Human Anatomy The Integument System

Function(s) 1.Physical protection 2.Thermoregulation 3.Excretion 4.Synthesis of vitamin D 3

Structure of Skin 2 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

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

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 Structures of 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

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