Histology: Types of Tissue Overview

Tissue Overview

• Tissue is a group of cells that share a common embryonic origin and work together to fulfill specific functions.
• Histoogy is the microscopic study of tissue structure, organization, and function.

Types of Tissues

• Epithelial Tissue (Epithelium)

  • Covers exterior body surfaces and lines internal cavities and passageways.
  • Forms certain glands involved in secretion.

• Connective Tissue

  • Binds cells and organs, providing support, protection, and integration of body parts.

• Muscle Tissue

  • Excitable and responsive to stimulation.
  • Has three main types:
    • Skeletal (voluntary)
    • Smooth
    • Cardiac (found in the heart)

• Nervous Tissue

  • Also excitable, facilitating the propagation of nerve impulses for communication within the body.

Embryonic Origin of Tissues

• Originates from the zygote, which undergoes rapid cell division to form the embryo.
• Early embryonic cells are totipotent, meaning they can differentiate into any cell type.
• Three main cell lineages develop as cell proliferation progresses.

Tissue Membranes

• Tissue membranes are thin layers covering body surfaces, organs, and internal passageways.
• Two main types:
  • Connective Tissue Membranes: Include synovial membranes and encapsulate organs, providing a protective layer.
  • Epithelial Membranes: Composed of epithelium over a connective tissue layer.

Connective Tissue Membranes

• Formed solely from connective tissue, lining movable joints and organs such as the kidneys.
• Synovial Membrane: A type of connective tissue membrane that produces synovial fluid to reduce friction in joints.

Epithelial Membranes

• Composed of epithelial tissue and a surrounding layer of connective tissue.
• Mucous Membrane: Composite of connective and epithelial tissues, containing lamina propria for support.
• Serous Membrane: Composed of mesothelium supported by connective tissue; lines cavities and covers organs.
• Cutaneous Membrane (Skin): A stratified squamous epithelial layer that protects against environmental threats.

Epithelial Tissue Origin

• Epithelial cells originate from all three embryonic layers:
  • Ectoderm: Forms the epithelia of skin and mucosal lining of mouth, nose, and anus.
  • Endoderm: Lining of airways and most parts of the digestive system.
  • Mesoderm: Vascular systems' lining (endothelium).
• Specialized structures called cell junctions form connections between adjacent cells.
• Epithelial cells are polarized, with the apical surface facing the external environment and a basal surface adjacent to underlying tissues.