6.2 Integumentary Structures Derived from Epidermis

Telogen Phase

The resting phase where the hair is shed. After 3 to 4 months in this phase the cells of the hair bulb start regrowing, and the follicle reenters the anagen phase.

Shaft

The third portion of the hair that extends beyond the skin surface. Consists of dead epithelial cells.

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.

Arrector Pili

Thin ribbons of smooth muscle that extend from the hair follicle to the dermal papillae.

Alopecia

Thinning of the hair.

Catagen Phase

A brief regression period where cell division ceases and the follicle undergoes involution. (3-4 weeks)

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 wall onto the nail body.

Anagen Phase

Active phase of growth where living cells of the hair bulb are rapidly growing ,dividing, and transforming into hair. (18mos - 7yrs)

Sweat Pore

An indented region that serves as the opening of a sweat gland on the epidermal surface.

Hair Follicle

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

Sebum

An oily, waxy secretion produced by sebaceous glands and is usually discharged into a hair follicle and onto the hair itself.

Sweat Gland Duct

Carries the secretion to the surface of the epidermis (in a merocrine gland) or a hair follicle (in an apocrine gland).

Terminal Hair

Coarser, pigmented, and longer than vellus. Grows on the scalp, eyebrows, eyelashes. At puberty it replaces vellus hair in the axillary and pubic regions and forms the beard on males

Hair Papilla

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

Hirsutism

Excessive male pattern hairiness in areas of the body that normally do not have terminal hair. Most commonly caused by an excess of androgens (a male hormone).

Vellus

Fine unpigmented or lightly pigmented hair that replaces Lanugo by birth. The primary human hair that is found on the upper and lower limbs

Cortex

Formed by several layers of flattened cells closer to the outer surface of the developing hair.

Ceruminous Glands

Modified apocrine sweat glands located only in the external acoustic meatus (ear canal( where their secretion forms a waterproof earwax called cerumen.

Mammary Glands

Modified apocrine sweat glands of the breasts that become functional only in pregnant and lactating females, when they produce milk, a secretion that nourishes offspring.

Merocrine Sweat Glands

Most numerous and widely distributed sweat glands. Simple, coiled tubular glands that discharge their secretions directly onto the surface of the skin.

Nail Matrix

The actively growing part of the nail at the nail root where the nail bed thickens.

Free Edge

The distal whitish edge.

Hyponychium

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

Medulla

A remnant of the soft core of the matric; composed of loosely arranged cells and air spaces, and contains flexible, soft keratin.

Cuticle

A single cell layer around the cortex, which coats the hair.

Hair Matrix

A structure immediately adjacent to the hair papilla in the hair bulb.

Nail Plate

Consists of the distal whitish free edge, a pinkish nail body, and a nail root (the proximal part embedded in the skin).

Male Pattern Baldness

Loss of hair first from only the crown region of the scalp rather than uniformly.

Epithelial Tissue Root Sheath

The inner sheath of a hair follicle which originates from the epidermis.

Nail Bed

The layer of the epidermis, found underneath the nail body, which contains only the deeper, living cell layers of the epidermis.

Connective Tissue Root Sheath (outer

The outermost sheath of a hair follicle; derived from dermis and composed of collagenous connective tissue, surrounds epithelial sheath and is somewhat denser than the adjacent dermal tissue.

Thermoregulation

The regulation of body temperature by evaporation of fluid from the skin.

Root

The zone of the hair extending from the bulb to the skin surface. Consists of dead epithelial cell.s

Sweat Gland

Tiny, coiled glands found on almost all body surfaces. Most numerous in palms and soles of feet. Coiled sweat glands originate in the dermis and straighten out to extend up through the epidermis. Two types: eccrine and apocrine sweat glands.

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. Their secretions differ from the sweat of the merocine glands in that they contain both proteins and lipids that are acted upon by bacteria to produce a distinct, noticeable odor.

Hairbulb

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

Sebaceous Glands

Glands that produce an oily substance called sebum, which discharges along the shafts of the hairs.

Diffuse Hair Loss

Hair is shed from all parts of the scalp.

Nail Folds

Folds of skin that overlap the nail along the lateral and proximal borders of the nail.

Epidermal Derivatives

The nails, hair, and exocrine glands of the skin all are derived from the epidermal epithelium.