section 3 Integumentary System: Hair, Nails, and Cutaneous Glands

Vocabulary flashcards covering the structures and functions of the hypodermis, hair, cutaneous exocrine glands, the hair growth cycle, and nails from the integumentary lecture notes.

Hypodermis

A subcutaneous layer that connects the skin to the underlying layer of bones or muscles; composed of well-vascularized, loose, areolar connective tissue and adipose tissue.

Hair shaft

The part of the hair that extends out of the hair follicle.

Medulla

The core of the hair shaft, made up of large cells and hollow spaces.

Cortex (Hair)

The thickest layer of the hair shaft, composed of flattened cells.

Cuticle (Hair)

A single layer of flattened, overlapping, heavily keratinized cells on the hair shaft.

Oval hair shaft

Cross-sectional shape of the hair shaft that produces smooth, silky, and wavy hair.

Flat hair shaft

Cross-sectional shape of the hair shaft that produces curly or kinky hair.

Round hair shaft

Cross-sectional shape of the hair shaft that produces straight and coarse hair.

Hair root

The part of the hair enclosed within the hair follicle.

Hair bulb

The deepest part of the hair, containing a blood supply and living, dividing cells that grow the hair structure.

Hair follicle

A two-layered indentation of the epidermis composed of an inner sheath that forms the hair and an outer sheath that supplies blood to the hair papilla, which nourishes dividing cells in the hair root.

Arrector pili muscles

Bands of smooth muscle attached to the sides of the hair follicle that pull hair upright.

Sebaceous glands

Exocrine glands that produce an oily secretion (sebum) that lubricates the skin and hair, and contains antibacterial chemicals.

Eccrine glands

Sweat glands that open to the surface by way of a sweat pore and secrete a highly acidic combination of water, salts, and traces of metabolic waste as part of the cooling mechanism.

Apocrine glands

Glands found in the armpit and genital region that secrete fatty acids and proteins; function is unknown.

Anagen

The hair growth cycle phase characterized by rapid mitotic division and hair shaft growth; lasts $2\text{ to }7\text{ years}$.

Catagen

The hair growth cycle phase in which the hair bulb is amitotic and detaches from the blood supply; lasts $2\text{ to }3\text{ weeks}$.

Telogen

The resting phase of the hair growth cycle where the hair dies and eventually falls out; lasts $2\text{ to }4\text{ months}$.

Nails

Scale-like modifications of the epidermis where dividing cells are pushed along the body of the nail, become highly keratinized, and die.

Nail matrix

The thickened region at the base of the nail where nail growth occurs.

Lunula

The thicker portion of the nail located over the nail matrix that obscures the underlying blood supply.