MH 002 Cells and Tissues

The following human tissues illustrate the broad spectrum of staining patterns, nuclear morphology, and cell sizes observed across different tissue types.

Blood

Blood consists of different cell types suspended in plasma, each with distinct morphological features visible in blood smears. Red blood cells (erythrocytes) comprise 99% of the cellular population, creating a striking numerical disparity between cell types.

• Cell Size: Small, uniform cells measuring 7.5 to 8.0 µm in diameter
  • Biconcave disc morphology optimized for gas exchange
• Nuclear Morphology: Absent in mature red blood cells, having been extruded during development
• Cytoplasm: Exhibits Intense acidophilic staining, producing bright red-pink staining
  • Uniform cytoplasmic density reflects the lack of internal organelles
  • High concentration of the oxygen-carrying protein hemoglobin

Blood

White blood cells () Toggle Label Visibility comprise less than 1% of the cellular population but can be identified and classified by their distinctive morphological features in blood smears.

• Cell Size: Variable, ranging from 10 to 25 μm in diameter, depending on cell type
  • Significantly larger than red blood cells
• Nuclear Morphology: Diverse shapes depending on cell type
  • Round nuclei () Toggle Label Visibility ; lymphocytes and monocytes)
  • Multilobed, segmented nuclei () Toggle Label Visibility ; neutrophils)
  • Bilobed nuclei () Toggle Label Visibility ; eosinophils)
• Cytoplasm:
  • Variable staining characteristics depending on cell type
  • May contain specific granules (neutrophilic, eosinophilic, or basophilic), reflecting diverse immune and inflammatory functions

The morphological diversity of blood cells facilitates rapid identification and differential counting in clinical hematology.

Trachea

When stained with hematoxylin and eosin (H&E), the trachea demonstrates a wide range of basophilic and acidophilic cellular components within a single tissue section.

• Acidophilic Structures: Multiple positively charged structures demonstrate eosin staining
  • Cellular Components: These cells produce a pink-red coloration due to their high protein content
    • Smooth Muscle Cells filled with contractile proteins (spindle-shaped nuclei)
    • Duct Cells with numerous mitochondria (euchromatic nuclei)
    • Red Blood Cells filled with hemoglobin (no nuclei)
  • Extracellular Components: Collagen fibers stain pink-red in the surrounding connective tissue
    • Collagen fibers are aggregates of long helix-forming proteins
    • Provides structural support for respiratory passages
• Basophilic Structures: Multiple negatively charged structures demonstrate hematoxylin staining
  • Cellular Components:
    • Nuclei stain dark blue-purple due to DNA
    • Negatively charged mucus (sulphated glycoproteins) in granules of the secretory gland cells
  • Extracellular Components:
    • Extracellular matrix of cartilage stains intensely due to large, highly negatively charged long chains of sugars (sulfated polysaccharides)
    • Cartilage Cells interspersed within the cartilaginous matrix display heterochromatic nuclei surrounded by lightly stained cytoplasm

Small Intestine

When stained with hematoxylin and eosin (H&E), the Small Intestine demonstrates a wide range of basophilic and acidophilic cellular components.

This tissue section exhibits poor preservation, with the surface epithelium detached from the underlying supportive tissue - a processing artifact that complicates interpretation.

The inner lining has finger-like projections known as Intestinal Villi.

• Surface Epithelium: Single layer of tall columnar cells measuring 20-25 µm in height
  • Polarized cells with distinct apical (lumen-facing) and basal (contacts underlying tissue) surfaces
    • Apical surface stains more intensely due to numerous small projections (microvilli)
  • Euchromatic nuclei are located in the lower third of the cells
  • Selective barrier facilitates nutrient absorption while protecting against pathogens
• Lamina Propria: Connective tissue forms the core of the villi beneath the surface epithelium
  • Diverse cell populations of varying sizes, chromatin patterns, and staining properties
    • Larger cells with euchromatic nuclei () Toggle Label Visibility
    • Many smaller cells with heterochromatic nuclei () Toggle Label Visibility
    • Blood vessels (capillaries) appear as linear arrangements of cells with elongated, flattened nuclei
• Smooth Muscle: Spindle-shaped cells organized in layers
  • Appearance varies by the orientation of cells
    • Inner Circular Layer: Smaller cross-section with nuclei measuring 4-5 µm in diameter
    • Outer Longitudinal Layer: Longitudinal sections show narrow, euchromatic nuclei measuring 15-20 µm in length
  • Smooth muscle contracts to move food through the intestine (peristalsis)
• Collagen Fibrils: extracellular fibers found throughout the intestinal wall
  • Exhibit bright acidophilic staining, producing intense red coloration () Toggle Label Visibility
  • Interspersed fibroblasts have spindle-shaped heterochromatic nuclei, indicating lower metabolic activity () Toggle Label Visibility
  • Fibers form a supportive framework that helps the intestinal wall withstand mechanical stress from food movement