PSIO110 Module 4 Tutorial: The Integumentary System Notes

Functions of the Skin

• List of Five Functions:
  1. Protection: Physical defense against force, friction, heat, and cold.
  2. Thermoregulation: Regulating body temperature.
  3. Storage of Blood: Storage of blood within the skin's blood vessels.
  4. Cutaneous Sensation: Sensory perception through nerve endings.
  5. Vitamin D Synthesis: Production of Vitamin D.
  6. Excretion and Absorption: Elimination of waste and absorption of substances.

Layers of the Skin

• Two Main Layers:
  • Epidermis
  • Dermis

Epidermis

• Layers of Thin Skin (Deep to Superficial):
  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum corneum
• Note: Stratum lucidum is present only in thick skin.

Types of Epidermal Cells

1. Keratinocytes: Found in all layers from stratum basale to stratum corneum.
2. Melanocytes: Primarily located in the stratum basale.
3. Intraepidermal Macrophages (Langerhans cells): Predominantly in the stratum spinosum.
4. Tactile Epithelial Cells (Merkel cells): Located in the stratum basale.

Dermis

• Two Regions:
  1. Papillary Region:
     • Contains collagen and elastin fibres.
     • Contains Meissner corpuscles (tactile receptors).
     • Contains free nerve endings.
  2. Reticular Region:
     • Contains collagen and elastin fibres.
     • Contains blood vessels, hair follicles, nerves, sebaceous glands, and sudoriferous glands.
     • Attached to the subcutaneous layer.
     • Contains fibroblasts and macrophages.

Skin Pigments

• Three Pigments Influencing Skin Color:
  1. Melanin: Ranges from pale yellow to reddish-brown.
  2. Haemoglobin: Red/pink color.
  3. Carotene: Yellow/orange color.

Sudoriferous Glands

• Two Types:
  1. Eccrine Sweat Glands:
     • Distributed throughout the body.
     • Mostly found in the forehead, palms, and soles.
  2. Apocrine Sweat Glands:
     • Found mainly on the skin of the axilla, groin, areola of breasts, and the bearded area of the face.

Accessory Skin Structures Labeling

• Key Structures:
  • Hair shaft
  • Hair root
  • Arrector pili muscle
  • Eccrine sweat gland
  • Sebaceous gland
  • Hair root plexus
  • Bulb
  • Blood vessels
  • Apocrine sweat gland

Nail Structure

• Components:
  • Nail root
  • Eponychium (cuticle)
  • Lunula
  • Nail bed
  • Nail body
  • Free edge

Skin Types: Thick vs. Thin

Vitamin D Synthesis

• Process Overview:
  1. UVB Exposure: Skin is exposed to UVB radiation.
  2. 7-dehydrocholesterol Conversion: 7-dehydrocholesterol in the skin converts to cholecalciferol (vitamin D3).
  3. Liver Conversion: Cholecalciferol is converted in the liver to 25-hydroxyvitamin D.
  4. Kidney Conversion: 25-hydroxyvitamin D is converted in the kidneys to 1,25-dihydroxyvitamin D, the active form of Vitamin D.
• Alternative Pathways:
  • Dietary intake of ergocalciferol (vitamin D2) from fortified foods and supplements.
  • Consumption of fish oils (D3).
• Equations:
  $UVB + 7-dehydrocholesterol \rightarrow cholecalciferol (vitamin D3)$
  $cholecalciferol \xrightarrow{Liver} 25-hydroxyvitamin D$
  $25-hydroxyvitamin D \xrightarrow{Kidney} 1,25-dihydroxyvitamin D$

Burns

Case Study: Melanoma Assessment

• Patient Background: Mrs. Sarah Thompson, 47, fair skin, history of mild sun exposure.
• Presentation: Dark, irregularly shaped spot on her left shoulder, present for years, recently grown and darkened.

Early Warning Signs of Melanoma (ABCDE Criteria)

• A - Asymmetry: The lesion has an irregular shape.
• B - Irregular Borders: The edges are not smooth.
• C - Uneven Colouration: The spot has multiple shades.
• D - Diameter: Larger than ordinary mole (6 mm).
• E - Evolving: Changing in size, shape, or color.

Case Study: Clinical Examination

• Application of ABCDE Criteria:
  • Asymmetry: Irregular shape, one side slightly larger.
  • Border: Slightly scalloped but generally well-defined.
  • Colour: Multiple shades of brown, no black, blue, or red.
  • Diameter: 5 mm.
  • Evolving: Mild darkening over the past year, no sudden changes, ulceration, or bleeding.

Case Study: Dermatological Assessment

• Referral: GP referred Mrs. Thompson to a dermatologist.
• Dermoscopic Examination: Symmetrical pattern, uniform pigmentation, no atypical vascular structures.
• Biopsy: Performed for confirmation.
• Histopathology: Revealed seborrheic keratosis, a common and harmless skin growth.

Case Study: Discussion

• Importance of Differentiation: Differentiating benign lesions from melanomas using the ABCDE criteria.
• Overall Assessment: Did not indicate malignancy despite some warning signs.
• Early Evaluation: Provides reassurance.
• Definitive Diagnosis: Dermoscopy and biopsy alleviated patient anxiety.
• Long-term Health: Regular skin checks and sun protection are essential.