Histology Overview Revision Sheet

1. 📌 Essentials

• Histology: study of tissues' microstructure, organization, and functions.
• Tissue: group of cells with shared origin and function, connected by extracellular matrix.
• Epithelium: forms protective, secretory, sensory layers; derived from ectoderm, mesoderm, endoderm.
• Basement membrane: basal layer of epithelium lies on it, separating from connective tissue.
• No vessels in epithelium: vessels run in underlying connective tissue.
• Main epithelium types: squamous, cuboidal, columnar, pseudostratified, stratified.
• Microvilli: increase absorptive surface area.
• Glandular epithelium: secretes via exocrine (ducted) or endocrine (bloodstream).
• Secretion modes: merocrine (exocytosis), apocrine (part detaches), holocrine (entire cell destroyed).
• Gland structures: acinus, tubulus, alveolae; classified as simple, branched, or compound.
• Pigmented epithelium (retina): protects against light; more pigment means less light penetration.

2. 🧩 Key Structures & Components