Support and also Movement The Integumentary device The Integumentary mechanism introduction
*

Figure 5.1 Your skin is a an essential part of her life and appearance (a–d). Part people select to embellish it v tattoos (a), assembly (b), and even piercings (c). (credit a: Steve Teo; credit b: “spaceodissey”/flickr; credit c: Mark/flickr; credit d: Lisa Schaffer)

CHAPTER OBJECTIVES

After studying the chapter, you will certainly be may be to: 

Describe the integumentary system and also the function it dram in homeostasisDescribe the layers of the skin and the features of every layerDescribe the accessory structures of the skin and the functions of eachDescribe the changes that take place in the integumentary system throughout the aging processDiscuss several common diseases, disorders, and also injuries that influence the integumentary systemExplain treatments for some typical diseases, disorders, and also injuries the the integumentary system

What execute you think when you watch at your skin in the mirror? do you think about covering it through makeup, including a tattoo, or probably a body piercing? Or perform you think about the reality that the skin belong to one of the body’s most essential and also dynamic systems: the integumentary system? The integumentary device refers come the skin and also its accessory structures, and it is responsible for much more than simply lending to your external appearance. In the adult human being body, the skin provides up around 16 percent of human body weight and covers one area the 1.5 come 2 m2. In fact, the skin and accessory structures room the biggest organ mechanism in the human being body. As such, the skin protects her inner organs and it is in need of day-to-day care and protection to preserve its health. This thing will introduce the structure and functions of the integumentary system, as well as some the the diseases, disorders, and also injuries that can impact this system.

You are watching: Exposure to ultraviolet light (sunlight) causes the skin to darken by increasing the production of


by the end of this section, you will certainly be may be to:Identify the materials of the integumentary systemDescribe the layers of the skin and also the attributes of every layerIdentify and describe the hypodermis and deep fasciaDescribe the duty of keratinocytes and their life cycleDescribe the role of melanocytes in skin pigmentation

Although you may not generally think of the skin together an organ, it is in reality made of tissues that occupational together as a solitary structure come perform distinctive and vital functions. The skin and its accessory structures make up the integumentary system, which offers the body with overall protection. The skin is do of multiple layers of cells and also tissues, which are held to underlying frameworks by connective tissue (Figure 5.2). The deeper layer of skin is fine vascularized (has numerous blood vessels). It likewise has plenty of sensory, and also autonomic and also sympathetic nerve yarn ensuring interaction to and also from the brain.

*

Figure 5.2 Layers the Skin The skin is composed of two key layers: the epidermis, do of very closely packed epithelial cells, and also the dermis, do of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. In ~ the dermis lies the hypodermis, which is composed greatly of loose connective and fatty tissues.

INTERACTIVE LINK

The skin consists of two key layers and also a closely connected layer. Check out this animation to learn much more about great of the skin. What space the simple functions of every of this layers?

The Epidermis

The epidermis is created of keratinized, stratified squamous epithelium. That is made of 4 or 5 layers of epithelial cells, relying on its location in the body. It does no have any type of blood vessels within it (i.e., the is avascular). Skin that has 4 layers of cells is described as “thin skin.” native deep to superficial, these layers room the stratum basale, stratum spinosum, stratum granulosum, and also stratum corneum. Many of the skin deserve to be classified together thin skin. “Thick skin” is discovered only top top the palms that the hands and the soles of the feet. It has a fifth layer, called the stratum lucidum, located between the stratum corneum and also the stratum granulosum (Figure 5.3).

*

The cell in every one of the layers other than the stratum basale are dubbed keratinocytes. A keratinocyte is a cell the manufactures and also stores the protein keratin. Keratin is an intracellular fibrous protein that offers hair, nails, and skin your hardness and also water-resistant properties. The keratinocytes in the stratum corneum room dead and regularly slough away, being replaced by cells from the deeper layers (Figure 5.4).

*

INTERACTIVE LINK

View the University that Michigan WebScope to discover the tissue sample in greater detail. If you zoom ~ above the cells at the outermost layer of this ar of skin, what carry out you notification about the cells?

Stratum Basale

The stratum basale (also dubbed the stratum germinativum) is the deepest epidermal layer and also attaches the epidermis to the basal lamina, listed below which lied the layers of the dermis. The cell in the stratum basale bond to the dermis via intertwining collagen fibers, described as the basement membrane. A finger-like projection, or fold, recognized as the dermal papilla (plural = dermal papillae) is uncovered in the superficial part of the dermis. Dermal papillae boost the stamin of the connection between the epidermis and dermis; the higher the folding, the more powerful the relationships made (Figure 5.5).

