4: Body Membranes and Integumentary System

Flashcards covering body membranes, the layers of the skin (epidermis, dermis, hypodermis), epidermal cell types, pigmentation types, skin cancers, and skin appendages based on the KINS 1131 lecture.

Body membranes

Thin sheets of tissue that cover the surface of the outer body, internal organs, and internal body cavities, typically composed of an epithelium bound to underlying connective tissue proper.

Mucous membranes

Wet membranes that line body cavities that open to the outside of the body, such as the digestive, respiratory, and urogenital tracts.

Serous membranes

Two-layered wet membranes (visceral and parietal) of closed ventral body cavities, separated by serous fluid to reduce friction.

Synovial membranes

Wet membranes that line the cavities of joints, tendon sheaths, and bursae, producing synovial fluid for lubrication and mobility.

Cutaneous membrane

A dry membrane known as the skin, consisting of keratinized stratified squamous epithelium (epidermis) on 80% dense irregular and 20% areolar connective tissue (dermis).

Integumentary system

A complex set of organs consisting of the skin and its appendages, including sweat and oil glands, hairs, and nails.

Epidermis

The multi-layered (stratified) surface epithelium and outermost protective shield of the body, which is non-vascularized.

Dermis

A tough, leathery layer making up the bulk of the skin composed mostly of dense connective tissue; it is the only layer of the skin that is vascularized.

Keratinocytes

The most common epidermal cells that produce keratin, the fibrous structural protein providing protective properties.

Callus

A thickening of the epidermis caused by persistent friction which accelerates keratin production.

Stratum corneum

The most superficial epidermal layer consisting of 20-30 layers of dead, flat membranous sacs filled with keratin and extracellular glycolipids.

Stratum basale

The deepest epidermal layer consisting of a single row of actively mitotic stem cells and occasional melanocytes and tactile epithelial cells.

Dendritic cells (Langerhans cells)

Immune cells arising from bone marrow that migrate to the epidermis to engulf foreign substances and present them to lymphocytes.

Tactile cells (Merkel cells)

Sensory receptors for touch located at the epidermal-dermal junction.

Melanocytes

Cells found in the deepest part of the epidermis that synthesize melanin to protect nuclei from UV radiation.

Eumelanin

A dark, UV-absorbent, and antioxidant pigment responsible for darkening the skin and providing photoprotection.

Pheomelanin

A pigment that imparts pinkish color to areas like the lips and nipples but produces free radicals in response to UV radiation.

Basal cell carcinoma

The most common and frequently occurring form of skin cancer.

Melanoma

The most serious form of skin cancer where UV-induced DNA damage triggers mutations in melanocytes leading to uncontrolled growth.

ABCDE approach

The method recommended by the American Academy of Dermatologist Association for checking moles regularly for potential cancer.

Papillary dermis

The thin, superficial layer of the dermis composed of areolar tissue containing capillaries that allows immune cells to patrol for bacteria.

Reticular dermis

The deep, coarse layer comprising approximately $80\%$ of dermal thickness, made of dense irregular connective tissue proper.

Dermal papillae

Peg-like projections of dermal tissue that indent the epidermis, containing capillaries or sensory receptors.

Friction ridges

Epidermal ridges lying atop dermal ridges that enhance gripping ability and leave identifying films of sweat called fingerprints.

Cleavage lines

Representations of separations between underlying collagen fiber bundles in the reticular dermis used to guide surgical incisions for better healing.

Hypodermis

Subcutaneous tissue under the dermis (not part of the skin) consisting mostly of adipose tissue that anchors skin and acts as a shock absorber.

Arrector pili

Small muscles attached to hair follicles that cause piloerection (goosebumps) and assist in sebum release.

Sebaceous glands

Small glands abundant in the scalp and face that secrete sebum, an oily antimicrobial substance, into hair follicles.

Eccrine glands

The major sweat glands of the human body that open directly onto the skin surface and are essential for thermoregulation and electrolyte homeostasis.

Apocrine glands

Larger sweat glands located in axillary and genital regions that develop during puberty and open into hair follicles, often associated with body odor.