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: Located in the basal layer, these cells synthesize the pigment melanin, which protects against UV radiation and determines skin color.

• Dendritic (Langerhans) Cells: Immune cells that arise from bone marrow and migrate to the epidermis. They help activate the immune response by presenting antigens.

• Tactile (Merkel) Cells: Found 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	Outermost layer; dead, flattened keratinocytes. Provides a tough, protective barrier.
Stratum Lucidum	Thin, clear layer found only in thick skin (palms, soles).
Stratum Granulosum	Cells contain granules of keratohyalin and lamellar granules; involved in waterproofing.
Stratum Spinosum	Several layers of keratinocytes connected by desmosomes; contains dendritic cells.
Stratum Basale	Deepest layer; single row of stem cells that divide to form new keratinocytes. Contains melanocytes and Merkel cells.

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 mainly of adipose 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 reduced blood flow.

• Erythema: Reddened skin, may indicate embarrassment, inflammation, or allergy.

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

• Bruises: Discoloration from damaged blood vessels and leaked blood.

• Brown/black "necklace" bruising: Hyperpigmentation, often associated with endocrine disorders.

Structure of Hair and Nails

Hair Anatomy

• Hair Shaft

• Hair Root

• Hair Follicle

• Arrector Pili Muscle

• Hair Bulb

• Hair Papilla

• Hair Follicle Receptor (root hair plexus)

• Blood Vessels

Nail Anatomy

• Lateral Nail Fold

• Lunule

• Free Edge

• Nail Plate

• Nail Bed

• Eponychium

• Proximal Nail Fold

• Nail Root

• Nail Matrix

Functions of Hair

• Protection (e.g., scalp guards against trauma, eyelashes shield eyes)

• Sensation (detects insects or objects on skin)

• Filtration (nose hairs filter particles)

Glands of the Skin

Types and Functions

• Apocrine Sweat Glands: Found in axillary and anogenital areas; secrete a milky, protein-rich sweat that can produce body odor.

• Eccrine (Merocrine) Sweat Glands: 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: Modified sweat glands in the ear canal; produce cerumen (earwax).

• Mammary Glands: Specialized glands that secrete milk.

Types of Skin Cancer

Classification and Features

• Basal Cell Carcinoma: Most common, least dangerous; arises from stratum basale cells. Slow-growing, rarely metastasizes.

• Squamous Cell Carcinoma: Arises from keratinocytes of the 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 Risks

• Family history of skin cancer

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

• History of blistering or peeling sunburns, especially as a child

• History of tanning bed use

• Compromised immune system

ABCD Rule for Skin Cancer Detection

Clinical Assessment

• Asymmetry: Two sides of the lesion do not match.

• Border Irregularity: Borders are not smooth.

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

• Diameter: Larger than 6 mm (size of a pencil eraser).

Burns: Classification and Consequences

Types of Burns

• First-degree: Only epidermis is damaged; redness, pain, no blisters.

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

• Third-degree: Full thickness; entire skin destroyed, may appear white, red, or blackened. No pain if nerve endings are destroyed; risk of infection and fluid loss.

Skin Changes Across the Lifespan

Developmental Changes

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

• Childhood: Resilient, healthy skin, often free of blemishes.

• Adolescence: Increased oil production, possible acne.

• Adulthood: Gradual loss of collagen, wrinkles, dryness.

• Old Age: Thinner, less elastic skin, increased dryness and fragility.

Vocabulary Table

Vocab 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.

Additional info: The study guide covers all major aspects of the integumentary system, including structure, function, clinical relevance, and vocabulary, making it suitable for college-level Anatomy & Physiology exam preparation.