The Integumentary System Lecture Notes
The Integumentary System
Lecture Overview
Presented by: Chasity O’Malley, Palm Beach State College
Notes by: Lori Garrett, Parkland College
Copyright: © 2018 Pearson Education, Inc.
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Section 1: Functional Anatomy of the Skin
Learning Outcomes
5.1: Describe the tissue structure and functions of the integumentary system.
5.2: Describe main structural features of the epidermis and explain their functional significance.
5.3: Explain individual differences in skin color; compare basal cell carcinoma with malignant melanoma.
5.4: Describe structures and functions of dermis and subcutaneous layer.
5.5: Classify burns and types of skin grafts.
Module 5.1: Overview of the Integumentary System
Definition: The integumentary system consists of the skin and various accessory structures.
Importance:
Most accessible organ system.
Represents 16% of total body weight.
Surface area of 1.5 to 2 m².
Functions as the body's first line of defense.
Components:
Cutaneous membrane:
Epidermis: Composed of stratified squamous epithelium.
Dermis:
Papillary layer: Areolar connective tissue.
Reticular layer: Dense irregular connective tissue.
Accessory structures:
Hairs
Nails
Exocrine glands:
Sebaceous glands
Sweat glands
Sensory receptors and nerve fibers
Arrector pili muscles
Cutaneous plexus (network of blood vessels)
Functions of the Integumentary System
Protective Functions:
Protects underlying tissues and organs from impact, abrasion, fluid loss, and chemical exposure.
Excretion:
Excretes salts, water, and organic wastes via integumentary glands.
Thermoregulation:
Maintains normal body temperature through insulation or evaporative cooling.
Pigmentation Production:
Produces melanin, safeguarding underlying tissues from ultraviolet radiation.
Keratin Production:
Produces keratin for abrasion resistance and as a water repellent.
Vitamin D3 Synthesis:
Synthesizes vitamin D3, which is converted to calcitriol, important for calcium metabolism.
Storage:
Stores lipids in adipocytes of the dermis and subcutaneous layer.
Sensory Detection:
Detects touch, pressure, pain, and temperature stimuli; relays information to the nervous system.
Module 5.2: The Epidermis
Structure Overview:
Composed of multiple strata (layers) with varying functions.
Primary Cell Type: Keratinocyte.
Deeper Layers: Form epidermal ridges adjacent to dermal papillae for increased surface area and attachment.
Types of Skin
Thin Skin:
Covers most body surfaces; contains four strata.
Example: Facial skin.
Thick Skin:
Found on palms and soles; contains five strata.
Example: Palmer skin.
Fingerprints
Unique patterns of epidermal ridges on fingertips; remain unchanged throughout a person's life.
Epidermal Layers (Deep to Superficial)
Stratum Basale:
Attached to basement membrane via hemidesmosomes.
Contains basal cells, stem cells dividing to replace superficial keratinocytes.
Houses Merkel cells responsive to touch.
Stratum Spinosum (Spiny Layer):
Composed of 8-10 layers of keratinocytes interlinked by desmosomes.
Contains dendritic (Langerhans) cells, involved in immune defense against pathogens and skin cancers.
Stratum Granulosum (Grainy Layer):
Composed of 3-5 layers of keratinocytes.
Cells cease division, initiating keratin and keratohyalin production.
Results in thinner, flatter cells; membranes thicken, reducing permeability.
Stratum Lucidum (Clear Layer):
Present only in thick skin.
Separates stratum corneum from underlying layers.
Composed of flattened, densely packed dead cells filled with keratin.
Stratum Corneum (Horn Layer):
Outermost protective layer with 15-30 layers of keratinized cells (filled with keratin).
Dead cells remain connected by desmosomes; water resistant but not waterproof.
Loss of water occurs through insensible perspiration and sensible perspiration (sweat).
Review Questions
A. Compare thin and thick skin.
B. Identify the five layers of the epidermis (from superficial to deep).
Dandruff: Excessive shedding from the stratum corneum.
Splinter example: If it penetrates the third layer, it is in the stratum granulosum.
Module 5.3: Factors Influencing Skin Color
Influencing Factors:
Presence of skin pigments such as carotene and melanin.
Dermal circulation and thickness of the stratum.
UV radiation exposure increases pigmentation despite genetic factors.
Primary Skin Pigments
Carotene: Orange-yellow pigment; contributes to skin color.
Melanin: Produced by melanocytes in stratum basale, it gives brown, yellow-brown, or black pigmentation.
Differences are due to the amount of melanin, not the number of melanocytes.
Melanosomes (vesicles) transport melanin to keratinocytes.
Effects of Blood Supply on Skin Color
Hemoglobin: Red pigment in blood, directly affects skin appearance.
