CH5.3 Integumentary system: Dermis

Vocabulary flashcards covering the structural composition, layers, markings, and tactile receptors of the dermis, epidermis, and subcutaneous layer.

Dermis

Strong, flexible connective tissue layer of the skin composed of collagen and elastic fibers, containing fibroblasts, macrophages, mast cells, and leukocytes; divided into papillary and reticular layers.

Papillary Layer

The superficial layer of the dermis composed of areolar connective tissue;

Forms dermal papillae and contains the subcapillary plexus, and dermal ridges (thick skin, forms friction ridges like fingerprints)

Sensory Structures: tactile (Meissner’s) corpuscles, and free nerve endings.

Dermal Papillae

Projections of the papillary dermis into the epidermis that increase surface area contact and contain capillary loops, free nerve endings, or tactile receptors.

Friction Ridges

Skin markings in thick skin consisting of epidermal ridges lying on top of dermal ridges, whose crests feature sweat duct openings that produce fingerprints.

Tactile (Meissner's) Corpuscle

Encapsulated tactile receptor located in dermal papillae, consisting of highly intertwined dendrites enclosed by modified neurolemmocytes and dense irregular connective tissue; detects discriminative touch, light pressure, textures, and shapes.

Free Nerve Endings

Unencapsulated dendritic endings of sensory neurons found in the deep epidermis and papillary layer of the dermis that act as thermoreceptors, nociceptors, or mechanoreceptors detecting touch, pain, temperature, pressure, and itch.

Reticular Layer

Deeper, thicker layer of the dermis composed of dense irregular connective tissue surrounding hair follicles, sebaceous glands, sweat glands, nerves, and blood vessels.

Cleavage Lines

Lines of tension in the skin created by the directional alignment of collagen and elastic fiber bundles in the reticular dermis; parallel surgical incisions heal more quickly with less gaping.

Flexure Lines

Dermal folds that occur where the dermis is tightly bound to deeper structures at or near joints, visible as deep skin creases on palms, wrists, toes, and soles.

Lamellated (Pacinian) Corpuscle

Encapsulated receptor with dendritic endings enclosed by an inner core of neurolemmocytes and concentric layers of connective tissue, located in the dermis and subcutaneous layer to sense deep pressure and high-frequency vibration.

Bulbous (Ruffini) Corpuscle

Encapsulated receptor consisting of dendritic endings within connective tissue located in the dermis, subcutaneous layer, and joint capsules; senses continuous deep pressure and skin distortion.

End Bulb

Encapsulated receptor with dendritic endings ensheathed in connective tissue, located in the dermis and mucous membranes; senses light pressure and low-frequency vibration.

Hair Follicle Receptor (Root Hair Plexus)

Unencapsulated dendritic endings of sensory neurons surrounding hair follicles in the reticular layer of the dermis; detects movement of hair and light touch.

Tactile (Merkel) Disc

Unencapsulated receptor composed of flattened dendritic endings adjacent to specialized tactile cells in the stratum basale of the epidermis; detects light touch.

Hypodermis (Subcutaneous Layer)

Layer deep to the dermis composed of areolar and adipose connective tissue; anchors skin, stores energy, provides thermal insulation and shock absorption, and is not part of the integument proper.

Subcapillary Plexus

Network of blood vessels situated in the papillary layer of the dermis that provides nourishment to dermal papillae and the lower epidermis.

Dermal Vascular Plexus

Network of blood vessels located at the deep boundary of the reticular layer of the dermis and hypodermis that supplies blood to skin structures.

Stratum Corneum

Most superficial layer of the epidermis, composed of 20 to 30 layers of dead, flattened, anucleate, keratin-filled keratinocytes.

Stratum Lucidum

Thin, clear layer of 2 to 3 layers of anucleate, dead cells found only in thick skin such as palms of hands and soles of feet.

Stratum Granulosum

Epidermal layer of 3 to 5 layers of keratinocytes containing distinct cytoplasmic granules, marking the region where keratinization begins.

Stratum Spinosum

Layer of the epidermis with several layers of keratinocytes bound together by desmosomes and containing epidermal dendritic cells.

Stratum Basale

Deepest epidermal layer formed by a single row of cuboidal to low columnar cells resting on the basement membrane, where active cell division (mitosis) occurs.