Integumentary System Lecture Flashcards

Comprehensive vocabulary flashcards covering the histology, cellular composition, layers, and clinical conditions of the integumentary system.

Keratinocytes

The major cell type of the epidermis, comprising approximately $90\%$ of epidermal cells, which produce keratin to waterproof and strengthen the skin.

Melanocytes

Cells comprising approximately $8\%$ of the epidermis that produce melanin within melanosomes to protect nuclear DNA from UV radiation.

Langerhans’ cells

Antigen-presenting cells located in the stratum spinosum that initiate immune responses and provide immune surveillance.

Merkel cells

Touch receptors located in the stratum basale that are responsible for detecting sustained touch and pressure.

Vitamin D Synthesis

The process by which UV radiation converts $7$-dehydrocholesterol into vitamin $D_3$ (cholecalciferol) in the skin.

Stratum Basale

The deepest epidermal layer consisting of a single layer of basophilic cuboidal to columnar stem cells responsible for regeneration.

Stratum Spinosum

A layer of $5\text{--}10$ layers of polygonal cells connected by desmosomes, where keratin synthesis begins.

Stratum Granulosum

Layers of flattened keratinocytes containing dark keratohyalin granules and lipid-filled lamellar bodies that create a water barrier.

Stratum Lucidum

A transparent layer of densely packed keratinized cells without nuclei, found only in the thick skin of the palms and soles.

Stratum Corneum

The outermost protective layer composed of flattened, anucleate keratinized cells called corneocytes embedded in a lipid matrix.

Papillary Layer

The superficial $1/5$ of the dermis composed of loose areolar connective tissue containing capillary loops and Meissner’s corpuscles.

Reticular Layer

The lower $4/5$ of the dermis composed of dense irregular connective tissue providing tensile strength and elasticity via collagen and elastic fibers.

Hypodermis

Also known as subcutaneous tissue, it is composed of loose connective and adipose tissue that anchors skin to underlying structures and provides insulation.

Langer’s lines

Tension lines in the dermis formed by the arrangement of collagen and elastin fibers; incisions parallel to these lines heal with minimal scarring.

Meissner’s corpuscles

Specialized nerve endings located in the dermal papillae of hairless skin that detect light touch and texture.

Pacinian corpuscles

Sensory receptors found in the deep dermis or hypodermis that respond to deep pressure and vibration.

Arteriovenous (AV) anastomoses

Dermal shunts between arterioles and venules that regulate body temperature by controlling blood flow to the skin surface.

Sebaceous Glands

Simple branched alveolar glands that use holocrine secretion to release sebum, an oily product that lubricates skin and hair.

Eccrine (Merocrine) Glands

Widely distributed simple coiled tubular glands that secrete watery sweat for thermoregulation through evaporative cooling.

Apocrine Glands

Large glands in the axillae and genital regions that secrete a viscous, protein-rich fluid into hair follicles, becoming odorous upon bacterial action.

Hair Matrix

The layer of mitotically active cells in the hair bulb, derived from the stratum basale, which produces the hair shaft.

Arrector pili

Smooth muscle attached to hair follicles that contracts in response to cold or fear, producing "goosebumps."

Albinism

An inherited condition characterized by a lack of melanin production due to enzyme defects, such as tyrosinase deficiency.

Keloids

Raised scars caused by fibroblast proliferation and overproduction of collagen during the wound healing process.

Decubitus ulcers

Ischemic necrosis or pressure sores caused by prolonged pressure over bony areas, leading to a lack of blood flow.

Eponychium

The cuticle of the nail, formed by the stratum corneum of the proximal nail fold, protecting the nail matrix from infection.

Desquamation

The continuous shedding of surface cells from the stratum corneum, regulated by proteolytic enzymes.

Keratohyalin granules

Diagnostic markers found in the stratum granulosum; they are absent in conditions like psoriasis due to defective keratinization.

Role of Keratin in Skin

Keratin provides structural strength to skin, making it resilient to damage and preventing water loss.

Function of Melanin

Melanin protects the skin from UV radiation and influences skin color.

Function of Sebum

Sebum lubricates and protects the skin and hair, preventing dryness and providing a barrier against pathogens.

Epidermal Renewal Process

The skin renews itself approximately every 28 days through the process of desquamation and regeneration.

Importance of Eccrine Sweat Glands

Eccrine glands are crucial for thermoregulation through sweat secretion that cools the body.

Structure of Hair Follicles

Hair follicles are complex structures derived from the epidermis that anchor hair and facilitate growth.

Function of the Hypodermis

The hypodermis provides insulation, stores energy, and anchors the skin to underlying tissues.

Role of Immune Cells in Skin

Langerhans' cells in the skin act as a first line of defense by presenting antigens to T cells.

Mechanism of Pressure Ulcers Formation

Decubitus ulcers form due to prolonged pressure depriving skin tissues of blood flow, leading to cell death.

Types of Skin

Skin can be classified into thin skin, which covers most of the body and has fewer layers, and thick skin, found on the palms and soles, which is more protective and resilient.

Microscopic Anatomy of Epidermis

The epidermis consists mainly of keratinocytes organized in layers (strata) that serve as a barrier to pathogens and water loss, along with melanocytes and Langerhans’ cells for protection and color.

Microscopic Anatomy of Dermis

The dermis comprises two layers (papillary and reticular) containing collagen and elastin fibers that provide structural support, elasticity, and housing for blood vessels and nerves.

Clinical Importance of Langer Lines

Langer lines indicate the orientation of collagen fibers in the dermis; incisions made parallel to these lines heal better and result in less scarring.

Keratinocytes

The primary cells of the epidermis that produce keratin, providing waterproofing and protection to the skin.

Melanocytes

Cells in the epidermis responsible for producing melanin, which protects against UV radiation and determines skin pigmentation.

Langerhans’ Cells

Dendritic cells in the epidermis that play a crucial role in immune response by presenting antigens to T cells, facilitating skin protection.

Merkel Cells

Specialized cells located in the stratum basale of the epidermis that function as touch receptors, participating in the sensation of light touch.

Sensory Functions of Skin

The skin contains various receptors (Meissner’s corpuscles, Pacinian corpuscles, etc.) that detect touch, temperature, and pain, acting as a sensory organ.

Structure of Hair

Hair is composed of keratinized cells formed in hair follicles, playing roles in protection, insulation, and sensory perception.

Structure of Nails

Nails are protective, keratinized structures that enhance tactile sensitivity and help in grasping objects.

Functions of Skin Glands

Sebaceous glands secrete sebum for lubrication, while sudoriferous (sweat) glands help with thermoregulation and waste removal through sweat.

Clinical Importance of Skin

The skin serves as the first line of defense against pathogens, regulates body temperature, and provides sensory feedback, highlighting its importance in overall health.