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, regulates temperature, and provides sensory information.

Cells of the Epidermis

Main Cell Types

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

• Melanocytes: Spider-shaped cells that synthesize melanin, the pigment responsible for skin color and protection against UV radiation.

• Dendritic (Langerhans) Cells: Arise from bone marrow and migrate to the epidermis. They are part of the immune system and help protect against 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, each with specialized cells and functions:

Layer	Description
Stratum Corneum	Dead, flattened keratinocytes; provides a tough, protective outer layer.
Stratum Lucidum	Thin, clear layer found only in thick skin (palms, soles).
Stratum Granulosum	Cells begin to die; keratinization occurs; contains granules.
Stratum Spinosum	Several layers of keratinocytes; contains dendritic cells.
Stratum Basale	Deepest layer; single row of stem cells; site of mitosis and melanocytes.

Layers of the Dermis

Dermal Structure

• Papillary Layer: Superficial layer made of areolar connective tissue; contains capillaries, lymphatic vessels, and sensory receptors (Meissner corpuscles).

• Reticular Layer: Deep layer made of dense irregular connective tissue; contains hair follicles, sweat glands, sebaceous glands, and pressure receptors (Pacinian corpuscles).

Hypodermis

Subcutaneous Layer

• Composed mostly of adipose tissue and areolar connective tissue.

• Acts as a shock absorber and insulator, reducing heat loss.

Skin Color and Clinical Conditions

Color Changes and Causes

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

• Pallor: Pale skin due to emotional stress or blood diversion.

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

• Jaundice: Yellow skin due to bilirubin buildup from liver dysfunction.

• Bruises: Discoloration from blood leakage due to trauma.

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

Hair Structure and Function

Parts of a Hair Follicle

• Hair Shaft

• Hair Bulb

• Hair Papilla

• Arrector Pili Muscle

• Hair Follicle Receptor (root hair plexus)

• Blood Vessels

Functions of Hair

• Protection (scalp, eyes, nose)

• Sensation (detecting insects, light touch)

• Thermal regulation

Nail Structure

Parts of a Nail

• Lateral nail fold

• Lunule

• Free edge

• Nail plate

• Nail bed

• Eponychium

• 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 milky, protein-rich sweat.

  • Eccrine (Merocrine): Widely distributed; secrete watery sweat for thermoregulation.

• Sebaceous (Oil) Glands: Secrete sebum, a mixture of lipids that lubricates and waterproofs skin and hair.

• Ceruminous Glands: Produce earwax (cerumen).

• Mammary Glands: Specialized sweat glands that secrete milk.

Types of Skin Cancer

Classification and Features

Type	Description
Basal Cell Carcinoma	Most common; slow-growing; arises from stratum basale; rarely metastasizes.
Squamous Cell Carcinoma	Arises from keratinocytes of stratum spinosum; can metastasize if not treated early.
Melanoma	Most dangerous; arises from melanocytes; highly metastatic and resistant to chemotherapy.

Risk Factors for Skin Cancer

Genetic and Personal Health Risks

• Genetic: Family history, fair skin, blue/green eyes, many moles, skin conditions increasing sun sensitivity.

• Personal: History of sunburns, excessive sun exposure, tanning bed use, compromised immune system.

ABCD Rule for Skin Cancer Detection

Clinical Signs

• Asymmetry: Uneven shape.

• Border Irregularity: Indented or uneven borders.

• Color: Multiple colors (black, brown, tan, blue, red).

• Diameter: Larger than 6 mm.

Burns: Classification and Consequences

Types of Burns

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

• Second-degree: Epidermis and part of dermis; blisters, pain, partial thickness.

• Third-degree: Full thickness; entire skin destroyed; risk of infection, fluid loss, and scarring.

Skin Changes Across the Lifespan

Developmental Changes

• Infancy: Soft, plump, smooth skin with abundant collagen.

• Childhood: Resilient, glowing skin; rapid healing.

• Adolescence: Oil production increases; acne may develop.

• Adulthood: Collagen decreases; wrinkles form; skin thins and dries.

Vocabulary Table

Term	Use in a Sentence	Synonym	Reminds me of...
Dermatology	She was very interested in skin diseases so she applied for a position in dermatology.	Skin science	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.	Skin system	The cosmetology program at Riverland.
Epidermis	The outermost layer of the skin containing melanocytes.	Top layer	Top sheet of bed.

Key Formulas and Scientific Terms

• Keratin: A fibrous protein providing strength and waterproofing.

• Melanin: Pigment responsible for skin color and UV protection.

• ABCD Rule: Asymmetry, Border, Color, Diameter for skin cancer detection.

Additional info: The study guide covers all major aspects of the integumentary system relevant for Anatomy & Physiology students, including cell types, layers, accessory structures, clinical conditions, and cancer risk factors.