Lecture Notes: Tissues, Membranes, Glands, and Skin - Focus on Membranes

Introduction

• Video Series: Tissues, Membranes, Glands, and Skin
• Current Focus: Membranes
  • Found lining and covering organs
  • Composed of more than one tissue, though some can be only epithelial or connective tissues
  • When composed of more than one tissue, they are considered simple organs

Learning Objectives

• Describe structure of different membranes: cutaneous, serous, mucous, and synovial
• Identify tissue types in the skin
• Reference: Saladin textbook, section 5.5, pages 160-166

Types of Membranes

Mucous Membranes (Mucosae)

• Location: Cavities open to the outside (e.g., respiratory system, GI tract)
• Function: Secrete mucus to keep the surface moist
• Tissue Composition:
  • Simple epithelium
  • Areolar connective tissue (lamina propria)
• Characteristics: Often called "wet membranes"

Serous Membranes (Serosa)

• Location: Closed body cavities (e.g., around lungs, heart, digestive organs)
• Function: Lubricate with serous fluid between layers
• Tissue Composition:
  • Simple squamous epithelium (mesothelium)
  • Areolar connective tissue
• Structure:
  • Double-layered: Visceral (close to organ) and Parietal (adheres to body wall)
  • Contains serous fluid between layers
  • Special Names: Pleura (lungs), Pericardium (heart), Peritoneum (digestive organs)

Cutaneous Membrane

• Example: Skin
• Characteristics: "Dry membrane," exposed to air
• Tissue Composition:
  • Keratinized, stratified squamous epithelium (epidermis)
  • Dense irregular connective tissue beneath
  • May include areolar connective tissue as a boundary layer

Synovial Membrane

• Location: Lining joint cavities in synovial joints (e.g., extremities)
• Characteristics: Not a true membrane, lacks true epithelial layer
• Structure:
  • Synoviocytes on areolar connective tissue
• Function:
  • Contains synovial fluid for lubrication
  • Provides nutrients and removes waste for cartilage

Additional Study Aid

• Compare and contrast mucous and cutaneous membranes using provided table
  • Focus on tissue composition, secretions, characteristics (wet vs. dry), and suitability for location/function

Interesting Note

• Example: Eastern Hellbender (giant salamander, state amphibian of Pennsylvania)
  • Secretes mucus, likened to a mucous membrane
  • Question posed: Is a mucus membrane well suited as a covering? Considerations
  • Additional reading provided on the subject

Next Topic

• Focus on the skin in upcoming discussions