Integumentary System

20.12

Structure of Skin

• Consists of 3 layers: the epidermis and the dermis and hypodermis

Epidermis

• stratified squamous epithelium (many layers of flat cells)

• new cells are pushed upward by the addition of new cells

• filled with keratin, and waterproofing glycolipids

• dead cells remain at the surface for up to two weeks

Dermis

• inner layer of the skin

• consists of fairly dense connective tissue with elastic fibers and collagen fibers

• contains hair follicles, oil, sweat glands, muscles, nerves, sensory receptors, and blood vessels

Hypodermis

• layer of adipose tissue (body fat)

• site of injections

Functions of the Skin

Epidermis

• provide waterproof covering that protects your body from dehydration

• prevents penetration by microbes

Dermis

• The sensory receptors in the skin provide important environmental information to your brain

• profusion of small blood vessels and sweat glands facilitate temperature regulation

Metabolic functions

• synthesis of Vitamin D

Hair and Nails

Hair

• flexible shaft of flattened keratin-filled dead cells, produced by a hair follicle

Oil Glands

• lubricate the hair

• condition the surrounding skin

Nails

• Protective covering composed of keratin