integumentary system includes the somatic senses

Integumentary System Includes the Somatic Senses

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Skin and Its TissuesThe skin is a large organ responsible for

maintaining homeostasis through

temperature regulation

protection of underlying tissues

retardation of water loss

housing sensory receptors

synthesizing certain chemicals

and excreting wastes

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Regulation of Body Temperature

The skin plays a major role in temperature regulation with the hypothalamus controlling it.

Active cells, such as those of the heart and skeletal muscle, produce heat.

Heat may be lost to the surroundings from the skin through radiation.

The body responds to excessive heat by dilation of dermal blood vessels and sweating.

The body responds to excessive cooling by constricting dermal blood vessels, inactivating sweat glands, and shivering.

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The skin consists of an outer epidermis and a dermis, connected to underlying

tissue by the subcutaneous layer (hypodermis).

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EpidermisThe epidermis is made up of stratified squamous

epithelium and lacks blood vessels.

The layer of reproducing cells (the stratum basale), which lies at the base of the epidermis ,is well-nourished by dermal blood vessels.

Cells are pushed outward as new cells are formed, and become keratinized as they die.

Four or five layers may be seen: stratum basale, stratum spinosum, stratum granulosum, and stratum corneum are always present and the stratum lucidum is found in the thicker palms and soles.

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EpidermisThe epidermis is

important because it protects against water loss, mechanical injury, chemicals, and microorganisms.

Melanocytes, which lie deep in the epidermis and underlying dermis, produce a pigment called melanin that protects deeper cells from the sun’s ultraviolet rays.

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Skin Color

Skin color results from a combination of genetic, environmental, and physiological factors.

Genetic differences in skin color result from differing amounts of melanin and in the size of melanin granules.

Exposure to sunlight causes darkening of skin as melanin production increases.

Circulation within dermal blood vessels affects skin color.

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Dermis

The dermis binds the epidermis to underlying tissues.

Epidermal ridges and dermal papillae cause the border to be uneven.

The dermis consists of connective tissue with collagen and elastic fibers within a gel-like ground substance.

Dermal blood vessels carry nutrients to upper layers of skin and help to regulate temperature.

The dermis also contains nerve fibers, sensory fibers, hair follicles, sebaceous glands, and sweat glands.

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Subcutaneous Layer

The subcutaneous layer (hypodermis) is composed of loose connective tissue and insulating adipose tissue.

It binds the skin to underlying organs and contains the blood vessels that supply the skin.

No sharp boundary exists between the dermis and subcutaneous layer.

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Nails

Nails are protective coverings over the ends of fingers and toes.

Nails consist of stratified squamous epithelial cells overlying the nail bed, with the lunula as the most actively growing region of the nail root.

As new cells are produced, older ones are pushed outward and become keratinized.

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Hair can be found in nearly all regions of the skin.

Individual hairs develop from cells at the base of the hair follicle.

As new cells are formed, old cells are pushed outward and become keratinized, and die forming the hair shaft.

Hair Follicles

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A bundle of smooth muscle cells, called the arrector pili muscle, attaches to each hair follicle. These muscles cause goose bumps when cold or frightened.

Hair color is determined by genetics; melanin from melanocytes is responsible for most hair colors. Dark hair has eumelanin while blonde and red hair have pheomelanin.

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Hair

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Sebaceous glands (oil glands) are associated with hair follicles and secrete sebum that waterproofs and moisturizes the hair shafts.

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Sebaceous Glands

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Sudoriferous Glands

Sudoriferous glands (sweat glands): eccrine - respond to body

temperature apocrine - respond to body

temperature, stress, and sexual arousal

Modified sweat glands secrete wax in the ear canal.

Mammary glands, another modified type of sweat glands, secrete milk.

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Skin as a Sensory Receptor

Sensory receptors detect changes in the environment and stimulate neurons to send nerve impulses to the brain.

There are 5 types of sensory receptors and 3 of these are types are found in the skin.

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Types of Receptors

Five general types of receptors are recognized.

