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Integumentary System

Learning Objectives

At the completion of this chapter, the student will be able to:

1.Identify the main components of the integumentary system and understand how they work.

2.Define the differences between the epidermis and the dermis as well as their functions.

3.Understand how the body adjusts to and maintains optimal body temperature.

4.Describe how the integumentary system influences the health of other body systems.

5.Explain common injuries to the skin and how their caused.

Case Study Introduction

Paramedics respond to a 911 call regarding a 70-year-old female who has been pulled by neighbors out of her burning house. The fire truck is already on scene extinguishing the house fire, which is believed to have been started by a cigarette. The woman is known to smoke while watching television and is believed to have fallen asleep. She was found lying on the living room sofa, which was nearly engulfed in flames when the neighbors entered the home, as were the curtains behind it.

When paramedics arrive, the woman is on the front lawn, covered by a sheet donated by one of the neighbors. Upon initial assessment by the paramedics, the woman has first, second, and third-degree burns over more than 40% of her body.

A visual inspection notes that some of the burns on her arms and shoulders are second-degree burns, as noted by their appearance; red and blistered, involving all layers of the epidermis and upper layers of the dermis. Burns on her torso are full-thickness and appear greyish-white in color with blackened edges. The edges of the skin have peeled back on itself from the edges of the burned area. The patient is unconscious and unresponsive.

Paramedics immediately secure her airway and provide oxygen and start a large bore (14 G) bolus IV in the right median cubital vein for fluid replacement in an effort to begin restoration of fluids. They take the unconscious woman’s vitals; her blood pressure is unstable at 60/40 and her heart rate is 172, respiratory rate 35, shallow and raspy. Her neighbors do not know her medical history nor whether she is taking any medications. She is placed onto a gurney and quickly transported to the hospital.

In the emergency room physicians immediately focus on her O2 levels and begin prophylactic endotracheal intubation because smoke inhalation is suspected. Peripheral pulses are checked to assess her circulatory status.

An additional large bore peripheral IV is inserted into the saphenous vein of her left calf as her left arm is too risky due to potential venous flow impairment. A urinary catheter to monitor urine output is also placed. A nasogastric tube is also inserted to facilitate suctioning to reduce the risk of gastric distention.

Nurses assess her for hypothermia, potential renal and/or liver failure, and decreased cardiac output. They prepare a lactated Ringer’s solution, which will be carefully monitored carefully for the next 24 to 72 hours in an attempt to regulate fluid volume in her body that has been lost post-trauma.

Damage to the integrity of the skin for this patient increases the risk for infection as well as increasing nutritional demand for healing processes. Protein may be lost through wound exudate. Fluid levels and electrolyte status will be continually evaluated. Additional metabolic aspects will also be evaluated, including increased protein metabolism and increased urinary excretion of nitrogen, a result of the body requiring greater amounts of protein for energy.

Physicians initially treat by replacing fluids and electrolytes to reduce the risk of hypovolemia and to maintain circulating blood volume. As soon as the patient is stabilized, she is transported to the burn unit. Nursing staff refers to Parkland’s formula for fluid resuscitation.

There, the patient will be assessed hourly and the burns irrigated with saline. The patient’s clothing is carefully removed and a neurologic examination proceeds. Covering the wounds may help to slightly reduce metabolic needs, reduce nitrogen losses, and reduce evaporation and help prevent infection.

Nursing staff will also carefully monitor the patient for loss of fluids and electrolytes. Her sodium levels are also closely followed to reduce hypovolemia, systemic edema, as well as kidney function. Potential kidney failure is a risk due to release of antidiuretic hormone and vasoconstriction. They will also monitor for hepatic perfusion, which may be compromised and can lead to possible liver ischemia.

Because of her age and the presence of partial and full-thickness burns, she is high-risk for infection, shock, drop in body temperature, and additional tissue loss.

 ■Introduction

Skin is considered the largest organ of the human body and comprises approximately 15% of a person’s total body weight. For an average-sized adult, skin can weigh anywhere from 7 to 11 pounds.1 In total surface area, skin can encompass roughly 20 ft.² of tissue.2

Thickness of the skin varies depending on its location on the body. It can measure anywhere from 1.5 mm to 4.0 mm, but regardless of thickness, its structure is the same.

Skin does more than just cover muscle and provide an aesthetic appearance; skin is the body’s first line of defense against temperature extremes in our environment; acts as a barrier against bacteria; and cushions the bones and other organs from blunt force injuries.

Figure 3-1 Integumentary system.

The skin is involved in the maintenance and health of numerous body systems and as such can take on a variety of appearances depending on our internal environment and status.

For this reason, regularly assessing skin condition provides healthcare personnel with a general indication of how a person responds to internal and external stressors.3

Dermatology is a field of medical study focusing on diagnoses and treatments for skin conditions and diseases. A physician who focuses and specializes in any number of skin conditions is called a dermatologist.

An overview of skin structures and characteristics will be explored in detail in this chapter, as will functions of the skin, hair, and nails. While on the outside, our skin looks different from individual to individual depending on age, gender, and heredity, the human integumentary system performs consistent functions for all. However, any number of medical conditions and aging processes can alter some of these functions, often to life-threatening degrees. Before delving deeper into common skin threats, it is important to understand the basic function of skin and skin structures.

 ■What is the Function of the Skin?

Skin is composed of literally millions upon millions of cells. These cells contain a number of biological components that protect our vital organs as well as our “exterior surface area”.

