BSC 2085: Anatomy and Physiology 1

Lecture on the Integumentary System

Introduction

• Instructor: Professor Mariah Evans
• Focus: Skin and bones for the next exam.

Overview of the Integumentary System

• Includes skin, hair, and nails.
• Involves sweat glands and sebaceous glands.

Structure of Skin

• Two Main Regions:
  • Epidermis: Superficial layer.
  • Dermis: Underlying layer.
• Hypodermis: Beneath the skin, not a true skin layer but shares components.

Layers of the Epidermis

• Thick Skin: 5 layers.
• Thin Skin: 4 layers.
• Layers (from deep to superficial):
  • Stratum Basale: Actively mitotic, basal layer.
  • Stratum Spinosum: Prickly layer with spiny keratinocytes.
  • Stratum Granulosum: Granular layer with keratohyalin granules.
  • Stratum Lucidum: Clear layer, only in thick skin.
  • Stratum Corneum: Horny layer, 20-30 layers of dead cells.

Cells in the Epidermis

• Keratinocytes: Contain keratin.
• Melanocytes: Produce melanin for skin color.
• Dendritic (Langerhans) Cells: Immune function, phagocytize invaders.
• Tactile (Merkel) Cells: Sensory receptors for touch.

Dermis

• Layers:
  • Papillary Layer: Areolar connective tissue, tactile corpuscles.
  • Reticular Layer: Dense irregular connective tissue, collagen fibers.
• Contains blood vessels and nerve fibers.

Skin Color

• Melanin: Pigment protein for skin, eye, and hair color.
• Carotene: Yellow-to-orange pigment.
• Hemoglobin: Pinkish hue in fair-skinned individuals.

Sun Exposure and Skin Damage

• UV damages DNA, can lead to cancer.
• Destroys folic acid, necessary for DNA synthesis.
• Photosensitivity from drugs (antibiotics, antihistamines).

Abnormal Skin Colors

• Cyanosis: Blue skin, lack of oxygen.
• Erythema: Redness from various causes.
• Pallor: Pale skin, can indicate anemia or fear.
• Jaundice: Yellow skin, often due to liver issues.
• Bronzing: Indicative of steroid hormone imbalance.
• Bruises: Blood clots under the skin.

Hair

• Functions: Sensory, protection, heat retention.
• Structure: Keratinized, color from melanin.
• Hair growth cycles and thinning with age.
• Alopecia: Hair loss.
• Hirsutism: Excessive hair growth.

Nails

• Made of hard keratin.
• Fingernails have free edges without nerve endings.

Glands

• Sweat Glands: Eccrine (most numerous), Apocrine (axillary/anogenital).
• Sebaceous (Oil) Glands: Secrete sebum, lubricate skin and hair, can lead to acne.

Functions of Skin

• Protection: Physical, chemical, and biological barriers.
• Body Temperature Regulation: Sweating and blood flow.
• Cutaneous Sensations: Sensory receptors for touch.
• Metabolic Functions: Vitamin D synthesis.
• Blood Reservoir: Holds 5% of blood volume.
• Excretion: Nitrogenous wastes through sweat.

Skin Cancer and Burns

• Types of Skin Cancer: Basal cell carcinoma, squamous cell carcinoma, malignant melanoma (most deadly).
• Burns:
  • First Degree: Epidermal damage.
  • Second Degree: Affects dermis, blistering.
  • Third Degree: Full thickness, requires grafting.

Conclusion

• Review of integumentary system structures and functions.