BMS Epithelium

Types of Tissue Membranes

• Tissues are sheets composed of cells lining internal cavities and structures.
• Four main types of membranes: Mucous, Synovial, Serous, and Cutaneous.

Mucous Membrane

• Located in open cavities like the oral cavity.
• Usually composed of multiple layers (stratified) for protection.
• Glands secrete mucus to maintain moisture.
• Functions include keeping the oral cavity moist and reducing friction.
• Condition known as xerostomia leads to a dry mouth, affecting moisture maintenance.

Synovial Membrane

• Lines cavities of freely movable joints, e.g., hip and knee.
• Houses synovial fluid, essential for joint function.
• Fibroblast cells produce hyaluronan, which traps water to form synovial fluid.
• Functions to prevent bone-to-bone contact, provide protection, and cushion joints.

Serous Membrane

• Does not open to external environment; surrounds organs like the heart.
• Composed of mesodermal tissue and simple squamous epithelium.
• Contains serous fluid that prevents friction between internal cavities and organs.
• Example includes the parietal pericardium (outer layer) and visceral pericardium (inner layer) surrounding the heart.

Cutaneous Membrane

• Refers to the skin, which is made of stratified squamous epithelial tissue.
• Located on top of connective tissue.
• Surface covered with dead keratinized cells, providing protection against pathogens (disease-causing organisms).

Overview of Epithelium

• Epithelial tissue covers internal and external body surfaces, made of tightly packed cells in one or more layers.
• It is one of four main tissue types in the human body, alongside muscle, connective, and nerve tissues.
• Epithelial cells line cavities and cover surfaces, making them the most prolific tissue type.

Characteristics of Epithelial Tissue

• Avascular: Lacks blood vessels; nutrients diffuse from underlying connective tissues.
• High cellularity with tightly packed cells that minimize space.
• Polarity: Distinct tops (apical) and bottoms (basal) with orientations.
• Supported by a basement membrane.
• Regenerative ability allows rapid cell division and replacement.
• Good nerve supply enhances sensation.

Functions of Epithelium

• Protection: Covers internal and external surfaces.
• Secretion: Movement of substances from one location to another.
• Absorption: Intake of liquids and gases across membranes.
• Transportation: Movement of materials, including transcellular transport.
• Sensation: Contains sensory nerve endings for stimuli, such as taste and touch.

Types of Epithelium

• Simple Epithelium: A single layer of cells.
  • Squamous: Flat cells, promoting easy material transfer (e.g., alveoli in lungs).
  • Cuboidal: Cube-shaped cells, involved in secretion and absorption (e.g., kidney tubules).
  • Columnar: Tall cells, often found in absorption or secretion areas (e.g., intestines).
  • Pseudostratified Columnar: Appears multi-layered due to varying cell heights but is a single layer; often ciliated (e.g., respiratory tract).
• Stratified Epithelium: Multiple layers providing protection.
  • Stratified Squamous: Protects against abrasion; can be keratinized (skin) or non-keratinized (oral cavity).
  • Stratified Cuboidal: Limited distribution, typically found in some gland ducts.
  • Stratified Columnar: Protection and secretion; found in parts of the male urethra and some glands.
• Transitional Epithelium: Multi-layered with cells that change shape; allows stretching (e.g., urinary bladder).

Membranes

• Composed of epithelial and connective tissue, covering or lining internal structures.
• Types of Membranes:
  • Mucous Membrane: Lines cavities open to the exterior, secretes mucus for lubrication and protection.
  • Serous Membrane: Lines closed body cavities, composed of parietal (outer) and visceral (inner) layers; secretes serous fluid for lubrication.
  • Synovial Membrane: Lines movable joints; produces synovial fluid that nourishes cartilage.
  • Cutaneous Membrane: Skin, a stratified squamous membrane, serves protective roles covered in dead keratinized cells.

Importance in Dentistry

• Understanding epithelial and membrane structures is crucial for recognizing abnormal changes and ensuring oral health.
• Knowledge helps in diagnosing conditions that may arise in dental practice related to epithelial and membranous tissues.