Skin and its “appendages” such as fingernails and hair, as well as glands of the integumentary system, may be beneficially influenced or negatively impacted by a number of processes going on inside the body. Some of these processes can include:

•Infection

•Illness

•Electrolyte and/or other fluid imbalances

•Inadequate diet

•Poor oxygenation

•Inefficient blood flow

In addition to being the body’s truly initial barrier of defense against attack by external dangers, the skin also provides a number of different functions. A few of the most critical are defined below.

Skin is vital in regulating body temperature through sweating (or not sweating). Body temperature is controlled by two main mechanisms. The first is radiation of heat from the skin’s surface, while the other is conduction of heat from the skin, which is then removed by the external environment (such as air) on the skin. This process involves convection and evaporation.

When the environment is extremely warm outside, the body typically loses heat through evaporation. Anything that resists this process can increase body temperature. Tiny blood vessels in the skin also help maintain and control body temperature. How? These blood vessels constrict in colder environments, triggering heat conservation. In a warm environment, the blood vessels dilate to encourage heat loss through radiation.

In addition to regulating body temperature, the skin serves as a major sensory organ. Skin contains microscopic nerve receptors sensitive to temperature, touch, and pain. A simple touch of our skin to an object can give us an immediate clue as to the environment, such as dipping your toes into a cold body of water or accidentally touching your hand to a hot stove. The number of receptors found in the skin differ depending on body part. For example, the fingertips and the hands contain many more nerve sensors than your forearm.

The skin also serves excretion. Water balances in the body are maintained with the help of the skin through this excretory process. For example, when you sweat after a workout or intense physical activity, water and salt is lost through sweat – this is excretion. Our bodies are capable of adapting to many different environments; the frigid temperatures of Alaska for example, or the oppressive heat of the open deserts of Arizona. In hot environments, excretion of water and salt decreases as the body becomes acclimated to the external environment. The same applies to colder environments. Over time, the body adapts (to a certain degree) to the colder temperatures.

Skin is also involved in vitamin D synthesis. This occurs through exposure to ultraviolet rays or sunlight. Vitamin D is an essential nutrient required for metabolism of other compounds in the body that include but are not limited to phosphorus and calcium.

Skin and skin appendages such as our fingernails and hair not only provide us with a sense of individuality in regard to our appearance, but also serve specific functions. Body hair also protects the skin from a number of environmental dangers.

Our hair often provides a visible indication of health and wellness. For example, hypertrichosis (excessive growth of hair) can be an indication of changing hormone levels in the body. Another type of excessive hair growth in women called hirsutism may be caused by adrenal dysfunction, tumors of the ovaries or exogenous introduction of androgens into the body, such as the case of anabolic-androgenic steroid use. Of course, sometimes it’s also related to genetics.

Alopecia (hair loss) is not that unusual in aging men, but abnormal and unexpected hair loss may be the cause of ill health, stress, substance abuse, thyroid issues, or hormonal imbalances.

Development of skin lesions, the surface appearance of fingernails, and changes in skin color or texture are also indications of possible illness or nutritional deficiencies. Some of the most common skin problems and threats to skin health and wellness will be discussed later in this chapter.

The skin also serves as a source of lubrication and cushioning for the body. Skin moves; it’s pliable and can stretch, such as during a woman’s progression through pregnancy, and then revert to its normal shape. It accommodates growth of muscle and grows with us as we age from infancy to old age.

 ■Skin Structure

The skin is composed of two layers: the epidermis and the dermis. The epidermis defines the outer layer of skin.

The dermis is considered the second layer, inside which belongs a unique network or framework of connective tissues. These two layers (epidermis and dermis) are generally referred to as “our skin”.

However, a third layer, known as subcutaneous tissue (also called the hypodermis) is not always considered part of the skin per se, depending on source. The third layer of skin contains fat deposits that are modified within the connective tissues. Some texts refer to the hypodermis/subcutaneous layer as superficial facia. This is due to its location being “superficial” to connective tissues that wrap skeletal muscle (facia) but consists of adipose tissue.4 These fat deposits are known as adipose tissue.

Four types of cells of the epidermis

The outermost layer of the skin – the epidermis – is constructed of keratinocytes that are able to regenerate continuously. Keratinocytes are also known as squamous cells. The keratinocytes produce keratin. Keratin is defined as a fiber-like protein that protects the uppermost surface of the skin. Keratin cells shed on a regular basis, typically every month, but are consistently replaced by brand new keratinocytes.

Another structure found in the outer layer of the skin are melanocytes. Melanocytes are responsible for the formation of pigment granules (melanosomes), which give our skin, eyes, and hair color. Melanocytes are also vital in protecting the skin from ultraviolet (UV) light.

Another component of the epidermis is the presence of Langerhans cells, also known as dendritic cells. They’re named after German pathologist and biologist Paul Langerhans (1847–1888).5 Langerhans is also recognized for the discovery of the Islets of Langerhans (pancreas). While more typically associated with bone marrow, Langerhans cells in the skin aid immune system function, most specifically in regard to antigens. These cells assimilate antigens in the peripheral tissues of the body, where they are then transported to the nearest lymph nodes to fight presence of bacteria. They’re also involved in antimicrobial immunity.6

Merkel cells are found in the deepest layer of the epidermis and typically behave as sensory receptors. Merkel cells were first identified by Friedrich Sigmund Merkel in 1875.7 Merkel cells, also known as Merkel-Ranvier cells and tactile cells, are ovoid in shape and located in the basal layer of the epidermis. They are most commonly known as “touch cells” and are found in close proximity to nerve tissues. These cells are thought to be unique and sensitive receptor cells that respond to pressure. The greatest number of Merkel cells are found in the mouth and mucosal areas of the body that are involved in tactile perception. Merkel cells can be found more often in skin that is exposed to sunlight than covered skin.8

Five layers of the epidermis

The epidermis itself is comprised of five layers, each independent on the stage of reproductive activity of the specific keratinocyte. From the outer to the inner:

•Stratum corneum (horny layer)

•Stratum lucidum (clear layer)

•Stratum granulosum (granular layer)

•Stratum spinosum (prickly layer)

•Stratum basale (basal layer)

Figure 3-2 Epidermal layers.

