Anatomy and Physiology / Unit 3: The Integumentary System
3.1 Layers of the Skin
Notes
The skin (cutaneous membrane) is the body's largest organ. It has two main layers over a fatty layer.
- Epidermis: stratified squamous epithelium, avascular, outermost. Dermis: dense connective tissue with blood vessels, nerves, glands and hair follicles. Hypodermis (subcutaneous layer, superficial fascia): mostly adipose; it is not technically part of the skin.
- The dermis has a papillary layer (dermal papillae form fingerprints) and a deeper reticular layer (collagen and elastic fibers).
- Dermal collagen gives strength; elastic fibers give recoil. Stretch marks (striae) come from tearing of dermal fibers.
- Example: an injection given into the hypodermis is a subcutaneous injection.
Practice
Which layer of the skin contains blood vessels, nerve endings and hair follicles?
The epidermis is avascular; the dermis holds vessels, nerves, glands and follicles.
The fat-storing layer that lies below the dermis is the:
The hypodermis (subcutaneous tissue) is mostly adipose tissue that insulates and cushions.
Fingerprints are formed by ridges in which skin region?
The dermal papillae project into the epidermis and form the friction ridges.
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