Lecture on Tissues

Introduction

• Tissues: Groups or clusters of cells.
  • Group of tissues = Organ
  • Group of organs = Organ system
  • Human body has 11 organ systems -> Organism
• Importance: Understanding structural levels of organization.

Categories of Tissues

1. Neural Tissue
2. Muscle Tissue
3. Connective Tissue
4. Epithelial Tissue

Neural Tissue

• Types: Neurons and Neuroglia
  • Neurons: Carry information to and from the brain.
    • Example: Touching something hot -> Neurons relay info -> Brain sends signal to withdraw hand.
  • Neuroglia: Supporting cells.
    • Functions: Provide nutrients, insulation, waste removal, etc.

Muscle Tissue

• Types: Smooth, Skeletal, Cardiac
  • Smooth Muscle: Found in walls of hollow organs (e.g., stomach, intestines, blood vessels).
  • Skeletal Muscle: Found on the body (e.g., biceps, deltoids, quadriceps, calf muscles, muscles for facial expressions).
  • Cardiac Muscle: Only found in the heart.
• Control: Voluntary vs Involuntary
  • Voluntary: Skeletal muscles (controlled consciously).
  • Involuntary: Smooth and cardiac muscles (operate without conscious control).

Connective Tissue

• Types: Blood, Bone, Fibrous, Cartilage
  • Fibrous Connective Tissue: Loose, Dense, Reticular
  • Cartilage: Hyaline, Elastic, Fibrocartilage

Epithelial Tissue

• Layers: Simple (1 layer) vs Stratified (multiple layers)
  • Simple Epithelial Tissue:
    • Squamous: Flat cells
    • Cuboidal: Cube-shaped cells
    • Columnar: Tall, column-like cells
  • Stratified Epithelial Tissue:
    • Squamous: Flat cells in multiple layers
    • Cuboidal: Cube-shaped cells in multiple layers
    • Columnar: Tall cells in multiple layers
    • Pseudostratified Columnar: Appears stratified but is actually a single layer
  • Transitional Epithelium: Can stretch and return to original shape (e.g., found in the bladder).

Summary

• Neural Tissue: Neurons (information relaying) and Neuroglia (supporting).
• Connective Tissue: Blood, Bone, Fibrous (with subtypes: Loose, Dense, Reticular), Cartilage (with subtypes: Hyaline, Elastic, Fibrocartilage).
• Epithelial Tissue: Classified by number of layers (Simple vs Stratified) and cell shape (Squamous, Cuboidal, Columnar, Transitional).
• Muscle Tissue: Smooth (involuntary, hollow organs), Skeletal (voluntary, attached to bones), Cardiac (involuntary, heart).

Recap

• Tissue types and their distinct functions help understand the human body's structure and function.
• Knowing the control (voluntary/involuntary) and location is crucial for each muscle type.
• Epithelial tissues have unique arrangements suited for different functions and locations in the body.