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Unit 5 Integumentary System

Discuss the functions of the skin as an organ system and its role in the homeostasis of body temperature.

  • The skin works to separate the inside environment from the outside environment, maintain boundaries (chemical, biological, & physical barrier).

    • cutaneous sensation (detects & responds to physical stimuli like bug crawling on skin), metabolic functions (synthesize vitamin d & disarm carcinogens), blood reservoir (hold up to 5% of total blood volume), excretion (sweat, nitrogenous wastes)

  • under normal resting condition, the skin produces ~500ml/day (insensible perspiration)

    • as body temp rises (hot), blood vessels dilate, and can produce 12L noticeable sweat (sensible perspiration) to cool the body when it evaporates

    • as body temp declines (cold), blood vessels constrict to preserve warmth

Describe the layers, structural components, and functions of the epidermis dermis and hypodermis.

  • The epidermis is avascular & made of epithelial & areolar CT

    • corneum: most top layer, 20-30 rows of dead cells that function to protect (maintain boundaries), makes ¾ of epidermal thickness

    • lucidum (only hands & feet): thick skin, translucent band of 2-3 rows of flat & dead keratinocytes

    • granulosum: 1-5 cell layers (thinnest layer), keratinization begins, cell apoptosis bc too far from dermal capillaries to survive, keratohyaline granules (form keratin in upper layers) & lamellar granules (contain water-resistant glycolipids, major in slowing water loss in epidermis)

    • spinosum: dendritic cells most abundant, cells contain thick bundles of intermediate filaments that have pre-keratin, desmosomes hold down shrunken cells after tissue preparation

    • basale: deepest layer, very active cell division (aka germinativum), 10-25% is melanocytes, 1 daughter cell goes to surface to mature & 1 stays for cell division takes 25-45 days for new cells to reach surface

  • the dermis is very vascular & made of fibrous & dense irregular CT, WBC & fibroblasts, contains nerves, capillaries, hair follicles, glands (oil & sweat), & lymphatic vessels

    • papillary: superficial, interlacing collagen & elastic fibers, loose fibers to make passage for phagocytes to patrol, dermal ridges in thick skin create fingerprints w/ sweat pores

    • reticular: makes ~80% of dermal thickness, dense irregular CT, elastic fibers give stretch-recoil, collagen fibers give strength & resistance but also bind h2o keep skin hydrated

  • the hypodermis is vascular & made of adipose & areolar CT

    • fat to absorb shock

Describe the basic structure and function of epidermal derivatives such as hair, nails, sweat, sebaceous, and ceruminous glands.

  • hair (pili): compressed, dead, keratinized cells

    • sense receptors, hair on head guards scalp against trauma, shield from sun, protects from heat loss, eyelashes shield eyes, nose hairs act as filter

    • hard keratin for maximum protection

    • shaft: area that extends above scalp (keratinization is complete)

    • root: inside scalp (ongoing keratinization)

    • bulb: expanded area at deep end of follicle

    • medulla in middle, next is cortex, and last is cuticle (from transverse view)

  • nails: flat, plate-like, dead, keratinized cells

    • nail matrix is responsible for nail growth

    • nail folds: skin folds that overlap nail border

    • eponychium (cuticle): nail folds project onto surface on nail body

    • lanule: thickened nail matrix, white part (think luna moon)

    • beau’s lines are horizontal line across nails & can indicate uncontrolled diabetes, heart attack, or cancer chemo

    • koilonchya (spoon nail): inward concavity of nail & may indicate iron deficiency

  • sebaceous: secrete sebum

    • not found on thick skin of hands & feet since they’re in hair follicles

    • inactive until puberty bc of hormones (androgens)

    • oily holocrine secretion that has bactericidal properties & softens hair & skin

  • sweat: sudoriferous glands

    • all skin (not nipples/some external genitalia) has

    • myoepithelial cells

    • 2 main types

      • eccrine (merocrine exocytosis): most numerous, abundant on hands, feet, & forehead, function in thermoregulation, 99% h2o, vit c, antibodies, dermcidin, metabolic wastes

      • apocrine (merocrine exocytosis): may act as sexual scent glands, confined to axillary and genital areas, secrete milky/yellow sweat that has fatty substance & proteins & leads to body odor, larger than eccrine

      • ceruminous: modified apocrine gland found in lining of external ear canal, mixes w/ sebum to make earwax thought to deter insects & foreign substance/objects

Discuss the classification of burns by degree and surface areas involved.

  • devastating threat bc of dehydration & electrolyte imbalance

  • classified by 3 stages:

    • 1st degree: only epidermis damaged, localized redness, swelling, & pain, usually heals 2-3 days on its own (sunburn)

    • 2nd degree: epidermal & upper dermal damage (partial-thickness burns), blisters appear, heals 3-4 weeks

    • 3rd degree: most dangerous, entire thickness of skin involved, skin is grey-white, cherry red, or blackened, no edema/pain since pain receptors (nerves) have been destroyed, skin grafting usually necessary

  • burns are critical if >25% of body has 2nd degree burns & >10% of body has 3rd degree

  • burn treatments include: debridement of skin, antibiotics, temporary covering, & skin grafts

  • percentages of burn on body

    • anterior & posterior head & neck= 9% (4 ½% each)

    • anterior & posterior upper limbs= 18% (4 ½% each side of each arm)

    • anterior & posterior trunk= 36% (18% each)

    • perineum= 1%

    • anterior & posterior legs= 36% (9% each side of each leg)

Discuss the three principal types of skin cancer and differentiate among them.

  • basal cell carcinoma: affects stratum basale

    • least malignant & most common

    • slowly invades dermis & below

    • 99% of times cured by excision

  • squamous cell carcinoma: affect keratinocytes of stratum spinosum

    • second most common & can get worse

    • scaly red papules on scalp, ears, lower lip, hand

    • good remission if treated w// radiation therapy/excision

  • melanoma: affects melanocytes

    • most dangerous bc highly metastatic & resistant to chemo

    • treated by surgical removal followed by immunotherapy

    • ABCD rule to detect

      • A: asymmetry - 2 sides of pigmented area are different

      • B: border irregularity - exhibits indentions/ diff texture

      • C: color - contains diff colors (blue, black, brown, tan)

      • D: diameter larger than 6mm