Chapter 6: Integumentary System
6.1 Introduction Why is skin considered to be an organ? What makes up the integumentary system?
Integumentary System Skin (cutaneous membrane) Skin derivatives Sweat glands Oil glands Hair Nails
6.2 Skin and its Tissues Skin is also know as a cutaneous membrane How is the skin vital in maintaining homeostasis? Skin has 2 layers Epidermis: most superficial; thin; stratified squamous epithelial tissue; keratinized Dermis: deep to epidermis; thicker; loose and dense connective tissue; contains appendages (hair, glands, blood vessels, nerves, etc) Subcutaneous layer or hypodermis lies deep to dermis; consists mostly of loose adipose connective tissue
Skin Structure Figure 4.3
A Closer look at the Epidermis Epidermis composed of keratinized stratified squamous epithelium. Structure: Principle Cell types and layers Keratinocytes makes up 90%, arranged in 4 to 5 layers, produce: Keratin: tough, fibrous, waterproof protein Lamellar granules: repel water Melanocytes 8%, produces pigment melanin, have long slender projections that transfer melanin to keratinocytes Melanin: brown/black pigment, absorbs UV light Langerhans cells aid in immune response; easily damaged by UV light Merkel cells contact sensory neuron, aid in sensation
Epidermal Cell layers (deepest to most superficial) Stratum basale (deepest or base layer) attached to basement membrane, contains most of the melanocytes, has cuboidal or columnar cells, mitosis. Stratum spinosum (spiny layer) 8-10 layers of irregular shaped keratinocytes, become flattened Stratum granulosum (granular layer) 3-5 layers of flat keratinocytes, undergoing cell death Stratum lucidum (clear layer) dead cells w/ lots of keratin; only in thick skin of finger tips, palms and feet Stratum corneum (most superficial, horny layer) 25 to 30 layers of flattened dead cells containing keratin, continuously shed and replaced by cells from deeper strata What is Keratinization?
Melanin Pigment (melanin) produced by melanocytes Melanocytes are mostly in the stratum basale Color is yellow to brown to black Amount of melanin produced depends upon genetics and exposure to sunlight
Normal Skin Color Determinants Melanin Yellow, brown, or black pigments Carotene Orange-yellow pigment from some vegetables Hemoglobin Red coloring from blood cells in dermal capillaries Oxygen content determines the extent of red coloring
Functions of epidermis Protection (damage, UV rays, etc) Growth / Repair (regeneration) Immune response Sensation Water-repellent & sealant Epidermal growth and repair Regeneration time for skin is about 35 days Shortened regeneration time results in increased thickness of stratum corneum making a callus (thick skin)
A Closer look at the Dermis Dermis: deep to the epidermis Structure of Dermis Much thicker than epidermis has 2 portions: Papillary Dermis (Superficial part of dermis): Loose areolar connective tissue Dermal Papillae: finger-like projections indenting epidermis; increase surface area Contain capillaries Contain corpuscles of touch (Meissner corpuscles) Reticular Dermis (Deep part of dermis): dense connective tissue Contains hair follicles, nerves, blood vessels, sebaceous (oil) glands, & sudoriferous (sweat) glands
Functions of the Dermis Sensitivity Strength / support Stretchable / elasticity Flexibility Dermal growth & repair Dermis does not continually shed and regenerate like epidermis If this layer is damaged, the fibroblasts form a dense mass of connective fibers forming a scar Extreme stretching may produce small tears causing striae or stretch marks
Skin Structure Subcutaneous tissue (hypodermis) is deep to dermis Not part of the skin Anchors skin to underlying organs Composed mostly of adipose tissue
Glands Sebaceous (oil) glands Secretes oil (sebum), keeps hair & skin soft/pliable, prevents water loss from skin Located in dermis, except for palms & soles Aids in formation of pimples & black heads 2 types of Sudoriferous (sweat) glands Eccrine glands. Apocrine glands
Appendages of the Skin Sebaceous glands Produce oil Lubricant for skin Prevents brittle hair Kills bacteria Most have ducts that empty into hair follicles; others open directly onto skin surface Glands are activated at puberty
Appendages of the Skin Figure 4.6a
Appendages of the Skin Sudoriferous (sweat) glands Produce sweat Widely distributed in skin Two types Eccrine Open via duct to pore on skin surface most common; secretes sweat, eliminates wastes, maintains core temp Apocrine Ducts empty into hair follicles activated during puberty, located in armpit, groin,
Appendages of the Skin Figure 4.6b
Sweat and Its Function Composition Mostly water Salts and vitamin C Some metabolic waste Fatty acids and proteins (apocrine only) Function Helps dissipate excess heat Excretes waste products Acidic nature inhibits bacteria growth Odor is from associated bacteria
Appendages of the Skin Ceruminous glands Located in ear canal Produces ear wax (cerumen) Too much wax can cause a blockage of ear canal, loss of hearing
Appendages of the Skin Hair follicles composed of epithelial cells, distributed all over body except for palms, anterior side of fingers, soles, genitalia, and lips Dermal and epidermal sheath surround hair root Genetics and hormones determine thickness and distribution of hair Hair is also important for protection and reproduction Melanocytes provide pigment for hair color Arrector pili muscle Smooth muscle Pulls hairs upright when cold or frightened (goose bumps)
Appendages of the Skin Figure 4.7c
Appendages of the Skin Hair anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized Figure 4.7b
Appendages of the Skin Figure 4.7a
