SC

Study Guide 4 '

4.1 Introduction to Tissues

  • Tissue: Group of similar cells performing a common function.

  • Histology: Study of tissues (microscopic anatomy).

  • 4 Primary Tissue Types:

    1. Epithelial: Covers surfaces, lines cavities, forms glands.
    2. Connective: Supports, binds, protects.
    3. Muscle: Contracts to produce movement.
    4. Nervous: Communication, control, coordination.

  • Histological Staining Techniques:

    • H&E Stain: Hematoxylin (blue, stains nuclei) and eosin (pink, stains cytoplasm).
    • Special Stains: Highlight connective tissue fibers, lipids, or carbohydrates.

4.2 Epithelial Tissue Characteristics

  • Polarity:

    • Apical Surface: Exposed surface of epithelial tissue.
    • Basal Surface: Attached surface to underlying connective tissue.

  • Basement Membrane: Attaches epithelium to underlying connective tissue.

  • Avascularity: No blood vessels; nutrients diffuse from underlying tissues.

  • High Regeneration Capacity: Notably found in skin and gastrointestinal (GI) tract.

Functions of Epithelial Tissue

  • Protection: Acts as a barrier to pathogens and injury.
  • Absorption: Involved in nutrient uptake.
  • Secretion: Produces and releases substances (e.g., hormones, enzymes).
  • Excretion: Removes waste substances.
  • Sensation: Contains nerve endings for sensory perception.

Classification of Epithelial Tissue

  • By Number of Layers:

    • Simple: One layer.
    • Stratified: Multiple layers.
    • Pseudostratified: Appears layered but all cells touch the basement membrane.

  • By Shape:

    • Squamous: Flat cells.
    • Cuboidal: Cube-shaped cells.
    • Columnar: Tall, rectangular cells.

Major Types & Locations of Epithelial Tissue

  • Simple Squamous:

    • Function: Diffusion, filtration.
    • Example Locations: Lungs (alveoli), blood vessels (endothelium).

  • Simple Cuboidal:

    • Function: Secretion, absorption.
    • Example Locations: Kidney tubules, glands.

  • Simple Columnar:

    • Function: Absorption, secretion.
    • Example Locations: GI tract, uterus.

  • Pseudostratified Columnar:

    • Function: Secretion, movement (cilia).
    • Example Locations: Trachea, upper respiratory tract.

  • Stratified Squamous:

    • Function: Protection.
    • Example Locations: Skin (keratinized), mouth/esophagus (nonkeratinized).

  • Stratified Cuboidal:

    • Function: Rare; secretion.
    • Example Locations: Sweat glands, mammary glands.

  • Stratified Columnar:

    • Function: Rare; protection, secretion.
    • Example Locations: Male urethra, large ducts.

  • Transitional Epithelium:

    • Function: Stretching.
    • Example Locations: Urinary bladder, ureters.

Glandular Epithelium

  • Exocrine Glands: Secrete into ducts (e.g., sweat, saliva).
  • Endocrine Glands: Secrete hormones into the bloodstream.
  • Modes of Secretion:
    • Merocrine: Exocytosis (e.g., sweat).
    • Apocrine: Part of the cell pinched off (e.g., mammary glands).
    • Holocrine: Cell ruptures (e.g., sebaceous glands).

4.3 Connective Tissue Characteristics

  • Most Abundant Tissue Type: Found throughout the body.
  • Functions:
    • Binding, support, protection, insulation, transport.
  • Common Features:
    • Cells: Fibroblasts, macrophages, mast cells, adipocytes.
    • Extracellular Matrix: Composed of fibers and ground substance.
    • Vascularity Varies:
    • Cartilage: Avascular.
    • Bone: Highly vascular.

Types of Connective Tissue Fibers

  • Collagen: Provides strong tensile strength.
  • Elastic: Allow stretch and recoil.
  • Reticular: Form delicate support networks.

Types of Connective Tissue

  1. Connective Tissue Proper:

    • Loose: (e.g., areolar, adipose, reticular).
    • Dense: (e.g., regular, irregular, elastic).

  2. Supporting Connective Tissue:

    • Cartilage: Types include hyaline, elastic, fibrocartilage.
    • Bone: Types include compact and spongy.

  3. Fluid Connective Tissue:

    • Blood: Composed of plasma, red blood cells (RBCs), white blood cells (WBCs), platelets.
    • Lymph: Plays a role in immune defense.

4.4 Muscle Tissue

  • Specialized for Contraction: Responsible for movement.
  • Highly Vascular: Contains a rich supply of blood vessels.

Types of Muscle Tissue

  1. Skeletal Muscle:

    • Structure: Long, multinucleated, striated fibers.
    • Control: Voluntary.
    • Function: Movement, posture, heat production.

  2. Cardiac Muscle:

    • Structure: Striated, branched fibers with intercalated discs.
    • Control: Involuntary, found only in the heart.
    • Function: Pumps blood.

  3. Smooth Muscle:

    • Structure: Spindle-shaped, no striations, single nucleus.
    • Control: Involuntary.
    • Locations: Walls of hollow organs (e.g., stomach, blood vessels, bladder).
    • Function: Peristalsis, blood vessel constriction.

4.5 Nervous Tissue

  • Location: Found in the brain, spinal cord, and nerves.

  • Neurons: Transmit electrical signals.

    • Components:
    • Soma: Cell body.
    • Dendrites: Receive input.
    • Axon: Sends output.

  • Neuroglia (Glial Cells): Support, protect, and nourish neurons.

    • Types Include:
    • Astrocytes.
    • Oligodendrocytes.
    • Schwann Cells.
    • Microglia.

4.6 Tissue Membranes

  • Definition: Thin sheets of tissue covering surfaces, lining cavities, and protecting structures.

Types of Tissue Membranes

  1. Mucous Membranes: Line body cavities open to the exterior (e.g., digestive, respiratory).
  2. Serous Membranes: Line closed cavities; secrete serous fluid (e.g., pleura, pericardium, peritoneum).
  3. Cutaneous Membrane: Skin, consisting of the epidermis and dermis.
  4. Synovial Membranes: Line joint cavities; secrete synovial fluid.

4.7 Tissue Injury and Repair

  • Inflammation: Nonspecific response to injury characterized by redness, heat, swelling, and pain.
  • Regeneration: Replacement of tissue with the same type of cells, primarily epithelial and connective.
  • Fibrosis: Replacement of tissue with scar tissue (dense connective tissue).

Capacity for Repair of Tissues

  • High: Epithelial, bone, areolar connective, dense irregular connective.
  • Moderate: Smooth muscle, dense regular connective.
  • Poor: Cartilage, skeletal muscle.
  • None: Cardiac muscle, nervous tissue (in central nervous system).

Chapter 4 Big Picture Summary

  • Epithelial Tissue: Covers and lines; specialized for secretion and absorption.
  • Connective Tissue: Supports, protects, and transports materials.
  • Muscle Tissue: Generates force and enables movement.
  • Nervous Tissue: Coordinates communication.
  • Body Membranes: Combine tissues for protection, lubrication, and exchange processes.
  • Tissue Repair: Involves inflammation, regeneration, and fibrosis processes.

Sample Exam Questions

  1. List the four primary tissue types and their general functions.
  2. Compare simple squamous epithelium with stratified squamous epithelium in structure and function.
  3. What is the difference between endocrine and exocrine glands? Provide examples.
  4. Explain the differences between collagen, elastic, and reticular fibers.
  5. Describe the structural differences among skeletal, cardiac, and smooth muscle types.
  6. What roles do neuroglia play in nervous tissue?
  7. Which tissues regenerate well, and which heal poorly? Why?