The Integumentary System

Diffuse Hair Loss

-A condition that is both dramatic and distressing, hair shed from all parts of the scalp. -Women primarily suffer from this condition, which may be due to hormones, drugs, or iron deficiency.

Stratum Lucidum

-A thin, translucent region of about two or three cell layers that is superficial to the stratum granulosum. -This stratum is found only in the thick skin within the palms of the hands and soles of the feet. -Cells occupying this layer appear pale and featureless and have indistinct boundaries. -The keratinocytes within this layer are flattened and filled with the translucent protein called ELEIDIN, which is an intermediate product in the process of keratin maturation. -This layer helps protect the skin from ultraviolet light.

Squamous Cell Carcinoma

-Arises from keratinocytes of stratum spinosum -Lesions usually appear on scalp, ears, lower lip, or dorsum of hand. -Early lesions are raised, reddened, scaly; later lesions form concave ulcers with elevated edges. -Treated by early detection and surgical removal of lesion -May metastasize to other parts of the body.

Male Pattern Baldness

-Causes loss of hair first from only the crown region of the scalp rather than uniformly. -It is caused by a combination of genetic and hormonal influences. -The relevant gene for male pattern baldness has two alleles, one for uniform hair growth and one for baldness. -The baldness allele is dominant in males and is expressed only in the presence of a high level of testosterone, which causes the terminal hair of the scalp to be replaced by thinner vellum, beginning on the top of the head and later at the sides. -In females, the baldness allele is recessive.

Apocrine Sweat Glands

-Coiled, tubular glands that release their secretion into hair follicles in the axillae, around the nipples, in the pubic region, and in the anal region. -Has a much larger lumen than that of a merocrine gland. -The secretion they produce is viscous and cloudy, and it contains both proteins and lipids that are acted upon by bacteria to produce a distinct, noticeable odor.

Stratum Granulosum

-Consists of 3 to 5 layers of keratinocytes superficial to the stratum spinosum. -Within this stratum begins a process called KERATINIZATION, where the keratinocytes fill up with the protein keratin, and in so doing, cause both the cell's nucleus and organelles to disintegrate and the cell dies. -Keratinization is not complete until the cells reach the more superficial epidermal layers. -A fully keratinized cell is dead (because it has neither a nucleus nor organelles), but it is structurally strong because of the keratin it contains.

Mesenchyme

-During the embryonic period, the mesoderm becomes the mesenchyme. -The mesenchymal cells begin to form the components of the dermis at eleven weeks.

Mammary Glands

-Modified apocrine glands. -These glands only become functional in pregnant and lactating females, when they produce milk, a secretion that nourishes offspring.

Ceruminous Glands

-Modified apocrine sweat glands located only in the external acoustic meatus (ear canal), where their secretion forms a waterproof earwax called cerumen. -Both cerumen and the tiny hairs in the meatus help trap foreign particles or small insects and keeps them from reaching the eardrum. -Cerumen also helps lubricate the external acoustic meatus and eardrum.

Basal Cell Carcinoma

-Most common type of skin cancer -Least dangerous type as it seldom metastasizes -Originates in stratum basale -First appears as small, shiny elevation that enlarges and develops central depression with pearly edge. -Usually occurs on face -Treated by surgical removal of lesion

Malignant Melanoma

-Most deadly type of skin cancer due to aggressive growth and metastasis -Arises from melanocytes, usually in a preexisting mole -Individuals at increased risk include those who have had severe sunburns, especially as children -Characterized by change in mole diameter, color, shape of border, and symmetry -Survival rate improved by early detection and surgical removal of lesion -Advanced cases (metastasis of disease) difficult to cure and are treated with chemotherapy, interferon therapy, and radiation therapy.

Sebum

-Oily, waxy secretion produced by sebaceous (holocrine) glands. -Usually discharged into a hair follicle and onto the hair itself. -Sebum acts as a lubricant to keep the skin and hair from becoming dry, brittle, and cracked. -The secretion of sebum in both sexes is stimulated by hormones, especially androgens (male sex hormones). -Sebaceous glands are relatively inactive during childhood; however, they are activated during puberty in both sexes, when the production of sex hormones increases.

