HUMHIS LEC - ENDTERM INTEGUMENTARY SYSTEM

The largest organ in the human body that forms the outer protective covering

Skin

The outermost layer of the skin composed of keratinized stratified squamous epithelium

Epidermis

The dominant cell type in the epidermis responsible for producing keratin

Keratinocytes

Epidermal cells located in the stratum basale that produce melanin pigment

Melanocytes

Specialized membrane-bound vesicles that package and transfer melanin to keratinocytes

Melanosomes

Form of melanin pigment responsible for brown and black coloration

Eumelanin

Form of melanin pigment responsible for red and yellow coloration

Pheomelanin

Antigen-presenting dendritic cells in the stratum spinosum that provide immune defense

Langerhans cells

Sensory mechanoreceptors located in the stratum basale involved in light touch perception

Merkel cells

Deepest epidermal layer consisting of a single row of cuboidal/columnar stem cells

Stratum basale

Thickest epidermal layer characterized by desmosome attachments giving cells a spiny appearance

Stratum spinosum

Intermediate filaments produced by keratinocytes in the stratum spinosum that bundle into tonofibrils

Tonofilaments

Epidermal layer consisting of 3 to 5 layers of flattened cells containing filaggrin-rich granules

Stratum granulosum

Protein component of keratohyalin granules found in the stratum granulosum

Filaggrin

Lipid-rich membrane-bound granules in the stratum granulosum that form a waterproof barrier

Lamellar bodies

Translucent layer of flattened dead eosinophilic cells filled with eleidin, found only in thick skin

Stratum lucidum

Clear intermediate protein present in dead keratinocytes within the stratum lucidum

Eleidin

Most superficial layer of the epidermis consisting of 20 to 30 layers of dead, anucleate squames

Stratum corneum

Connective tissue layer beneath the epidermis that reaches a maximum thickness of 4 mm on the back

Dermis

Superficial dermal layer composed of loose (areolar) connective tissue forming papillae

Papillary layer

Finger-like projections of the papillary dermis that interdigitate with epidermal ridges

Dermal papillae

Deeper dermal layer made of dense irregular connective tissue rich in type I collagen and elastic fibers

Reticular layer

Subcutaneous layer composed of loose connective tissue and adipocytes providing insulation and cushioning

Hypodermis

Hairless skin type found on the palms, soles, lips, glans penis, clitoris, and labia minora

Glabrous skin

Visible portion of the hair that projects above the skin surface

Hair shaft

Epidermal invagination that surrounds the root of the hair

Hair follicle

Smooth muscle attached to the hair follicle that contracts to produce goosebumps

Arrector pili muscle

Active growth phase of the hair growth cycle

Anagen

Involution phase of the hair growth cycle

Catagen

Resting phase of the hair growth cycle

Telogen

Branched acinar glands that secrete sebum into hair follicles

Sebaceous glands

Secretory process where entire cells disintegrate to release their product, as seen in sebaceous glands

Holocrine secretion

Coiled tubular sweat glands distributed across most of the body that function in thermoregulation

Eccrine sweat glands

Larger sweat glands located in the axilla, areola, and perineum that activate at puberty and produce odor after bacterial action

Apocrine sweat glands

Encapsulated tactile receptors in the papillary dermis that detect light touch and low-frequency vibration

Meissner's corpuscles

Large sensory receptors located in the deep dermis and hypodermis sensitive to deep pressure and vibration

Pacinian corpuscles

Sensory receptors in the dermis that detect skin stretch and tension

Ruffini endings

Unencapsulated nerve endings in the epidermis and dermis that detect pain and temperature

Free nerve endings

Hard keratinized plates situated on the dorsal surface of each distal phalanx

Nails

Proximal part of the nail embedded beneath the skin fold that generates the nail plate

Nail root

Epithelial layer beneath the nail plate continuous with stratum basale and stratum spinosum

Nail bed

Crescent-shaped white region at the proximal end of the nail plate representing the visible matrix

Lunula

Cuticle fold of stratum corneum extending over the base of the nail plate

Eponychium

Thickened epidermal layer beneath the free edge of the nail plate

Hyponychium

Skin type found on palms and soles containing stratum lucidum and lacking hair follicles

Thick skin

Epidermal precursor molecule converted by UV light into vitamin D3

7-dehydrocholesterol