*

Figure 5.5 Layers that the Epidermis The epidermis of special skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and also stratum corneum.

The stratum basale is a solitary layer that cells mostly made that basal cells. A basal cell is a cuboidal-shaped stem cell that is a precursor of the keratinocytes that the epidermis. All of the keratinocytes are produced from this single layer of cells, which are constantly going with mitosis to produce new cells. As new cells room formed, the existing cells are thrust superficially far from the stratum basale. Two other cell varieties are uncovered dispersed amongst the basal cell in the stratum basale. The an initial is a Merkel cell, which functions as a receptor and is responsible because that stimulating sensory nerves that the brain perceives together touch. These cells are specifically abundant ~ above the surface of the hands and feet. The 2nd is a melanocyte, a cell the produces the pigment melanin. Melanin gives hair and skin that is color, and likewise helps defend the living cell of the epidermis from ultraviolet (UV) radiation damage.

In a cultivation fetus, fingerprints type where the cells of the stratum basale meet the papillae that the basic dermal great (papillary layer), resulting in the formation of the ridges on your fingers the you identify as fingerprints. Fingerprints are distinct to every individual and are supplied for forensic analyses because the patterns carry out not adjust with the growth and aging processes.

Stratum Spinosum

As the name suggests, the stratum spinosum is spiny in appearance due to the protruding cell procedures that join the cell via a structure dubbed a desmosome. The desmosomes interlock through each other and also strengthen the bond between the cells. That is amazing to keep in mind that the “spiny” nature the this class is an artifact the the staining process. Unstained epidermis samples carry out not exhibition this properties appearance. The stratum spinosum is created of eight come 10 class of keratinocytes, formed as a an outcome of cell department in the stratum basale (Figure 5.6). Interspersed amongst the keratinocytes of this layer is a type of dendritic cell called the Langerhans cell, which attributes as a macrophage through engulfing bacteria, foreign particles, and also damaged cells that happen in this layer.

*

INTERACTIVE LINK

View the University the Michigan WebScope to check out the tissue sample in greater detail. If you zoom on the cell at the outermost layer of this section of skin, what do you notification about the cells?

The keratinocytes in the stratum spinosum begin the synthesis of keratin and also release a water-repelling glycolipid the helps stop water loss from the body, make the skin fairly waterproof. As new keratinocytes are produced atop the stratum basale, the keratinocytes of the stratum spinosum room pushed into the stratum granulosum.

Stratum Granulosum

The stratum granulosum has a grainy appearance due to further alters to the keratinocytes as they are moved from the stratum spinosum. The cells (three to 5 layers deep) come to be flatter, their cell membrane thicken, and they generate huge amounts the the protein keratin, which is fibrous, and keratohyalin, i m sorry accumulates together lamellar granules within the cells (see Figure 5.5). These 2 proteins comprise the mass of the keratinocyte mass in the stratum granulosum and give the great its grainy appearance. The nuclei and other cell organelles disintegrate together the cells die, leaving behind the keratin, keratohyalin, and cell membranes the will type the stratum lucidum, the stratum corneum, and the accessory structures of hair and nails.

Stratum Lucidum

The stratum lucidum is a smooth, look at translucent layer of the epidermis situated just over the stratum granulosum and also below the stratum corneum. This slim layer of cells is found only in the special skin of the palms, soles, and also digits. The keratinocytes that compose the stratum lucidum space dead and flattened (see Figure 5.5). This cells are densely pack with eleiden, a clear protein well-off in lipids, obtained from keratohyalin, which provides these cells your transparent (i.e., lucid) appearance and also provides a obstacle to water.

Stratum Corneum

The stratum corneum is the most superficial class of the epidermis and is the great exposed to the outside setting (see Figure 5.5). The raised keratinization (also dubbed cornification) of the cells in this layer provides it that is name. There space usually 15 to 30 class of cell in the stratum corneum. This dry, dead layer helps protect against the penetration of microbes and the dehydration of underlying tissues, and provides a mechanically protection against abrasion for the more delicate, basic layers. Cells in this layer are burned periodically and also are replaced by cells moved up native the stratum granulosum (or stratum lucidum in the situation of the palms and soles of feet). The entire layer is replaced during a period of around 4 weeks. Cosmetic procedures, such together microdermabrasion, assist remove few of the dry, upper layer and aim to store the skin looking “fresh” and healthy.

Dermis

The dermis might be thought about the “core” the the integumentary mechanism (derma- = “skin”), as distinct from the epidermis (epi- = “upon” or “over”) and hypodermis (hypo- = “below”). It has blood and also lymph vessels, nerves, and also other structures, such as hair follicles and sweat glands. The dermis is make of two layers that connective organization that create an interconnected mesh the elastin and also collagenous fibers, developed by fibroblasts (Figure 5.7).

