space 4' → mediastinitis. Clinical: fascial space infections spread rapidly, produce little pus initially, cause airway or mediastinal compromise.

Incorrect. Infection spreads along fascial spaces (potential spaces between fascial layers). These are the paths of least resistance for pus and infection.

Correct! A retinaculum is a band of thickened deep fascia that holds tendons in position as they cross a joint (preventing bowstringing). Examples: flexor retinaculum (wrist — forms carpal tunnel), extensor retinaculum (wrist and ankle), superior/inferior extensor retinacula (ankle).

Retinaculum examples: Flexor retinaculum (wrist) = carpal tunnel. Superior extensor retinaculum (ankle) = holds anterior compartment tendons. Inferior extensor retinaculum = Y-shaped, ankle. Peroneal retinacula = hold peroneal tendons. Tarsal tunnel (flexor retinaculum of ankle) = analogous to carpal tunnel.

Incorrect. Retinacula are thickened fascial bands that keep tendons close to bones at joints (prevent bowstringing). Examples: flexor retinaculum at wrist (carpal tunnel) and ankle (tarsal tunnel).

Correct! A split-thickness (partial-thickness) skin graft includes the epidermis and a variable portion of the dermis (typically 0.15–0.45 mm). The donor site retains dermal appendages (hair follicles, sweat glands, sebaceous glands) which allow re-epithelialization. Full-thickness grafts include the complete dermis.

Skin grafts: STSG (split thickness) = epidermis + part of dermis → donor site heals spontaneously (appendages remain) → good for large areas, but less cosmetically ideal. FTSG (full thickness) = epidermis + full dermis → better cosmesis, less contraction → donor site needs closure → used for face, hands. Flaps include subcutaneous tissue/vascularity.

Incorrect. STSG = epidermis + part of dermis. Donor site can re-epithelialize because dermal appendages remain. FTSG = epidermis + full dermis (but donor site must be primarily closed or grafted).