Integumentary system

INTEGUMENTARY SYSTEM

System composed of the skin and its associated structures (hair, nails, glands) that protects the body, regulates temperature, prevents fluid loss, and provides sensation

INTEGUMENT

Waterproof covering protecting deeper tissues by keeping out foreign materials including microorganisms; prevents loss of body fluids, regulates body temperature, and provides a large sensory surface for touch, pain, and temperature

SKIN

Acts as an excretory organ where sweat and sebaceous glands discharge products; site of Vitamin D synthesis under UV rays; composed of epidermis (superficial), dermis (deeper connective tissue), and subcutaneous layer that anchors skin to deeper structures; surface shows ridges and grooves (fingerprints) for grip

EPIDERMIS

Stratified squamous epithelium containing keratin in upper layers (cornified), forming a protective barrier between external and internal environments

1) Stratum basale 2) Stratum spinosum 3) Stratum granulosum 4) Stratum lucidum 5) Stratum corneum

5 LAYERS OF EPIDERMIS

STRATUM BASALE

Lowermost layer; wavy columnar cells separated by basement membrane; site of mitosis; also called stratum germinativum; contains melanocytes that produce melanin

STRATUM SPINOSUM

Layer of irregularly shaped cells; some undergoing mitosis

STRATUM GRANULOSUM

Contains 2–5 layers of flattened cells with keratohyaline granules

STRATUM LUCIDUM

Clear, narrow layer found only in thick skin; cells in stages of degeneration

STRATUM CORNEUM

Outermost layer of keratinized, flattened, dead cells; thick in palms and soles to resist abrasion; forms calluses and corns when thickened

DERMIS

Layer beneath epidermis; made of dense irregular connective tissue; contains blood vessels, nerves, and fibers

1) Papillary layer 2) Reticular layer

2 LAYERS OF DERMIS

PAPILLARY LAYER

Contains finger-like papillae projecting upward; has blood vessels and sensory receptors for touch

RETICULAR LAYER

Contains coarse collagenous and elastic fibers arranged parallel to the skin surface

HAIR

Present on most skin except palms, soles, and lips; functions in protection, temperature regulation, and sensation; composed of cuticle and cortex; consists of shaft (above skin) and root (in dermis); grows from follicle with bulb of proliferating cells; associated with arrector pili muscle causing goosebumps

ARRECTOR PILI MUSCLE

Smooth muscle attached to hair follicle; contracts in response to cold, causing hair to stand (goose pimples) and compressing sebaceous glands

SEBACEOUS GLANDS (GENERAL)

Associated with hair follicles; secrete sebum that lubricates and protects skin and hair

SEBACEOUS GLANDS (DETAILED)

Found throughout body except palms, soles, and dorsum of distal digits; also present in hairless areas (lips, areola, genitals); size 0.2–2 mm (largest at nose); alveolar type; cells break down to produce sebum; involved in acne, blackheads (comedo), and cysts; ciliary glands are modified sebaceous glands

SEBUM

Oily secretion of sebaceous glands; lubricates hair and skin and prevents drying

ACNE

Infection/inflammation of sebaceous glands with accumulation of sebum; blockage leads to blackheads or cysts

SWEAT GLANDS

Coiled secretory glands in subcutaneous layer; ducts open to surface through pores; produce watery secretion for cooling and excretion of wastes

MODIFIED SWEAT GLANDS

Large glands in armpits and anus; ducts open to surface or hair follicles; odor caused by bacteria

CERUMINOUS GLANDS

Modified sweat glands found in the external ear

MAMMARY GLANDS

Highly modified sweat glands responsible for milk production

NAILS

Made of cornified nail plate (modified stratum corneum) over nail bed; function in protection, grasping, and scratching; composed of root (hidden), body (visible), eponychium (cuticle), and lunula (white crescent)

HYPODERMIS

Subcutaneous layer with fibroblasts, fat cells, lymphocytes, macrophages, mast cells; varies in thickness; major fat storage site; contains blood vessels and nerves supplying the skin

RULE OF 9

Method to estimate body surface area affected by burns: Head & neck 9%, anterior trunk 18%, posterior trunk 18%, upper extremities 18%, lower extremities 36%, perineum 1%

9%

rule of 9: percentage of head and neck

18%

rule of 9: percentage of anterior and posterior trunk

18%

rule of 9: percentage of upper extremities

36%

rule of 9: percentage of lower extremities

1%

rule of 9: percentage of perineum

CUTANEOUS NERVES

Nerves supplying the skin for sensation and autonomic control

1) Afferent somatic fibers 2) Efferent autonomic (sympathetic) fibers

2 TYPES OF CUTANEOUS NERVES

AFFERENT SOMATIC FIBERS

Carry sensory information such as pain, touch, pressure, heat, and cold

EFFERENT AUTONOMIC FIBERS

Supply smooth muscles of blood vessels, arrector pili muscles, and sweat and sebaceous glands