Histology of Epithelium & Nucleus Overview

Epithelium & Non-Epithelial Cells Study Notes

• Epithelium: Covers body surfaces and lines hollow organs, cavities, and forms glands.
• Primary Function: Protection (covering surfaces).
• **Other Functions:**Secretion (glands), absorption.
• Basic Cell Morphology & Structure: Includes intermediate filaments, ribosomes, rough endoplasmic reticulum, nucleus, nucleolus, chromatin, Golgi apparatus, Golgi vesicles, cytoplasm, vacuoles, mitochondria, plasma membrane, microtubules, centrosome, microfilaments, lysosomes, smooth endoplasmic reticulum, secretory vesicles, and peroxisomes.

Nucleus

• Contains DNA, histones, and other proteins.
• Chromatin: Represents the complex structure of DNA and proteins, making up chromosomes. Staining with hematoxylin shows increased staining (hyperchromasia) with increased chromatin load.
• Nucleoli: Small, basophilic spherical bodies involved in ribosome RNA synthesis. Presence can be physiological or an indicator of a malignant process.
• Nuclear Shape: Typically smooth spheres or spheroids.

Epithelium: Classification

• Number of Cell Layers: Simple (single layer) or Stratified (multiple layers).
• Pseudostratified: Cells layered but not all reach the surface.
• Surface Layer Morphology: Squamous (thin, flat, scale-like), Cuboidal (about equal height and width), Columnar (height greater than width).
• Specific Examples: Simple squamous epithelium (lining of lungs, blood vessels), Simple cuboidal epithelium (Kidney tubules, glands), Simple columnar epithelium (digestive tract), Stratified squamous epithelium (skin), Stratified cuboidal epithelium (some ducts), Stratified columnar epithelium (some ducts), Pseudostratified columnar epithelium (respiratory tract), Transitional epithelium (urinary bladder).

Non-Epithelial Cells

• RBCs: Often stain red, pink, or orange in Pap stains.
• Neutrophils: Found in large numbers during acute inflammation or infection.
• Macrophages: Variable in size and appearance, have foamy cytoplasm, and an eccentric bean-shaped nucleus.
• Lymphocytes: Small round cells with a narrow rim of cytoplasm, round nuclei.
• Plasma Cells: Larger than mature lymphocytes, contain more cytoplasm, and have characteristics chromatin patterns (clockface/cartwheel) with eccentric nuclei.
• Stromal cells: Elongated, spindle-shaped, with round to oval nuclei, scant, wispy cytoplasm; they tend to cluster together in disorganized aggregates.

Cytologic Criteria of Malignancy (Neoplasia)

• Cell Size and Shape: Variation (pleomorphism) in size and shape among cells.
• Nuclear Size and Shape: Enlarged nuclei, irregular in shape, often larger than normal for that cell type.
• Nuclear-to-Cytoplasmic Ratio (NCR): Increased nuclear size relative to cytoplasm (low NCR is usually benign).
• Chromatin Pattern: Coarse, clumped, and uneven distribution of chromatin; loss of a smooth, fine appearance.
• Regularity of Nuclear Membrane: Irregular or distorted shape in malignant cells.
• Intensity of Nuclear Staining: Hyperchromasia (increased staining) is common.
• Multinucleation and Nucleoli: Multinucleated cells and larger, irregular nucleoli are often seen in cancer.
• Mitosis and Mitotic Figures: Increased number and/or abnormal mitotic figures (abnormal cell division).

Low-Grade Squamous Intraepithelial Lesion (LSIL)

• Increase in NCR: Increase in the nucleus-to-cytoplasm ratio in cells.
• Nucleus: Still fairly round, chromatin is coarser than normal and hyperchromatic.

Squamous Cell Carcinoma

• Pleomorphic Nuclei: Variable sizes and shapes of nuclei in cells.
• Cytoplasm: Dense and basophilic (dark staining).

Programme Learning Outcomes (PLOs)

• PLO 1: Analyse and validate findings in medical laboratories using fundamental and advanced knowledge.
• PLO 2: Perform and supervise medical laboratory procedures, implement new methodologies, and evaluate equipment.
• PLO 3: Collaborate with healthcare professionals using interpersonal, leadership, social, and teamwork skills.
• PLO 4: Demonstrate sensitivity and responsibility towards the community, environment, adhering to legal, ethical principles, and professional conduct in medical labs.
• PLO 5: Present information, coherently to medical and lab members using verbal and written communication skills
• PLO 6: Critically analyse problems and challenges in medical practices using supervised research.
• PLO 7: Demonstrate lifelong learning, using ICT and information management systems to enhance career development.
• PLO 8: Demonstrate managerial and entrepreneurial skills to effectively manage daily laboratory activities, quality management, and Good Laboratory Practices (GLP).

Course Learning Outcomes (CLOs)

• CLO 1: Discuss various techniques used in cytopathology investigations.
• CLO 2: Integrate fundamental knowledge to perform cytopathology diagnostic lab techniques (sample collection, staining, screening).
• CLO 3: Prepare cytopathology reports in the required format.

Lesson Learning Outcomes

• Describe the morphology, structure, and functions of epithelium and non-epithelial cells.
• Describe the cytologic criteria of malignancy.

Lesson Outline

• Epithelial cells: morphology, structure, and function
• Non-epithelial cells
• Cytologic criteria of malignancy