Enhanced blood flow results in a redder coloration; reduced flow leads to pale skin.
Severe reductions in blood supply can result in cyanosis, observed in thin-skinned areas.
Skin Conditions
Basal Cell Carcinoma:
Most common skin cancer originating in stratum basale due to UV-induced mutations.
Malignant Melanoma:
Highly dangerous skin cancer originating from melanocytes; rapid metastasis through the lymphatic system.
If detected early, 5-year survival rate is 99%; if detected late, drops to 14%.
Review Questions
A. Name the two pigments in the epidermis.
B. Why does sunlight exposure darken skin?
C. Why does light-skinned skin appear red during exercise?
D. Why is basal cell carcinoma less dangerous than malignant melanoma?
E. Reason for potential yellow-orange skin in a 6-month-old.
Module 5.4: The Dermis and Subcutaneous Layer
Dermis Location: Situated between the epidermis and hypodermis.
Contains collagen and elastic fibers.
Dermis Layers
Papillary Layer:
Named for dermal papillae; composed of areolar tissue with capillaries, lymphatic vessels, and sensory neurons.
Reticular Layer:
Dense irregular connective tissue interwoven meshwork containing collagen and elastic fibers; hosts blood vessels, lymphatic vessels, nerve fibers, and accessory organs (hair follicles, sweat glands).
Subcutaneous Layer (Hypodermis)
Not part of the skin but separates it from deeper fascia; composed mainly of adipose tissue for energy storage.
Adipose Accumulation Patterns
Men: Accumulation in neck, arms, lower back, buttocks.
Women: Accumulation in breasts, hips, thighs; minimal on backs of hands and soles.
Sensory Receptors in Skin
Epidermis: Free nerve endings sensitive to touch or pressure; tactile corpuscles detect steady pressure.
Dermis:
Meissner corpuscles detect light touch and vibration.
Pacinian corpuscles detect deep pressure and vibration.
Ruffini corpuscles respond to skin pressure and stretch.
Tension (Cleavage) Lines
Formed by collagen and elastic fiber arrangement; significant for surgical considerations—cuts parallel heal better with less scarring.
Review Questions
A. Describe dermis layers.
B. Predict scarring extent after a horizontal cut above the eyebrow.
Module 5.5: Clinical Module on Burns
Overview of Burns: Injuries from heat, friction, radiation, chemical agents damaging skin integrity; affect large areas, risking vital functions.
Severity determined by penetration depth and surface area affected.
Burn Classifications
Partial-thickness Burns:
First-degree: Affects only the surface of the epidermis (e.g., sunburn). Characterized by redness (erythema), inflammation.
Second-degree: Damages the entire epidermis and may reach the dermis. Symptoms: blisters, pain, swelling; heals in 1-2 weeks.
Full-thickness Burns:
Third-degree: Destroys epidermis, dermis, and extends into the subcutaneous layer. Often painless due to nerve damage; requires skin grafting for repair.
Affected Functions of Skin Due to Burns
Fluid and electrolyte balance;
Thermoregulation;
Protection from infections.
Evaluation of Burns in Clinical Settings
Depth Assessment: Using a pin—loss of sensation indicates a third-degree burn.
Percentage Calculation: Rule of nines for estimating % surface area burned; modified for pediatric patients.
Rule of Nines Overview**
Adult:
Head: 9%; Upper limbs: 9% each; Trunk: 36%; Genitalia: 1%; Lower limbs: 18% each.
Child:
Head: 15%; Trunk: 32%; Upper limbs: 9% each; Genitalia: 1%; Lower limbs: 17% each.
Emergency Treatment
Replace fluids/electrolytes; provide nutrients for healing; prevent infection through cleaning/bandaging; assist repair process through skin grafting.
Skin Grafts
Types:
Split-thickness graft: Transfers epidermis and superficial dermis.
Full-thickness graft: Transfers epidermis and entire dermis.
Source material:
Autograft: patient's own skin (ideal); Allograft: cadaver skin; Xenograft: animal skin.
Recovery Statistics
Young patients with >80% burns: 50% recovery chance with suitable medical treatment. Advances in cell culture improve survival rates by growing new epidermis in labs for transplantation.
Review Questions
A. Distinguish first-degree, second-degree, and third-degree burns.
B. Which burn type usually requires grafting and why?
C. Describe three types of skin grafts; which is best and why?
Section 2: Accessory Structures of the Skin
Learning Outcomes
5.6: Describe main functions of skin accessory structures.
5.7: Describe hair production and structural basis for hair texture and color.
5.8: Describe types of exocrine glands in the skin and their secretions.
5.9: Describe structure of a typical nail.
5.10: Summarize effects of aging on the skin.
5.11: Explain skin’s response to injury and repair mechanisms.