1. Receptors sensitive to changes in chemical concentration are called chemoreceptors.

2. Pain receptors detect tissue damage.

3. Thermoreceptors respond to temperature differences.

4. Mechanoreceptors respond to changes in pressure or movement.

5. Photoreceptors (rods and cones in the retina of the eyes) respond to light energy.

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Somatic Senses

Receptors associated with the skin, muscles, joints, and viscera make up the somatic senses.

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Touch and Pressure Senses

Three types of receptors detect touch and pressure.

1. Free ends of sensory nerve fibers in the epithelial tissues are associated with touch and pressure.

2. Meissner's corpuscles are flattened connective tissue sheaths surrounding two or more nerve fibers and are abundant in hairless areas that are very sensitive to touch, like the lips.

3. Pacinian corpuscles are large structures of connective tissue and cells that resemble an onion. They function to detect deep pressure.

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Temperature Senses

Temperature receptors include two groups of free nerve endings: heat receptors and cold receptors which both work best within a range of temperatures.

Both heat and cold receptors adapt quickly.

Temperatures near 45o C stimulate pain receptors; temperatures below 10o C also stimulate pain receptors and produce a freezing sensation.

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Sense of Pain Pain receptors consist of free nerve endings that are

stimulated when tissues are damaged, and adapt little, if at all.

Many stimuli affect pain receptors such as chemicals and oxygen deprivation.

Visceral pain receptors are the only receptors in the viscera (organs within a cavity like the abdominal cavity) that produce sensations.

Referred pain occurs because of the common nerve pathways leading from skin and internal organs.

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Referred Pain Chart

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Pain Nerve Fibers CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Fibers conducting pain impulses away from their source are either acute pain fibers or chronic pain fibers. Acute pain fibers are thin, myelinated fibers that

carry impulses rapidly and cease when the stimulus stops.

Chronic pain fibers are thin, unmyelinated fibers that conduct impulses slowly and continue sending impulses after the stimulus stops.

Pain impulses are processed in the gray matter of the dorsal horn of the spinal cord.

Pain impulses are conducted to the thalamus, hypothalamus, and cerebral cortex.

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Regulation of Pain Impulses

A person becomes aware of pain when impulses reach the thalamus, but the cerebral cortex judges the intensity and location of the pain.

Other areas of the brain regulate the flow of pain impulses from the spinal cord and can trigger the release of enkephalins and serotonin, which inhibit the release of pain impulses in the spinal cord.

Endorphins released in the brain provide natural pain control.

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Healing of Wounds and Burns

Inflammation, in which blood vessels dilate and become more permeable, causing tissues to become red and swollen, is the body's normal response to injury.

Superficial cuts are filled in by reproducing epithelial cells.

Deeper cuts are closed off by clots, covered by scabs, and eventually filled in by fibroblasts, making connective tissue.

Blood vessels extend into the area, injured tissues are replaced, and the scab falls off.

Large wounds leave scars and healing may be accompanied by the formation of granulations.

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Keloid Scars• result of an overly

aggressive healing process

• extend beyond the original injury

• may affect mobility

• Possible treatments include surgical removal, or injections with steroids

Contracture scars

• If your skin has been burned, you may have a contracture scar, which causes tightening of skin that can impair your ability to move; additionally, this type of scar may go deeper to affect muscles and nerves.

Hypertrophic scars

• Raised and red scars that are similar to keloids, but do not breach the boundaries of the injury site.

• Possible treatments can include injections of steroids to reduce inflammation.

Acne Scars

• If you've had severe acne, you probably have the scars to prove it.

FYI……

• Epithelial Tissue regenerate easily.

• Connective tissue including bone regenerate easily as well.

• Skeletal Muscle regenerates poorly, if at all.

• Cardiac Muscle and Nervous tissue are replaced only by scar tissue.

