Integumentary System: Structure, Function, and Skin Disorders

Major functions of the integumentary systen

Protection/Barrier

Absorbing vitamin D

Sensory perception

Thermoregulation

Epidermis

Outer layer, stratified squamous epithelial cells, 4-5 distinct layers.

Dermis

Between epidermis and hypodermis (middle layer), split into papillary dermis & reticular dermis.

Papillary dermis

Upper ⅕ of dermis, loose (areolar) CT, immune cells fight invaders, strong connection with epidermis, lots of blood vessels.

Reticular dermis

Lower ⅘ of dermis, dense irregular CT, collagenous fibers that give skin strength & resiliency, elastin allows skin to stretch & recoil.

Hypodermis

Deepest layer, mostly adipose, some areolar CT, stores energy, gives insulation and padding, anchors skin to structures underneath.

Sweat glands

Sweats to cool body and remove waste; 2 types: Merocrine & Apocrine sweat glands.

Hair

Protection, reduce heat loss, senses touch.

Sebaceous gland

Secretes sebum (oil) to lubricate and make skin & hair waterproof.

Hair follicle

Structure where hair grows.

Arrector pili muscle

Small muscle that causes hair to stand up (goosebumps).

Sensory nerve fibers

Detects pain, temperature, pressure, touch.

Tactile (Meissner's) corpuscle

Detects light touch & texture.

Lamellated (Pacinian) corpuscle

Detects deep pressure & vibration.

Stratum basale

Contains Keratinocytes, Melanocytes, and Merkel cells.

Stratum spinosum

Contains Keratinocytes and Langerhans' cells.

Stratum granulosum

Contains Keratinocytes only.

Stratum lucidum

Contains dead keratinocytes.

Stratum corneum

Contains dead keratinocytes.

Keratinocytes

Structure.

Melanocytes

Pigment.

Merkel cells

Sensation.

Langerhans' cells

(Phagocytes) immune defense.

Hyperplasia

↑ in cell number

Hypertrophy

↑ in cell size

Neoplasia

abnormal new cell growth (can be cancer)

Regeneration of skin

replacement of damaged cells with the same type

Fibrosis

replacement of tissue w/ scar tissue

Atrophy

↓ in cell size or tissue shrinkage

Necrosis

premature death of cells/tissue

Gangrene

death of tissue due to loss of blood supply, (often from infection/injury)

Bedsore

tissue damage from prolonged pressure that cuts off blood flow

Inflammation

blood vessels dilate, white blood cells clean debris

Organization

granulation tissue forms; new capillaries grow

Regeneration/Fibrosis

epithelium regenerates, scar tissue may form

Melanin

pigment made by melanocytes in the stratum basale; protects DNA from UV radiation and gives skin color

Carotene

yellow-orange pigment from diet (carrots)

Hemoglobin

red pigment in blood = pink tone skin

Freckles and moles

local overproduction or clustering of melanin

Erythema

redness - increased blood flow

Hematoma

bruise - broken blood vessels under skin

Cyanosis

blue skin - to low oxygen

Pallor

pale skin - low blood flow or shock

Jaundice

yellow skin - liver problems

Skin cancer

Uncontrolled cell division due to DNA damage (often UV exposure)

Benign tumors

noncancerous, doesn't spread

Malignant tumors

cancerous, spreads to other tissues

Basal cell carcinoma

from stratum basale cells - most common, least dangerous

Squamous cell carcinoma

from stratum spinosum cells - may spread if untreated

Malignant melanoma

from melanocytes - most dangerous, spreads rapidly

ABCDEs of detecting melanoma

A - Asymmetry; B - Border irregularity; C - Color variation; D - Diameter > 6 mm; E - Evolving (changes over time)

First-degree burn

only epidermis damaged; red, painful

Second-degree burn

epidermis + upper dermis damaged; blisters

Third-degree burn

entire skin destroyed; gray/black, nerves destroyed

Third-degree burns painless

Because nerve endings are destroyed