Integumentary System: Medical Terminology and Clinical Concepts

Integumentary System Overview

Introduction

The integumentary system consists of the skin and its accessory structures, including hair, nails, sebaceous glands, and sweat glands. It is the largest organ system in the body and serves multiple essential functions for protection, regulation, sensation, and secretion.

Anatomy and Physiology of the Skin

Layers of the Skin

The skin is composed of two primary layers: the epidermis and the dermis. Beneath these lies the subcutaneous layer (hypodermis), which supports and insulates the skin.

• Epidermis: The outermost layer, thinnest on the eyelids and thickest on the palms and soles. It is divided into five strata: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

• Dermis: Also called the corium or true skin, it contains connective tissue, blood vessels, nerves, lymphatics, sebaceous and sweat glands, elastic fibers, and hair follicles. It is divided into the papillary (upper) and reticular (lower) layers.

• Subcutaneous Layer: Composed mainly of fat and connective tissue, it attaches the skin to underlying structures and provides insulation and cushioning.

Functions of the Skin

Main Functions

The skin performs four main functions:

• Protection: Acts as a barrier against bacteria, mechanical injury, water loss, and ultraviolet radiation. It also helps produce vitamin D.

• Regulation: Maintains body temperature through vasodilation, vasoconstriction, and sweat production.

• Sensation: Contains sensory receptors for pain, touch, heat, cold, and pressure.

• Secretion: Sweat glands secrete perspiration for cooling; sebaceous glands secrete sebum for lubrication.

Accessory Structures of the Skin

Hair

Hair is a thin, threadlike structure formed in hair follicles. Each hair consists of a visible shaft and a root embedded in the follicle. The arrector pili muscle attaches to the follicle, causing hair to stand up when contracted. Hair in the nose, ears, and around the eyes helps filter foreign particles.

Nails

Nails are hard keratin structures of the epidermis. The nail body is the visible part, covering the nail bed. The nail root is hidden under the cuticle (eponychium), and the lunula is the pale, crescent-shaped area at the base. Nail growth varies with age, disease, and hormones.

Glands

• Sebaceous (Oil) Glands: Secrete sebum into hair follicles for lubrication. Secretion is regulated by hormones and varies with age and physiological state.

• Sudoriferous (Sweat) Glands: Two types: eccrine (widely distributed, secrete sweat for cooling) and apocrine (in armpits, nipples, groin; secrete a thicker fluid).

Developmental and Age-Related Changes

• Before birth, the fetus is covered with vernix caseosa and lanugo hair.

• Newborns have less subcutaneous fat, making them more sensitive to temperature changes.

• With aging, skin loses elasticity, hair may gray or thin, and nails may become brittle.

Common Diseases and Conditions

Acne

Acne is a common inflammatory condition of the sebaceous glands, often seen in adolescents. Severe forms, such as acne fulminans, can cause ulcerative lesions and systemic symptoms.

Photodermatitis

Photodermatitis is an abnormal skin reaction to sunlight, often presenting as redness and inflammation.

Alopecia

Alopecia areata is an autoimmune condition causing patchy hair loss. Androgenetic alopecia is a hereditary form of hair loss, commonly known as male or female pattern baldness.

Skin Cancer

Basal cell carcinoma (BCC) is the most common skin cancer, usually slow-growing and associated with sun exposure. Early surgical removal is recommended.

Bites and Infestations

• Brown recluse spider bites can cause necrotic skin lesions.

• Tick bites may transmit infectious diseases.

• Flea bites present as small, itchy red bumps.

Burns

Burns are classified by depth:

Degree	Skin Layers Involved	Characteristics
First (Superficial Partial Thickness)	Epidermis	Redness, pain, no blisters (e.g., sunburn)
Second (Partial Thickness)	Epidermis + part of dermis	Blisters, pain, heals in 10-14 days
Third (Full Thickness)	All skin layers	White, brown, or black skin, no pain (nerve damage), requires grafting

Other Skin Disorders

• Candidiasis: Fungal infection, often in moist areas.

• Carbuncle: Cluster of boils caused by bacterial infection.

