Lecture Notes: Cells, Tissues, Organs, and Systems

Overview

• Multicellular organisms have a hierarchical structure:
  • Cells -> Tissues -> Organs -> Organ Systems -> Organism
• Groups of similar cells form tissues, tissues combine to form organs, organs form systems, and systems constitute an organism.

Cells

• Examples of Cells:
  • Red Blood Cells (RBCs): Carry oxygen.
  • White Blood Cells: Part of the immune system.
  • Nerve Cells: Transmit nerve impulses.
  • Cheek Cells/Epithelial Cells: Surface cells.
• Common Characteristics: All cells have a nucleus and are genetically identical within an organism, yet differentiated for specific functions.
• Differentiation: Process where cells become specialized.
  • Although they share DNA, specific genes are activated to give cells their function and structure.

Tissues

• Four Types of Tissues:
  • Connective Tissue
  • Epithelial Tissue
  • Muscle Tissue
  • Nervous Tissue (not detailed in this lecture)

Epithelial Tissue

• Types:
  • Squamous: Flat cells, found in lungs and capillaries.
  • Columnar: Long, thin cells, found in intestines and kidneys.
  • Ciliated: Cells with cilia, found in trachea and oviducts; increase surface area.

Connective Tissue

• Roles: Hold tissues and organs together.
• Examples:
  • Bone Tissue: Made of bone cells, provides structure and support.
  • Fibrous Tissue: Flexible, forms tendons and ligaments.
  • Adipose Tissue: Stores fat, provides insulation and energy.

Muscle Tissue

• Types:
  • Cardiac Muscle: Heart muscle, involuntary and non-fatiguing.
  • Skeletal Muscle: Attached to bones, controls movement.
  • Smooth Muscle: Lines intestines, blood vessels, involuntary movement.

Organs

• Definition: Structures composed of various tissues serving a specific function.
• Examples:
  • Intestines: Made of epithelial, connective, smooth muscle, and nerve tissues.
  • Heart: Composed of fibrous, cardiac muscle, epithelial, and nerve tissues.
  • Lungs: Include connective, smooth muscle, epithelial, and nerve tissues.

Organ Systems

• Definition: Group of organs that work together for a specific function.
• Systems:
  • Skeletal & Muscular Systems: Support and movement, involve bones and muscles.
  • Circulatory System: Heart, blood vessels, transports oxygen and nutrients.
  • Digestive System: Stomach, intestines, liver; digestion and absorption.
  • Urinary/Excretory System: Skin, kidneys, lungs; removal of waste.
  • Nervous System: Brain, spinal cord; communication and control.
  • Reproductive System: Testes, ovaries; reproduction.
  • Lymphatic/Immune System: Spleen, thymus; defense against pathogens.
  • Endocrine System: Glands; hormone regulation, slow but lasting control.
  • Respiratory System: Lungs and trachea; gas exchange.

Conclusion

• Reviewed the structure hierarchy: cells -> tissues -> organs -> systems -> organism.
• Highlighted the interconnectedness of biological structures and their functions.