5. Integumentary System

Comprehensive vocabulary flashcards covering the anatomy, cellular composition, epidermal and dermal layers, hair structures, and gland classifications of the integumentary system.

Integumentary system

The body system that consists of the skin and all associated structures, including hair, skin glands, paw pads, horns, nails, and hooves.

Epidermis

The avascular outermost layer of the skin, composed of keratinized stratified squamous epithelial tissue, containing four distinct cell types and up to five layers.

Keratinocyte

An epidermal cell that produces keratin to protect underlying tissue.

Melanocyte

An epidermal cell that produces melanin to protect keratinocytes from ultraviolet (UV) light damage.

Langerhans cell

A macrophage and specialized monocyte-derived white blood cell residing in the epidermis to provide immune support.

Merkel cell

An epidermal sensory cell that interacts with a Merkel disc nerve structure to transmit touch sensation.

Stratum basale

The deepest, metabolically alive layer of the epidermis (also called stratum germinativum) that contains stem cells continuously providing new cells for superficial layers.

Stratum spinosum

A metabolically alive epidermal layer consisting of 20 to 30 layers of non-keratinized, polyhedral-shaped squamous cells that provide flexibility and house specialized cells.

Stratum granulosum

The epidermal layer transitioning between metabolically alive and dead cells that marks the boundary where keratinization begins; absent in thin skin.

Stratum lucidum

A clear, metabolically dead epidermal layer lacking nuclei and organelles that serves as a line of defense; found only in thick skin.

Stratum corneum

The outermost, metabolically dead epidermal layer composed of 20 to 30 layers of keratinized squamous cells that continuously shed to provide defense against the external environment.

Dermis

The vascular connective tissue layer beneath the epidermis that contains nerve fibers, glands, hair follicles, and two distinct layers: papillary dermis and reticular dermis.

Dermal papillae

Cone-like projections extending from the papillary dermis that anchor the dermis to the deep epidermis to reduce movement and friction.

Papillary dermis

The superficial dermal layer composed of areolar tissue and mostly dense irregular connective tissue that forms dermal papillae.

Reticular dermis

The deeper dermal layer composed of dense irregular connective tissue with elastic fibers, which provides strength and elasticity to the skin.

Hypodermis

The deep subcutaneous layer composed mainly of adipose tissue and some areolar tissue that provides thermal insulation, shock absorption, deep sensation, and serves as an injection site.

Paw pads

Heavily insulated thick skin structures featuring a very thick stratum corneum, underlying adipose tissue, all five epidermal layers, and exocrine sweat glands in small animals.

Planum nasale

The pigmented and hairless surface of the nose that represents thin skin lacking both the stratum lucidum and stratum granulosum layers.

Primary hair

Thick, long guard hairs that are slightly water-repellent and assist in temperature regulation.

Secondary hair

Shorter, thinner, often wavy hairs that serve as an undercoat.

Tactile hair

Thick, long, heavily innervated sensory touch hairs (commonly appearing as whiskers) that act as touch receptors.

Arrector pili muscle

Smooth muscle tissue attached to a hair follicle that contracts to make the hair shaft rigid and erect for thermal insulation in large animals or behavioral displays in small animals.

Sebaceous glands

Holocrine exocrine glands that secrete sebum into the hair follicle to moisten hair, prevent desiccation, and provide surface immunity.

Endocrine glands

Glands composed of glandular epithelium that secrete their substances directly into the bloodstream.

Exocrine glands

Glands lined by cuboidal or columnar epithelium that secrete substances onto the apical surface of an epithelium, cavity, lumen, or body exterior.

Merocrine gland

A classification of exocrine gland that produces and secretes substances directly without loss of cellular material.

Apocrine gland

A classification of exocrine gland where secretory product accumulates at the cell's apical surface and is released by pinching that portion of the cell off.

Holocrine gland

A classification of exocrine gland where secretory cells accumulate substance and completely disintegrate to release their contents.

Eccrine sweat glands

Sweat glands that discharge secretory products directly onto the skin surface, found specifically in the paw pads of small animals.

Apocrine sweat glands

Sweat glands in the epidermis that empty their contents directly into hair follicles via merocrine secretion; found in the external ear canal of small animals.

Anal sacs

Paired cutaneous structures located at the 4 and 8 o'clock positions of the anus, connected by a single duct and lined with sebaceous glands, that secrete a foul-smelling substance.

Tail glands

Glandular structures situated on the dorsal aspect of the tail containing sebaceous and apocrine glands used for inter-animal identification.

Cutaneous pouches of the sheep

Skin infoldings located in the infraorbital, interdigital, and inguinal regions that contain numerous sebaceous glands secreting lanolin.