Integumentary System - Hair, Glands, Repair, and Development

Vocabulary flashcards covering hair types and structures, various exocrine glands, stages of wound healing, and clinical conditions related to the integumentary system.

Lanugo

Fine, unpigmented, downy hair that appears in the last trimester of fetal development.

Vellus

Fine hair that is the primary human hair and is found on the upper and lower limbs.

Terminal hair

Coarser, pigmented, and longer hair found on the scalp, eyebrows, and eyelashes; it replaces vellus hair in axillary and pubic regions during puberty.

Hair bulb

Swelling at the base where hair originates in the dermis; it is the only region containing living epithelial cells.

Root

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

Shaft

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

Hair matrix

Structure at the base of the hair bulb where epithelial cells divide to produce new cells that are pushed toward the surface.

Medulla

A remnant of the matrix consisting of flexible, soft keratin.

Cortex

Relatively hard, flattened cells located closer to the outer hair surface.

Cuticle

A single cell layer located around the cortex.

Hair follicle

An oblique tube surrounding the hair root that consists of an outer connective tissue root sheath and an inner epithelial tissue root sheath.

Arrector pili

Thin ribbons of smooth muscle that extend from the hair follicle to dermal papillae and cause "goosebumps" ($\text{cutis anserina}$) upon contraction.

Anagen

The active phase of the hair growth cycle.

Catagen

A brief regression period in the hair growth cycle where cell division stops.

Telogen

The resting phase of the hair growth cycle, which is the period when hair is usually shed.

Alopecia areata

An autoimmune disorder where hair follicles are attacked, resulting in spots of baldness on the scalp and body.

Hirsutism

A condition characterized by excessive hairiness.

Merocrine (eccrine) sweat glands

Simple, coiled tubular glands that discharge a secretion (99% water) via exocytosis directly onto the skin surface for thermoregulation.

Apocrine sweat glands

Coiled, tubular glands that discharge viscous, cloudy secretions containing proteins and lipids into hair follicles in the axillae, nipples, and pubic/anal regions.

Sebaceous glands

Holocrine glands that produce sebum, an oily lubricant that is bactericidal and discharges into a hair follicle.

Ceruminous glands

Modified apocrine sweat glands located in the external ear canal that produce a waterproof earwax called cerumen.

Mammary glands

Modified apocrine sweat glands of the breast that function during pregnancy to produce breast milk.

Regeneration

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

Fibrosis

A repair process where a gap is filled with scar tissue (collagen produced by fibroblasts), but functional activities are not restored.

Granulation tissue

Vascular connective tissue that initially forms in a wound during the third stage of healing.

Psoriasis

A chronic autoimmune skin disease where T-lymphocytes attack keratinocytes, causing rapid overgrowth of skin cells and whitish, scaly plaques.

First-degree burns

Burns that involve only the epidermis and result in slight redness and pain.

Second-degree burns

Burns that involve the epidermis and part of the dermis, resulting in blistered, painful skin and slight scarring.

Third-degree burns

Burns involving the epidermis, dermis, and subcutaneous layer; they require hospitalization and treatment for dehydration and infection.

Rule of nines

A method used to estimate the surface area of burns to measure burn severity.

Vernix caseosa

A coating on fetal skin produced by a mix of sebum and sloughed-off periderm.

Botox

A treatment using $Clostridium\,botulinum$ toxin Type A to block nerve impulses to facial expression muscles, temporarily eliminating wrinkles.