Chapter 6: Layers of the Integument

What is the integument?

• skin

• covers body and consists of skin and accessary tissues (nails, hair, sweat glands, sebaceous glands)

• cutaneous membrane, barrier to the outside world (first line of defense)

• visual indicator of our physiology and health

What are the layers of the integument?

• epidermis: stratified squamous epithelium

• dermis: deeper (reticular) layer; primarily dense irregular connective tissue

• subcutaneous layer (hypodermis): deep to dermis, layer of alveolar and CT, not part of integumentary system

What is the epidermis?

• epithelium of the integument, keratinized, stratified squamous epithelium

• First three layers composed of living keratinocytes

• consists of stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

What is the stratum basale of the epidermis?

• deepest epidermal layer,

• single layer of cuboidal to low columnar cells

• three types of cells

  • keratinocytes

  • melanocytes

  • tactile

What are the keratinocytes of the stratum basale layer?

• stratum basale are large stem cells

F: divide to regenerate new cells, synthesize keratin, a protein that strengthens epidermis

L: Found in all layers,

What are the melanocytes of the stratum basale layer?

S:

F: produce and store pigment (melanin) in response to ultraviolet light, transfer pigment granules (melanosomes) into keratinocytes, shield nuclear DNA from UV radiation

L: Scattered among keratinocytes in stratum basale

What are the tactile cells of the stratum basale?

S: Merkel cells, few in number

F: sensitive to touch, when compressed, release chemicals, stimulate sensory nerve endings

L:

What is the stratum spinosum?

• Several layers of polygonal keratinocytes

• new cells from stratum basale pushed into this layer

• nondividing keratinocytes attached by desmosomes

• epidermal dendritic cells (Langerhans cells)

What is the stratum granulosum?

• 3 to 5 layers of keratinocytes that begin to fill with keratin

• nucleus and organelles to disintegrate

• cells are dead

What are epidermal dendritic cells?

• initiate immune response

• found un spinosum and granulosum

What is the stratum lucidum?

• translucent layer

• 2 to 3 cell layers thick

• found only on thick skin on palms and soles

What is the stratum corneum?

• superficial stratum composed of 20 to 30 layers of dead

• interlocking, anucleate (lacking a nucleus), keratinized cells, dry,

• thickened surface is protective against abrasion and infection