BIO 201: Ch. 5 The Integumentary System

Epidermis

The superficial layer of the skin consists of stratified squamous keratinized epithelium. It is avascular and depends on the diffusion of oxygen and nutrients from the dermis.

Dermis Layer

The deeper layer of skin consists of loose and dense, irregular collagenous connective tissue.

Hypodermis

The layer of adipose tissue deep to the skin; also known as subcutaneous tissue.

Eccrine Sweat Glands

Glands in the skin that produce a watery sweat as part of the body's thermoregulatory mechanism. These are the most numerous types and are active in all ages.

Apocrine Sweat Glands

Sweat glands found in the axillae, the anal area, and the areola that secrete a thick sweat that is rich in proteins. They become active at puberty, and when bacteria feed on the secretions, they produce a gas that is odiferous.

Functions of the Integumentary System

Protection, sensation, thermoregulation, excretion, synthesis of vitamin D (which is required for calcium ion absorption.)

Excretion

Eliminating wastes and toxins from the body.

Negative feedback loops for control of body temperature

If body temperature is too high, thermoreceptors in the skin detect the increase in temperature, and the message is sent to the control center in the hypothalamus. The hypothalamus stimulates sweating and vasodilation as the response. When the temperature returns to normal, the thermoreceptors stop sending the signal to the hypothalamus, which reduces the sweating and vasodilation.

If the body temperature drops below the normal range, usually due to cold environmental conditions, the thermoreceptors in the skin detect the decrease in body temperature below the normal range and relay this to the hypothalamus. The hypothalamus stimulates the effector to respond by vasoconstriction (blood vessels in the dermis narrow, or constrict, reducing the amount of blood flow which limits the heat lost to the environment.) Blood is also redirected to deeper tissues.

Layers of the epidermis (from top to bottom)

Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale.Thick skin has all 5 layers; thin skin has 4 layers (it does not have the stratum lucidum.) Remember the mnemonic (Come Let's Get SunBurned.) Thick skin is found on the palms of the hands and soles of the feet and does not have hair follicles.

Keratinocytes

Make up 95% of the epidermis. These cells manufacture keratin, which is tough and protects the epidermis from mechanical damage and also makes the skin water-resistant.

Stratum basale

Lowest layer of epidermis, where most mitosis takes place.

Stratum spinosum

Thickest layer of epidermis

Stratum granulosum

Cells fill with keratin in this layer.

Stratum lucidum

Only found in thick skin

Stratum corneum

Top layer. It takes 40-50 days for cells to migrate to this layer.

Dendritic (Langerhans) cells

Phagocytes of the immune system that protect skin and deeper tissues.

Merkel cells

Oval cells in the stratum basale that detect light touch and discriminate shapes and textures

Melanocytes

Melanin producing cells.

Callus

Place where additional layers of stratum corneum have formed in either thick or thin skin in response to repetitive pressure.

Dermis

Deeper layer of the skin consisting of loose and dense irregular collagenous connective tissue. Consists of the papillary layer (superficial and consists of loose connective tissue) and the reticular layer (deep and consists of mostly dense, irregular connective tissue.)

Lamellated (Pacinian) corpuscles

Sensory receptors located in the reticular layer of the dermis that detect pressure and vibration stimuli. Resemble the layers in a sliced onion.

Epidermal ridges

Folded patterns of the epidermis in thick skin that enhance gripping ability and also produce fingerprints.

Melanin

Pigment that is produced in melanocytes and ranges in color from brown-black to orange-red and gives protection from UV radiation.

Carotene

Orange pigment found in carrots, sweet potatoes, etc.

Hemoglobin

Iron-containing red pigment that binds to oxygen and is found in red blood cells.

Cyanosis

Blue appearance that is the result of lack of oxygen.

Erythema

Redness that occurs when blood flow in the dermis increases such as when one exercises or has a fever.

Pallor

Color loss due to a decrease in blood flow to the dermis.

Hair

(also known as pili) small filamentous structures that protrude from the surface of the skin and cover the entire body except in the regions with thick skin, the lips, and parts of the external genitalia. The shaft is the portion that projects above the skin's surface. The root is embedded in the hair follicle, which is located in the dermis.

Mole

Area of increased pigmentation due to a local proliferation of melanocytes.

Arrector pili

A small band of smooth muscle cells that cause hair to stand on end when they contract.

Lanugo

Thin, non-pigmented hair is found covering the body of the fetus.

Terminal hair

Thick, coarse, and pigmented hair (like that found on the head.)

Vellus hair

Thin, non-pigmented hair. Terminal hair replaces much of the vellus hair at puberty. The amount replaced is greater in males than in females.

Nail plate

The portion of the nail that rests on the superficial epidermal nail bed.

Nail body

The visible portion of the nail plate covers the nail bed.

Eponychium

cuticle

Hyponichium

Anchors distal end of nail plate to underlying nail bed.

Lanula

Half-moon shaped region of proximal nail plate.

Wound

A disruption in the skin's integrity.

First degree burn

Least severe type of burn. Skin may be red and slightly painful with no permanent damage.

Second degree burn

Partial thickness burn. Blisters develop and may scar.

Third degree burn

Most severe type of burn. It is a full-thickness burn. Usually requires skin grafts.

Rule of nines

Divides the body into 11 sections which each represents 9% the body (plus 1% for the perineal area.) Give medical professionals a way to estimate the severity of the burns and determine appropriate treatment and fluid replacement.

Cancer

Mutations in the DNA that cause the cell to lose control of the cell cycle

Basal cell carcinoma

Type of skin cancer that is least likely to metastasize.

Squamous cell carcinoma

Cancer of the keratinocytes of the stratum spinosum. Scaly plaques that may ulcerate and bleed are found on the head and neck region of the body. More likely to metastasize than basal cell but surgical removal is still useful.

Malignant melanoma

Cancer of the melanocytes. Most likely type of skin cancer to metastasize.

ABCDE rule

Used to distinguish skin cancer from normal moles.

A- Asymmetry

B- Border

C- Color

D- Diameter

E- Evolving