Laboratory 2.3: Integumentary System Activities

Thermoregulation (skin)

The skin cools the body through evaporation of sweat; faster evaporation dissipates more heat and lowers skin temperature.

Sweat and thermoregulation

Sweat evaporates from the skin surface, removing heat energy from the body and lowering skin temperature.

Alcohol vs. water evaporation

Alcohol evaporates faster than water because it has a lower boiling point (82°C vs. 100°C), making it feel cooler on the skin.

Dermal papillae

Projections in the dermis that genetically determine the pattern of epidermal (friction) ridges, giving rise to fingerprints.

Friction ridges

Epidermal ridges produced by dermal papillae that help fingers and feet grip objects and form unique fingerprint patterns.

Fingerprint uniqueness

Fingerprints are unique to each individual because sweat pores make the ridge pattern visible and the pattern is genetically determined.

Common fingerprint patterns

The three common fingerprint patterns are arch, loop, and whorl.

Unusual fingerprint patterns

Uncommon fingerprint patterns include accidental and other mixed/irregular ridge configurations.

Capillary refill time (CRT)

A clinical test that measures how quickly skin color returns after pressure is released, used to assess blood circulation.

Normal capillary refill time

Normal CRT is approximately 2 seconds in newborns, 3 seconds in adults, and slightly more than 3 seconds in elderly individuals.

Conditions affecting CRT

Dehydration, anaphylaxis, shock, hemorrhage, burns, and hyper/hypothermia can impair circulation and prolong capillary refill time.

Temperature and CRT

Warmer temperatures cause vasodilation, speeding refill time; colder temperatures cause vasoconstriction, slowing refill time.

Elderly and CRT

Elderly patients have slightly longer CRT due to decreased cardiovascular efficiency and reduced skin elasticity with age.

Hydration and CRT

Dehydration reduces blood volume, decreasing the pressure available to refill capillaries, which prolongs refill time.

Mechanoreceptors

Somatosensory receptors in the skin that detect pressure, stretch, touch, or vibration as part of the nervous system.

Meissner's corpuscles

Tactile mechanoreceptors in the upper dermis projecting into the epidermis, found on fingertips and eyelids; detect light touch and vibration.

Pacinian corpuscles

Mechanoreceptors located deep in the dermis that detect deep pressure and vibration.

Ruffini endings

Mechanoreceptors found deep in the dermis that are stimulated by skin stretch and warmth.

Merkel's disks

Mechanoreceptors at the base of the epidermis in the papillary layer, densely found on fingertips and lips; respond to light touch.

Two-point discrimination test (2PD)

A clinical test measuring skin sensitivity by determining the minimum distance at which two distinct touch points can be felt separately.

Tactile agnosia

An inability to process tactile stimuli, indicating neurological damage, which can be identified using the two-point discrimination test.

Receptor density and sensitivity

Areas with higher mechanoreceptor density (e.g., fingertips, lips) can detect two points closer together, indicating greater tactile sensitivity.

Most sensitive body area (2PD)

Fingertips and lips have the smallest two-point discrimination distance due to the highest density of Merkel's disks and Meissner's corpuscles.

Dermis vascularization

The dermis is highly vascularized to supply oxygen and nutrients to the deeper layers of the epidermis.

Capillary pressure response

Applying pressure to skin pinches dermal capillaries, stopping blood flow and causing the skin to pale temporarily.