TISSUES (4)

• Tissue - is a group of cells that usually have a common origin in an embryo and function together to carry out specialized activities
• four basic types of tissue:

  
  

  epithelial

  connective

  muscle

  nervous
• Epithelial tissue - covers the inside of the body cavities and lines the outside of the body.
• Surfaces of Epithelial Tissue

  • Apical Surface
  • Lateral Surface
  • Basal Surface
• Apical Surface


  Faces the body surfaces, a body cavity, the lumen of an internal organ, or a tubular duct that receives cell secretions
• Lateral Surface


  Faces the adjacent cells on either side, may contain tight junctions, adherens junctions, desmosomes, and/or gap junctions
• Basal Surface


  Opposite to the apical surface, the deepest layer of epithelial cells adhered to extracellular materials
• Basement Membrane


  Thin extracellular layer that commonly consists of two layers: Basal Lamina and Reticular Lamina
• Basal Lamina


  Thin layer, contains proteins such as laminin and collagen, as well as glycoproteins and proteoglycans
• Reticular Lamina


  Closer to the underlying connective tissue, contains proteins such as collagen, fibroblasts
• Connective Tissue


  • Provides structural support, protection, and metabolic support to other tissues and organs in the body
  • Characterized by cells dispersed within an extracellular matrix, which may include fibers such as collagen, elastin, and reticular fibers, as well as ground substance
  • One of the most abundant and widely distributed tissues in the body
• Connective Tissue Cells

  • Fibroblasts
  • Macrophages
  • Plasma Cells
  • Mast Cells
  • Adipocytes
  • Leukocytes
• Muscle Tissue


  • Specialized type of tissue composed of elongated cells called muscle fibers or myocytes
  • Capable of contracting in response to electrical or chemical stimuli, resulting in movement or tension generation
• Types of Muscle Tissue

  • Cardiac Muscle
  • Skeletal Muscle
  • Smooth Muscle
• Cardiac Muscle


  • Found exclusively in the walls of the heart
  • Short, branched fibers with striations
  • Intercalated discs between adjacent cells allow for rapid electrical signal transmission
  • Forms a synchronized, involuntary pumping action to propel blood through the circulatory system
• Skeletal Muscle


  • Long, multinucleated fibers with striations (stripes) visible under a microscope
  • Each fiber contains parallel arrays of contractile proteins called actin and myosin
  • Skeletal muscle fibers are organized into bundles called fascicles, surrounded by connective tissue layers
  • Attached to bones via tendons, allowing for voluntary movements of the skeleton
• Smooth Muscle


  • Found in the walls of hollow organs (e.g., digestive tract, blood vessels, bladder) where it controls involuntary movements like peristalsis and regulates blood flow
  • Spindle-shaped cells lacking striations
  • Cells are arranged in layers and exhibit slow, involuntary contractions
  • Smooth muscle contraction regulates the flow of substances through organs and maintains organ shape
• Nervous Tissue


  • Main component of the nervous system, which includes the brain, spinal cord, and nerves
  • Structurally consists of two main types of cells: Neurons and Glial cells (neuroglia)