Chapter 5: The Integumentary System Overview

Integumentary System

Includes skin and accessory structures.

Cutaneous Membrane

Another name for the integument.

Accessory Structures

Includes hair, nails, glands, blood vessels.

Epidermis

Outer layer of skin, composed of epithelium.

Dermis

Inner layer of skin, composed of connective tissue.

Subcutaneous Layer

Also called hypodermis, provides insulation.

Keratinocytes

Cells producing keratin, make up 90% of epidermis.

Melanocytes

Cells producing melanin, protect against UV damage.

Langerhans Cells

Macrophages involved in immune responses.

Merkel Cells

Cells functioning in touch sensation.

Skin Thickness Range

1-5 mm, thinnest at eyelids, thickest at heels.

Skin Weight

Weighs 4.5-5 kg, about 16% of body weight.

Skin Area

Approximately 2 square meters (22 square feet).

Sloughing Off

Natural loss of dead skin layers.

Skin Functions

Protection, temperature regulation, sensory perception.

Vitamin D Synthesis

Occurs from cholesterol due to sunlight exposure.

Epidermal Layer Composition

Composed of keratinized stratified squamous epithelium.

Simple Cuboidal Epithelium

Found separating epidermis from dermis in thinner skin.

Simple Columnar Epithelium

Found in thicker skin, separating epidermis from dermis.

Stratum Basale

Deepest layer of epidermis, continuous cell division.

Stratum Spinosum

Fourth layer, contains 8-10 keratinocytes.

Stratum Granulosum

Third layer, non-dividing cells filled with keratin granules.

Stratum Lucidum

Fourth layer, present only in thick skin.

Skin Recycling Rate

Approximately 1 kg of skin epithelium lost yearly.

Emotional Expression

Facial expressions facilitated by skin.

Blood Vessels in Skin

Provide nourishment and temperature regulation.

Nerves in Skin

Dispersed throughout, provide sensation.

Adipose Connective Tissue

Provides insulation and cushioning in subcutaneous layer.

Stratum Corneum

Outermost epidermal layer of dead keratinocytes.

Keratinization

Process of replacing viable cells with keratin.

Callus

Thickened skin from constant friction.

Dandruff

Excess keratinized cells shed from the scalp.

Thin Skin

Covers all body regions except palms and soles.

Thick Skin

Covers palms, digits, and soles.

Melanin

Pigment produced by melanocytes in stratum basale.

Eumelanin

Brown to black pigment in skin.

Pheomelanin

Yellow to red pigment in skin.

Freckles

Clusters of concentrated melanin from sun exposure.

Nevi

Benign chronic lesions also known as birthmarks.

Malignant Melanoma

Cancer of melanocytes, a serious skin condition.

Vitiligo

Chronic disorder causing depigmentation patches.

Albinism

Absence of pigment due to enzyme defect.

Dermis

Layer composed of loose and dense connective tissue.

Papillary Region

Upper dermis with areolar connective tissue.

Dermal Papillae

Structures containing capillary loops and touch receptors.

Reticular Region

Lower dermis with dense irregular connective tissue.

Stretch Marks

Tears in dermis due to excessive stretching.

Lines of Cleavage

Tension lines indicating collagen fiber direction.

Sebaceous Glands

Oil glands in the dermis.

Sudoriferous Glands

Sweat glands in the dermis.

Corpuscles of Touch

Receptors for touch sensation in papillary region.

Free Nerve Endings

Nerve endings for pain and temperature sensation.

Keratinocytes

Cells that produce keratin in the epidermis.

Areolar Connective Tissue

Connective tissue linking dermis and epidermis.

Epidermal Ridges

Contours from dermal papillae; basis for fingerprints.

Collagen Ridges

Accumulated collagen fibers causing epidermal speed bumps.

Firmness of Grip

Increased friction from collagen ridges enhances grip.

Dermis

Skin layer primarily composed of collagen fibers.

Fibroblasts

Cells producing collagen; repair dermal layer during injury.

Subcutaneous Layer

Hypodermis; anchors skin to tissues and organs.

Pacinian Corpuscles

Sensory receptors detecting external pressure on skin.

Epidermis

Fast turnover layer providing protection to tissues.

Temperature Stability

Dermis maintains body temperature and prevents dehydration.

Sensory Receptors

Detect various tactile sensations like touch and pressure.

Merkel Discs

Sensory receptors for light touch located superficially.

Meissner Corpuscles

Sensory receptors for light touch in the dermis.

Hair

Pili; present on most body surfaces except palms.

Keratinization

Process where hair cells become keratinized and dead.

Hair Shaft

Part of hair above the skin surface.

Hair Follicle

Structure below skin level housing the hair root.

Epithelial Root Sheath

Protective layer surrounding the hair root.

Dermal Root Sheath

Connective tissue layer anchoring hair in dermis.

Sebaceous Gland

Oil gland merging with hair follicle for hydration.

Hair Papilla

Nerve-associated structure providing touch sensation.

Lanugo

Fine, nonpigmented hairs covering fetal body.

Vellus Hairs

Short, fine hairs barely visible to naked eye.

Terminal Hairs

Long, coarse, pigmented hairs like facial hair.

Melanin

Pigment determining hair color and type.

Exocrine Glands

Epithelial cells secreting substances like oil.

Accessory Structures

Components like hair and glands associated with skin.

Skin Insulation

Subcutaneous layer stores fat and insulates body.

Sebum

Oily substance preventing dehydration and inhibiting bacteria.

Eccrine Sweat Glands

Most common sweat glands, cover most body areas.

Apocrine Sweat Glands

Sweat glands in axilla, groin, and facial regions.

Thermoregulation

Process of maintaining body temperature through sweating.

Emotional Sweating

Sweating due to emotional stress like fear.

Ceruminous Glands

Modified sweat glands producing earwax in ear canal.

Nail Structure

Includes free edge, nail body, and nail root.

Keratinization

Process of cell death and hardening in nails.

Physical Barrier

Dense tissue and keratin protecting against pathogens.

Biological Barrier

White blood cells providing immune defense in skin.

Chemical Barrier

Water, acids, and oils protecting skin from chemicals.

Microbe Protection

Non-pathogenic bacteria prevent harmful bacteria attachment.

Langerhans Cells

Skin WBCs involved in immune response.

Melanin

Pigment blocking UV rays, secreted by melanocytes.

Adipose Tissue

Insulates body, providing cold protection under skin.

Burn

Tissue damage from heat, electricity, or chemicals.

First-Degree Burn

Affects only epidermis; mild pain and redness.

Second-Degree Burn

Destroys epidermis and part of dermis; some loss.

Sweat Production

Eccrine glands secrete 600 ml of sweat daily.