Integumentary System

The skin and its accessory organs, such as hair, nails, glands, and specialized receptors, constitute the integumentary system.

Skin

• Organ: Group of tissues working together to perform a common, specialized function. Skin and its accessory organs (hair, nails, glands, receptors) are considered the integumentary system.

Dermatology

• Branch of medicine dealing with the diagnosis and treatment of skin disorders.

Factors affecting appearance of skin

a. nutritionb. hygienec. circulationd. agee. immunity (allergy)f. genetic traitsg. psychological statesh. drugsi. sunj. smoking (wrinkles and vasodilation)

Structure

1. Outer epidermis (predominantly epithelial tissue).

2. Inner dermis (connective tissue layer).

3. Subcutaneous layer: attaches skin to underlying structures (adipose and connective tissue).

Structure

•

Functions 1. Regulation of body temperature (sweat, shunting

of blood). 2. Protection: physical barrier (microbes,

dehydration, UV light). 3. Sensation: temperature, touch, pressure, pain.4. Excretion: water, salt, urea, other organic

compounds. 5. Immunity: nonspecific immunity (ie: physical

protection). Langerhans cells of the epidermis destroy foreign invaders.

6. Synthesis of Vitamin D: via UV light. Vitamin D helps absorption of calcium and phosphorus from digestive system into the blood.

Epidermis

4 cell types:

• Keratinocytes

• Melanocytes

• Langerhans Cells

• Merkel’s cells.

Keratinocytes• produce keratin (water proofing protein).

Protects underlying tissues from light, heat, bacteria, chemicals. Nucleus and organelles degenerate and cell dies (becomes dead package of keratin).

Melanocytes

• produces melanin, a pigment which absorbs UV light radiation.

Langerhans Cells

• immune functioning cells

Merkel’s cells

• epithelial cells in Merkel’s discs (receptors) that are sensitive to touch

Layers (from deepest to the surface)

• Stratum basale

• Stratum Spinosum

• Stratum granulosum

• Stratum lucidum

• Stratum corneum

Epidermis

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Epidermis - layers

• a. Stratum basale: regenerative cells and melanocytes. Single layer of cuboidal or columnar epithelial cells. Termed basal epithelial stem cells

• b. Stratum Spinosum: about 10 layers of cells (thick layer). Cells have "spinelike" projections that interlock and confer strength to the skin.

Epidermis - layers

• c. Stratum granulosum: thin layer of granulated cells (keratohyalin).

• d. Stratum lucidum: layer in thick skin only (palms of hands, soles of feet).

• e. Stratum corneum: 15-30 layers of highly keratinized cells that are sloughed off and replaced. Protect from light, dehydration, heat, trauma, bacteria).

Dermis • Predominantly connective tissue. Thick and thin in

different body regions. Few cells (adipocytes, fibroblasts, macrophages). Collagen and elastic fibers confer extensibility and elasticity. Predominantly connective tissue. Thick and thin in different body regions. Few cells (adipocytes, fibroblasts, macrophages). Collagen and elastic fibers confer extensibility and elasticity.

Receptors: • a. Meissner’s corpuscles: nerve endings sensitive to

light touch.• b. Pacinian corpuscles: receptors for pressure

(sustained touch).• c. Pain and temperature receptors.

Dermis

•  4. Hair follicles, nerves, sebaceous (oil) glands, sudoriferous (sweat) glands.

• 5. Blood vessels (arteries and veins) and lymphatics.

• 6. Dermal papillae project up into epidermal ridges and create ridges on skin to help us grip things (fingerprints).

Striae (stretch marks)

• Combination of collagen and elastic fibers gives the skin estensibility and elasticity. Extreme stretching may produce small tears in the dermis causing striae.

Fingerprints• During fetal development the basal layer

begins to grow faster than either the epidermis or dermis in the tips of the finger. This leads to an increased stress in the basal layer, which causes it to buckle inwards, creating ridges on the surface of the skin.

Subcutaneous layer (Hypodermis)

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Subcutaneous layer (Hypodermis)

• A. Location: Between dermis and underlying bone or muscle.

• B. Structure: Composed of areolar connective tissue, many blood vessels, adipose tissue, and nerves.

• C. Function: Provides cushioning, protection, insulation, energy reserve. Attaches skin to underlying structures.

Skin Color

A. Due to melanin, carotene, and hemoglobin. The amount of melanin determines the darkness of the skin.

B. Melanin confers a brownish tint to the skin. Carotene confers a yellow-orange color. Hemoglobin confers a pink to reddish color to the skin. An inherited inability of an individual of any race to produce melanin results in albinism (no pigment in hair, eyes, or skin. All races have about the same amount of melanocytes, thus variations in skin color are due to amount of pigment they produce. Freckles result from patches of melanin.

• Malignant melanoma: cancer of the melanocytes. Fast growing, dangerous cancer.

Accessory Organs

• Hair

• Glands -Sebaceous - Sudoriferous - Ceruminous

• Nails

Hair

1. Outgrowths of the epidermis.

2. Functions:

a. protects from sun rays (UV light).

b. insulates.

c. provides sensitivity.

d. eyelashes and eyebrows protect eyes from foreign particles.

e. nasal hairs protect from inhaled foreign substances.

Hair

• Hair is composed of strong structural protein called keratin. This is the same kind of protein that makes up the nails and the outer layer of skin.

Hair Structure• a. Shaft: external, exposed portion of hair• b. Root: portion below surface in dermis of skin• c. Follicle: • - External sheath and internal sheath of epidermal

cells covered by a connective tissue sheath.• - follicle surrounded by nerve ending: sensitive to

hair movement• d. Bulb: contains papilla of hair which contains

blood vessels for growing hair nourishment, and the matrix where new hair cells are derived from. Melanocytes of matrix produce melanin for hair coloring.

Hair Structure

• Growth rate of hair affected by illness, radiation therapy, chemotherapy, nutrition, age, stress, genetics, and gender.

•  Arrector pili muscles (smooth) contract to pull hair erect. Results in “goose bumps”. Provides some insulation when cold, warning when frightened.

Glands - Sebaceous (oil) glands:

• a. connected to hair follicles or open directly to skin’s surface.

• b. no sebaceous glands on palms of hands or soles of feet.

• c. secrete sebum that prevents hair from drying out, dessication of skin, bacterial growth.

• d. Pimple, blackhead: build-up of oil and bacteria in a sebaceous gland.

•

Sudoriferous (sweat) glands:

a. produce perspiration (sweat).

b. perspiration evaporates allowing heat to be lost; excretes some wastes.

• Two types: Eccrine – since birthApocrine – Puberty – same components + lipids and proteins

Ceruminous (wax) glands

• a. located in the outer ear canal.

• b. combined secretions of ceruminous and sebaceous glands is termed cerumen. Cerumen and hairs of the outer ear canal provide a sticky barrier against foreign invaders.

Nails

1. plates of tightly packed, hard, keratinized cells of the epidermis.

2. grow about 1mm per week.

3. help to grasp and manipulate small objects; provide protection for the ends of the digits; scratch an itch.

Common Disorders - Burns• 1. First degree: minor damage to the

epidermis only with no blistering.• 2. Second degree: involves both

epidermis and dermis. Redness, blistering, edema, and pain.

• 3. Third degree: most severe burns. Burns through dermis to subcutaneous layer, or deeper. Destroys epidermis, dermis, and epidermal organs, and skin functions are lost.

Burns

• First second third

Pressure Sores: bedsores.

• Constant deficiency of blood to tissues over bony projections that have been subjected to prolonged pressure against an object like a bed, cast, or splint.

Sunburns

• Burns due to overexposure to UV light.