Epidermal Dendritic Cells (Langerhans)

-The fourth epidermal cell type. -Epidermal dendritic cells are immune cells that help fight infection in the epidermis. These immune cells are often present in the STRATUM SPINOSUM and STRATUM GRANULOSUM, but they are not identifiable in standard histologic preparations. -Their phagocytic activity initiates an immune response to protect the body against pathogens that have penetrated the superficial epidermal layers as well as epidermal cancer cells.

Thermoregulation

-The major function of merocrine sweat glands. -The regulation of body temperature by evaporation of fluid from the skin. -Merocrine sweat gland secretions provide a means for the loss of both water and electrolytes. -The secretions also may help eliminate a number of ingested drugs.

Merocrine Sweat Glands

-The most numerous and widely distributed sweat glands. -Simple, coiled tubular glands that discharge their secretions directly onto the surface of the skin. -Merocrine sweat gland secretions provide some protection from environmental hazards both by diluting harmful chemicals and by preventing the growth of microorganisms (antibacterial and anti fungal activity).

Stratum Corneum

-The most superficial layer of the epidermis. -This is the stratum you see when you look at your skin. -Consists of about 20-30 layers of dead, scaly, interlocking keratinized cells. -The dead cells are anucleate (lacking a nucleus) and are tightly packed together. -A keratinized, or cornified, epithelium contains large amounts of keratin. -After keratinocytes are formed from stem cells within the stratum basale, they change in structure and in their relationship to their neighbors as they progress through the different strata until they eventually reach the stratum corneum and are sloughed off its external surface.

Fibrosis

-The process of scar tissue deposition during healing. -Serves to bind the damaged parts together. -The replacement scar tissue is produced by fibroblasts and is composed primarily of collagen fibers.

Regeneration

-The replacement of damaged or dead cells with the same cell type. -This restores organ function.

Alopecia

-Thinning of the hair. -Can happen in both sexes. -Usually a result of aging.

Sweat Gland Duct

-Transports the secretion to the surface of the epidermis (in a merocrine sweat gland) or into a hair follicle (in an apocrine sweat gland).

Lanugo

A fine, unpigmented, downy hair that first appears on the fetus in the last trimester of development.

Eponychium (Cuticle)

A narrow band of epidermis extending from the margin of the nail walk into the nail body.

Hyponychium

A region of thickened stratum corneum over which the free nail edge projects.

Granulation Tissue

A vascular connective tissue that initially forms in a healing wound.

ABCDE Rule

Asymmetry Border Color Diameter Evolving

Vernix Caseosa

Coats the skin of the fetus.

Hair Papilla

Composed of a small amount of connective tissue containing tiny blood vessels and nerves.

Hair Bulb

Consists of epithelial cells and is a swelling at the base where the hair originates in the dermis.

Hirsutism

Excessive male pattern hairiness in areas of the body that normal do not have terminal hair is called this. -This hair growth typically occurs on the face, chest, and back and may affect both sexes, but is especially distressing for women. -Hirsutism most commonly is caused by an excess of male sex hormones called androgens, either through a medical condition (such as polycystic ovarian syndrome) or by certain medications that cause a rise in androgens.

Hair Buds

Hair follicles begin to appear between 9 and 12 weeks of development as pockets of cells, called hair buds, invade the dermis from the overlying stratum basal of the epidermis.

Vasodilation

Means that the diameter of the vessels increase, so relatively more blood can travel through them.

Vasoconstriction

Means that the diameters of the vessels narrow, so relatively less blood can travel through them.

Connective Tissue Root Sheath

Originates from the dermis.

Epithelial Tissue Root Sheath

Originates from the epidermis.

Nail Matrix

The actively growing part of the nail.

Epidermis

The epithelium of the integument.

