DERMATOLOGY MG

The Integumentary System

  • Comprises skin and associated structures.

  • Functions include protection, regulation, sensation, and vitamin D synthesis.

Layers of Skin

3 Main Layers

  • Epidermis: Thin, cellular membrane layer.

  • Dermis: Dense, fibrous connective tissue layer.

  • Subcutaneous Tissue (Hypodermis): Thick layer containing fat.

Epidermis

  • Outermost Layer: Composed of squamous epithelium, arranged in several layers (strata).

  • Types of Skin Cells:

    • Stratum corneum: Outermost layer of dead cells.

    • Stratum lucidum: Clear layer; found only in thick skin.

    • Stratum granulosum: Transitional layer.

    • Stratum spinosum: Also known as prickle cell layer.

    • Stratum germinativum: Basal cell layer where cell division occurs.

  • Lacks blood vessels; relies on dermis for nutrients.

Dermis

  • Inner Layer: Composed of collagen and elastic fibers.

  • Collagen: Fibrous protein; provides strength.

  • Structure: Contains blood vessels, lymph vessels, nerve fibers, hair follicles, sweat glands, and sebaceous glands.

  • Stretch Marks: Result from overstretching during pregnancy.

Subcutaneous Layer (Hypodermis)

  • Innermost Layer: Thickest; contains lipocytes (fat cells).

  • Functions: Protection of deeper tissues, heat insulation.

Sweat Glands (Sudoriferous glands)

  • Number: Approximately 2 million across the body.

  • Function: Produce sweat (perspiration).

  • Composition of Sweat: Mostly water with dissolved salts (1% of total).

  • Odor Formation: Breakdown of substances in sweat by skin bacteria contributes to body odor.

Sebaceous Glands

  • Location: Dermal layer; absent in palms and soles.

  • Secretion: Sebum lubricates skin and hair; helps minimize water loss.

  • Relation to Hair Follicles: Influenced by sex hormones.

  • Acne Formation: Caused by overproduction of sebum.

Hair

  • Composition: Meshwork of horny cells and melanocytes.

  • Growth Rate: About ½ inch (1.3 cm) a month.

  • Distribution: Approximately 100,000 hairs on the scalp.

Nails

  • Nail Structure: Hard keratin plate covering the dorsal surface of fingers and toes.

  • Components:

    • Nail plate: Exposed part.

    • Lunula: Half-moon region; appears whitish.

    • Cuticle: Band of epidermis at the base and sides.

    • Paronychium: Soft tissue around the nail border.

Skin Structures

  • Components include hair shaft, pore, epidermis, melanocyte, nerve cell, dermis, sebaceous gland, arrector pili muscle, sudoriferous gland, hair root, and blood vessels.

Skin Lesions

  • Cyst: Closed sac containing fluid or solid material (e.g., pilonidal cyst).

  • Fissure: Crack-like sore in skin or mucous membrane (e.g., anal fissure).

  • Fistula: Abnormal passageway (e.g., recto-vaginal fistula).

  • Ulcer: Open sore or erosion in mucous membrane (e.g., pressure ulcer).

  • Macule: Small flat discoloration of the skin (e.g., bruises, freckles).

  • Polyp: Stalk-like growth from membrane surface (e.g., nasal polyp).

  • Vesicle/Bullae: Small clear fluid collections; larger vesicle known as bullae (e.g., burns).

  • Hives (Urticaria): Red, itchy raised areas due to allergies.

Skin Disorders

  • Alopecia Areata: Hair-loss condition typically affecting the scalp.

  • Ecchymosis: Bruise resulting from ruptured capillaries.

  • Albinism: Congenital disorder characterized by absence of melanin.

  • Vitiligo: Loss of pigmentation in skin.

  • Acne Vulgaris: Common skin disease; characterized by papules and pustules.

  • Burns: Classified into degrees based on severity.

    • First Degree: Superficial, no blisters.

    • Second Degree: Involves dermis, blisters present.

    • Third Degree: Damaged and destroyed tissue.

Skin Cancer Types

  • Basal Cell Carcinoma (BCC): Malignant tumor of the basal epidermis.

  • Squamous Cell Carcinoma (SCC): Tumor from squamous epithelial cells.

  • Malignant Melanoma: Highly malignant skin cancer originating in melanocytes.