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 – 2.0m2 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 ridgesOpenings 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 2nd 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