Integumentary System Ms Clark PVMHS

Integumentary System Made up of the skin and its accessory structures – Accessory structures: Hair Nails Glands Sensory receptors

The skin is the largest organ in the body – It is an organ because it consists of different tissues that are joined to perform specific activities Dermatology is the branch of medicine that specializes in diagnosing and treating skin disorders

Functions of Skin 1.Regulation of body temperature 2.Protection 3.Sensation 4.Excretion 5.Immunity 6.Synthesis for Vitamin D

Functions of Skin 1.Regulation of body temperature – Evaporation of sweat, changes in flow of blood 2.Protection 3.Sensation 4.Excretion 5.Immunity 6.Synthesis for Vitamin D

Functions of Skin 1.Regulation of body temperature 2.Protection – Barrier from abrasion, bacteria, dehydration, UV radiation 3.Sensation 4.Excretion 5.Immunity 6.Synthesis for Vitamin D

Functions of Skin 1.Regulation of body temperature 2.Protection 3.Sensation – Nerve endings detect stimuli 4.Excretion 5.Immunity 6.Synthesis for Vitamin D

Functions of Skin 1.Regulation of body temperature 2.Protection 3.Sensation 4.Excretion – Small amounts of water, salts, etc excreted by sweat glands 5.Immunity 6.Synthesis for Vitamin D

Functions of Skin 1.Regulation of body temperature 2.Protection 3.Sensation 4.Excretion 5.Immunity – Langerhans cells help fight foreign invaders 6.Synthesis for Vitamin D

Functions of Skin 1.Regulation of body temperature 2.Protection 3.Sensation 4.Excretion 5.Immunity 6.Synthesis for Vitamin D – Exposure to UV radiation initiates synthesis of the active form on vitamin D (aids in the absorption of calcium and phosphorus)

Structure of Skin Two parts – Epidermis Outer, thinner portion, which is composed of epithelium (mostly stratified squamous) – Dermis Deeper, thicker part composed of connective tissue

Structure of Skin Subcutaneous layer also called hypodermis which attaches the skin to underlying structures (deep to dermis) – Adipose and areolar connective tissue Serves as storage for fat Contains large blood vessels supplying the skin Contains sensory nerve endings sensitive to pressure

Epidermis Avascular 5 layers (strata) Stratified squamous cells Keratinocytes produce keratin (tough, fibrous protein; functions are protection and durability)

Layers of the Epidermis From superficial to deep Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

Stratum corneum Outermost epidermal layer Made up of cell layers – Flat, dead keratinocytes – Constant exposure to friction or pressure leads to formation of a callus – an abnormal thickening Keratinization: cells gain keratin and are constantly shed and replaced by new cells

Stratum lucidum Consists of about 5 layers of clear, flat, dead cells Found only in the thick skin of the palms and soles

Stratum granulosum Contains about 5 layers of flattened keratinocytes Cells contain granules that release lipids, functioning as a water-repellant Upper layers beginning to die

Stratum spinosum 8-10 layers of keratinocytes with spiny projections Also contains Langerhans cells and projections of melanocytes Some cell division occurs here Receives some nourishment from the dermis (by diffusion)

Stratum basale One row of cells right above dermis Cells constantly reproducing through cell division – Cells multiply, push up, and become part of more superficial layers Adequate blood supply from dermis Melanocytes, Langerhans cells, Merkel cells

Epidermal Layers Cats Like Good Smelly Beef Can Lexie Get Some Band-Aids Carl Likes Green Soggy Bagels Clark Loves Going to Sunny Beaches

How does the skin do it? Cells in the lower strata of the epidermis (mostly in the stratum basale and some in stratum spinosum) are constantly undergoing cell division (millions of new cells made daily) and the new cells are pushed upward, away from the blood supply of the dermis to become part of the layers that are closer to the skin’s surface. As the cells move upward toward the stratum corneum, they start to die off and become flatter. These cells have more protective keratin in them.

Dermis Major parts are collagen, reticular fibers (thin protein fibers that add support), and elastic fibers Two layers – Papillary layer (loose connective tissue) – Reticular layer (dense connective tissue)

Papillary Layer Directly beneath epidermis Connects to it via papillae (finger-like projections)

Reticular Layer Deep to papillary layer Contains collagen fibers, Pacinian corpuscles, sensory receptors, sweat glands, hair follicles, lymph vessels