Stratum corneum – the outermost layer. This layer of skin is formed by flat skin cells that contain keratin, a fiber-like protein material as mentioned earlier. This layer of the epidermis encompasses most of its thickness, approximately 20 to 30 cell layers thick.9 This outermost layer of skin is actually constructed of dead skin cells that have made their way to the surface from inner layers of skin. For this reason, the cells, which overlay each other much like roofing shingles, have a horny appearance, hence their name or nickname as horny cells. Dead skin cells are constantly replaced by new cells that push the old, dead skin cells outward or upward from deeper layers found in the epidermis. We mostly refer to these dead skin cells as dry skin, dander, or dandruff.

The skin can shed as many as 50,000 dead cells every minute. The average person will shed approximately 40 pounds of dead skin flakes in their lifetime.10

The stratum corneum also contains granules of pigment known as melanin. Melanin aids in the protection of the body from over-exposure to ultraviolet light. The amount of melanin found in the epidermis differs between races as well as geographical regions.

Stratum lucidum – This layer of skin is known as the clear layer, which under microscopic evaluation appears as a translucent layer or band of skin that serves as a boundary of sorts between the stratum corneum and the next layer of skin, the stratum granulosum. It’s much narrower than that of stratum corneum, maybe three cells thick.

Stratum granulosum – Known as the granular layer, stratum granulosum is also relatively thin and averages one to five layers in cell thickness. Within this skin layer, keratinocytes are constantly morphing due to a process known as keratinization. During this process, the cells change shape; they flatten while their organelles and nuclei disintegrate. During this process, they collect two types of granules. One type is the keratohyalin granule and the other is the lamellar granule. The keratohyalin granules are involved in the production of keratin. The lamellar granules contain glycolipid – a water-resistant lipid that aids in water retention of the epidermis. The function of the stratum granulosum layer is to inhibit loss of water from the epidermis, and ergo serves as an effective water barrier.

Stratum spinosum – This layer of the skin is known as the prickly layer, again several cell layers thick. Its primary function is to aid in flexibility and add a layer of strength and protection to areas of the skin that may experience greater friction or abrasion, such as the palms or the soles of the feet. The cells of the stratum spinosum actually interconnect into a network much like a spider’s web. They appear under a microscope as round balls with spikes extending from them. In this layer of skin, keratinocytes appear to have prickly ridges or spines, hence their name.

Stratum basale – The basal cell layer can be thought of as the “basement” membrane or layer of the epidermis. It’s also known as the stratum germinativum. This layer is about one cell thick and is mainly responsible for replenishing or replicating through mitosis. For this reason, this layer of skin is often nicknamed the germinating layer. Following cellular division in this layer, one basal cell from each cell division remains behind while the other migrates outward. That migrating cell passes through what are known as intermediate layers of the epidermis. As the migrating cell passes through each of those intermediate layers, it flattens still further and differentiates. It takes an average of 28 days for a mature keratinocyte to reach the stratum corneum or the outer layer of the epidermis.11

In a healthy, natural, and uninjured state, the epidermis protects the body against invasion by germs. It also provides padding and protects the body against potentially dangerous heat or water loss.

The dermis is the second layer of skin, found directly beneath the epidermis.

The dermis, also known as the cutis, measures anywhere from 1 mm to 4 mm in thickness and serves as a foundational support to the skin, as well as to its mass. The dermis itself comprised of numerous components of connective tissues that include:

•Elastin

•Collagen

•Reticulum fibers

•Water

•Sensory nerves

•Postganglionic nerves

•Blood vessels

•Lymphatics

The dermis is also known as the corium. Two distinct layers of the dermis include the papillary layer and a reticular layer.

The papillary layer contains blood vessels and connective tissues that provide nutrients to the outer skin layer (epidermis). The papillary layer also helps to maintain temperature of the skin.12

The reticular dermis is a thicker, bottom layer of the dermis, which also contains blood vessels and connective tissues in support of the skin, but in addition also contains sweat glands, oil, and hair follicles.13

This layer of skin contains a network of fibrous, elastic-like connective tissues as well as other components including:

•Sebaceous glands

•Sweat glands

•Nerves

•Lymphatics

•Blood vessels

•Involuntary muscle fibers

Not all layers of dermis are the same thickness. Compare the difference between the skin of the eyelid and the skin on the palm of your hand or the sole of your foot.

The third layer of skin, the subcutaneous layer, typically consists of lipocytes (aka adipocytes) or fat cells. These fat cells are separated by fiber-like walls of the blood vessels and collagen. Adipose or fat tissue serves as the body’s insulator against heat. Subcutaneous tissues also serve as a/an:

•cushioning barrier between bones and the outside environment

•storage site (for calories)

•an aid for anchoring of bone, muscle, and tendons

Figure 3-3 Skin glands.

Thickness or density of subcutaneous (adipose) tissues varies depending on location in the body. This is why humans tend to have more “cushioning” around the waist or the hips and very little in the eyelids for example. A number of factors can influence subcutaneous tissue distribution such as genetics, age, diet, and hormones.

 ■Your Sweat Glands

Three types of glands are also found in the dermis:

•Apocrine sweat glands

•Eccrine sweat glands

•Sebaceous glands

Sweat glands are known as sudoriferous glands.

We have two different types of sweat glands: apocrine and eccrine.

