The Integumentary System Chapter 5

Integumentary System The Body Covering Includes: skin, nails & hairs Skin = cutaneous membrane

Structure Two main parts = Epidermis- surface epithelial layer Dermis -deeper connective tissue layer Deep dermis not part of the skin = subcutaneous layer or Hypodermis

Figure 5.1

Epidermis Keratinized stratified squamous epithelium 4 cell types: Keratinocytes Melanocytes Langerhans cells Merkel cells

Epidermal Cells Keratinocytes 90% of epidermal cells 4-5 layers Produce keratin Protect skin Waterproof skin

Epidermal Cells Melanocytes - produce melanin Transfer pigment to keratinocytes 8% of epidermal cells

Epidermal Cells Langerhans Cells- immune response Merkel cells – sensory Include tactile disc and neuron = touch sensation

Epidermal Layers Generally 4 strata (layers) Stratum basale –includes stem cells Stratum spinosum – 8-10 cell layer Cells beginning to look flattened Stratum granulosum –keratin Losing cell organelles and nuclei Include lamellar granules = waterproofing lipid Stratum corneum – flattened dead cells Cells shed and are replaced from below- mostly keratin-filled

Skin Color Melanin- dark color Carotene- yellow orange Darkness depends on amount of melanin produced. gives some protection against UV Carotene- yellow orange In stratum corneum and adipose layers- Hemoglobin in blood- pink-red Depends on blood flow

Accessory Structures Hair Skin glands Nails

Hair Found on most skin surfaces Made of fused keratinized cells Not on palmar surfaces of hand and fingers or plantar surfaces of feet Made of fused keratinized cells Consists of shaft & root Surrounded by hair follicle Base is bulb which includes growing matrix producing cells Nerves- hair root plexuses Muscle- arrector pili

Figure 5.3

Glands sebaceous gland- secrete oily sebum sudoriferous or sweat gland Connected to hair follicles sudoriferous or sweat gland Eccrine sweat gland Wide distribution- thermoregulation apocrine sweat gland Axilla, groin, areolae, beard Contain other cell material and produce pheromes Ceruminous Glands- external auditory canal Combine with sebum to produce earwax

Nails Plates of packed hard dead keratinized cells Nail body- major visible portion Free edge- part extending past finger or toe Root – part not visible

Figure 5.4a

Figure 5.4b

Functions Temperature Regulation Protection Sensory reception Excretion & Absorption -small Vitamin D synthesis

Aging Adolescence- can develop acne Mostly dermis- visible ~ age 40 Loss of collagen fibers Loss of elasticity Loss of immune responses Decreased melanocyte functions- gray hair, blotches Thinning