Epithelial Tissues Flashcards

General Characteristics of Epithelial Tissue

• Epithelial tissue exhibits polarity with an apical surface and a basal surface.
• Composed of closely packed cells with minimal extracellular matrix, ensuring high cellularity.
• Supported by connective tissue, providing structural integrity.
• Avascular, relying on diffusion from underlying tissues for nutrient supply.
• Possesses regenerative abilities, allowing for quick healing after injury.

Classification of Epithelial Tissues

• Classified based on the arrangement of layers—simple (one layer) or stratified (multiple layers).
• Cell shape also determines classification: squamous (flat), cuboidal (cube-shaped), columnar (tall and elongated).

Functions of Epithelia

• Simple epithelia serve primarily for filtration and diffusion, as seen in alveoli and kidneys.
• Stratified epithelia primarily protect against abrasion due to their layered structure.

Locations of Specific Epithelial Types

• Ciliated epithelium lines the trachea and upper respiratory tract, aiding in the movement of mucus upward to prevent lower lung infection.
• Superficial epithelium can be found at the edges of tissues or surrounding hollow spaces in internal organs.

Types of Simple Epithelia

• Simple Squamous: Features flat disc-shaped nuclei and minimal cytoplasm; essential for rapid diffusion in alveoli and filtration in kidneys.
• Simple Cuboidal: Characterized by oval nuclei, found in kidney tubules; functions in secretion of waste and nutrients.
• Simple Columnar: Possesses elongated nuclei; located in the digestive tract, responsible for nutrient absorption and secretion of mucus and enzymes.
• Pseudostratified Ciliated: Composed of varying height simple columnar cells with cilia, enhancing mucous movement.

Impact of Smoking on Pseudostratified Ciliated Cells

• Smoking leads to increased mucus secretion and impairment of ciliary function, resulting in clogged bronchioles and chronic lung inflammation.

Stratified Epithelial Types

• Stratified Squamous Epithelium: Composed of many flattened cells, can be keratinized (skin) or non-keratinized (esophagus, mouth, vagina) to provide protection against abrasion.

Symptoms of Burns

• First Degree Burn: Causes pain and redness, least severe type.
• Second Degree Burn: Leads to blistering and discomfort.
• Third Degree Burn: Most severe with exposure of blood vessels, risking severe injury and complications.

Dual Nature of Epithelial Cells

• Epithelial cells are beneficial due to their avascularity and regeneration capabilities, which aid recovery from injury.
• However, their regenerative nature can contribute to cancer proliferation, as abnormal epithelial cells can invade surrounding tissues and lymphatic systems.