• Cellulitis: Acute infection of the skin and subcutaneous tissue.

• Dermatitis: Inflammation of the skin, often due to contact with irritants or allergens.

• Erythema: Redness of the skin due to increased blood flow.

• Excoriation: Superficial loss of skin due to scratching or abrasion.

• Impetigo: Contagious bacterial skin infection, common in children.

• Keloid: Overgrowth of scar tissue at the site of a healed skin injury.

• Melanoma: Malignant tumor of melanocytes, highly aggressive skin cancer.

• Miliaria: Heat rash caused by blocked sweat ducts.

• Onychomycosis: Fungal infection of the nails.

• Pediculosis capitis: Infestation of the scalp with head lice.

• Psoriasis: Chronic autoimmune condition with red, scaly patches.

• Purpura: Purple spots due to bleeding under the skin.

• Rosacea: Chronic facial redness and swelling.

• Scabies: Infestation by the mite Sarcoptes scabiei.

• Seborrheic keratosis: Benign, wart-like skin growths.

• Striae: Stretch marks due to rapid stretching of the skin.

• Telangiectasia: Small, dilated blood vessels near the skin surface.

• Tinea corporis: Fungal infection of the body (ringworm).

• Ulcer: Open sore or lesion of the skin.

• Varicella: Chickenpox, a viral infection with vesicular rash.

• Wart: Benign growth caused by human papillomavirus (HPV).

Medical Terminology Building Blocks

Word Construction

• Causalgia: caus = heat, -algia = pain (burning pain)

• Excoriation: ex- = out, coriat = corium, -ion = process (scraping away of skin)

• Hypodermic: hypo- = under, derm = skin, -ic = pertaining to (under the skin)

• Rhytidoplasty: rhytid/o = wrinkle, -plasty = surgical repair (surgical repair of wrinkles)

Drug Highlights

• Emollients: Oily substances for dry skin.

• Keratolytics: Promote loosening of keratin layers.

• Local anesthetics: Reduce pain by inhibiting nerve impulses.

• Antihistamines: Prevent histamine action (allergy relief).

• Antipruritics: Relieve itching.

• Antibiotics: Destroy or inhibit microorganisms.

• Antifungals: Inhibit fungi and yeast.

• Antivirals: Combat viral diseases.

• Anti-inflammatories: Relieve swelling, redness, and pain.

• Antiseptics: Prevent pathogen growth.

• Other drugs: Retin-A (acne), Rogaine (hair loss), Botox (wrinkle reduction).

Diagnostic and Laboratory Tests

• Tuberculosis Skin Test (Mantoux): Intradermal injection of PPD to detect TB infection.

• Interferon-gamma Release Assays (IGRAs): Blood test for TB infection.

• Scratch/Prick Test: Allergy test by introducing allergens to the skin.

• Sweat Test (Chloride): Measures chloride in sweat, used for cystic fibrosis diagnosis.

• Tzanck Test: Microscopic exam of tissue from a pustule to identify viral infection.

• Wound Culture: Identifies microorganisms in wound exudate.

• Biopsy: Microscopic exam of tissue to distinguish benign from malignant lesions.

• Erythrocyte Sedimentation Rate (ESR): Measures rate of red blood cell settling, indicating inflammation.

Selected Abbreviations and Acronyms

Students should familiarize themselves with common abbreviations related to the integumentary system, such as BCC (basal cell carcinoma), TB (tuberculosis), and ESR (erythrocyte sedimentation rate).

Summary Table: Integumentary System at-a-Glance

Structure	Description	Function
Skin	Largest organ, two main layers (epidermis, dermis)	Protection, regulation, sensation, secretion
Hair	Threadlike structures in follicles	Protection, filtration
Nails	Hard keratin plates	Protection, fine manipulation
Sebaceous glands	Oil-secreting glands	Lubrication
Sudoriferous glands	Sweat glands (eccrine, apocrine)	Temperature regulation

Additional info: This guide expands on the textbook content with definitions, clinical context, and logical groupings for exam preparation. Images are included only when directly relevant to the adjacent text.