Skin !
The skin of the leg is its outer covering, from hip to toes; it protects the tissues beneath, helps control temperature and senses touch, pain and pressure.
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What it is
The outer covering of the lower limb.
What it does
Protects the deeper layers. Turn it off in Layers to see inside.
Key facts
- Where
- Covers the whole body surface; continuous with the mucous membranes at the body openings; thickest on the soles and back, thinnest on the eyelids
- Blood supply
- Dermal and subdermal plexuses fed by direct cutaneous, musculocutaneous and fasciocutaneous perforator arteries
- Nerve
- Cutaneous branches of spinal and cranial nerves, arranged in dermatomes; sympathetic fibres to sweat glands, arrector pili muscles and vessels
- Function
- Barrier against water loss, microbes and UV light; temperature control; touch, pain and temperature sensation; vitamin D synthesis
Relations
- Superficial
- Stratum corneum, the dead keratinised barrier, continuous with the mucous membranes at the body openings
- Deep
- Hypodermis, then the deep fascia; cutaneous nerves and superficial veins run in the subcutaneous fat
- Contents
- Epidermis: keratinocytes, melanocytes, Langerhans and Merkel cells; dermis: collagen and elastic fibres, hair follicles, sebaceous and sweat glands, Meissner and Pacinian corpuscles
How to find it
Dermatomes are mapped at key sensory points; in the lower limb, L4 over the medial malleolus, L5 on the dorsum of the foot at the third MTP joint and S1 on the lateral heel. In the sole, fibrous septa tie the skin to the plantar aponeurosis and divide the heel fat into cushioning chambers.
Examination
- Light touch and pinprick tested dermatome by dermatome locate a nerve root or spinal cord lesion
- Monofilament test on the sole: failure to feel it marks loss of protective sensation in diabetic neuropathy
- Two-point discrimination is finest on the fingertips and lips and coarsest on the back
On imaging
High-frequency ultrasound shows the epidermis, dermis and subcutaneous tissue, and finds abscesses and foreign bodies; dermoscopy magnifies pigmented lesions.
Clinical notes
- Burn depth: superficial (epidermis only), partial thickness (into the dermis, painful, blistered), full thickness (through the dermis, leathery and insensate)
- Pressure injuries develop over bony prominences such as the sacrum, the heels and the ischial tuberosities
- Neuropathic ulcers of the sole form under the metatarsal heads and the heel, where load is highest
- Keloids grow beyond the original wound edges, unlike hypertrophic scars, and are more common in darker skin
- Burn size is a percentage of total body surface area (about 1.6–1.8 m² in adults); each whole lower limb is about 18% by the rule of nines (Lund–Browder chart in children); it guides fluid resuscitation
Development
The epidermis comes from surface ectoderm, the dermis from mesoderm, and melanocytes from neural crest cells.
Memory aid
Epidermal layers from the surface down: "Come, Let's Get Sun Burned" (corneum, lucidum, granulosum, spinosum, basale).
Related conditions
- Arsenic poisoning
- Oculocutaneous albinism
- Porphyria cutanea tarda
- Erythropoietic protoporphyria
- Neonatal jaundice
- Methemoglobinemia
- Kwashiorkor
- Xeroderma pigmentosum
- Bloom syndrome
- Ehlers–Danlos syndrome
- Scurvy (vitamin C deficiency)
- Pellagra (niacin deficiency)
- Zinc deficiency (acrodermatitis enteropathica)
- Melanoma
- Basal cell carcinoma
- Cutaneous squamous cell carcinoma
- Pressure injury (pressure ulcer)
- Atopic dermatitis
- Psoriasis
- Stevens–Johnson syndrome and toxic epidermal necrolysis
- Urticaria and angioedema
- Scabies
- Impetigo
- Dermatophytosis (tinea) and onychomycosis
- Acne vulgaris
- Contact dermatitis (irritant and allergic)
- Pemphigus vulgaris
- Bullous pemphigoid
- Seborrheic dermatitis
- Erythema multiforme
- Cutaneous drug reactions and DRESS
- Pediculosis (head, body and pubic lice)
- Cutaneous and mucocutaneous candidiasis
- Diaper dermatitis
- Abscess, furuncle and carbuncle
- Pityriasis versicolor
- Viral warts (verruca)
- Vitiligo
- Rosacea
- Actinic keratosis
