Study Guide: The Integumentary System (Anatomy & Physiology)

Chapter 5: The Integumentary System

Overview

The integumentary system is composed of the skin and its accessory structures, including hair, nails, and glands. It serves as the body's first line of defense, provides protection, regulates temperature, and enables sensory perception.

Cells of the Epidermis

Main Cell Types and Their Functions

• Keratinocytes: Produce keratin, a fibrous protein that provides strength and waterproofing to the skin. These cells are tightly connected by desmosomes and form the majority of the epidermis.

• Melanocytes: Synthesize the pigment melanin, which protects underlying cells from ultraviolet (UV) radiation.

• Dendritic (Langerhans) Cells: Arise from bone marrow and migrate to the epidermis. They are part of the immune system and help detect and fight pathogens.

• Tactile (Merkel) Cells: Located at the epidermal-dermal junction, these cells are associated with sensory nerve endings and function as touch receptors.

Layers of the Epidermis

Structure and Function

The epidermis consists of five distinct layers, listed from deepest to most superficial:

1. Stratum Basale (Germinativum): Deepest layer; single row of stem cells that continually divide to form new keratinocytes.

2. Stratum Spinosum: Several layers of keratinocytes unified by desmosomes; contains thick bundles of intermediate filaments.

3. Stratum Granulosum: Three to five layers of flattened cells; organelles deteriorate, and keratinization begins.

4. Stratum Lucidum (only in thick skin): Thin, clear layer of dead keratinocytes.

5. Stratum Corneum: Outermost layer; 20–30 layers of dead, keratinized cells that provide a tough, protective barrier.

Layers of the Dermis

Dermal Structure

• Papillary Layer: Superficial layer made of areolar connective tissue; contains dermal papillae, capillaries, and sensory receptors.

• Reticular Layer: Deeper, thicker layer made of dense irregular connective tissue; contains collagen and elastic fibers, glands, hair roots, and pressure receptors (e.g., lamellar/Pacinian corpuscles).

Hypodermis (Subcutaneous Layer)

Structure and Function

• Composed mainly of adipose and areolar connective tissue.

• Anchors skin to underlying structures, acts as a shock absorber, and insulates the body to reduce heat loss.

Skin Color and Clinical Conditions

Color Changes and Their Causes

• Cyanosis: Blue tint due to lack of oxygenated hemoglobin.

• Pallor: Pale skin from emotional stress or anemia (blood diverted from skin).

• Erythema: Reddened skin from embarrassment, fever, inflammation, or allergies.

• Jaundice: Yellowing due to bilirubin buildup from liver dysfunction.

• Bruises: Black/blue marks from blood vessel damage and blood leakage.

• Brown/black "necklace" bruising: Hyperpigmentation, often a sign of endocrine disorder.

Hair and Hair Follicle Anatomy

Parts of a Hair/Hair Follicle

• Hair Shaft

• Hair Root

• Hair Follicle

• Arrector Pili Muscle

• Hair Bulb

• Hair Papilla

• Hair Follicle Receptor (root hair plexus)

• Blood Vessel

Functions of Hair

• Protection (e.g., scalp from trauma, eyelashes from debris)

• Sensory input (detecting insects or light touch)

• Thermal insulation

Nail Anatomy

Parts of a Nail

• Lateral nail fold

• Lunule

• Free edge

• Nail plate

• Nail bed

• Eponychium (cuticle)

• Proximal nail fold

• Nail root

• Nail matrix

Glands of the Skin

Types and Functions

• Sudoriferous (Sweat) Glands:

  • Apocrine: Found in axillary and anogenital areas; secrete a viscous, milky sweat that may produce body odor.

  • Eccrine (Merocrine): Most numerous; found on palms, soles, and forehead; secrete watery sweat for thermoregulation.

• Sebaceous (Oil) Glands: Secrete sebum, an oily substance that lubricates skin and hair.

• Ceruminous Glands: Modified sweat glands in the ear canal; secrete cerumen (earwax).

• Mammary Glands: Specialized sweat glands that secrete milk.

Types of Skin Cancer

Classification and Characteristics

• Basal Cell Carcinoma: Most common and least malignant; arises from stratum basale; slow-growing and rarely metastasizes.

• Squamous Cell Carcinoma: Arises from keratinocytes of the stratum spinosum; can metastasize if not removed.

• Melanoma: Most dangerous; arises from melanocytes; highly metastatic and resistant to chemotherapy.

Risk Factors for Skin Cancer

Genetic and Personal Health Risks

• Family history of skin cancer

• Fair skin, blue or green eyes, blond or red hair

• History of frequent sunburns, especially in childhood

• Excessive sun exposure or tanning bed use

• Compromised immune system

ABCD Rule for Skin Cancer Detection

Clinical Assessment

• Asymmetry: Two sides of the pigmented spot or mole do not match.

• Border irregularity: Borders are not smooth, but have indentations.

• Color: Contains several colors (black, brown, tan, sometimes blue or red).

• Diameter: Spot is larger than 6 mm (about the size of a pencil eraser).

Burns: Classification and Consequences

Degrees of Burns

• First-degree: Only the epidermis is damaged; redness, pain, and swelling.

• Second-degree: Epidermis and upper dermis are damaged; blisters, pain, and possible regeneration without scarring.

• Third-degree: Entire thickness of skin is destroyed; skin appears gray-white, cherry red, or blackened; not painful initially due to nerve damage; risk of fluid loss and infection.

Skin Changes Across the Lifespan

Developmental Changes

• Infancy: Skin is soft, smooth, and full of collagen.

• Childhood: Skin remains resilient and free of blemishes.

• Adolescence: Increased oil production, possible acne.

• Adulthood and Aging: Skin loses collagen, becomes thinner, wrinkles form, and dryness increases.

Vocabulary Table: Integumentary System Terms

Vocab Term	Use in a Sentence	Synonym	Picture/Image	Reminds me of...
Dermatology	She was very interested in skin diseases so she applied for a position in dermatology.	Skin science	[Image of dermatologist, omitted]	Going to a dermatologist for help with a skin rash.
Integumentary System	The parts of the integumentary system include the skin, hair, nails, and glands.		[Diagram of skin layers]	The cosmetology program at Riverland.
Epidermis	The outermost layer of the skin containing melanocytes.	Top layer	[Diagram of skin layers]	Top sheet of bed

Additional info: The notes also include self-assessment questions, diagrams for labeling, and vocabulary exercises to reinforce learning of the integumentary system.