Chapter 5
Describe the functions of the vertebrate integumentary system. Discuss the structure of the skin and how it relates to function. Explain the basis for different skin colors. Describe the structure and functions of hair, skin, glands, and nails.
Consists of: Cutaneous membrane (skin) epidermis dermis hypodermis Accessory structures hair nails glands
The skin is the largest organ in the body 16% of body weight 1.5 2.0m 2 in area
Protects underlying tissues & organs Excretes salts, water, and organic wastes (glands) Maintains body temperature (insulation & evaporation)
Synthesizes vitamin D3 Stores lipids Detects touch, pressure, pain, and temperature
Stratified squamous 5 layers From innermost layer: Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
Cell division to replace superficial cells
Cells that are made are passed through these layers Accumulate large amounts of keratin protein
Depends on: Blood supply Epidermal pigmentation
3 pigments responsible: Melanin yellow to reddish brown to black dark skin colors freckles & moles = local accumulations of melanin Carotene yellow to orange on palms and soles Hemoglobin pinkish hue
Oxygenated red blood contributes to skin color Blood vessels dilate from heat, skin reddens Blood flow decreases, skin pales Cyanosis Bluish skin tint Caused by severe reduction in blood flow or oxygenation
2 layers: Papillary layer (surface) Contains blood vessels and sensory nerves Reticular layer (deeper) Collagen and elastic fibers (resists tension)
Friction Ridges Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints Friction ridges Openings of sweat gland ducts
Stabilizes the skin s position against underlying organs and tissues
Body is covered with hair, except: Palms Soles Lips Portions of external genitalia Hair originates in hair follicles
Alert body to presence of insects Guard scalp against: physical trauma heat loss sunlight
Growth phase followed by resting phase Growth phase varies: scalp: 6-10 years eyebrows: 3-4 months Hair thinning Alopecia hair thinning in both sexes after age 40
Sebaceous gland Discharges sebum into hair follicle Sweat glands Apocrine sweat glands Produce an odorous secretion Eccrine (merocrine) sweat glands Produce perspiration
Mammary glands (breasts) Produce milk Ceruminous glands (ears) Produce cerumen (earwax)
Protection! Nail body covers the nail bed Nail root where nail is produced Cuticle over nail root Free edge extends over the hyponychium
Regeneration can occur: Scab Granulation tissue Scar tissue
Most tumors are benign Risk factors: overexposure to UV radiation frequent irritation of the skin 3 main types: Basal Cell Carcinoma least malignant, most common Squamous Cell Carcinoma 2 nd most common Melanoma most dangerous
Cured by surgical excision in 99% of cases
Most common on scalp, ears, lower lip, and hands Good prognosis if treated by radiation therapy or removed surgically
Highly metastatic and resistant to chemotherapy Characteristics (ABCD rule) A: Asymmetry; the two sides of the pigmented area do not match B: Border exhibits indentations C: Color is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser)
Integument thins Blood flow decreases Cellular activity decreases repairs occur more slowly Epidermal replacement slows skin becomes thin, dry, and itchy Subcutaneous fat and elasticity decrease, cold intolerance and wrinkles Increased risk of cancer
The two main components of the integumentary system are. A. the cutaneous membrane and the accessory structures B. the epidermis and the hypodermis C. the hair and the nails D. the dermis and the subcutaneous layer
Each of the following is a function of the integumentary system, except. A. protection of underlying tissue B. excretion of salts and wastes C. maintenance of body temperature D. synthesis of vitamin C E. storage of nutrients