Appendages of the Skin Figure 4.8
Appendages of the Skin Nails Plates of tightly packed, hard, keratinized cells of epidermis Very protective of ends of fingers; aids in grasping and manipulating small objects; scratching Stratum basale extends beneath the nail bed Responsible for growth Lack of pigment makes them colorless
Appendages of the Skin Nails can indicate health issues Bluish nail beds may indicate circulation issue White nail bed or oval depressions can indicate anemia Pigmented spot (not injury) can indicate melanoma Horizontal furrows may indicate period of illness or malnutrition Disorders of heart, liver, or lungs may cause extreme curvature of nails Red streaks in nails may be traced to RA, uclers, or hypertension
Nails: Figure 6.4 Free edge extends past end of finger Nail plate / body visible part of nail Nail root sides and bottom of nail in groove, hidden by cuticle Nail bed skin surface that is covered by nail plate Cuticle skin around bottom of nail (stratum corneum) Lunula half-moon shaped white area at base of nail; the most active growing region average growth is 0.5 to 1 mm per week
Appendages of the Skin Figure 4.9
Skin Functions Table 4.1 (1 of 2)
Skin Functions Table 4.1 (2 of 2)
Overall Functions of the Integumentary System Regulation of body temperatures Sensitivity Excretion and absorption Vitamin D synthesis Protection Barrier to microorganisms Barrier to chemical hazards Reduces injury to underlying structures Prevents dehydration Protects (via melanin) excessive UV exposure Surface film protective barrier over skin s surface; (like wax on your car)
6.4 Regulation of Body Temp. How does your skin aid in regulating body temperature? What portion of the brain controls the set point for body temperature? Differentiate between hypothermia and hyperthermia. Discuss the consequences of each.
6.5 Healing of Wounds What is inflammation? Is it normal or abnormal and why? Differentiate between the healing processes of a superficial wound and a deeper wound. Which one would result in a scar?
Skin Homeostatic Imbalances Infections Athlete s foot (tinea pedis) Caused by fungal infection Itchy, red, peeling condition of skin between the toes Boils and carbuncles Caused by bacterial infection Cold sores Common on dorsal neck, inflammation of hair follicles and sebaceous glands. Caused by virus (herpes simplex) activated by stress, fever, illness, and UV Radiation Small fluid-filled blisters that itch and sting
Homeostatic Imbalances
Skin Homeostatic Imbalances Infections and allergies Contact dermatitis Exposures cause allergic reaction Impetigo Itching, redness, and swelling of skin progressing to blistering Caused by bacterial infection Psoriasis Pink, water-filled, raised lesions (nose and mouth) that develop a yellow crust and eventually rupture Cause is unknown Triggered by trauma, infection, stress Overproduction of skin cells, reddened epidermal lesions covered with dry, silvery scales that itch, burn, crack and sometimes bleed.
Skin Homeostatic Imbalances Figure 4.10
Skin Homeostatic Imbalances Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Dehydration Electrolyte imbalance Circulatory shock
Rule of Nines Way to determine the extent of burns Body is divided into 11 areas for quick estimation Each area represents about 9% of total body surface area
Rule of Nines Figure 4.11a
Severity of Burns First-degree burns Only epidermis is damaged Skin is red and swollen Second-degree burns Epidermis and upper dermis are damaged (partial-thickness burn) Skin is red with blisters Third-degree burns Destroys entire skin layer (full-thickness burn) Burn is gray-white or black
Severity of Burns Figure 4.11b
Critical Burns Burns are considered critical if Over 25% of body has second-degree burns Over 10% of the body has third-degree burns There are third-degree burns of the face, hands, or feet
Skin Cancer Cancer abnormal cell mass Classified two ways Benign Does not spread (encapsulated) Malignant Metastasized (moves) to other parts of the body Skin cancer is the most common type of cancer
Skin Cancer Types Basal cell carcinoma Least malignant 99% cure in which lesion is removed surgically Most common type Sun Exposure Arises from stratum basale cells are altered so that they cannot form keratin They invade dermis and subcutaneous tissue Symptoms: shiny, dome-shaped nodule that later develop a central ulcer with a pearly beaded edge.
Skin Cancer Types Figure 4.12a
Basal Cell Carcinoma
Skin Cancer Types Squamous cell carcinoma Metastasizes to lymph nodes if not removed Early removal allows a good chance of cure Believed to be sun-induced Arises from stratum spinosum Symptoms: lesion, scaly, reddened papule (small, rounded elevation), that gradually forms a shallow ulcer with a firm, raised border. Grows rapidly and metastasizes to adjacent lymph nodes if not removed If caught early and removed surgically or by radiation the cure rate is good.
Squamos Cell Carcinoma
Skin Cancer Types Figure 4.12b
Skin Cancer Types Malignant melanoma Most deadly of skin cancers Cancer of melanocytes Metastasizes rapidly to lymph and blood vessels Detection uses ABCD rule Cause: Genetics, accumulated damage to DNA in skin cells Symptoms: arise as a spreading brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels Chance of survival is 50% Accounts for 5% of skin cancers
Skin Cancer Types Figure 4.12c
Malignant Melanoma
ABCD Rule A = Asymmetry Two sides of pigmented mole do not match B = Border irregularity Borders of mole are not smooth C = Color Different colors in pigmented area D = Diameter Spot is larger then 6 mm in diameter E = Elevation/Evolves Spot is elevated or changes over time