Imbalances of the Skin

• Infections and Allergies• Athlete’s Foot• Boils and Carbuncles• Cold Sores• Contact dermatistis• Impetigo• Psoriasis

• Burns• 1st degree• 2nd degree• 3rd degree

• Skin Cancer• Basal cell carinoma• Squamous cell carcinoma• Malignant melanoma• ABCD RULE

• Other Disorders• Erythema• Pallor• Jaundice• Decubitus ulcer• bruises

Infections and Allergies

• Athlete’s Foot: • itchy fungal infection of the toes

Infections and Allergies

• Boils and Carbuncles: • inflammation of

hair follicles and sebaceous glands

Infections and Allergies

• Cold Sores: • fever blisters;

small fluid filled blisters that itch an sting, caused by herpes simples infection

Infections and Allergies

• Contact dermatitis: • itching, redness, and

swelling of the skin, progressing to blistering• Caused by exposure of

the skin to chemicals like poison ivy that provoke allergic responses

Infections and Allergies

• Impetigo• Pink, water-filled

raised lesions that develop a yellow crust and eventually rupture• Causes by a highly

contagious staphylococcus infection

Infections and Allergies• Psoriasis• Chronic condition characterized

by reddened epidermal lesions covered with dry, silvery scales

Other Skin Disorders

• Jaundice• an abnormal yellow skin

tone usually indicates a liver disorder in which excess bile pigments are absorbed into the blood, circulated throughout the body, and deposited in body tissues.

Other Skin Disorders

• Decubitus ulcer• Restriction of blood

supply to the skin results in cell death, and if severe or prolonged, ulcers.

• Occur in bedridden patients who are not turned regularly

Other Skin Disorders

• Bruises• Reveal sites where blood has escaped from

the circulation and has clotted in the tissue spaces

• Hematoma: clotted blood mass• An unusual tendency to bruising may signify a

deficiency of vitamin C in the diet or hemophilia

Burns

• Tissue damage and cell death caused by intense heat, electricity, UV radiation (sunburn), or certain chemicals (acids)

• When the skin is burned, two life threatening problem result:• Dehydration• Infection

1st threat: Dehydration

• The body loses fluids containing proteins and electrolytes

• This can lead to a shutdown of the kidneys and circulatory shock

2nd threat: Infection

• Leading cause of death

• Burned skin is sterile for about 24 hours, but after that pathogens easily invade and multiply rapidly

Rule of Nines• Divides the body area into 11 areas, each

accounting for 9 percent of the total body surface, plus 1% surrounding the genitals

BURNS

Burns

• 1st degree• Only the epidermis

is damaged• Becomes red and

swollen• Not usually serious

and generally heal in two to three days without any special attention• sunburn

Burns• 2nd degree• Involve injury to the

epidermis and the upper region of the dermis

• Skin is red and painful and blisters appear

• Re-growth of the epithelium can occur

• No permanent scars result if care is taken to prevent infection

Burns• 3rd degree• Destroy the entire

thickness of the skin• Appears gray-white or

blackened • Nerve endings are

destroyed so the burn is not painful

• Regeneration is not possible

• Skin grafting must be done to cover the underlying exposed tissues

Burns

• Considered critical if any of the following conditions exists:• 1. Over 25 % of the body has 2nd degree burns• 2. Over 10% of the body has 3rd degree burns• 3. Any third-degree burn of the face, hands,

or feet

Skin Cancer

• Most skin tumors are benign and do not spread

• Some are malignant (cancerous) and tend to invade other parts of the body

• Skin cancer is the most common type of cancer in the body

Basal Cell Carcinoma

• Least malignant and most common

• Full cure rate in 99% of patients

Squamous Cell Carcinoma

• Believed to be sun-induced

• If it is caught early and removed surgically, good chance of complete cure

Malignant Melanoma• Cancer of the

melanocytes

• Accounts for 5% of skin cancers

• Often deadly

• Usually appears as a spreading brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels

ABCD Rule

• Asymmetry: the two sides of the pigmented spot of mole do not match

• Border Irregularity: The borders of the lesion are not smooth but exhibit indentations

• Color: the pigmented spot contains areas of different colors

• Diameter: the spot is larger than 6 mm in diameter (size of pencil eraser)