Human Anatomy

The Integument System

Function(s)

1. Physical protection

2. Thermoregulation

3. Excretion

4. Synthesis of vitamin D3

Structure of Skin2 layers – epidermis and dermis

A. Epidermis

• Consists only of epithelial cells

• Avascular – no blood supply

• No nerve supply

• 5 distinct layers of epithelial cells

Epidermis

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5

1. Stratum Basale (Germinativum)

• Deepest layer, in contact with dermis

• Single layer of cells

• Only layer of epidermis capable of cell division

• Contain melanocytes

Melanocytes

Melanocytes

Melanocytes

• Capable of producing the brown pigment, melanin

• Melanin can absorb energy from ultraviolet (UV) light

• UV light contains high energy photons that can damage DNA – mutations

• Melanin can prevent damage to DNA, helps to prevent skin cancer

Melanocytes

2. Stratum Spinosum

• Several layers thick

• Cells of this layer begin to produce keratin

• Keratin is a water-insoluble protein that protects the body from water

2. Stratum Spinosum

3. Stratum Granulosum

• Multilayer and cells become compressed

• Keratin crystallizes into granuoles within the cytoplasm

• Cells are metabolically dead

3. Stratum Granulosum

4. Stratum Lucidum

• Clear layer of cells

• Only present in thick skin

• Cells nothing more than a bag of keratin

4. Stratum Lucidum

5. Stratum Corneum

• Multiple layers of flattened, dead cells

• Number of layers depends on region of the body

• More friction, more layers of cells

Accessory Structuresof the Integument

1. Hair follicles

2. Oil and sweat glands

3. Nails

Skin Color

• Is determined by 3 pigments

1. Hemoglobin – red pigment within RBC

2. Melanin – brown pigment in melanocytes

3. Carotene – orange-yellow pigment found in both epidermal cells and dermal fat cells

B. Dermis

• Consists of other 3 tissue types

1. CT (connective tissue)

2. Muscle

3. Nervous

• Has blood supply and nerves

Dermis

Dermis

1. CT adds collagen and elastic fibers which give strength and stretch properties

Dermis

2. Muscle – arrector pili which is attached to shaft of hair follicle

Dermis

3. Nervous – detects light touch, stretch, deep pressure, vibration and temperature