Chapter 04 | Tissues

Slide 3: Introduction to Tissues

  • Four Main Types of Tissues:

    • Epithelial Tissue: Forms protective coverings for all body surfaces, lines hollow organs, body cavities, and ducts. Involved in secretion, absorption, and protection.

    • Connective Tissue: Provides support and structure. It is the most abundant tissue type, connecting different tissues and storing energy.

    • Muscle Tissue: Enables movement by contracting in response to stimulation. Essential for bodily functions and maintenance of posture.

    • Nervous Tissue: Facilitates communication between different body parts through nerve impulses, ensuring coordination and control.

Slide 4: Epithelial Tissue Overview

  • Definition: Tissue that covers surfaces, lines body cavities, and forms glands.

  • Characteristics:

    • Cells are closely packed, with minimal extracellular material.

    • Serves as a barrier against physical, chemical, and biological agents.

    • Polarity: Epithelial cells have an apical surface (exposed to the body exterior or cavity) and a basal surface (attached to underlying connective tissue).

    • Avascular but Innervated: Epithelial tissues do not have blood vessels but receive nutrients through diffusion from underlying connective tissues.

    • Regeneration: Epithelial cells have a high capacity for regeneration, especially in areas prone to friction and injury.

Slide 5: Classification by Cell Shape (Epithelial Tissue)

  • Shapes of Epithelial Cells:

    • Squamous: Thin, flat cells for efficient gas exchange and filtration (e.g., lining of the lungs and capillaries).

    • Cuboidal: Cube-like cells, often involved in secretion and absorption (e.g., glands, kidney tubules).

    • Columnar: Tall, column-shaped cells specialized for absorption and secretion (e.g., lining of intestines).

    • Transitional: Cells that change shape depending on stretching, found in organs like the urinary bladder.

    • Function Overview: The shape of epithelial cells is closely linked to their function. For example, squamous cells facilitate diffusion due to their thin structure, while columnar cells are suited for absorption.

Slide 6: Classification by Arrangement (Epithelial Tissue)

  • Cell Arrangements:

    • Simple Epithelium: A single layer of cells; typically found in locations where absorption, secretion, and filtration occur (e.g., blood vessels, air sacs of lungs).

    • Stratified Epithelium: Multiple layers; offers protection against abrasion and found in high-wear areas (e.g., skin, lining of the mouth).

    • Pseudostratified Epithelium: Appears to be stratified but is actually a single layer with nuclei at different levels, giving a stratified appearance.

Slide 7: Simple Squamous Epithelium

  • Structure: Single layer of flat, scale-like cells.

  • Function: Facilitates diffusion and filtration due to its thinness.

  • Location: Found in alveoli of the lungs, lining of the heart, and blood vessels.

  • Special Characteristics: Thinness allows for rapid exchange of gases and nutrients.

Slide 8: Stratified Squamous Epithelium

  • Structure: Multiple layers of cells, with flat cells at the surface.

  • Function: Provides protection against mechanical stress and pathogens.

  • Location: Found in skin, mouth, esophagus, and vagina.

  • Keratinized vs. Non-Keratinized: The keratinized type forms the skin's outer layer, providing a waterproof barrier, while the non-keratinized type lines moist body openings.

Slide 9: Simple Cuboidal Epithelium (Part 1)

  • Structure: Cube-shaped cells arranged in a single layer.

  • Function: Secretion and absorption; forms the structural foundation of many glands.

  • Location: Kidney tubules, glands such as the thyroid, and gland ducts.

  • Special Characteristics: Cells have large, central nuclei, aiding in their secretory functions.

Slide 10: Simple Cuboidal Epithelium (Part 2)

  • Secretion Types:

    • Secretes substances like saliva, digestive enzymes, and hormones.

    • Can secrete directly into ducts, blood, or onto surfaces depending on their function.

    • Examples of Glands: Salivary glands, thyroid gland, and pancreas.

Slide 11: Simple Columnar Epithelium

  • Structure: Tall, column-like cells arranged in a single layer.

  • Special Feature: Contains goblet cells that produce mucus, aiding in lubrication and protection.

  • Function: Specialized for absorption and secretion.

  • Location: Lining of the digestive tract (stomach to anus), aiding in nutrient absorption.

  • Special Adaptations: May have microvilli to increase surface area for absorption, especially in the small intestine.

Slide 12: Stratified Transitional Epithelium

  • Structure: Multiple layers that can change shape from cuboidal to squamous.

  • Function: Allows organs like the urinary bladder to stretch without tearing.

  • Location: Found in areas that need to accommodate stretching, such as the bladder.

  • Special Characteristics: Provides protection while accommodating volume changes.

Slide 13: Pseudostratified Epithelium

  • Structure: Appears layered, but each cell touches the basement membrane.

  • Function: Typically contains cilia and goblet cells, helping to move substances like mucus.

  • Location: Lines the trachea and upper respiratory tract, playing a role in trapping and moving particles.

  • Cilia Function: The cilia move mucus and trapped particles out of the respiratory tract to keep airways clear.

Slide 14: Connective Tissue Overview

  • Definition: Supports, binds, and protects other tissues.

  • Characteristics: Few cells embedded in a matrix, which varies in consistency (fluid, gel, or solid).

