Chapter 5: The Integumentary System

A comprehensive set of vocabulary flashcards covering the major terms and concepts from Chapter 5: The Integumentary System.

Integumentary System

The skin and its derivatives; makes up about 16% of body weight and acts as the body's first line of defense.

Skin (Cutis; Integument)

Largest organ system; covers about 20 square feet of surface; exposed to environment.

Epidermis

Superficial epithelium; keratinized stratified squamous epithelium; avascular and derived from ectoderm.

Dermis

Underlying connective tissue layer two parts: papillary (superficial) and reticular (deep); provides strength and mechanical support.

Hypodermis (Subcutaneous Layer)

Deep to the dermis; loose connective tissue and adipose; not part of the skin but anchors and insulates.

Accessory Structures (Adnexa)

Hair, exocrine glands, and nails; located mainly in the dermis and projecting through the epidermis.

Keratinized Stratified Squamous Epithelium

Epidermal tissue that produces keratin and forms a tough, protective barrier.

Desquamation

Continuous shedding of dead keratinocytes to maintain epidermal thickness.

Ectoderm

Embryonic origin of the epidermis.

Papillary Layer

Most superficial dermal layer; areolar tissue with capillaries and tactile receptors; supports epidermis.

Reticular Layer

Deeper dermal layer; dense irregular connective tissue with collagen and elastic fibers.

Stratum Basale

Deepest epidermal layer; attached to basement membrane; contains basal (germinative) cells, melanocytes, and Merkel cells.

Stratum Spinosum

Spiny layer; 8–10 cell layers; desmosomes connect cells; contains Langerhans (dendritic) cells.

Stratum Granulosum

Granular layer; keratinization begins; keratohyalin granules; cells die as organelles disintegrate.

Stratum Lucidum

Clear layer found only in thick skin; appears glassy due to eleidin; 3–5 layers of dead keratinocytes.

Stratum Corneum

Outermost horny layer; 15–30 layers of dead, keratinized cells; water resistant.

Epidermal Ridges

Ridges formed by epidermis that interlock with dermal papillae to create fingerprints.

Dermal Papillae

Projections of the dermis into the epidermis; increase surface area and nutrients to epidermis.

Epidermal Ridge

Ridge pattern in epidermis contributing to fingerprints and grip.

Basal Cells (Germinative Cells)

Stem cells in stratum basale that divide to replace keratinocytes.

Melanocytes

Pigment cells in stratum basale; produce melanin and transfer it to keratinocytes.

Melanin

Pigment determining skin color; protects against UV; produced as eumelanin or pheomelanin.

Langerhans Cells (Epidermal Dendritic Cells)

Antigen-presenting cells in the epidermis; part of the immune defense.

Merkel Cells (Tactile Epithelial Cells)

Touch receptor cells located in the deepest epidermal layer; associate with nerve endings.

Tactile Discs (Merkel Discs)

Sensory nerve endings associated with Merkel cells for light touch.

DEJ (Dermoepidermal Junction)

Unique basement membrane gluing epidermis to dermis; mechanical support.

Papillary Layer (of Dermis)

Areolar tissue with capillaries and sensory receptors; nourishes epidermis.

Reticular Layer (of Dermis)

Dense irregular connective tissue; strength and elasticity; houses glands and follicles.

Frictions Ridges (Epidermal Ridges)

Ridges on skin surface that improve grip and create fingerprints.

Tension Lines (Cleavage Lines)

Patterns of collagen fiber orientation; incisions parallel to lines heal with less scarring.

Flexure Lines

Dermal folds near joints where skin is tightly bound to deeper structures.

Cutaneous Plexus

Deep vascular network in the dermis supplying blood to the skin.

Subpapillary Plexus

Superficial vascular network in the papillary layer of the dermis.

Nerve Endings in Skin

Dense innervation; sensory receptors monitor touch, temperature, pain, and more.

Subcutaneous Layer (Hypodermis) Anatomy

Adipose-rich layer beneath the dermis; acts as insulation and energy reserve; site for injections.

Adipose Tissue

Fat tissue for energy storage and insulation; predominant in the subcutaneous layer.

Hair Follicle

Structure in the dermis that produces hair; surrounds a hair root; contains root hair plexus.

