Integumentary

Integumentary System

The body system made up of the skin, hair, nails, glands, and sensory receptors that protects the body and helps regulate temperature.

Functions of the Skin

Includes protection, sensation, Vitamin D synthesis, blood storage, temperature regulation, and excretion of wastes.

Epidermis

The outer layer of skin made of keratinized stratified squamous epithelium; functions in protection.

Dermis

The middle layer made of connective tissue (areolar and dense irregular); contains blood vessels, glands, nerves, and hair follicles.

Hypodermis

The deepest skin layer that attaches skin to underlying tissues; made of areolar and adipose tissue for cushioning and insulation.

Exteroreceptors

Sensory receptors in the skin that detect stimuli from outside the body (e.g., touch, temperature, pain).

Tactile Receptors

Specialized receptors that respond to touch, pressure, stretch, and vibration.

Nociceptors

Pain receptors in the skin that detect tissue damage or potentially harmful stimuli.

Hair

Dead cells filled with hard keratin that provide protection, warmth, and sensation.

Hair Follicle

The structure in the dermis that produces hair; includes the root and papilla for nourishment.

Nails

Hard keratin structures at the tips of fingers and toes that protect and assist in grasping.

Nail Matrix

The growth region at the base of the nail where new nail cells form.

Lunula

The whitish half-moon area above the nail matrix; visible part of the growing region.

Cuticle (Eponychium)

The fold of skin at the base of the nail that protects the nail root from infection.

Sebaceous Glands

Oil glands connected to hair follicles that secrete sebum to soften skin and hair, reduce water loss, and fight bacteria.

Sebum

An oily, acidic mixture of fats, cholesterol, and lysozyme secreted by sebaceous glands.

Eccrine Sweat Glands

Most common sweat glands found across the body; produce watery sweat (99% water + salts/wastes) for thermoregulation.

Apocrine Sweat Glands

Found in axillary and genital areas; secrete sweat with fats and proteins into hair follicles; function unclear.

Metabolic Rate

The rate of energy release from the body, measured by heat production or oxygen consumption.

Basal Metabolic Rate (BMR)

The energy rate at rest under standard conditions (fasting, relaxed, normal temperature, no exercise).

Factors Increasing BMR

Exercise, stress, thyroid hormone, epinephrine, pregnancy, higher body temp, and food intake.

Thyroid Hormone

Hormone that increases metabolic rate, stimulates mitochondria, and enhances carbohydrate, fat, and protein metabolism.

Core Temperature

The temperature of internal organs (brain, thoracic, and abdominal cavities).

Shell Temperature

The skin’s surface temperature, where heat is lost from the body.

Vasodilation

Widening of skin blood vessels to increase heat loss when the body is too warm.

Vasoconstriction

Narrowing of skin blood vessels to reduce heat loss and keep blood in the body core.

Radiation

Heat loss by infrared energy transfer between objects not touching.

Conduction

Heat transfer through direct contact between objects.

Convection

Heat loss enhanced by moving air currents.

Evaporation

Heat loss when sweat turns from liquid to vapor, removing heat from the skin.

Thermoregulation

The process of maintaining a stable body temperature by balancing heat gain and heat loss.

Thermoreceptors

Receptors that detect changes in body or environmental temperature.

Hypothalamus (Preoptic Area)

The control center for body temperature that activates cooling or heating mechanisms.

Hyperthermia

Body temperature above 100°F caused by excess heat.

Hypothermia

Body temperature below 95°F caused by prolonged cold exposure.

Heat Exhaustion

Overexposure to heat with fluid and electrolyte loss; symptoms include dizziness, fainting, weak pulse; treat with rest and fluids.

Heat Stroke

Life-threatening condition where the body cannot regulate temperature; temperature >104°F, confusion, no sweating; needs immediate cooling and fluids.

Fever

An abnormally high body temperature triggered by pyrogens that reset the hypothalamus.

Exogenous Pyrogens

Fever-causing substances from bacteria, viruses, fungi, or medications.

Endogenous Pyrogens

Fever-inducing chemicals from WBCs and injured cells (e.g., IL-1, IL-6, TNF).

Prostaglandins

Substances made in the hypothalamus that reset the body’s temperature set point during a fever.

First-Degree Burn

Superficial burn damaging only the epidermis; red, painful, heals in 3–5 days.

Second-Degree Burn

Partial-thickness burn damaging epidermis and part of dermis; red, blistered, painful; heals in 10–21 days.

Third-Degree Burn

Full-thickness burn destroying epidermis, dermis, and possibly deeper tissues; skin appears white or charred, no pain or sensation.

Rule of Nines

Method to estimate body surface area (BSA) burned using percentages assigned to body regions.

Lund–Browder Method

Hospital assessment that adjusts BSA estimates for body size differences between children and adults.

Basal Cell Carcinoma

Most common skin cancer; appears as a white tumor with rolled edges and central ulcer.

Squamous Cell Carcinoma

Firm lesions that may be red, yellow, or crusted; can invade deeper skin layers.

Malignant Melanoma

Deadly skin cancer that is asymmetric with irregular borders, varied color, and >6 mm diameter.

ABCDE Rule

Guide for spotting melanoma: Asymmetry, Border irregularity, Color variation, Diameter >6 mm, Evolving changes.