Glandular Epithelium Overview

Glandular Epithelium

• Functions in secretion to protect the body.
• Classified into exocrine and endocrine glands.
• Exocrine glands secrete substances over short distances, affecting nearby surfaces.
• Endocrine glands release hormones into interstitial fluid, diffusing into the bloodstream for distribution to target tissues.
• Mixed glands contain both exocrine and endocrine features, such as the pancreas.
• Hormones, like thyroxin, regulate various homeostatic processes.

Exocrine Glands

• Exocrine glands release products through ducts to the body's surface or into hollow organs.
• Include sweat glands, sebaceous (oil) glands, and digestive glands that secrete into the small intestine.
• Can be unicellular (example: Goblet cells) or multicellular, primarily classified by functionality:
  • Merocrine glands: Secrete via exocytosis, most common type.
  • Apocrine glands: Release products only from the apical surface through exocytosis (e.g., mammary glands).
  • Holocrine glands: Store secretions in the cytosol and release by rupturing mature cells (e.g., sebaceous glands associated with acne).

Summary of Glandular Epithelium Secretion Types

• Merocrine: secretion through exocytosis.
• Apocrine: secretion from apical surface via exocytosis.
• Holocrine: secretion through cell rupture.

Connective Tissues

• Less common at body surfaces, generally vascularized with nerves and blood vessels, except some types.
• Comprised of two main components:
  • Extracellular Matrix (ECM): made of protein fibers and ground substance, varying in consistency (liquid, solid, gel-like).
  • Cells: sparsely distributed throughout the ECM, derived from embryonic mesenchymal cells.

Cells of Connective Tissue

• Fibroblasts: Most abundant, secrete ECM for loose and dense connective tissue.
• Macrophages: Phagocytic cells that act in immune response.
• Plasma cells: Produce antibodies for immune defense.
• Mast cells: Secrete inflammatory chemicals; play a role in allergic responses.
• Adipocytes: Store triglycerides as fat cells in adipose tissue.
• Leukocytes: White blood cells that migrate to connective tissue during infection.

Extracellular Matrix of Connective Tissues

• Comprised of fibers that connect cells and provide structural support, hydrated extensively.
• Ground substance: Material that fills spaces between cells and fibers, determining tissue's properties.
• Protein fiber types:
  • Collagen fibers: The most prevalent protein, providing tensile strength and resistance to compression.
  • Elastic fibers: Made of elastin, allow stretching and return to original shape.
  • Reticular fibers: Thinnest, support tissue structures, including blood vessels and basement membranes.

Differences Between Epithelial and Connective Tissues

• Epithelial tissues have more cells relative to their ECM compared to connective tissues.
• Epithelial tissues are avascular, while connective tissues are typically vascularized.
• Epithelial layers commonly form the outer layer of organs, overlaying connective tissues to serve functional roles.

Overview of Embryonic Connective Tissue

• Mesenchymal tissue: Composed of mesenchymal cells, semi-fluid ground substance, and reticular fibers, gives rise to various types of connective tissues.

Test your knowledge on glandular epithelium, focusing on the functions and classifications of exocrine and endocrine glands. This quiz covers the secretion processes and examples of mixed glands such as the pancreas. Perfect for biology enthusiasts and students alike!