Lab 2 Cells, Tissues, & Histology

Lab 2: Cells, Tissues, & Histology

Introduction to Cells

• Basic Units of Life: Cells are essential as they can take in nutrients, reproduce, and contain genetic material.

• Cell Estimates: Average adult male has ~36 trillion cells, female ~28 trillion, and a 10-year-old ~17 trillion.

• Tissues: Cells form functional groups called tissues; histology studies these microscopically, aiding in disease diagnosis, treatment plans, and forensic investigations.

Histological Techniques

• Fixation: Tissue (1cm cube) exposure to fixative chemicals (usually 4% formaldehyde) to cross-link proteins and harden tissue, preventing enzyme degradation.

• Dehydration and Embedding: Tissue's water replaced with xylene for embedding in warm paraffin wax, allowing for thin sectioning.

• Staining: Commonly, Hematoxylin (binds to nucleic acids, stains blue/purple) and Eosin (binds to proteins, stains pink/red) are used.

• Properties of Stains:

  • Hematoxylin: Positively charged dye staining negatively charged structures like nuclei.

  • Eosin: Negatively charged dye staining positively charged proteins in the cytoplasm and organelles.

Microscopic Observations

• Clear Areas: Plasma in blood samples and lumens in other tissues may appear clear.

• Cellular Components:

  • Erythrocytes (anucleated cells), platelets (fragments), nucleic acids in nuclei (purple staining), and extracellular matrix (pink staining).

• Sectioning: Proper sectioning reveals more cellular details, aiding in differentiating between healthy and diseased tissues.

Epithelial Tissue

• Function and Location: Covers body surfaces, lines vessels, and forms glands. It protects, secretes, and absorbs.

• Characteristics:

  • Avascular: Lacks blood vessels, relies on basement membrane for nutrient diffusion.

  • Stem Cells: Constantly renew via mitosis.

• Classification:

  • Layers: Simple (one layer), Stratified (multiple layers), Pseudostratified (appears layered but is one).

  • Shape: Squamous (flat), Cuboidal (cubical), Columnar (tall), Transitional (variable).

  • Special Features: Cilia, keratin, and microvilli may be present.

Connective Tissue (CT)

• Role: Supports and anchors tissues and organs, highly vascularized, and aids in nutrient and waste movement.

• Types of CT:

  • CT Proper: Loose (Areolar) and Dense (Regular/Irregular).

  • Specialized CT: Adipose, cartilage, bone, blood.

• Components: Cells (e.g., fibroblasts), ground substance (fluid medium), and fibers (collagen, elastin).

Muscle Tissue

• Overview and Function: Major role in contraction and force generation. Composed of myocytes, limited ECM.

• Types:

  • Skeletal Muscle: Striated, multinucleated, voluntary contraction.

  • Cardiac Muscle: Striated, branched, involuntary contraction, intercalated discs present.

  • Smooth Muscle: Non-striated, involuntary contraction.

Nervous Tissue

• Composition and Function: Found throughout the body; consists of neurons for rapid communication and glial cells for support.

• Neurons: Categorized by shape (multipolar, bipolar, unipolar) and function (motor, sensory, interneurons).

• Glial Cells: Essential for neuron support and maintaining functionality, influencing health outcomes.

Practical Applications

• Microscopy: Engage with histology slides to identify and label various tissues.

• Observational Skills: Enhance understanding through practice in identifying tissue types and structures under the microscope.

Conclusion

• Lab Reports: Ensure completion and submission via Canvas.

This lab covers fundamental concepts of cellular biology, histological techniques, tissue types, and their identification via microscopy observations, providing a comprehensive overview for understanding tissue architecture and function.