*

Figure 5.7 Layers of the Dermis This stained slide mirrors the two materials of the dermis—the papillary layer and the reticular layer. Both room made of connective tissue v fibers the collagen expanding from one come the other, do the border between the two rather indistinct. The dermal papillae prolonging into the epidermis belong to the papillary layer, vice versa, the dense collagen fiber bundles below belong to the reticular layer. LM × 10. (credit: change of work by “kilbad”/Wikimedia Commons)

Papillary Layer

The papillary layer is made of loose, areolar connective tissue, which method the collagen and elastin yarn of this layer kind a loose mesh. This superficial class of the dermis projects into the stratum basale that the epidermis to type finger-like dermal papillae (see Figure 5.7). In ~ the papillary layer are fibroblasts, a small number of fat cell (adipocytes), and an abundance of little blood vessels. In addition, the papillary layer contains phagocytes, defensive cells that assist fight bacteria or various other infections that have actually breached the skin. This layer likewise contains lymphatic capillaries, nerve fibers, and also touch receptors referred to as the Meissner corpuscles.

Reticular Layer

Underlying the papillary layer is the lot thicker reticular layer, composed of dense, rarely often, rarely connective tissue. This great is well vascularized and also has a rich sensory and sympathetic nerve supply. The reticular layer appears reticulated (net-like) due to a chop meshwork the fibers. Elastin fibers provide some elasticity come the skin, allowing movement. Collagen fibers administer structure and also tensile strength, through strands of collagen extending into both the papillary layer and the hypodermis. In addition, collagen binding water to store the skin hydrated. Collagen injections and also Retin-A creams aid restore skin turgor by either presenting collagen externally or stimulating blood flow and also repair that the dermis, respectively.

Hypodermis

The hypodermis (also referred to as the subcutaneous layer or superficial fascia) is a layer directly below the dermis and also serves to attach the skin come the underlying fascia (fibrous tissue) the the bones and also muscles. The is not strictly a part of the skin, although the border between the hypodermis and dermis can be daunting to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which attributes as a setting of fat storage and provides insulation and cushioning because that the integument.

EVERYDAY CONNECTION

Lipid Storage

The hypodermis is home to most of the fat the concerns world when they are trying to store their weight under control. Adipose tissue existing in the hypodermis consists of fat-storing cells called adipocytes. This stored fat deserve to serve as an energy reserve, insulate the human body to prevent warm loss, and act together a cushion to protect underlying structures from trauma.

Where the fat is deposited and also accumulates within the hypodermis counts on hormone (testosterone, estrogen, insulin, glucagon, leptin, and others), as well as genetic factors. Fat distribution transforms as our bodies mature and also age. Males tend come accumulate fat in different areas (neck, arms, reduced back, and also abdomen) than execute women (breasts, hips, thighs, and also buttocks). The body mass index (BMI) is regularly used together a measure up of fat, back this measure is, in fact, acquired from a mathematical formula the compares body load (mass) to height. Therefore, the accuracy together a health indicator have the right to be called into concern in people who are incredibly physically fit.

In numerous animals, there is a pattern of storing overabundance calories as fat to be offered in times once food is not readily available. In lot of the developed world, inadequate exercise coupled v the ready availability and intake of high-calorie foodstuffs have caused unwanted accumulations of adipose tissue in numerous people. Back periodic accumulation of excess fat may have detailed an evolutionary benefit to ours ancestors, who knowledgeable unpredictable bouts of famine, it is now coming to be chronic and considered a significant health threat. Current studies indicate that a distressing percentage of our populace is overweight and/or clinically obese. Not just is this a problem for the people affected, however it also has a severe impact on our health care system. Changes in lifestyle, particularly in diet and exercise, room the ideal ways to manage body fat accumulation, especially when the reaches levels that rise the danger of heart condition and diabetes.

Pigmentation

The shade of skin is affected by a number of pigments, consisting of melanin, carotene, and also hemoglobin. Recall the melanin is created by cells dubbed melanocytes, i beg your pardon are uncovered scattered throughout the stratum basale the the epidermis. The melanin is transferred right into the keratinocytes via a cellular vesicle called a melanosome (Figure 5.8).

*

Figure 5.8 Skin Pigmentation The family member coloration of the skin depends of the amount of melanin developed by melanocytes in the stratum basale and taken increase by keratinocytes.

