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INTEGUMENT Surface Anatomy • Palpation • Bony landmarks • Dermatomes Neural assessment Integument Histology • Epidermis: Stratified squamous epithelium Resting on: • Basement membrane Resting on: • Dermis: Dense irregular connective tissue Epidermis • The epidermis is a stratified squamous epithelium. • It is made up of many layers of cells. • The stratum germinativum is the deepest layer: Area of high mitotic activity. Epidermis • The stratum corneum is the most superficial layer: The cells in this layer are dead and keratinized. • Between the stratum germinativum and the stratum corneum are several transitional layers represented by cells from the stratum germinativum that are transforming into dead, keratinized cells. Epidermis • The epidermis is innervated. • The epidermis is avascular. Dermis • The dermis is the deepest region of the integument. • The dermis is classified as dense irregular connective tissue • The dermis has an abundance of collagen fibers • There may also be some elastic fibers: Decrease with age. Dermis • The dermis is vascularized. • Refer to Figure 1 in your course packet. Thick Skin vs. Thin Skin • Classification into thin and thick skin depends on the structure of the epidermis. • Layers of epidermis are well-formed in thick skin. • Layers of epidermis are not as well-formed or thick in thin skin. Thick Skin • Thick skin is found only on the palms of the hands and the soles of the feet. • The epidermis of thick skin is 0.4 – 0.6 mm thick • Thick skin has no hair follicles. Thin Skin • Thin skin is found over the rest of the body. • The epidermis of thin skin is 0.075 – 0.150 mm thick. • Total skin thickness is 0.5 – 3 mm thick. Skin Thickness • Thickest skin found on back (= thin skin) • Thinnest skin found on eyelids (= thin skin) • Thicker on extensor surfaces than flexor surfaces. Superficial Fascia: Synonyms • • • • Subcutaneous fascia Superficial fascia Hypodermis SubQ Superficial Fascia • Consists of loose bundles of collagen and elastic fibers with variably sized aggregations of lipocytes (fat cells) • May be loosely or tightly attached • Supports cutaneous nerves and blood vessels Deep Fascia • Synonyms: Membranous fascia Investing fascia • Usually several thin layers of tough collagen material • Tightly adherent to muscles, bones, tendons, etc. Cutaneous Derivatives • Glands. • Hairs. • Nails. Glands • Glands are epithelial structures • Glands are classified according to the presence or absence of a secretory duct: Exocrine Endocrine Epidermal Glands • • • • Sudoriferous glands Sebaceous glands Ceruminous glands Mammary glands Sudoriferous Glands • Are long, simple, tubular glands. • Their method of secretion is merocrine . Sebaceous Glands • Are holocrine . • Sebaceous glands are associated with hair follicles. Ceruminous Glands • Are located in the external auditory canal. • Secrete ear wax. Mammary Glands • Are modified sweat glands • Method of secretion is apocrine Hairs • Hairs develop during 3rd month of gestation. • The earliest fine embryonic hair = lanugo. • Lanugo is Shed before birth except around eyebrows, scalp, and eyelids. Hairs • A new downy coat of hair appears a few months after birth. • This new coat is called vellus. • Vellus is converted to terminal hair at puberty: Vellus represents 95% of the hair coverage in males. Vellus represents 35% of the hair coverage in females. Parts of a Hair • Shaft: Made up of dead cornified epidermal cells. • Follicle: Derived from both epidermis and dermis. • Dermal papilla with matrix. Parts of a Hair • Arrector pili muscle. • Sebaceous glands. • Hair bulb and connective tissue papilla. Hair Growth • Anlagen Active growth: Scalp hair = 2-3 years Eyebrow hair = 3-4 months Hair Function and Location • Hair follicles are innervated, and hairs serve as sensory receptors. • Hairs are found everywhere except palms, soles, dorsal distal phalanges, anal and urogenital apertures Nails • Ungis: Modified stratum corneum Flattened Avascular and not innervated Travels over a nail bed guided by lateral nail grooves • Matrix: Stratum germinativum produces ungis • Subungis Melanocytes • Found in deep layers of epidermis • Derived from nervous system components • Form: Melanosomes: Passed off to keratinocytes (cells of epidermis). Phagocytized by keratinocytes. Melanocytes • All individuals produce same number of melanosomes. • Skin color depends on number of remaining melanosomes. Langer’s Lines • Represent tension lines created by orientation of collagen fibers in the dermis of the skin. • Used by surgeons as guides for incisions: Incisions normally made parallel to Langer’s lines Dermatomes • Specific region of skin innervated by a specific spinal cord level. • Refer in syllabus to figure 3