Chapter 5: The Integumentary System

Chapter 5: The Integumentary System

Layers of the Skin

The skin is composed of three layers:

1. Epidermis – Superficial layer, made of keratinized stratified squamous epithelium.

2. Dermis – Deep layer, contains blood vessels, nerves, and glands.

3. Hypodermis (Subcutaneous Tissue) – Not part of the skin; adipose tissue for insulation and shock absorption.

Layers of the Epidermis (Mnemonic: "Before Signing, Get Legal Counsel")

1. Stratum Basale – Deepest layer; mitotic cells (actively dividing).

   • Contains melanocytes (produce melanin) and Merkel cells (sensory receptors).

2. Stratum Spinosum – Several layers of keratinocytes, connected by desmosomes for strength.

3. Stratum Granulosum – Cells begin to die, produce keratohyalin granules (for waterproofing).

4. Stratum Lucidum – Only in thick skin (palms, soles); transparent layer.

5. Stratum Corneum – Outermost layer, made of dead keratinized cells; provides protection.

Functions of the Skin

1. Protection – Chemical, physical, and biological barriers.

2. Temperature Regulation – Sweating, blood vessel dilation/constriction.

3. Cutaneous Sensation – Touch, pain, temperature receptors.

4. Metabolic Functions – Vitamin D production.

5. Blood Reservoir – Stores 5% of body’s blood.

6. Excretion – Removes salts & wastes through sweat.

Skin Cancer & Burns

• Basal Cell Carcinoma – Most common, least dangerous; originates in stratum basale.

• Squamous Cell Carcinoma – Can spread, originates in stratum spinosum.

• Melanoma – Most dangerous, arises from melanocytes.

  • ABCD Rule: Asymmetry, Border irregularity, Color variation, Diameter >6mm.