Copy of Chapter 3 - Tissues

Chapter 3 - Tissues

1. Introduction

• Main tissue types:

  • Epithelial

  • Connective

  • Muscle

  • Nervous

• Functions:

  • Protection

  • Secretion

  • Absorption

  • Connection

  • Movement

  • Information processing

• Tissue membranes:

  • Epithelial membranes:

    • Mucous

    • Serous

    • Cutaneous

  • Connective tissue membranes:

    • Synovial membranes (found in joints)

2. Types of Tissues

• Four categories:

  • Epithelial: Covers surfaces, lines cavities

  • Connective: Supports, connects, transports

  • Muscle: Enables movement

  • Nervous: Sends and receives signals

• Embryonic origin: Derived from ectoderm, mesoderm, endoderm

3. Epithelial Tissue

• Characteristics:

  • Closely packed cells

  • Avascular (lack of blood vessels)

  • Polarity (distinct apical and basal surfaces)

  • Rapid regeneration capability

• Cell Junctions:

  • Tight junctions: Barrier function, e.g., intestines

  • Anchoring junctions: Provide stability, e.g., skin

  • Gap junctions: Allow communication, e.g., heart

• Types:

  • Simple: One layer

  • Stratified: Multiple layers

  • Shapes:

    • Squamous (flat)

    • Cuboidal (cube-shaped)

    • Columnar (tall)

  • Specialized types:

    • Pseudostratified: Appears layered but isn’t

    • Transitional: Stretchable, e.g., bladder

• Glands:

  • Endocrine: Ductless, secretes hormones into bloodstream

  • Exocrine: Has ducts, secretes onto surfaces

  • Modes of secretion:

    • Merocrine: Uses exocytosis, e.g., sweat glands

    • Apocrine: Pinched off portion of cell, e.g., mammary glands

    • Holocrine: Entire cell disintegrates, e.g., sebaceous glands

4. Connective Tissue

• Structure:

  • Cells dispersed in extracellular matrix (ground substance + protein fibers)

• Fiber types:

  • Collagen: Strong and flexible

  • Elastic: Stretchy

  • Reticular: Supportive framework

• Categories:

  • Proper:

    • Loose (Areolar, Adipose, Reticular)

    • Dense (Regular, Irregular, Elastic)

  • Supportive:

    • Cartilage: Hyaline, elastic, fibrocartilage

    • Bone: Osteocytes in lacunae, vascularized

  • Fluid:

    • Blood: Contains red blood cells (RBCs), white blood cells (WBCs), plasma

    • Lymph: Plays a role in immune function

• Functions:

  • Structural support

  • Transport (e.g., blood)

  • Immune defense

  • Energy storage (e.g., adipose tissue)

5. Muscle Tissue

• Properties:

  • Excitable

  • Contractile

• Types:

  • Skeletal:

    • Striated

    • Voluntary

    • Attached to bones

  • Cardiac:

    • Striated

    • Involuntary

    • Found in heart muscle, with intercalated discs

  • Smooth:

    • Non-striated

    • Involuntary

    • Present in digestive, respiratory, and reproductive systems

6. Nervous Tissue

• Function: Conducts electrical impulses, processes information

• Cell types:

  • Neurons: Transmit signals via axons and dendrites

  • Neuroglia: Support, protect, and nourish neurons

7. Tissue Injury & Aging

• Inflammation response:

  • Signs: Redness, swelling, heat, pain

• Healing process:

  • Clotting → Granulation tissue → Regeneration/scarring

• Aging effects:

  • Reduced regeneration

  • Increased scarring

  • Tissue stiffness

• Cancer:

  • Mutations disrupt normal tissue function, leading to uncontrolled growth

Examples to Memorize

• Simple squamous epithelium: Lungs (gas exchange)

• Stratified squamous epithelium: Skin (protection)

• Cuboidal epithelium: Kidney tubules (filtration)

• Columnar epithelium: Digestive tract (absorption)

• Dense regular connective tissue: Tendons & ligaments (high tensile strength)

• Hyaline cartilage: Nose, trachea (flexibility, support)

• Skeletal muscle: Biceps (voluntary movement)

• Cardiac muscle: Heart (pumps blood)

• Neurons: Brain, spinal cord (information transmission)