Fall 2026 Tissues Comprehensive Study Notes

Organization and Classification of Tissues

  • Context & Scope: Fall 2026 TISSUES lecture outline.

  • Levels of Organization (Figure 1.3):

    • Chemical level: Atoms and molecules.
    • Cellular level: A cell is the basic unit of structure and function, and the smallest living structure in humans.
    • Tissue level: A tissue.
    • Organ level: An organ.
    • Organ system level: Multiple organs involved in a common function.

  • Definitions:

    • Tissue: A group of similar cells in an extracellular matrix that perform a common function.
    • Extracellular matrix: Non-cellular substance produced and secreted by cells, surrounding and supporting cells within a tissue.
    • Histology: The microscopic study of tissues.

  • Four Basic Types of Tissues (Table 4.1):

    • Epithelial tissue (epithelium, singular; epithelia, plural):
      1. Covers body and organ surfaces.
      2. Lines body cavities and lumens.
      3. Forms glands.
    • Connective tissue: Binds, protects, and supports organs and body structures.
    • Muscle tissue: Produces movement through active contraction.
    • Nervous tissue: Conducts electrical impulses for communication and control.

  • Integration of Lecture and Lab:

    • Review tissue histology using the slides in the A225 Virtual Microscope.

Epithelia

  • Characteristics of Epithelia (Figure 4.1):

    • Cellularity: Composed almost entirely of tightly packed cells with minimal extracellular matrix.
    • Polarity:
      • Apical surface: Exposed to an external surface or internal body cavity/space.
      • Basal surface: Attached to the underlying basement membrane and connective tissue.
    • Basement Membrane Attachment: Bound to underlying tissue by a basement membrane.
    • Avascularity: Lacks blood vessels; nutrients are acquired via diffusion from underlying connective tissues.
    • High Regenerative Capacity: Rapidly replaces damaged or lost cells through high rates of cell division.

  • Classification by Layers (Figure 4.2, Figure 4.3):

    • Simple epithelium: One layer thick.
    • Stratified epithelium: Many layers thick.

  • Classification by Cell Shape:

    • Squamous: Flattened cells.
    • Cuboidal: About as tall as they are wide.
    • Columnar: Taller than wide shaped cells.

  • Kinds of Simple Epithelia (Table 4.2):

    • Simple Squamous Epithelium:
      • Definition: One layer of flattened cells.
      • Function: Rapid diffusion, filtration, and secretion in serous membranes.
      • Locations: Air sacs in lungs (alveoli), lining of blood vessels (endothelium), lining of serous membranes (mesothelium).
    • Simple Cuboidal Epithelium:
      • Definition: One layer of cells about as tall as they are wide, and cells may be rounded.
      • Functions: Absorption and secretion.
      • Locations: Kidney tubules, ducts of glands, surface of ovaries.
    • Simple Columnar Epithelium:
      • Definition: One layer of tall cells.
      • Functions: Absorption and secretion; movement of mucus or egg cells if ciliated.
      • Locations: Lining of most of digestive tract (non-ciliated), lining of uterine tubes (ciliated).
      • Specializations: Microvilli (forming a brush border) and goblet cells.
    • Pseudostratified Columnar Epithelium:
      • Definition: Cells are columnar and irregularly shaped. All cells are attached to the basement membrane, but not all reach the apical surface, giving a false stratified appearance.
      • Function: Protection; secretion and movement of mucus by cilia.
      • Location: Lining of upper respiratory tract (nasal cavity, trachea, bronchi).
      • Specializations: Cilia and goblet cells.

  • Kinds of Stratified Epithelia (Table 4.3):

    • Stratified Squamous Epithelium:
      • Definition: Superficial layers of cells are flattened, deeper layers of cells are cuboidal.
      • Function: Protection against friction, abrasion, and physical wear.

Glands

  • Definition of Glands (Figures 4.4–4.7):

    • Exocrine glands are formed from epithelial tissues and secrete their materials onto a free surface.

  • Unicellular Exocrine Glands:

    • Composed of a single cell.
    • Example: Goblet cell.

