Integumentary System - 3 layers of skin

integumentary system basic functions

• protection

• sensation

• production

• temperature

• excretion

epidermis

superficial layer of epithelial tissue; lacks blood vessels/nerves

4 types of cells in epidermis

keratinocytes, melanocytes, langerhans cells, merkel cells

keratinocytes

produce keratin, dies and forms a hardened, waterproof layer

lamellar granules

produced from keratinocytes, release waterproof lipid sealant for skin

melanocytes

produce pigment melanin, transferred to keratinocytes

melanin

pigment that contributes to skin, hair, and eye color and absorbs UV radiation

langerhans cells

participate in immune response to microbes that invade skin

merkel cells

act as touch receptios and are in contact with sensory neurons, found in deepest layer of epidermis

5 layers of stratified squamous epithelium (in epidermis)

• stratum basale

• stratum spinosum

• stratum granulosum

• stratum lucidum

  • stratum corneum

stratum basale

deepest layer, some stem cells, contains melanocytes, merkel cells, and langerhans cells

stratum spinosum

8-10 layers of keratinocytes that fit closely together, most prevalent location of Langerhans cells

stratum granulosum

contain membrane bound granules that produce lipid-rich secretion that enters extracellular space and waterproofs; undergoing apoptosis

stratum lucidum

3-5 layers of flat, clear, dead keratinocytes with large amounts of keratin (present only in thick skin)

stratum corneum

25-30 layers of dead/flat keratinocytes shed/replaced

• completely filled with keratin and lipid secretions

dermis

mainly connective tissue containing collagen and elastic fibers

types of cells found in dermis

fibroblasts, macrophages, adipocytes

composition of dermis

blood vessels, nerves, glands, hair follicles

papillary region

• upper 20% of dermis

  • increased surface area due to small, upward projections into epidermis called dermal papillae

dermal papillae

form papillary ridges (fingerprints) on surface of fingers/toes, contain sensory nerves

meissner corpuscle

touch receptors found in some dermal papillae that are sensitive to light touch

reticular region (dermis)

• dense irregular connective tissue

• collagen and elastic fibers

• adipose cells, hair follicles, nerves, capillaries, sebaceous glands, sudoriferous glands

hypodermis

loose connective tissue and adipose, attaches dermis to underlying organs, contains nerve endings called Pacinian corpuscles that are sensitive to pressure