The body contains an estimated 2 million sweat glands.14 Two major types of sweat glands are identified here: apocrine and eccrine.

Figure 3-4 Apocrine sweat gland.

Apocrine glands are those found in mammary, anal, and pubic areas of the body and typically provide access to hair follicles. Apocrine glands are found around the:

•Umbilical area

•Axilla

•Genitals

•Breasts

•Eyelids

•External ear canal

Interestingly, apocrine glands are quite mysterious, with no specific biological function although they can be triggered by epinephrine and norepinephrine to secrete. On the surface of the skin, these secretions make contact with bacteria found on the skin or in hair follicles, producing body odor.

Two additional glands are associated with apocrine sweat glands: ceruminous glands and mammary glands, although mammary glands secrete milk rather than sweat. We’ll discuss functions of the mammary glands in greater detail in a later chapter. For now, we consider the mammary glands as part of the integumentary system.

Ceruminous glands line the outside of the external ear canal. Secretions of the ceruminous glands combine with sebum from nearby glands and form cerumen, more commonly known as earwax. Earwax is a major deterrent when it comes to protecting the ear canals from dirt, foreign materials, and even insects.

Eccrine glands are found on the trunk, the extremities, the head, and on the hands as well as the soles of the feet.

These glands are involved in heat regulating functions and mechanisms, activated and controlled by the sympathetic nervous system.

Such functions will be discussed later in this chapter. A number of emotional (mental), gustatory, and thermal stimulus promotes secretions of eccrine glands. Eccrine glands are found throughout the skin’s surface area and their main function is to help the body sweat or dissipate heat.

Eccrine glands look like a coiled bundle of string that originate in the secretory portion of the sweat gland. One end rises toward the surface of the skin in a relatively straight line, then forms a number of spirals that make their way upward through the corium (dermis). This ‘tube’ extends from the sweat gland up to the surface of the skin, where the ‘outlet’ is found in a skin pore.

It is estimated that sweat glands, under certain conditions, produce and secrete up to two quarts of sweat daily.15

The sebaceous glands secrete sebum or oily secretions. Sebaceous glands are found just about everywhere on the body except for the hands and feet.

Most of us are more familiar with these glands because of their association with hair follicles and development of acne. These glands are quite densely found on the scalp, the chest, the face, and the back. They’re influenced by androgenic hormones and produce sebum, a substance that serves as a lubricant and is also partly responsible for the manufacture and perpetuation of vitamin D in the skin. In fact, acne is defined as a sebaceous gland disorder or malfunction.16

Figure 3-5 Eccrine gland.

 ■Hair and Fingernails

Hair and fingernails are considered accessory structures of the integumentary system. In medical scenarios, pattern of hair growth, hair growth itself, and distribution of hair on the scalp or body are often perceived as general indicators of health and wellness.

Earlier in the chapter, two conditions affecting the hair were mentioned: hypertrichosis and alopecia.

Another example involves lack of hair growth on the toes. While many people shave the hair from their toes for aesthetic reasons, ‘natural’ hair loss on the toes can indicate a lack of adequate circulation. Hair thickness, volume, and growth changes over time, affected by nutrition, hormones, and general aging patterns.

Figure 3-6 Hair follicles.

In mammals, hair is intended to help keep animals warm. In human beings, hair is more functional as a protectant rather than for warmth. For example, our eyelashes protect our eyes. Nose hairs (which many people pluck) are designed to filter air and restrict particles or insects from entering nasal passages. The hair on our head protects our scalp from direct sunlight and reduces loss of heat.

Structure of hair

Hair in medical terminology is known as pili. Hair is manufactured in hair follicles, producing individual and flexible strands that contain mainly keratinized or dead skin. However, there is a difference between keratin cells: one is the soft keratin of the epidermal cells of the skin, while the other is termed hard keratin that is mainly found in the fingernails and hair. Hard keratin is extremely durable and – as its name implies – hard, and resistant to flaking.

The most prominent part of hair is the hair shaft. At the base of the hair shaft is the root; this is where the shaft of hair embeds in the skin of the scalp. The shape of the hair shaft defines the general appearance of hair; a flat shaft produces curly or kinky hair. An oval shaft produces wavy and soft hair. A round shaft typically produces coarser hair.

Hair contains three layers of keratinized cells. These layers are concentric and include the:

•Medulla – this layer is known as the inner layer and is typically the only portion of hair that contains soft keratin. A microscopic view of the medulla displays large air spaces and cells.

•Cortex – the middle layer surrounds the medulla and is composed of layers of flattened cells.

•Cuticle – the cuticle is the outermost layer of a hair shaft, and like that of dermis, is composed of a single-cell layers that overlap one another. The overlapping of cells separates one hair from another, and resists clumping. The cuticle also contains high levels of keratin and is responsible for mainly providing structure for the inner layers. The cuticle takes a good deal of abuse from the environment and vigorous hair brushing, and is the portion of hair that has a greater tendency to damage. This damage is commonly known as a ‘split end’.

Figure 3-7 Anatomy of hair.

A number of melanocytes are found at the base of the hair follicle. Different amounts of melanin (which around found in numerous colors such as yellowish, rusty, brown, or black) combine together to produce a certain hair color. These melanocytes are absorbed into the cortical cells and are what define hair pigmentation or color. As production of melanin decreases due to aging and diminished hormone production, air bubbles inside the hair shaft replace the melanin, turning hair gray.

Hair follicle structure

The structure of the hair follicle is precise and does not change between gender or ethnicity. As mentioned, the main structure of hair is the hair follicle. At the base of the hair follicle, just below the surface of the skin, is the hair bulb.