Hair Shaft

Visible part of hair above the skin surface; keratinized column.

Hair Root

Portion of hair within the follicle; anchors hair in the skin.

Hair Matrix

Layer at base of hair bulb; proliferates to form hair; contains melanocytes for color.

Hair Papilla

Vascularized cell cluster at base of hair; nourishes hair growth.

Arrector Pili Muscle

Smooth muscle that causes hair to stand (goose bumps) when stimulated.

Sebaceous Glands

Holocrine glands that secrete sebum into hair follicles; lubricates and protects skin.

Sebum

Oily lipid secretion; softens hair/skin; provides water loss protection and antibacterial properties.

Vernix Caseosa

Protective coating of sebum and shed cells on newborn skin.

Sweat Glands (Sudoriferous)

Glands producing sweat; two types: eccrine and apocrine.

Eccrine (Merocrine) Sweat Glands

Most common sweat glands; secrete directly onto skin surface; thermoregulation.

Apocrine Sweat Glands

Glands secreting into hair follicles; located in axillae, areolae, groin; viscous, odorous secretion; active at puberty.

Mammary Glands

Modified apocrine glands that produce milk; development regulated by hormones.

Ceruminous Glands

Modified sweat glands in external ear canal; produce cerumen (earwax) with sebaceous glands.

Nails

Keratinized plates protecting fingertips and toes; nail bed, lunula, eponychium, hyponychium.

Nail Matrix

Site of nail production; located at the base of the nail; contains keratinocytes and melanocytes.

Lanugo

Fine, unpigmented fetal hair; usually shed before birth.

Vellus Hair

Fine, light hair covering most of the body; provides insulation.

Terminal Hair

Coarser, pigmented hair found on the scalp, eyebrows, eyelashes; occurs after puberty on other areas.

Hair Growth Cycle

Periodically cyclic sequence: Anagen (growth), Catagen (transition), Telogen (resting), Exogen (shedding).

Anagen

Growth phase; long duration (2–8 years on scalp); majority of hairs are in this phase.

Catagen

Transition phase; ~2 weeks; hair follicles shrink and growth slows.

Telogen

Resting phase; ~2–3 months; hair not growing; shedding may occur.

Exogen

shedding phase; old hair falls out as new hair begins growth.

Actinic Keratosis

Precancerous sun-damaged patch; may progress to squamous cell carcinoma.

Melanoma

Malignant cancer of melanocytes; highly dangerous if metastasizes; ABCDE warning signs (Asymmetry, Border, Color, Diameter, Evolution).

Basal Cell Carcinoma (BCC)

Most common skin cancer; arises from basal cells; slow-growing; rarely metastasizes.

Squamous Cell Carcinoma (SCC)

Second most common skin cancer; arises from squamous cells; can metastasize; usually sun-exposed areas.

Jaundice

Yellowing of skin/eyes due to excessive bilirubin; indicates liver/gallbladder/pancreas issues.

Vitiligo

Autoimmune loss of melanocytes causing white patches; variable incidence.

Psoriasis

Chronic autoimmune skin disease; rapid keratinocyte turnover; plaques; treated with steroids, UV light, and systemic therapies.

Carotene

Orange-yellow pigment from diet; accumulates in skin; converted to vitamin A.

Hemoglobin and Skin Color

Red pigment in blood; vascular dilation or constriction alters skin color; cyanosis indicates high deoxygenated hemoglobin.

Vitamin D Synthesis (Calcitriol Pathway)

UV light converts 7-dehydrocholesterol to cholecalciferol (D3) in skin; liver and kidneys convert to active calcitriol, essential for calcium absorption.

Rickets

Bone disease from vitamin D/calcium/phosphate deficiency; prevented by vitamin D fortification.

Dermis Components

Papillary layer (areolar, nutrients, sensory) and Reticular layer (dense irregular connective tissue, strength, elastic fibers).

Dermal Tension Lines vs Flexure Lines

Tension lines indicate fiber orientation for surgical incisions; flexure lines are skin folds at joints.

Vascularization in Skin

Skin receives blood via cutaneous and subpapillary plexuses; important for thermoregulation and nourishment.