Reviewer on the Integumentary System
I. Overview of the Integumentary System The integumentary system consists of the skin and its
appendages, including hair, nails, and glands. The skin is the bodyโs largest organ and serves as a
protective barrier, regulating temperature and preventing dehydration.
II. Structure of the Skin The skin has three main layers:
1. Epidermis โ The outermost layer composed of keratinized stratified squamous epithelium.
2. Dermis โ The thick, connective tissue layer beneath the epidermis.
3. Hypodermis (Subcutaneous Layer) โ Not part of the skin but provides insulation and cushioning.
III. Layers of the Epidermis (from deep to superficial)
1. Stratum basale โ Deepest layer, contains mitotically active cells and melanocytes.
2. Stratum spinosum โ Provides strength and flexibility.
3. Stratum granulosum โ Contains keratohyaline granules for keratin production.
4. Stratum lucidum โ Found only in thick skin (palms, soles); transparent layer.
5. Stratum corneum โ Outer layer of dead, keratinized cells that protect against friction and water
loss.
IV. Cells of the Epidermis
1. Keratinocytes โ Produce keratin, making the skin tough and waterproof.
2. Melanocytes โ Produce melanin, which protects against UV radiation.
3. Dendritic (Langerhans) Cells โ Help in immune response.
4. Tactile (Merkel) Cells โ Act as sensory receptors for touch.
V. Dermis The dermis is divided into two layers:
1. Papillary Dermis โ Composed of areolar connective tissue, contains dermal papillae responsible
for fingerprints.
2. Reticular Dermis โ Deepest part of the dermis, made of dense irregular connective tissue;
contains sweat and sebaceous glands, blood vessels, and sensory receptors.
VI. Functions of the Skin
โข Protection โ Acts as a barrier against pathogens and environmental damage.
โข Thermoregulation โ Sweat glands and blood vessels help maintain body temperature.
โข Sensation โ Contains nerve endings for touch, pain, pressure, and temperature.
โข Excretion โ Sweat glands remove waste products.