Around each hair bulb is a bundle of sensory nerve endings. Depending on source, these nerve endings are called the root hair plexus or the hair follicle receptor. When you pluck out a shaft of hair, you may notice a tiny spot of dermal tissue. This is known as the hair bulb or root ball, which contains capillaries that supply nutrients to the hair.

The actual wall of a follicle of hair is composed of two sheaths; the outermost sheath is known as the peripheral connective tissue sheath or fibrous sheath. The inner sheath is known as the epithelial root sheath. The peripheral or connective tissue fibers sheath is manufactured from the dermis while the epithelial root sheath is manufactured from the epidermis.

Figure 3-8 Hair bulb.

Immediately above the hair “bulb” are cells that compose the matrix that actually manufactures the hair, called the hair bulge. This bulge is situated just above the hair bulb. Chemical signals trigger cells to migrate upward toward the papilla, where they produce hair cells. This is how hair grows; as the matrix manufactures new hair cells, the older parts of the hair shaft are pushed in an upward direction. Eventually, these cells are keratinized.

Another interesting aspect of hair follicles is the origination of that sensation a person gets when hair follicles are stimulated (goosebumps). How do goosebumps appear? Each hair follicle is linked to arrector pili, a small muscle constructed of smooth muscle cells literally translated “raiser of hair”.

Figure 3-9 Fingernail construction.

As hair protrudes past the scalp, it does so at a small angle. Arrector pili muscles attach to hair follicles in such a way that when they contract, the hair stands straighter and causes raised areas to appear on the surface of the skin. This reaction is typically caused either by cool temperatures or the adrenaline-triggered fear response.

 ■Fingernails and Toenails

What’s the purpose of fingernails and toenails – other than aesthetics, of course? Actually, they’re quite effective tools, both in humans and animals. While animals have claws, humans have fingernails and toenails.

Fingernails and toenails are composed of and contain hard keratin. The main components of fingernails and toenails are mentioned here:

•Edge – also called the “free edge” - the part of the finger or toenail that produces the familiar white bridge along the tip of the fingernail or toenail.

•Nail plate – also known as the “body” of the nail, is the overall surface area of the nail.

•Proximal root or proximal nail fold-this is the portion of the nail located at the juncture of the skin of the finger or toe where it disappears under the skin. This area is often called the nail bed.

The root of the nail evolves into the nail matrix. The matrix is the portion of the fingernail or toenail that is responsible for its growth.

In some conditions, the appearance of the fingernails and toenails can indicate an illness or nutritional deficiency. For example, thick, ridged, and yellowish-looking nails can be an indication of a fungal infection (onychomycosis).

A concave nail might indicate iron deficiency, while horizontal ridges across the nail surface may be a sign of malnutrition. Students should note however, that vertical (longitudinal) lines (onychorrhexis) on the nail body are relatively normal and are often caused by general aging processes.

 ■Regulation of Body Temperature

Regulating body temperature is one of the main functions of our skin. Skin helps our body maintain a regular or homeostatic temperature, neither too hot nor too cold. Homeostasis provides the optimal environment for body functions, and the integumentary system is a vital component in how the body functions in this way.

Our temperature is considered normal at roughly 98.6°F. Some people can run a bit higher or lower than that, which is perfectly normal. However, in cases where body temperature increases, the nervous system kicks into action, stimulating blood vessels in the dermis to dilate. This triggers secretion of the sweat glands.

Figure 3-10 Toenail with fungus.

On hot days, this sweat is visible. Depending on environment, a body may sweat up to 3 gallons of body water daily.17 As water evaporates from the skin’s surface, body heat is dissipated, promoting cooling. Insensible water loss (water lost through respiration, skin, and water in feces) also plays a role in water balances in the body.

When the outside air temperature is cooler than that of our bodies, the blood vessels in the dermis constrict, reducing sweating. This constriction activity restricts flow of warm blood to the surface of the skin and away from the skin’s surface, allowing skin temperature to drop. This activity reduces passive heat loss and is effective in helping the body conserve heat.

Figure 3-11 Sweat depends on environment.

The hypothalamus, located in the brain, is considered the body’s thermostat. A constant and optimal body temperature may remain consistent as long as heat loss and heat production are balanced. Every tissue in the body does produce heat. At rest, most of the body’s heat is produced metabolically by the brain, the endocrine organs, the kidneys, the brain, and the liver.

When it’s cold and we shiver, that active shivering helps to warm the body. Shivering is actually defined as involuntary contractions or shuddering-like contractions of muscle that are triggered by the hypothalamus. This involuntary contraction activity increases muscle tone. As this occurs, stretch receptors in the skin respond, as do antagonistic muscles. This response raises body temperature because the activity of the muscle produces heat.

Likewise, when our environment is colder than that of our body, our metabolism increases.

For example, if you go outside and walk in a wintry environment where the temperature is at freezing or below, your body automatically kicks into action to stay warm.

Cold weather effectively stimulates the adrenal medulla. This inner part of the adrenal gland manufactures adrenaline (epinephrine) and norepinephrine. This activity occurs in response to stimuli of the sympathetic nervous system. So too does the endocrine system; for example, thyroid levels increase in cold weather.

During exercise or intense physical labor, our skeletal muscles produce more heat than other portions of the body. This is why engaging in activity when it’s cold can actually help warm your body and increase body temperature.

Body temperature also affects enzyme activities in the body. Normal body temperature (96° to 101°F) is considered optimal for such activities. As the body heats up, enzyme catalysis also increases. However, if body temperature gets too high or elevates above optimal homeostatic levels (hovering around 106°F), proteins denature and neurons are depressed. This can lead to a life-threatening situation.

