Integumentary System

What are the two parts of the integumentary system?

The skin (integument) and its derivatives (sweat and oil glands, hair, nails).

What are the main functions of the integumentary system?

Protection, temperature regulation, excretion, vitamin D synthesis, sensory reception.

How does the skin protect against mechanical damage?

Keratin toughens cells; pressure receptors alert the body.

How does the skin protect against chemical damage?

Keratinized cells are almost impermeable to chemicals.

How does the skin protect against bacterial damage?

Unbroken surface + sweat (antimicrobial).

How does the skin protect against UV radiation?

Melanin (from melanocytes) absorbs UV.

How does the skin protect against thermal damage?

Heat, cold, and pain receptors detect changes.

How does the skin prevent desiccation (drying out)?

Waterproofing substances and keratin prevent water loss.

How does the integumentary system regulate temperature?

• Heat loss: sweat glands activated, blood flushes to skin capillaries.

• Heat retention: blood kept from skin capillaries.

What waste products are excreted through the skin?

Urea and uric acid (in sweat).

How does the skin synthesize vitamin D?

Modified cholesterol in skin converts to vitamin D in sunlight.

Why is vitamin D important?

Regulates calcium and phosphorus levels; deficiency causes bone density issues.

What does “cornified” mean?

Hardened; top skin layer contains keratin, preventing water loss.

What are cutaneous sensory receptors?

Nervous system receptors in skin for touch, pressure, temperature, and pain.

What are the three main layers of skin (top to bottom)?

Epidermis → Dermis → Hypodermis (subcutaneous tissue).

What type of tissue makes up the epidermis?

Stratified squamous epithelium (keratinized).

Is the epidermis vascular or avascular?

Avascular

What is the most common epidermal cell type?

Keratinocyte (produces keratin)

What other important cell is in the epidermis?

Melanocyte (produces melanin)

What are the five layers (strata) of the epidermis?

Stratum basale, spinosum, granulosum, lucidum, corneum.

Which epidermal layer is the site of cell division?

Stratum basale

Which epidermal layer is only found in thick, hairless skin (palms, soles)?

Stratum lucidum

What layer is the top protective barrier of dead, keratin-filled cells?

Stratum corneum

How often is the epidermis completely replaced?

Every 25–45 days.

What type of tissue makes up the dermis?

Dense connective tissue

What are the two regions of the dermis?

Papillary layer (upper), Reticular layer (lower).

What are dermal papillae?

Fingerlike projections that form fingerprints; may contain capillaries and sensory receptors

What receptors are in the papillary layer?

Pain receptors + Meissner’s corpuscles (touch)

What is found in the reticular layer?

Blood vessels, sweat/oil glands, Pacinian corpuscles (deep pressure), phagocytes, collagen, and elastic fibers.

What role does collagen play in skin?

Provides toughness and binds water to keep skin hydrated.

What role do elastic fibers play in skin?

Provide elasticity (loss leads to wrinkles).

How does the dermis help regulate temperature?

Capillaries dilate (release heat) or constrict (conserve heat).

What tissue makes up the hypodermis?

Adipose

What are the functions of the hypodermis?

Cushioning, protection, insulation, anchoring skin to organs.

Is the hypodermis part of the skin?

No, but it supports and connects it.

What causes blisters?

Epidermis and dermis separate, interstitial fluid builds up.

What are decubitus ulcers (bedsores)?

Cell death caused by restricted blood supply (common in bedridden patients)

How deep does an intradermal injection go?

Into the dermis

How deep does a subcutaneous injection go?

Into the hypodermis (insulin, heparin).

How deep does an intramuscular injection go?

Into the muscle (flu shot, epipen).

How do transdermal patches work?

Drugs pass through the epidermis into dermal blood vessels.