  • Multicellular Exocrine Glands (Figure 4.7):

    • Secrete materials through a duct.
    • Classified into 3 types by their mode of secretion:
      1. Merocrine Glands:
        • Most common multicellular exocrine gland.
        • Secretion passes from cell via exocytosis.
        • Cell remains intact.
        • Examples: Sweat glands, salivary glands.
      2. Apocrine Glands:
        • Top part of the cell is pinched off and becomes the secretion.
        • Cell repairs itself and remains functional.
        • Example: Mammary glands.
      3. Holocrine Glands:
        • Whole cells rupture, die, and become the secretion.
        • Old cells are replaced by mitosis.
        • Example: Sebaceous (oil) glands.

  • Review and Learn Resources:

    • Watch the Epithelial Tissue Overview on the MH Connect site (to time 4:21).
    • Complete the Epithelium Memory Matrix.

Connective Tissue

  • Characteristics of Connective Tissue (CT) (Figure 4.8, Figure 4.9):

    • Derived from mesenchyme (embryonic CT).
    • CT typically is vascular.
    • Composed of:
      1. Cells
      2. Protein fibers
      3. Ground substance
    • Refer to Figure 4.9 for a visual organization of the types of connective tissue.

  • Classification of Connective Tissue:

    • Connective Tissue Proper (Table 4.6):

      • Loose Connective Tissue (Table 4.7):
        1. Areolar Connective Tissue:
          • Cells: Fibroblasts.
          • Vascularity: Very vascular.
          • Functions: Surrounds and protects organs, binds epithelia to deeper tissues, provides nutrient diffusion.
        2. Adipose (Fat Tissue):
          • Cells: Adipocytes.
          • Functions: Energy storage, thermal insulation, cushioning and protection of organs.
      • Dense Connective Tissue (Table 4.8):
        1. Dense Irregular Connective Tissue:
          • Cells: Fibroblasts.
          • Vascularity & Structure: Good vascularity with collagen (protein) fibers found in 'clumps' running in multi-directional orientations.
          • Functions: Withstands stress applied in all directions.
        2. Dense Regular Connective Tissue:
          • Cells: Fibroblasts.
          • Vascularity & Structure: Poor vascularity with collagen (protein) fibers densely packed, with fibers running parallel.
          • Functions: Attaches muscle to bone or bone to bone, resists mechanical stress along a single axis.

    • Cartilage (Table 4.9):

      • Characteristics: 1. Cells: Chondrocytes (mature cartilage cells) located in spaces called lacunae. 2. Matrix & Vascularity: Semisolid ground substance and avascular when mature. 3. Covering: Usually surrounded by perichondrium. 4. Three Types: Hyaline Cartilage, Fibrocartilage, Elastic Cartilage.

    • Bone (Osseous Connective Tissue) (Table 4.10):

      • Characteristics: 1. Cells: Osteocytes (mature bone cells) in spaces called lacunae. 2. Matrix & Vascularity: Mineralized (solid) matrix and very vascular. 3. Covering: Surrounded by a periosteum.

    • Fluid Connective Tissue (Blood) (Table 4.11):

      • Note: Discussed in Block 4.

Muscle Tissue

  • Classification (Table 4.12, Table 10.6):
    • Skeletal Muscle Tissue:
      • Function: Voluntary body movement, locomotion, and stabilization.
    • Cardiac Muscle Tissue:
      • Location: Only found in the heart.
      • Function: Involuntary contraction to pump blood through the circulatory system.
    • Smooth (Visceral) Muscle Tissue:
      • Function: Involuntary movement and propulsion of materials through hollow visceral organs and blood vessels.

Nervous Tissue

  • Overview of Nervous Tissue:
    • Note: Discussed in Block 3.

Review Questions

  • Self-Quiz Review Questions:

    • Instructions: Once you have reviewed the material, have someone quiz you by asking you these questions. If you can answer them without having to look at your notes, you know the material! Be able to explain and describe ideas with many details!
    1. What are the 4 basic kinds of tissues, and what are their functions?
    2. What are the characteristics common to all kinds of epithelia? What is the difference between simple and stratified epithelia?
    3. Describe the different kinds of epithelia discussed in the lecture.
    4. From what tissue are exocrine glands formed? What is the difference between multicellular and unicellular glands? Name the 3 different kinds of multicellular glands, and list at least one example of each in the body.
    5. What are the characteristics common to all kinds of connective tissue? How do epithelia and connective tissue differ?
    6. Describe the different kinds of connective tissues and their key characteristics.
    7. What are the 3 kinds of muscle tissue?