Lower body temperatures are effective in reducing not only metabolism, but nutrient and oxygen requirements to the heart and other vital body organs, as well as body tissues. It’s for this reason that some people who succumb to sustained immersion in an icy lake don’t experience any physical damage after their body is warmed. Of course, the length of time in cold water and other factors also influence negative outcomes.

Different areas of the body maintain different “resting” temperatures. Our core (skull, thoracic, and abdominal regions) typically has a higher temperature than the skin, which has the lowest.18

When the skin is warmer than the outside or external environment, the body loses heat as blood floods into the capillaries found in the skin.

However, in colder environments, when heat is preserved, blood bypasses the capillaries in the skin. In this way, our skin helps our body’s core temperature to remain constant, even while withstanding drastic variations in external temperature.

 ■Common Skin Conditions

Our skin is incredibly durable and tough, but a number of threats can interfere with this protective layer for the body. Depending on the integrity of the skin, the body is susceptible to hundreds of skin conditions and infections caused by yeast, bacteria, and viruses. Skin lesions and conditions like dermatitis not only cause damage to the skin, but in some situations, have a negative influence and impact on our psychological state of well-being, our appearance, and our level of confidence.

Common skin problems afflict many of us. Some skin problems are caused by bacterial, fungal, or viral infection. Others are caused by autoimmune disorders or hereditary ‘glitches’ in our development.

At regular doctor office visits, whether you notice or not, the doctor is likely assessing your skin for signs of skin issues. Certain demographics are more likely to undergo a more thorough skin assessment, especially the elderly, where their skin is evaluated for color, temperature, moisture, elasticity (turgor and mobility) as well as texture and thickness.

Figure 3-12 Sensory stimulus on the skin.

Skin lesions

Skin lesions are fairly common but can look different in regard to shape, color, and texture. The most common skin lesions include:

•Macule – Typically called freckles, a macule can also be a flat mole, or non-palpable such as rubella.

•Plaque – Common with psoriasis, a plaque lesion defines a lesion that is slightly elevated though flat-topped, rough, and has a firm surface.

•Nodule – Most often palpable, elevated, and firm, typically one to two cm in diameter.

•Scale – This type of skin lesion is defined as keratinized cells of regular shape (thick or thin) and often silvery-white in color. These lesions often present with flaky exfoliation such as with psoriasis or exfoliative dermatitis.

•Papule – An elevated lesion that is firm yet palpable, and typically measures less than 1 cm in diameter, such as a wart.

•Wheal – This type of lesion is often irregular shaped, elevated, and can be solid or transient with variable diameters. It’s typical with insect bites or urticaria.

•Crust – A lesion that is slightly elevated, composed of dried blood, serum, or other type of exudate, commonly seen in scab formation or conditions such as eczema.

Figure 3-13 Bacteria attach to skin.

Skin lesions can also be defined in a manner that is dependent upon their appearance. For example:

•Discreet – this type of lesion is distinct in size, shape, and spacing.

•Confluence – a group of lesions merged together. Example, urticaria.

•Linear – appear as a stripe, streak, or distinct line.

•Grouped – the lesions form into clusters that are grouped in a specific area. Example: contact dermatitis.

•Gyrate – this type of lesion looks like a snake or a worm.

•Polycyclic – this type of lesion has distinct rounded edges that are closely grouped to one another.

Figure 3-14 Dermatitis and normal skin.

Some skin problems are inherited, while others are due to inadequate diet or nutritional deficiencies. Others are caused by environmental conditions. Some are caused by disorders of the immune system.

 ■Common Causes of Skin Problems

A number of factors can contribute to common skin problems. Various forms of fungal bacterial and viral infections are common triggers. These can typically be described based on their pathophysiology. For example, see the lists of common skin infections and their classifications listed below:

Viral

•Herpes simplex

•Herpes zoster

•Warts

Acne

•Acne vulgaris

•Acne rosacea

Eczematous

•Contact dermatitis

•Atopic dermatitis

•Lichens simplex chronicus

•Seborrheic dermatitis

Fungal infections

•Candidiasis

•Tinea (tinea corporis/tinea cruris)

Bacterial infection

•Folliculitis

•Impetigo

•Boils (furuncles)

•Carbuncle

Figure 3-15 Sunbathing and skin damage.

More serious threats, but less common, are traumatic injury or disease to the skin, including cancers and burns.

Common skin threats

According to the American Academy of Dermatology, skin cancer is rated as a leading cause of cancer in the US, with estimations that one in five Americans has a likelihood of developing some type of skin cancer during their lifetime.19

Incident rates of skin cancer, types of skin cancer, survival rates, mortality rates, and risk factors have increased globally, with nearly 10,000 Americans diagnosed with skin cancer daily.20

One of the most prevalent contributory causes of skin cancer is overexposure to sunlight or UV radiation.

Most cancers are caused by mutations of DNA in skin cells. Three major types of skin cancer are most prevalently diagnosed:

•Basal cell carcinoma

•Squamous cell carcinoma

•Melanoma

The major cause of overexposure? Tanning.

Basal cell carcinoma is the most common form of skin cancer and the least malignant. Basal cell carcinoma typically appears on areas of the skin constantly exposed to sunlight, such as the face. It’s a slow-growing carcinoma, and in many cases, metastasizes before it’s even been noticed by the individual. The good news is that through surgical excision, a person has a 99% chance of cure.21

The second most common type of skin cancer is called squamous cell carcinoma. This type of cancer grows rapidly and will metastasize if not removed in a timely manner. In general, when caught early and removed through surgical excision or radiation therapy, prognosis is good.

Melanoma, otherwise known as cancer of the melanocytes, is the most dangerous and the most resistant to chemo-therapy. Melanoma is extremely metastatic. While not as common as basal cell or squamous cell carcinoma, it can prove deadly.