Melanin occurs in two primary forms. Eumelanin exists together black and also brown, conversely, pheomelanin offers a red color. Dark-skinned people produce an ext melanin 보다 those with pale skin. Exposure to the UV beam of the sun or a tanning salon reasons melanin come be manufactured and built up in keratinocytes, as sunlight exposure stimulates keratinocytes to secrete chemicals the stimulate melanocytes. The buildup of melanin in keratinocytes outcomes in the darkening that the skin, or a tan. This boosted melanin buildup protects the DNA that epidermal cell from UV beam damage and also the malfunction of folic acid, a nutrient necessary for ours health and also well-being. In contrast, too lot melanin deserve to interfere v the manufacturing of vitamin D, vital nutrient associated in calcium absorption. Thus, the quantity of melanin existing in ours skin is dependent on a balance between obtainable sunlight and also folic mountain destruction, and protection indigenous UV radiation and vitamin D production.

It requires about 10 days after initial sunlight exposure because that melanin synthetic to peak, i m sorry is why pale-skinned individuals tend to suffer sunburns of the epidermis initially. Dark-skinned people can additionally get sunburns, but are more protected than space pale-skinned individuals. Melanosomes space temporary frameworks that space eventually destroyed by combination with lysosomes; this fact, in addition to melanin-filled keratinocytes in the stratum corneum sloughing off, renders tanning impermanent.

Too much sun exposure can ultimately lead to wrinkling due to the damage of the cellular framework of the skin, and in serious cases, can reason sufficient DNA damage to result in skin cancer. When there is one irregular buildup of melanocytes in the skin, summer sprouts appear. Mole are larger masses the melanocytes, and although many are benign, they must be monitored for alters that can indicate the existence of cancer (Figure 5.9).

*

Figure 5.9 Moles Moles range from bright accumulations that melanocytes come melanomas. These structures populate the see of our skin. (credit: the nationwide Cancer Institute)

DISORDERS of THE...

Integumentary System

The first thing a clinician watch is the skin, and so the examination of the skin must be part of any type of thorough physical examination. Most skin obstacle are reasonably benign, yet a few, including melanomas, have the right to be deadly if untreated. A couple of the much more noticeable disorders, albinism and also vitiligo, affect the appearance of the skin and also its accessory organs. Although neither is fatal, it would be hard to claim that they space benign, at least to the people so afflicted.

Albinism is a genetic disorder the affects (completely or partially) the colour of skin, hair, and eyes. The defect is primarily because of the inability of melanocytes to create melanin. Individuals with albinism tend to show up white or an extremely pale because of the absence of melanin in your skin and hair. Recall the melanin helps protect the skin from the harmful results of UV radiation. Individuals with albinism often tend to need an ext protection native UV radiation, as they are more prone to sunburns and also skin cancer. They likewise tend to be much more sensitive come light and also have vision difficulties due to the lack of pigmentation ~ above the retinal wall. Treatment of this disorder usually requires addressing the symptoms, such together limiting UV irradiate exposure come the skin and also eyes. In vitiligo, the melanocytes in certain areas shed their capability to develop melanin, possibly as result of an autoimmune reaction. This leader to a lose of shade in job (Figure 5.10). Neither albinism nor vitiligo straight affects the expectancy of an individual.

See more: How Much Sperm Does A Dog Produce ? How Much Sperm Does A Dog Produce

*

Figure 5.10 Vitiligo Individuals through vitiligo endure depigmentation that results in lighter fancy patches of skin. The problem is particularly noticeable ~ above darker skin. (credit: Klaus D. Peter)

Other alters in the illustration of skin coloration can be indicative the diseases associated with other body systems. Liver disease or liver cancer can cause the buildup of bile and the yellow colors bilirubin, bring about the skin showing up yellow or jaundiced (jaune is the French word for “yellow”). Tumors the the pituitary gland can an outcome in the secretion of big amounts the melanocyte-stimulating hormone (MSH), which outcomes in a darkening of the skin. Similarly, Addison’s disease can stimulate the relax of excess amounts of adrenocorticotropic hormone (ACTH), i m sorry can provide the skin a deep bronze color. A sudden drop in oxygenation can influence skin color, bring about the skin to at first turn ashen (white). V a prolonged reduction in oxygen levels, dark red deoxyhemoglobin becomes dominant in the blood, make the skin appear blue, a condition referred to together cyanosis (kyanos is the Greek word because that “blue”). This happens as soon as the oxygen supply is restricted, as when someone is experiencing challenge in breathing since of asthma or a heart attack. However, in these situations the impact on skin color has nothing carry out with the skin’s pigmentation.

INTERACTIVE LINK

This ABC video clip follows the story that a pair of fraternal African-American twins, among whom is albino. Watch this videoto learn about the difficulties these children and also their family face. Which ethnic backgrounds do friend think room exempt indigenous the possibility of albinism?