- Erythema nodosum
- Hidradenitis suppurativa
- Lichen planus
- Pityriasis rosea
- Molluscum contagiosum
- Dermatitis herpetiformis
- Seborrheic keratosis
- Melanocytic nevi and dysplastic nevus
- Alopecia areata
- Melasma
- Discoid lupus erythematosus
- Keloid and hypertrophic scar
- Infantile hemangioma
- Staphylococcal scalded skin syndrome
- Kaposi sarcoma
- Cutaneous larva migrans
- Tungiasis and furuncular myiasis
- Pyoderma gangrenosum
- Acanthosis nigricans
- Sweet syndrome (acute febrile neutrophilic dermatosis)
- Epidermolysis bullosa acquisita
- Mucous membrane (cicatricial) pemphigoid
- Polymorphous light eruption
- Snakebite envenomation (Bothrops, Lachesis, Crotalus)
- Coral snake envenomation (Micrurus)
- Scorpion envenomation (Tityus)
- Anticholinergic toxicity (incl. scopolamine «burundanga»)
- Electrical and lightning injury
- Spider bites (loxoscelism and latrodectism)
- Hymenoptera stings (bees, wasps, ants)
- Mammalian bites (dog, cat, human)
- Frostbite
- Marine envenomations and seafood poisoning (ciguatera, scombroid, jellyfish, stingray)
- Elder abuse and neglect
- Skin tears in older adults
- Incontinence-associated dermatitis
- Immune thrombocytopenia (ITP)
- Heparin-induced thrombocytopenia
- Von Willebrand disease
- Graft-versus-host disease
- Merkel cell carcinoma
- Mycosis fungoides and Sézary syndrome (cutaneous T-cell lymphoma)
- Mastocytosis (cutaneous and systemic)
- Dyskeratosis congenita and other telomere biology disorders
- Meningococcal disease (meningococcemia)
- Leprosy (Hansen disease)
- Rickettsial infections (spotted fever)
- Lyme disease
- Toxic shock syndrome
- Necrotizing soft tissue infection (necrotizing fasciitis, gas gangrene)
- MRSA and other multidrug-resistant organism infections
- Anthrax
- Endemic mycoses: blastomycosis and coccidioidomycosis
- Sporotrichosis and other subcutaneous mycoses
- Mpox
- Mycetoma (actinomycetoma and eumycetoma)
- Yaws and endemic treponematoses
- Tularaemia
- Chromoblastomycosis
- Onchocerciasis (river blindness)
- Calciphylaxis (calcific uremic arteriolopathy)
- Measles
- Varicella (chickenpox)
- Rubella and congenital rubella syndrome
- Scarlet fever
- Wiskott–Aldrich syndrome
- Roseola infantum (exanthem subitum)
- Erythema infectiosum (fifth disease, parvovirus B19)
- Hand, foot and mouth disease
- Sturge–Weber syndrome
- Hyper-IgE syndrome (Job syndrome)
- Chédiak–Higashi syndrome
- Systemic sclerosis (scleroderma, including CREST)
- Inflammatory myopathies (dermatomyositis, polymyositis)
- IgA vasculitis (Henoch–Schönlein purpura)
- Behçet disease
- Cryoglobulinemic vasculitis
- Adult-onset Still disease
- Complex regional pain syndrome
- Cutaneous small-vessel (leukocytoclastic, hypersensitivity) vasculitis
- Burns (thermal, chemical, electrical; inhalation injury)
- Surgical site infection
- Open fracture
- Wound dehiscence and evisceration
- Pilonidal disease
Test yourself
Think of the answer, then tap the question to see it.
Which dermatomes are tested at the medial malleolus, the dorsum of the foot at the third MTP joint and the lateral heel?
L4, L5 and S1 respectively: these are the key sensory points for the lower limb dermatomes.
Why are skin incisions placed along Langer (cleavage) lines?
They heal with narrower scars, because Langer lines follow the orientation of the dermal collagen.
What does failure to feel the monofilament on the sole of the foot indicate?
Loss of protective sensation from diabetic neuropathy, which puts the sole at risk of neuropathic ulcers under the metatarsal heads and heel.
How does a keloid differ from a hypertrophic scar?
A keloid grows beyond the original wound edges; a hypertrophic scar stays within them. Keloids are more common in darker skin.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- cutis TA2 7041
- Official Spanish (DeCS)
- Piel DeCS D012867
- English (TA2)
- Skin
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Skin (Integument); Physiology, Integument; Anatomía humana (4.ª ed.), tomo 1, cap. 53: Integumento común. Sentido del tacto.
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Representative model, for educational purposes only.
