Lecture Notes: The Integumentary System

Overview

• First organ system covered in A&P1.
• Focus: layers, cells, functions, and appendages of the integument.

Layers of the Integument

Primary Layers

• Epidermis: Most superficial layer.
• Dermis: Below the epidermis.
• Hypodermis: Supports the integument, rich in adipose tissue, not a part of the skin.

Characteristics

• Epidermis: Includes five sub-layers:
  • Stratum Corneum: Dead, keratin-packed cells.
  • Stratum Lucidum: Only in thick skin (palms, soles).
  • Stratum Granulosum: Keratinization starts here.
  • Stratum Spinosum: Contains dendritic cells, melanocytes.
  • Stratum Basale: Actively dividing stem cells.
• Dermis:
  • Papillary Layer: Loose areolar connective tissue, includes dermal papillae.
  • Reticular Layer: Dense irregular connective tissue, contains collagen and elastic fibers.

Functions of the Integument

• Protection: Acts as chemical, physical, and biological barriers.
• Thermoregulation: Via sweat glands and blood vessels.
• Sensation: Nerve endings and encapsulated receptors.
• Metabolic Functions: Vitamin D synthesis.
• Blood Reservoir: Holds up to 5% of blood volume.
• Excretion: Via sweat.

Appendages of the Skin

Hair

• Composed of hard keratin.
• Follicle structure includes:
  • Hair bulb and papilla.
  • Arrector pili muscle causes goosebumps.

Glands

• Sweat Glands:
  • Eccrine: Directly to the epidermis, important for thermoregulation.
  • Apocrine: Associated with hair follicles.
• Sebaceous Glands: Produce sebum, lubricates hair and skin.

Homeostatic Imbalances

Skin Color Diagnostics

• Cyanosis: Blue skin, low oxygen.
• Erythema: Redness, inflammation.
• Pallor: Pale, low blood pressure/anemia.
• Jaundice: Yellow, liver disorder.
• Bronzing: Addison's disease sign.
• Bruising: Blood clots under skin.

Skin Cancer

• Basal Cell Carcinoma: Least malignant.
• Squamous Cell Carcinoma: Involves keratinocytes, red and scaly.
• Melanoma: Dangerous, needs early detection (ABCD rule: Asymmetry, Border, Color, Diameter).

Burns

• First Degree: Epidermis only.
• Second Degree: Epidermis and upper dermis, blisters.
• Third Degree: Full thickness, requires skin grafting.

Summary

• Understand the anatomy and functions of the integumentary system.
• Know the layers, cell types, and their roles.
• Recognize skin appendages and their functions.
• Identify homeostatic imbalances and their implications.