Chapter 5: The Integumentary System

onset of puberty

It is most common along with the ________ due to associated hormonal changes, but can also occur in infants and continue into adulthood.

excrete sebum

They generate and ________, a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer of keratinized cells of the stratum corneum, keeping it pliable.

skin cancers

It is the most fatal of all ________, as it is highly metastatic and can be difficult to detect before it has spread to other organs.

pale skin

Dark- skinned individuals produce more melanin than those with ________.

Skin

________ and its underlying tissue can be affected by excessive pressure.

Mutations

________ can lead to uncontrolled cell proliferation and malignancies.

fourth degree burn

A(n) ________ is even more severe, affecting the underlying muscle and bone.

second degree burn

A(n) ________ goes deeper and affects both the epidermis and a portion of the dermis.

**keratinocyte**

is a cell that manufactures and stores the protein keratin.

**Keratin**

is an intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties.

absence of sun exposure

The ________ can lead to a lack of vitamin D in the body, leading to a condition called rickets, a painful condition in children where the bones are misshapen due to a lack of calcium, causing bowleggedness.

**stratum basale**

(also called the stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis.

**dermal papilla**

(plural = dermal papillae) is found in the superficial portion of the dermis.

The skin is composed of two main layers

the epidermis, made of closely packed epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures

**basal cell**

is a cuboidal-shaped stem cell that is a precursor of the keratinocytes of the epidermis.

**melanocyte**

a cell that produces the pigment melanin. 

**Melanin**

gives hair and skin its color, and also helps protect the living cells of the epidermis from ultraviolet (UV) radiation damage.

**stratum spinosum**

**i**s spiny in appearance due to the protruding cell processes that join the cells via a structure called a *desmosome*.

**Langerhans cell**

Interspersed among the keratinocytes of this layer is a type of dendritic cell called the

**stratum granulosum**

has a grainy appearance due to further changes to the keratinocytes as they are pushed from the stratum spinosum.

**keratohyalin**

which accumulates as lamellar granules within the cells.

**stratum lucidum**

is a smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum.

**eleiden**

a clear protein rich in lipids, derived from keratohyalin, which gives these cells their transparent (i.e., lucid) appearance and provides a barrier to water.

**stratum corneum**

is the most superficial layer of the epidermis and is the layer exposed to the outside environment.

**dermis**

might be considered the “core” of the integumentary system (derma- = “skin”), as distinct from the epidermis (epi- = “upon” or “over”) and hypodermis (hypo- = “below”).

**papillary layer**

is made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh.

**Elastin fibers**

provide some elasticity to the skin, enabling movement.

**hypodermis**

(also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) of the bones and muscles.

**melanosome**

The melanin is transferred into the keratinocytes via a cellular vesicle called a

**hair follicle**

Strands of hair originate in an epidermal penetration of the dermis called the

**hair shaft**

is the part of the hair not anchored to the follicle, and much of this is exposed at the skin’s surface.

**hair root**

The rest of the hair, which is anchored in the follicle, lies below the surface of the skin and is referred to as the

**hair matrix**

The hair root ends deep in the dermis at the **hair bulb**, and includes a layer of mitotically active basal cells called the

**hair papilla**

which is made of connective tissue and contains blood capillaries and nerve endings from the dermis

**internal root sheath**

The cells of the ___ surround the root of the growing hair and extend just up to the hair shaft.

**external root sheath**

The **___**, which is an extension of the epidermis, encloses the hair root.

**glassy membrane**

is a thick, clear connective tissue sheath covering the hair root, connecting it to the tissue of the dermis.

**arrector pili**

Each hair root is connected to a smooth muscle called the

**anagen phase**

, during which cells divide rapidly at the root of the hair, pushing the hair shaft up and out.

**catagen phase**

lasts only 2 to 3 weeks, and marks a transition from the hair follicle’s active growth. 

**telogen** phase

 , the hair follicle is at rest and no new growth occurs.

**nail body**

The is formed on the **nail bed**

**eponychium**

The nail fold that meets the proximal end of the nail body forms the **nail cuticle**, also called the

**lunula**

The nail bed is rich in blood vessels, making it appear pink, except at the base, where a thick layer of epithelium over the nail matrix forms a crescent-shaped region called the___(the “little moon”).

**hyponychium**

The area beneath the free edge of the nail, furthest from the cuticle, is called the

**eccrine sweat gland**

is a type of gland that produces a hypotonic sweat for thermoregulation.

**apocrine sweat gland**

is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions.

**sebaceous gland**

is a type of oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair.

*cholecalciferol*

In the presence of sunlight, a form of vitamin D3 called *__*is synthesized from a derivative of the steroid cholesterol in the skin.

**rickets**

a painful condition in children where the bones are misshapen due to a lack of calcium, causing bowleggedness.

**Basal cell carcinoma**

is a form of cancer that affects the mitotically active stem cells in the stratum basale of the epidermis.

**melanoma**

is a cancer characterized by the uncontrolled growth of melanocytes, the pigment-producing cells in the epidermis.

**Eczema**

is an allergic reaction that manifests as dry, itchy patches of skin that resemble rashes.

**Acne**

is a skin disturbance that typically occurs on areas of the skin that are rich in sebaceous glands (face and back).

**first-degree**

is a superficial burn that affects only the epidermis.

**second-degree**

burn goes deeper and affects both the epidermis and a portion of the dermis.

**third-degree**

  burn fully extends into the epidermis and dermis, destroying the tissue and affecting the nerve endings and sensory function

**fourth-degree**

burn is even more severe, affecting the underlying muscle and bone.

**scar**

is collagen-rich skin formed after the process of wound healing that differs from normal skin.

**stretch mark**

results when the dermis is stretched beyond its limits of elasticity, as the skin stretches to accommodate the excess pressure.

**corn**

is a specialized form of callus.