Sweat Pore

The opening of the sweat gland duct on the epidermal surface is an indented region called a sweat pore.

Shaft

The third portion of the hair that extends beyond the skin surface.

Root

The zone of the hair extending from the bulb to the skin surface.

Stratum Basale

This single layer of cuboidal to low columnar cells is tightly attached to an underlying basement membrane that separates the epidermis from the connective tissue of the adjacent dermis.

Catagen Phase

—A brief regression period where cell division ceases and the follicle undergoes involution. —This very short phase lasts for about 3 to 4 weeks.

Keratin

—A protein that strengthens the epidermis. —The keratinocytes found in epidermal cells of the skin are called cytokeratins. Their structure in these cells gives skin strength and makes the epidermis almost waterproof.

Hair Follicle

—An oblique tube that surrounds the hair root. —It always extends into the dermis and sometimes into the subcutaneous layer.

Vellus

—At birth, most of lanugo has been replaced by similarly fine unpigmented or lightly pigmented hair. —It is the primary human hair and is found on upper and lower limbs.

Arrector Pili

—Extending from the hair follicle to the dermal papillae are thin ribbons of smooth muscle that are called the arrector pili. —Stimulation of this is usually a result of an emotional state, such as fear or rage, or as a response to exposure to cold temperatures. —Upon stimulation, the arrector pili contracts, pulling on the hair follicle and elevating the hair, producing "goose bumps."

Hair Matrix

—Hair production involves a specialized type of keratinization that occurs within the hair matrix. —This is a structure immediately adjacent to the hair papilla in the hair bulb.

Medulla

—Not found in all hair types. —Composed of loosely arranged cells and air spaces and contains flexible, soft keratin.

Melanocytes

—Produce and store the pigment melanin in response to ultraviolet light exposure. —This pigment accumulates around the nucleus of the keratinocytes and shields the nuclear DNA from ultraviolet radiation.

Tactile Cells (Merkel Cells)

—Sensitive to touch and, when compressed, they release chemicals that stimulate sensory nerve endings, providing info about objects touching the skin.

Stratum Spinosum

—Several layers of polygonal keratinocytes form this. —Each time a keratinocyte stem cell in the stratum basale divides, a daughter cell is pushed toward the external surface from the stratum basale, while the other cell remains as a stem cell in the stratum basale. -Once this new cell enters the stratum spinosum, it begins to differentiate into a non-dividing, highly specialized keratinocyte. -Sometimes the deepest cells in this layer still undergo mitosis to help replace epidermal cells that exfoliate from the surface. -The non-dividing keratinocytes in the stratum spinosum attach to their neighbors by many membrane junctions called DESMOSOMES.

Anagen Phase

—The active phase of growth where living cells of the hair bulb are rapidly growing, dividing, and transforming into hair. —It is the longest part of the growth cycle and lasts from 18 months to as much as 7 years, depending on the genetics of the person. —During this phase, each hair stand grows about one-third of a millimeter per day, which equals 0.5 to 1.0 cm per month.

Keratinocytes

—The most abundant cell type in the epidermis and are found throughout all epidermal strata. —Dominated by large keratinocyte stem cells, which divide to generate new cells that replace dead keratinocytes shed from the surface.

Epidermal Derivatives (Appendages)

—The nails, hair, and exocrine glands of the skin are all derived from the epidermal epithelium. —These structures are also known as _________.

Telogen Phase

—The resting phase and is usually the phase where the hair is shed (these hairs are the ones we find in or brush). —After 3 to 4 months in the telogen phase, the cells of the hair bulb start regrowing, and the follicle reenters the anagen phase.

Lunula

—The whitish semilunar area of the proximal end of the nail body. —It has a whitish appearance because a thickened stratum basale obscures the underlying blood vessels.

Terminal Hair

—Usually coarser, pigmented, and longer than vellus. —It grows on the scalp, and it is also the hair of eyebrows and eyelashes. —At puberty, terminal hair replaces vellus hair in the axillary and pubic regions, and it forms the beard on the faces of males.