  • Matrix Components: Composed of fibers (collagen, elastic, and reticular) and ground substance, which provides structural and biochemical support.

Slide 15: Types of Connective Tissue (Part 1)

  • Areolar Tissue:

    • Function: Loose tissue that acts like "glue," holding organs together and providing a reservoir of water and salts.

    • Special Features: Contains fibroblasts, macrophages, and a variety of fibers, contributing to its flexibility and support.

  • Adipose Tissue (Fat):

    • Function: Stores energy, insulates against heat loss, and cushions organs.

    • Location: Found under the skin, around internal organs, in bone marrow, and in breast tissue.

Slide 16: Types of Connective Tissue (Part 2)

  • Fibrous Tissue:

    • Function: Dense tissue with bundles of collagen fibers, providing strength and support.

    • Example: Tendons (connect muscle to bone) and ligaments (connect bone to bone).

    • Characteristics: Very strong, non-elastic fibers that provide resistance to pulling forces.

  • Bone Tissue:

    • Matrix: Calcified, providing rigidity.

    • Function: Supports and protects, stores calcium, and aids movement.

    • Cell Types: Osteocytes are mature bone cells, and osteoblasts are bone-forming cells.

Slide 17: Types of Connective Tissue (Part 3)

  • Cartilage:

    • Matrix: Gel-like, providing flexibility and support.

    • Cell Type: Chondrocytes, which reside in spaces called lacunae.

    • Types of Cartilage: Hyaline (found in joints), elastic (found in the ear), and fibrocartilage (found in intervertebral discs).

  • Blood:

    • Matrix: Fluid (plasma).

    • Function: Transport of gases, nutrients, and immune cells.

    • Components: Red blood cells (carry oxygen), white blood cells (immune function), and platelets (blood clotting).

Slide 18: Skeletal Muscle Tissue

  • Structure: Long, striated fibers; multinucleated.

  • Function: Voluntary control; enables movement of bones.

  • Location: Attached to bones, aiding in body movement.

  • Special Features: Striations are due to the arrangement of actin and myosin filaments, essential for contraction.

Slide 19: Cardiac Muscle Tissue

  • Structure: Striated, branched cells connected by intercalated discs.

  • Function: Involuntary contractions pump blood throughout the body.

  • Location: Only in the heart.

  • Intercalated Discs: Specialized connections that facilitate synchronized contractions of cardiac muscle.

Slide 20: Smooth Muscle Tissue

  • Structure: Non-striated, spindle-shaped cells; single nucleus per cell.

  • Function: Involuntary movements in internal organs.

  • Location: Walls of hollow organs, such as intestines, blood vessels, bladder.

  • Special Characteristics: Capable of sustained contractions, important for peristalsis in the digestive tract.

Slide 21: Nervous Tissue Overview (Part 1)

  • Function: Responsible for communication and control within the body.

  • Components:

    • Neurons: Specialized for transmitting electrical impulses.

    • Neuroglia (Glial Cells): Supportive cells aiding neurons.

    • Neuroglia Types: Astrocytes (support neurons), oligodendrocytes (produce myelin in the CNS), Schwann cells (produce myelin in the PNS).

Slide 22: Nervous Tissue Overview (Part 2)

  • Neurons:

    • Function: Conduct electrical impulses for rapid communication.

    • Components: Cell body, axon, and dendrites.

    • Special Features: Axons can be myelinated, which increases the speed of impulse transmission.

Slide 23: Neuron Processes

  • Axon:

    • Carries impulses away from the cell body.

    • Typically one per neuron.

    • Myelin Sheath: Insulates the axon, allowing faster transmission of electrical signals.

  • Dendrites:

    • Carry impulses toward the cell body.

    • Neurons may have many dendrites, receiving signals from other cells.

Slide 24: Glia (Neuroglia)

  • Function: Support and nourish neurons, maintain the extracellular environment, and form protective myelin.

  • Types of Glial Cells:

    • Astrocytes: Form the blood-brain barrier and provide nutrients to neurons.

    • Microglia: Act as phagocytes, cleaning up debris in the nervous system.

    • Oligodendrocytes and Schwann Cells: Produce myelin to insulate neuronal axons.

Slide 25: Tissue Repair Overview

  • Definition: Repair and replacement of tissue, usually achieved by regeneration.

  • Tissue Types: Epithelial and connective tissues regenerate effectively, ensuring restoration after injury.

  • Fibrosis: In some cases, fibrous connective tissue replaces the original tissue, leading to scarring.

Slide 26: Tissue Regeneration Examples

  • Epithelial Tissue:

    • Example: Skin healing after cuts or abrasions, as epithelial cells rapidly regenerate.

    • Mechanism: Basal cells divide and migrate to cover the wound.

  • Connective Tissue:

    • Example: Bone healing after fractures, using osteoblasts to lay down new bone matrix.

    • Process: Formation of a hematoma, followed by a fibrocartilaginous callus, and then bone remodeling.

Slide 27: Keloid Formation

  • Definition: Overgrowth of collagen during tissue repair, resulting in a raised, thickened scar.

  • Characteristics: Common in individuals with darker skin; can form after surgery or injury.

  • Formation Process: Excessive fibroblast activity and collagen production during the wound healing process.