1. The Integumentary System

2. Integumentary System The Body Covering Includes: Skin, Nails & Hairs
Skin A.K.A. Cutaneous Membrane
Functions:
Body Temperature Regulation: Sweating at surface and adjusting blood flow in dermis.
Protection: Keratin protects from microbes, abrasions, heat and chemicals, lipids slow evaporation of water, melanin protects from UV rays.
Cutaneous Sensations: Sensory input/output
Excretion and Absorption: Eliminates substances, passage of materials into body cells (drugs)
Synthesis of Vitamin D: UV light activates creation of Vit D

3. Structure Skin is divided into two main parts:
Epidermis (epi = above) Surface epithelial layer
Dermis: Deeper connective tissue layer
Subcutaneous Layer Deep dermis not part of the skin.
Fibers from dermis anchor skin to this layer which then allows for attachment to other tissue and/or organs.
Structure

4. Epidermis Made of keratinized stratified squamous epithelium
Capable of regeneration (new cells ~ q4 weeks)
4 cell types:
Keratinocytes: 90% of epidermal cells, 4 – 5 layers, produces keratin (rough fibrous protein that protects skin), waterproofs skin.
Melanocytes: 8% of epidermal cells, produce the pigment melanin, transfer melanin to kertinocytes, susceptible to UV light damage.
Langerhans cells: Produce immune response against pathogens entering skin.
Merkel cells: Detect touch/sensory sensations.

5. Dermis Consists of two distinct regions:
The superficial part is composed of areolar connective tissue.
The deeper part is composed of dense irregular connective tissue.
Attaches to the subcutaneous layer.
The outer layer contains nerve endings for touch, thermal sensations, pain, tickling, and itching.

6. Skin Color
Skin color is due to the melanin in the epidermis, carotene in the dermis, and hemoglobin in the capillaries of the dermis.
Melanin (Brown-Black pigment)
Darkness depends on amount of melanin produced.
Gives some protection against UV
Malignant melanoma, (cancer of the melanocytes), is a particularly serious skin cancer. Liver or age spots, are non-cancerous clusters of melanin.
Carotene (Yellow-Orange pigment)
In deeper skin and adipose layers
Hemoglobin (Pink-Red pigment)
Found in blood
Depends on blood flow

7. Review What are the 5 functions of skin?
What are the two main parts of skin called?
What 4 cells make up the superficial/thinner part of the skin?
What is the function of the subcutaneous layer?
Which skin layer contains nerve endings?
What pigments contribute to skin color?
The shade of your skin depends on what factor?
What are the characteristics and functions of keratinocytes?