The Integumentary System: Structure, Function, and Pathology - Med Term CH 16

The Integumentary System

Introduction

The integumentary system consists of the skin and its accessory structures, including hair, nails, and glands. It serves as the body's primary barrier against environmental hazards and plays a crucial role in sensation, thermoregulation, and metabolic functions.

Structure of the Skin

Layers of the Skin

The skin is composed of three main layers, each with distinct functions and cellular compositions:

• Epidermis: The outermost layer, consisting of stratified squamous epithelium. It includes the basal layer (site of cell division), stratum corneum (keratinized cells), and melanocytes (pigment-producing cells).

• Dermis: The middle layer, made of dense connective tissue containing collagen fibers, blood vessels, nerve endings, and glands.

• Subcutaneous Layer: The innermost layer, composed mainly of adipose tissue, providing insulation and energy storage.

Example: The basal layer continuously produces new epidermal cells, which migrate upward and become keratinized.

Accessory Structures of the Skin

Hair

Hair is composed of keratinized cells and grows from follicles embedded in the dermis. Melanocytes at the root determine hair color. Hair serves protective and sensory functions.

• Hair Follicle: The sac within which each hair grows.

• Hair Root: The base of the hair, where growth occurs.

• Melanocytes: Cells that produce pigment for hair color.

Nails

Nails are hard keratin plates covering the fingers and toes. They protect the distal phalanges and aid in fine manipulation.

• Lunula: The whitish, half-moon-shaped area at the base of the nail.

• Cuticle: The band of epidermis at the base and sides of the nail plate.

• Paronychium: The soft tissue surrounding the nail border.

Glands

The skin contains two main types of glands:

• Sebaceous Glands: Secrete oily sebum into hair follicles to lubricate skin and hair.

• Sweat Glands: Include eccrine (most numerous, produce watery sweat for cooling) and apocrine (located in axilla and genital areas, produce thicker secretions).

Functions of the Skin

Protective and Regulatory Functions

The skin acts as a protective membrane, regulates body temperature, and serves as a receptor for sensations such as pain, temperature, pressure, and touch. It also produces sweat and sebum, which help cool and lubricate the skin.

• Thermoregulation: Sweat glands produce a watery secretion that evaporates to cool the body.

• Sensation: Nerve endings in the skin detect environmental stimuli.

• Barrier: Prevents entry of pathogens and loss of water.

Medical Terminology Related to Dermatology

Combining Forms and Colors

Medical terms often use combining forms to describe colors and conditions of the skin. Understanding these forms aids in interpreting medical reports.

Combining Form	Meaning	Terminology
albin/o	white	albinism
melan/o	black	melanocyte
xanth/o	yellow	xanthoma
erythr/o	red	erythrocyte
cyan/o	blue	cyanosis
leuk/o	white	leukoderma
chlor/o	green	chlorophyll
anthrac/o	black (as coal)	anthracosis
jaund/o	yellow	jaundice

Cutaneous Lesions

Types of Lesions

Lesions are abnormal changes in the skin's structure or appearance. Common types include:

• Crust (scab): Dried serum and cellular debris.

• Cyst: Closed sac containing fluid or semisolid material.

• Erosion: Loss of superficial epidermis.

• Fissure: Deep groove or crack.

• Macule: Flat, colored spot.

• Nodule: Solid, raised lesion.

• Papule: Small, raised bump.

• Pustule: Elevated lesion containing pus.

• Ulcer: Open sore with loss of tissue.

• Vesicle: Small, fluid-filled blister.

• Wheal: Raised, red area due to allergic reaction.

Signs and Symptoms of Skin Disorders

Alopecia

Alopecia is the absence of hair where it normally grows, often resulting from autoimmune or genetic factors.

Ecchymosis

Ecchymosis refers to blue-purple marks on the skin, commonly known as bruises, caused by bleeding under the skin.

Petechia

Petechia are small, pinpoint hemorrhages resulting from capillary bleeding.

Urticaria

Urticaria (hives) is an acute allergic reaction characterized by red, round wheals on the skin.

Abnormal Skin Conditions

Acne

Acne is a papular and pustular eruption of the skin with increased production of sebum, often resulting in blackheads and inflammation.

Tinea

Tinea is a fungal infection of the skin, commonly known as ringworm. It presents as circular, red, scaly patches.

Vitiligo

Vitiligo is the loss of pigment in areas of the skin, resulting in white patches.

Skin Neoplasms

Basal Cell Carcinoma

Basal cell carcinoma is a malignant tumor of the basal cell layer of the epidermis. It is the most common type of skin cancer and typically appears as a raised, pearly lesion.

Squamous Cell Carcinoma

Squamous cell carcinoma is a malignant tumor of the squamous epithelial cells of the epidermis. It often presents as a scaly, red patch or nodule.

Laboratory Tests and Clinical Procedures

Laboratory Tests

• Bacterial Analyses: Examination of pus or fluid samples to detect microorganisms.

• Fungal Tests: Skin scrapings are cultured and examined microscopically after treatment with potassium hydroxide (KOH).

Clinical Procedures

• Cryosurgery: Destruction of tissue using subzero temperatures (liquid nitrogen).

• Curettage: Scraping of lesions with a sharp curet.

• Electrodesiccation: Destruction of tissue by burning with an electric spark.

• Mohs Surgery: Removal of thin layers of growth for microscopic examination, especially for basal and squamous cell carcinomas.

• Skin Biopsy: Removal of skin tissue (punch or shave) for pathological examination.

• Skin Test: Testing the body's reaction to allergens (scratch or patch tests).

Abbreviations in Dermatology

Abbreviation	Meaning
ABCDE	Asymmetry, Border, Color, Diameter, Evolution (characteristics of melanoma)
Bx	Biopsy
Derm.	Dermatology
DLE	Discoid lupus erythematosus
PPD	Purified protein derivative
PUVA	Psoralen-ultraviolet A light therapy
SLE	Systemic lupus erythematosus
SC	Subcutaneous

Suffixes Commonly Used in Dermatology

Suffix	Meaning
-algia	Pain
-derma	Skin
-esis	Condition
-lysis	Breakdown; separation; destruction; loosening
-ose	Full of; pertaining to; sugar
-osis	Condition, usually abnormal
-ous	Pertaining to
-plakia	Plaque
-plasty	Surgical repair
-rrhea	Flow; discharge

Summary

The integumentary system is essential for protection, sensation, and regulation. Understanding its structure, functions, and common pathologies is fundamental for students in anatomy and physiology courses.