Integumentary System Functions and Anatomy

Study Notes

The Integumentary System is responsible for a variety of functions essential to the body.
Protection: It forms a barrier against chemical, physical and biological threats.
Temperature regulation: The body regulates temperature through blood vessel dilation and constriction, as well as sweat gland activity.
Sensory perception: The skin contains nerve endings that allow for sensing touch, pressure, pain, and temperature.
Excretion: The skin excretes oil and electrolytes.
Vitamin D synthesis: The skin facilitates the synthesis of Vitamin D when exposed to sunlight.
Cosmetic appearance and identity: The skin contributes to our visual appearance and individual features.
Metabolic function: The skin plays a role in metabolic processes.
Blood reservoir: The skin contains blood vessels that serve as a reservoir for blood.

The skin is the largest organ of the body, comprising approximately 15% of body weight.
It’s composed of two distinct layers: the epidermis and the dermis.
The epidermis is the outermost layer, made of keratinized stratified squamous epithelium.
The dermis is the deeper layer, composed of reticular connective tissue.
The hypodermis (subcutaneous layer) lies beneath the dermis, containing adipose connective tissue (fat cells).

The epidermis is not vascularized and relies on the dermis for nutrient diffusion.
It has extensive innervation responsible for sensory perception.
The thickness of the epidermis varies depending on the body area.
The epidermis is composed of four main cell types: keratinocytes, melanocytes, Merkel cells, and Langerhans’ cells.
The epidermis consists of five distinct layers:
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale

Stratum corneum: This layer comprises mature keratinocytes containing fibrous proteins (keratins). It’s responsible for shedding dead cells and acting as a barrier against foreign substances and fluid loss.
Stratum lucidum: This layer resides beneath the stratum corneum, containing living keratinocytes that mature and form the stratum corneum. It’s only found in thick skin.
Stratum granulosum: This layer is crucial for water retention and heat regulation.
Stratum spinosum: This layer provides protection to the stratum basale layer.
Stratum basale: This layer is the site of continuous cell division, producing new keratinocytes to replace those shed from the surface. It also houses melanocytes responsible for skin pigmentation.

The rete peg region acts as the interface between the epidermis and the dermis.
It consists of epidermal-dermal ridges that increase the surface area between the epidermis and the dermis.