Types of Tissues in the Human Body

Types of Tissues

• Four Main Types of Tissues:
  1. Epithelial Tissue (上皮組織)
  • Functions:
    • Covers body surfaces and organs.
    • Lines body cavities and hollow structures (e.g., heart, blood vessels, digestive tract).
  1. Connective Tissue (結締組織)
  • Binds and supports body parts.
  1. Muscular Tissue (肌肉組織)
  • Responsible for contraction and movement.
  1. Nervous Tissue (神經組織)
  • Responds to stimuli and transmits signals between different body parts.
• "4Cs" Concept:
  • Tissues Cover, Connect, Contract, Communicate.
• Example of Organ Composition:
  • The heart is composed of:
  • Epithelial tissue covering the surface.
  • Connective tissue supporting the valves.
  • Cardiac muscle that pumps blood.
  • Nerves regulating heart rate.

Epithelial Tissue (上皮組織)

• Characteristics:
  • Tightly packed with minimal interstitial space.
  • Capable of rapid cell division to replace lost or damaged cells (e.g., skin cells, intestinal lining cells).
  • Avascular: Lacks blood vessels, obtaining nutrients from underlying connective tissues.
  • Functions:
  • Externally: Protection from drying, injury, and bacterial invasion.
  • Internally: Various additional functions such as filtration and secretion.
    • Example: Cilia in respiratory epithelium helps sweep impurities.
    • Example: Mucus secretion along the digestive tract protects the lining from enzymes.
    • Example: Microvilli in kidney tubules enhance absorption.

Classification of Epithelial Tissue

• By Cell Layers:
  1. Simple Epithelium:
  • Composed of a single layer of cells.
  1. Stratified Epithelium (複層上皮):
  • Composed of two or more layers of cells.
• By Cell Shape:
  1. Cuboidal Epithelium (立方上皮):
  • Cube-shaped cells.
  1. Columnar Epithelium (柱狀上皮):
  • Tall, elongated cells.
  1. Squamous Epithelium (鱗狀上皮):
  • Flattened cells.
• Specialized Types:
  • Transitional Epithelium (變移上皮): Cells change shape depending on the state of stretch.
  • Pseudostratified Columnar Epithelium (偽複層柱狀上皮): Appears stratified but is a single layer.

Types of Simple Epithelial Tissue

• Simple Squamous Epithelium:
  • Characteristics:
  • Single layer of flattened cells.
  • Broad, elongated nuclei.
  • Function: Allows simple diffusion.
  • Locations: Found in air sacs of lungs (alveoli) and lining of capillaries. Facilitates gas exchange between oxygen and carbon dioxide.

Types of Stratified Epithelial Tissue

• Stratified Squamous Epithelium (複層鱗狀上皮):
  • Characteristics:
  • Composed of multiple cell layers with the superficial layer being squamous-shaped.
  • Deep layers may be cuboidal or columnar.
  • Function: Provides protection.
  • Forms include:
  • Stratified Non-Keratinized Squamous Epithelium (複層非角化鱗狀上皮):
    • Lining for moist surfaces (e.g., mouth, vagina, anus).
    • Protects against abrasion and drying (desiccation).
  • Stratified Keratinized Squamous Epithelium (角化鱗狀上皮):
    • Forms the outer layer of skin.
    • New cells generate in the basal layer, accumulating keratin as they approach the surface and eventually die.

Overview of Epithelial Tissue Types

• Epithelial Tissue Types, Descriptions, and Locations:
  

• Connective Tissue Proper:
  • Connects and supports structures throughout the body.
  • Contains both loose and dense connective tissues:
  • Types of Loose Connective Tissue:
    1. Areolar Connective Tissue
    2. Adipose Tissue
    3. Reticular Connective Tissue
  • Types of Dense Connective Tissue:
    1. Dense Regular Connective Tissue
    2. Dense Irregular Connective Tissue
    3. Elastic Connective Tissue

Characteristics of Loose Connective Tissue

• Areolar Connective Tissue:
  • Contains fewer cells and fibers than dense connective tissue.
  • Appearance:
  • Spider-web like structure.
  • Cells:
  • Primarily fibroblasts, which produce extracellular fibers.
  • Matrix:
  • Jellylike ground substance that contains collagen and elastin fibers.

Types of Dense Connective Tissue

• Adipose Tissue (脂肪組織):
  • Type of loose connective tissue where fibroblasts store fat and have a limited extracellular matrix.
  • Appearance:
  • Irregular honeycomb structure.
  • Functions:
  • Protects and cushions organs (e.g., eyes, kidneys).
  • Stores energy and insulates against cold.
• Reticular Connective Tissue (網狀結締組織):
  • Fibroblasts are known as reticular cells.
  • Contains reticular fibers and scattered white blood cells.
  • Functions:
  • Partakes in the immune system, found in tissues and organs that promote defense against infections (e.g., red bone marrow, lymph nodes, thymus, spleen).

Characteristics of Dense Connective Tissue

• Dense Regular Connective Tissue:
  • Contains parallel fiber bundles, mainly composed of collagen.
  • Function:
  • Provides strength and resistance; Found in tendons (connecting muscles to bones) and ligaments (connecting bones at joints).
• Dense Irregular Connective Tissue (緻密不規則結締組織):
  • Characterized by fibers running in multiple directions.
  • Locations:
  • Present in the inner portion of the skin (dermis) and joint capsules.
• Elastic Connective Tissue (彈性結締組織):
  • Contains primarily elastic fibers.
  • Locations:
  • Found in the walls of large arteries and vocal cords.

Muscular Tissue (肌肉組織)

• Composition:
  • Made up of muscle fibers containing actin and myosin protein filaments.
• Types of Muscles:
  1. Skeletal Muscle:
  • Attached to the skeleton by tendons.
  • Under conscious control, moves limbs and body parts.
  1. Smooth Muscle:
  • Contracts more slowly than skeletal muscle but can maintain contractions longer.
  • Contracts rhythmically and can be modified by nervous and endocrine systems.
  • Found in the walls of hollow organs (e.g., intestines).
  1. Cardiac Muscle:
  • Found only in the heart.
  • Has striations like skeletal muscle, but contraction is involuntary.
  • Similar to smooth muscle, contractions are intrinsic and rhythmical, modified by nervous and endocrine systems.