Module 5.6: Accessory Structures Overview
Include hair follicles, exocrine glands, and nails; collectively referred to as epidermal derivatives.
Development: Originates from epidermis during embryological development; consists of epithelial columns growing down into the dermis.
Functions of Accessory Structures
Hair Follicles: Produce hair for protection and sensory functions.
Exocrine Glands:
Sweat glands: Aid in thermoregulation and waste excretion.
Sebaceous glands: Provide lubrication for the epidermis.
Nails: Protect and support the tips of fingers and toes; assist in limiting digit distortion under stress.
Review Questions
A. Define epidermal derivatives.
B. What exocrine glands are found in the integument?
Module 5.7: Hair
Composed of dead, keratinized cells; produced in specialized hair follicles.
Location: Found on nearly all body surfaces except palms, soles, sides of fingers/toes, lips, and external genitalia.
Hair Types
Terminal Hairs: Large, darkly pigmented (e.g., scalp hair).
Vellus Hairs: Smaller, delicate (general body surface).
Hair Structure and Regions
Hair Shaft: Visible part of hair; Hair Root: Anchors hair in skin; Root Hair Plexus: Sensory nerve collection around follicle base; Arrector Pili: Smooth muscle making hair erect; Sebaceous Gland: Oils hair and skin surface.
Hair Formation Process
Begins at the hair bulb surrounding the papilla (blood vessels and nerves); hair matrix facilitates cell division.
Layers Composed:
Medulla: Soft keratin core;
Cortex: Stiff keratin;
Cuticle: Tough outer layer providing protection.
Hair Growth Cycle
Active Phase: Lasts 2-5 years; growth rate is 0.33 mm/day.
Resting Phase: Hair loses follicle attachment, becoming club hair.
Regression and Transition Phase: Follicle reactivation triggers regeneration.
Review Questions
A. Describe a typical strand of hair.
B. What happens when an arrector pili muscle contracts?
C. Describe the four phases of the hair growth cycle.
Module 5.8: Exocrine Glands in Skin
Sebaceous Glands
Holocrine glands releasing sebum (mix of triglycerides, cholesterol, proteins).
Functions: Lubricates hair, skin surface, and has antimicrobial properties.
Sweat Glands
Types:
Apocrine Sweat Glands: Found in axillae, nipples, and pubic regions; produce sticky secretion affected by hormones.
Merocrine (Eccrine) Sweat Glands: Abundance in palms/soles; release watery secretion aiding thermoregulation.
Review Questions
A. Identify and describe functions of skin exocrine glands.
B. Describe sebum's role and secretion method.
Module 5.9: Nails
Composed of thick, keratinized epidermal cells that protect digit tips.
Nail Body: Visible part bordered by grooves and folds; Lunula is the pale crescent; Free edge is distal part.
Nail Root: Epidermal fold structures where new nail formation occurs.
Eponychium: Cuticle covering nail root; Hyponychium: Area under the free edge.
Nail appearance can indicate various health conditions (e.g., pitted nails in psoriasis).
Review Questions
A. Where does nail production occur?
B. Define hyponychium.
Module 5.10: Clinical Module on Age-Related Changes
Fewer melanocytes lead to paler skin and increased sun sensitivity.
Drier epidermis due to decreased sebaceous activity; thinning skin from decreased basal activity.
Connections between epidermis and dermis weaken, increasing injury risk.
Reduced vitamin D3 production leads to muscle weakness/brittle bones.
Review Questions
A. Why does hair turn gray/white with age?
B. Explain the context around heat tolerance and heat-related illness as one ages.
Module 5.11: Endocrine Functions and Ultraviolet Radiation
Skin interacts with hormones to regulate bodily functions.
Steroid Hormones: Affect skin barrier efficacy.
Thyroid Hormones: Control blood flow to dermis.
Sex Hormones: Thickening epidermis, enhancing wound healing.
Growth Hormones: Stimulate fibroblasts and epidermal growth.
Vitamin D3 Production
Initiated by UV radiation; essential for calcium absorption leading to bone health. Deficiencies result in disorders like rickets in children and decreased bone density in the elderly.
Review Questions
A. List essential hormones needed for integument health.
B. Explain sunlight's relationship to vitamin D3 production.
Module 5.12: Integumentary System Repair
Skin undergoes four phases post-injury:
Inflammation: Bleeding and mast cell activation;
Migration: Formation of blood clot, stratum basale cells migrate;
Proliferation: Healing progresses with scabs undermined, new tissue forms;
Scarring: Injury marks remain as scar tissue develops.
Keloids: Raised scar tissue beyond the initial injury site, culturally significant for body decoration in some societies.
Review Questions
A. Identify the first step in skin repair.
B. Describe granulation tissue.