Integument Flashcards
Basal Layer (Stratum Basale)
Adjacent to the dermis. Once cell layer thick. Mitotically active cuboidal or low columnar cells (ie stem cells) that give rise to the cell layers above. Cytoplasm is basophilic due to abundance of ribosomes. Cells synthesize keratin and forms keratin filaments or tonofilaments. Cells contain pigment granules called melanosomes that form a cap over the nucleus to protect from the sun.
Spinous Layer (Stratum Spinosum)
Thickest of the four layers. Cells are cuboidal or flattened cuboidal. Basal cells that lose their adherence to the basement membrane. Cells are tightly bound with desmosomes and numerous cytoplasmic processes that look like “spines” under a light microscope. Keratin filaments in the cytoplasm form bundles called tonofibrils that are anchored to the attachment plaques of the desmosomes.
Granular Layer
3-5 layers of flattened nucleated cells that contain keratohyaline granules. Compact the tonofibrils together. Basophilic. Membrane coating granules (lamellar bodies) that discharge their contents into the EC spaces to form a barrier for water retention.
Cornified Layer (Stratum Corneum)
Most superficial layer comprised of dead cells filled with keratin. Deepest cells are coated with lipids to form the water barrier. Deepest have desmosomes; superficial do not. Major difference between thick and thin skin is the thickness of this layer.
Keratosis Pilaris
Excessive accumulation of keratin/dead cells in hair follicles. More common in people with dry skin or eczema.
Stratum Lucidum
Thick skin between the granular and and cornified layers. Extremely flattened cells without organelles.
Melanocyte
Derived from neural crest cells. Reside in basal layer. Cells produce melanin in melanosomes, which are phagocytosed by keratinocytes. Extensive contact with as many as 30 keratinocytes in basal and spinal layer. Phagocytosed melanosomes and reside superior to the nucleus. Protects DNA. Color variations is the amount of melanosomes. Pale cytoplasm.
Langerhans Cells
Pale staining with numerous dendritic processes. Found in all living layers of the epidermis. Antigen presenting cells to T lymphocytes. Cutaneous hypersensitivity reactions. Contact allergic dermatitis.
Merkel’s Cells
Modified keratinocytes that reside in the basal layer. Most associated with nerve terminals and function as mecanosensory receptors. Rounded cells. Fine touch and discrimination of form and texture. Neuroendocrine or nerve terminal.
Dermis
Connective tissue that supports the epidermis.
Papillary Layer
Superficial layer comprised of loose CT. Characterized by papillae that interdigitate with epidermal ridges. Strengthen epidermal-dermal junction. Thick skin has dermal ridges, whose pattern is responsible for finger prints. Contains blood vessels, nerves, and cells such as fibroblasts, mast cells, and macrophages. Provide nutrients to the non vascular epidermis.
Reticular Layer
Thick layer of dense CT. More fibers (collagen and elastic) and fewer cells. Blood vessels, nerves, and glands are present.
Hypodermis
Loose CT. Epidermal derivatives (eg glands) fat, vessels, nerves. “Superficial fascia.” Loosely bind skin to underlying structures so the skin slides freely over them. Insulation and shock absorber.
Hair Follicle
Tube of epithelial cells that encloses a hair. Hair bulb: dilated portion where the hair is anchored. Dermal papilla: CT + capillaries that nourish the follicle. Melanocytes: color of hair. Hair matrix: cells surrounding papilla. Germinative cells that form hair.
Hair
Root and shaft. Inner core: medulla. Middle layer: Cortex. Outer layer: cuticle. Cells are like shingles.
Pilosebaceous Unit
Arrector pili muscle and one or more sebaceous glands.
Arrector Pili Muscle
Smooth muscle that is anchored to the hair follicle at one end and the dermis at the other. Causes follicle to become more vertical when it contracts. “Elevated” areas of skin and pulls dermis down. Effort to trap warm air near the skin surface for insulation.
Sebaceous Glands
Oily secretion called sebum which is discharged into the hair follicle and lubricates the hair. Holocrine secretion. Dermis and hypodermis of the skin. Simple branched acinar glands (several round secretory units that empty into one duct). Blockage of the duct causes acne.
Seborrhea
Overactivity of sebaceous gland. “Cradle Cap” in infants and dandruff in adults. They do not shed normally.
Sweat Glands
Simple coiled tubular glands. Merocrine. Myoepithelial cells expel secretions. Eccrine and apocrine types.
Eccrine Sweat Glands
Evaporate cooling. Reside in the dermis or hypodermis. Also participate in excretion of salts, lactate, and urea. Secretory portion: simple cuboidal epithelium with myoepithelium (help expel secretions). Duct: stratified cuboidal (2 layers). Dark and clear cells in the secretory portion.
Dark Cells
Pyramidal cells with secretory granules containing glycoproteins.
Clear cells
Produce water and electrolytes; no granules.
Apocrine Sweat Glands
Axillary and anogenital regions. Simple coiled tubular associated with hair follicles. Secretions stored in lumen of glands before release. Pheromones and odor comes from bacteria. Lumen is wider than sweat glands.
