Skin Structure and Functions Quiz

Merkel Cells

• Merkel cells are mechanoreceptors responsible for light touch
• Eccrine glands regulate thermoregulation, mostly found in palms and soles
• Apocrine glands begin functioning at puberty, in axillary and inguinal regions, associated with the pilosebaceous apparatuses
• Sebaceous glands present throughout the body, excluding palms and soles
• Macule: flat discoloration less than 1 cm
• Patch: flat discoloration greater than 1 cm
• Papule: elevated solid lesion less than 1 cm, can merge into plaques
• Plaque: elevated solid lesion greater than 1 cm
• Nodule: elevated solid lesion with depth, a large nodule might be considered a tumor
• Vesicle: collection of free fluid less than 1 cm
• Bulla: collection of free fluid greater than 1 cm
• Pustule: collection of pus with free fluid
• Wheal: superficial, pale swelling, surrounded by erythema, lasting less than 24 hours, seen in urticaria
• Scale: excess dead epidermal cells due to abnormal keratinization and shedding
• Crust(scab): collection of dried serum and cellular debris
• Erosion: focal loss of epidermis, heals without scars
• Ulcer: focal loss of dermis and epidermis, heals with scars
• Fissure: linear loss of dermis and epidermis, sharp edges
• Scar: abnormal formation of connective tissue after injury or surgery, can be atrophic or hypertrophic

Diagnostic Skin Lesions

• Excoriation: linear erosion caused by scratching
• Comedone (blackhead): dilated opening of pilosebaceous duct, hypercornification
• Closed comedone: narrow opening
• Acne: milia, small keratin cysts without openings
• Cyst: circumscribed lesion with a lumen
• Petechiae: blood deposit less than 1 cm
• Purpura: blood deposit larger than 1 cm
• Burrow (tunnel): narrow, winding channel from parasites like Sarcoptes scabiei (scabies)
• Lichenification: thickened epidermis from scratching, accentuated skin lines
• Telangiectasia: dilated superficial blood vessels

Cutaneous Manifestations of Systemic Diseases

• Diabetes Mellitus
  • 30% develop skin disorders
  • Necrobiosis lipoidica
  • Granuloma annulare
  • Acrochordons
• Necrobiosis Lipoidica
  • 75-1% of patients have or will develop DM
  • Occurs on the anterior lower leg
  • Oval, slow-expanding patch with red border, central atrophy/ulceration possible
  • Small risk of squamous cell carcinoma

Granuloma Annulare

• 12% of patients with GA have DM, chronic relapsing GA
• Can be generalized or localized, affecting the hands and feet
• Skin-colored papules, undergoing central regression, forming rings

Dyslipoproteinemia and Xanthomas

• Lipid deposits in skin and tendons (xanthomas)
• Xanthelasma: most common form, eyelids
• Eruptive xanthoma: indication of hypertriglyceridemia; papules on buttocks and limbs
• Plane xanthomas: palmar creases
• Tuberous xanthomas: elbows, knees
• Tendinous xanthomas: tendons on elbows/knees, Achilles tendon, persistent
• Neurofibromatosis
  • Skin, CNS, eyes, bones
  • Hamarmatou tumors surrounding nerves
  • NF-1: most common
  • NF-2: bilateral acoustic neuroma + other tumors
  • NF-5: segmental

NF-1 Criteria

• 7 criteria, satisfying 2 sufficient for diagnosis
• Café au lait macules
• Neurofibromas
• Axillary freckling
• Lisch nodules (melanocytic hamartomata)
• Optic glioma
• Osseous lesions
• 1st degree relative with NF-1
• High lifetime malignancy risk