Figure 3-16 Tanning and skin cancer risk.

Most of us are (or should be) familiar with the ABCDs for recognizing a melanoma growth, which often starts out looking like a freckle or a mole. As a refresher:

•Asymmetry – one of the most recognizable signs of a melanoma is asymmetry, or a spot whose sides don’t match. For example, one side of the melanoma might be larger than the other.

•Border irregularities – a melanoma, unlike most freckles, is not round or rather consistent in shape. Its borders can look jagged or irregular.

•Color – a melanoma is a spot of pigmentation that can contain a variety of colors; dark brown, black, tan, and even a bluish or reddish tinge. Changes in color or tone are often noticeable.

•Diameter – most freckles and moles are not large, but the diameter of a melanoma is often measured by equating its diameter in millimeters to that of a pencil eraser. If the spot is larger than 6 mm, or larger than the average pencil, it may be a melanoma. Get it checked.

Another thing to watch for is changes in the size or shape of the spot. If it changes shape, grows, or seems to be evolving, this may also be a prime indication of melanoma.

The American Cancer Society recommends that we all take the time to regularly check our skin for any new appearance of moles, freckles, or spots, summer and winter.

Burns

Burns are another common skin threat that can leave the body vulnerable to multiple types of infection as well as limited mobility. Damage caused by burns is typically measured as:

•First – degree: Defining damage only to the epidermis. This is typical with sunburns that cause redness, tenderness, and some swelling. In most cases, a first-degree burn will heal within a few days.

•Second – degree: This type of burn damages not only the epidermis, but the upper layer of the dermis. Signs and symptoms are similar to that of first-degree burns (redness, pain, swelling), but also with the appearance of fluid-filled blisters. In most cases, the body heals from second-degree burns with little scarring within four weeks, as long as the individual takes care to protect the area from infection.

•Third – degree: The most severe degree of burn, a third-degree burn is also known as a full-thickness burn. It impacts all thicknesses of the skin. It can take a long while for such severe burns to heal, during which time the individual is vulnerable to infection as well as fluid loss. In such cases, skin grafting is a common option.

Figure 3-17 Burns measured in degrees.

Another common cause of declining skin condition is caused by general aging processes.

Aging skin

Another common skin threat is general aging.

As we age, replacement of epidermal cells slows down. Hormone levels decrease. The skin grows thinner and is more susceptible to injury, damage, or bruising.

Endogenous lubrication of the skin due to declining hormone levels or even nutrition often declines and the skin becomes less elastic. Levels of collagen fibers decline and the skin grows stiffer and sags. Even fibers of elastin tend to clump together. For many, a diminishing subcutaneous fat layer not only changes the volume of the skin, but can leave an older individual vulnerable to drastic changes in temperature.

Lack of elasticity and subcutaneous (adipose) tissue contributes to the appearance of wrinkles. Hair begins to thin because hair follicles don’t replenish as frequently as they did during our younger years, contributing not only to male pattern baldness, but graying hair.

The good news is that through proper nutrition, skin protection, and resisting over exposure to UVA and UVB sunrays promotes fewer wrinkles and those dreaded “liver spots” often associated with old age.

 ■Conclusion

Hundreds, if not thousands of skin conditions have been identified, some mild and easily treatable, others more serious and sometimes life-threatening. Nutrition, adequate sunlight, and environment plays a role in the health and wellness of the integumentary system. Patient education plays a vital role for all age groups when it comes to skin health and wellness, maintaining the integrity of the skin, and avoiding issues.

Figure 3-18 Aging skin process.

The integumentary system not only provides cushioning and acts as a first barrier of defense for the body, but plays an important role in the health and wellness of internal body organs and systemic activities. By understanding the structures of skin and their associated functions, healthcare professionals are more readily able to able to identify changes in the skin associated with a number of illnesses, disease processes, as well as physiological aging processes.

Case Study Conclusion

The elderly burn patient is carefully monitored during her first 24 hours in the burn unit, where the primary focus is to replace fluid and maintain blood volume and reduce edema. For the next 24 to 72 hours, nurses and ancillary support staff in the burn unit regularly assess her urine, electrolytes, and serum levels until blood volume has been stabilized. Nursing staff also monitors for indications of pulmonary edema or water intoxication.

At this stage of treatment, focus has been on maintaining adequate ventilation, reducing risk of infection, providing pain relief, and monitoring body temperature.

Within 48 hours, adequate fluid resuscitation has been achieved, as well as stabilization of PO2 and PCO2 levels. The patient has adequate urine output, electrolytes are within normal limits, and pH stabilized.

Tissue edema and fluid weight gain is minimal and the patient exhibits no signs of pulmonary edema.

Only after the patient has been fully stabilized will actual wound care begin. The patient’s burns are treated but the elderly woman’s journey toward recovery will be extensive. Collaborative care management is achieved via a multi-disciplinary team of surgeons, nurses, physical and occupational therapists, and psychologists, as well as other support personnel.

Within the next three days to three weeks, the patient will undergo skin grafting procedures to accelerate healing processes, to reduce potential for contracture, and shorten overall convalescent time.

 ■Questions

1.Identify the five layers of the epidermis.

A.Stratum corneum, Stratum lucidem, melanocytes, Langerhans cells, and the hypodermis.

B.Stratum corneum, Stratum granulosum, Stratum spinosum, Stratum basale, Stratum lucidem.

C.Corneul, gramulosa, Stratum lucido, keratinocytes, and Stratum reticula.

D.Stratum corneum, Stratum lucidem, Stratum granulosum, Stratum reticular, and Stratum lamellar.

Answer: B. In order from outermost to innermost; Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, and Stratum basale.

Learning Objective: 1

2.Describe how the skin reacts to colder temperatures and how that function warms the body.

A.When external temperature drops, blood vessels in the dermis contract. This keeps blood away from the skin’s surface and reduces passive heat loss and conserves body heat.

B.When temperature drops, the parasympathetic nervous system triggers the body’s muscles to constrict, increasing blood flow to warm the surface of the skin.

C.When external temperature drops, enzyme levels also drop and the hypothalamus triggers the body to release epinephrine, which constricts blood vessels, increasing blood flow that warms the skin.

D.As temperatures drop, the body causes the hair on the scalp and arms to stand up, triggering nerves in the skin to constrict, creating a more solid barrier against the cold.

Answer: A. Constriction of blood vessels in the second skin layer reduces amount of blood that reaches the epidermis, serving to conserve body heat.

Learning Objective: 3

3.How does the dermis differ from the epidermis?

A.The dermis is composed of five layers that offer different functions in addition to protection against bacteria.

B.The epidermis consists of a reticular and papillary layer, while the dermis contains five distinct layers responsible for immunity.

C.The dermis is considered the second layer of skin beneath the epidermis and is where the keratinocytes and the melanocytes are manufactured.

D.The epidermis is defined as the uppermost layer of the skin and is composed of five layers, while the dermis is defined as the second layer of skin and is composed of two distinct layers.

Answer: D. The epidermis is composed of five layers; the Stratum corneum, the Stratum lucidum, the Stratum granulosum, the Stratum spinosum, and the Stratum basale. The dermis consists of two distinct layers; the reticular and the papillary layers.

Learning Objective: 2

4.In which basic ways does the integumentary system influence other body systems?

A.The skin aids in balance of electrolytes, provides barriers against infection, helps regulate body temperature, and conserves or evaporates body fluids.

B.Skin is involved in filtration of vitamins A and D, homeostasis, and serves as the foundation for hair growth, which helps the body stay warm and protects it from UV rays.

C.The basic role of the skin is to produce heat in order to maintain body temperature at 98.6°F. This function is regulated by the pituitary gland and ensures that regardless of environmental temperature changes, the body maintains optimal body heat.

D.All of the above.

Answer: A. The integumentary system, though constantly challenged by environmental and physical challenges, provides the body with its first line of defense that protects internal environment. This includes body temperature, fluid balances, immune system support, and more.

Learning Objective: 4

 ■References

1.			Elaine Marieb and Katja Hoehn, Human Anatomy and Physiology. 10th ed. (San Francisco, CA: Pearson, 2016), 150 p.
2.			Carolee Sormunen. Terminology for Allied Health Professionals. 5th ed. (Canada, Thomson, 2003), 87 p.
3.			Wilma Phipps, Frances Monahan, Judith Sands, Jane Marek, Marianne Neighbors. Medical-Surgical Nursing Health and Illness Perspectives. 7th ed. (St. Louis: Mosby, 2003), 1934 p.
4.			Elaine Marieb and Katja Hoehn, Human Anatomy and Physiology. 1oth ed. (San Francisco, CA: Pearson, 2016), 151 p.
5.			Deutsches Zentrum fur Diabestsforschung, Paul Langerhans Institut Dresden, Helmholtz Zentrum Munich; University Hospital and Faculty of Medicine Dresden Accessed April 2017. Available from: http://plid.de/en/paul-langerhans.html
6.			Pubmed [Internet] Chomiczewska D, Trznadel-Budzko E, Kaczorowska, A, Rotsztein H, Pol Merkur Lekarski. “The role of Langerhans cells in the skin immune system” Pol Merkur Lekarski (2009. Mar;26(153): 173–7. Accessed April 2017. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19388527
7.			PMC [Internet] Munde, P, Khandekar S, Dive A, Sharma A. Pathophysiology of the Merkel cell. J Oral Maxillofac Pathol. 2013 Sep-Dec; 17(3): 408–412. doi: 10.4103/0973-029X.125208 Accessed April 2017. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3927344/
8.			Ibid.
9.			Ibid.
10.			Ibid.
11.			Wilma Phipps, Frances Monahan, Judith Sands, Jane Marek, Marianne Neighbors. Medical-Surgical Nursing Health and Illness Perspectives. 7th ed. (St. Louis: Mosby, 2003), 1934 p.
12.			Pub Med Health [Internet] Papillary dermis. Accessed April 2017. Available from https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT 0022670/.
13.			Ibid.
14.			Carolee Sormunen. Terminology for Allied Health Professionals. 5th ed. (Canada: Thomson, 2003), 89 p.
15.			Ibid.
16.			Vitamin D Council. Acne. Accessed April 2017. Available from: https://www.vitamindcouncil.org/health-conditions/acne/ Vitamin D Council.
17.			Elaine Marieb and Katja Hoehn. Human Anatomy and Physiology. 10th ed. (San Francisco: Pearson, 2016), 163 p.
18.			Ibid.
19.			Guy GP, et al. “Vital signs: melanoma incidence and mortality trends and projections” – United States, 1982–2030. MMWR Morb Mortal Wkly Rep. 2015; 64 (21): 591–596. Accessed April 2017 Available from: https://www.ncbi.nlm.nih.gov/pubmed/26042651
20.			Rogers HW, et al. “Incidents estimate of nonmelanoma skin cancer (keratinocyte carcinomas) in the US population” JAMA Dermatol. Accessed April 2017. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25928283
21.			Elaine Marieb and Katja Hoehn. Human Anatomy and Physiology. 10th ed. (San Francisco: Pearson, 2016), 165 p.