Biology: Tissues

• What is the primary method through which small, unicellular organisms obtain nutrients?

  Through diffusion
• Why is cell size constrained by the surface area-to-volume ratio?

  Because as the cell gets larger, this ratio decreases
• What happens to the surface area-to-volume ratio as a cell increases in size?

  It decreases, which is not favorable
• How do larger organisms manage cell size?

  They have more cells, not larger cells
• Which animals do not have distinct and well-defined tissues?

  Sponges
• What is the role of cell-to-cell junctions in tissues?

  They join cells together to form a tissue
• What are the three types of cell-to-cell junctions?

  Tight junctions, gap junctions, and anchoring junctions

  
• What are the four main types of animal tissues?

  • Epithelium: lines cavities and surfaces
  • Connective: connects tissues and provides support
  • Muscle: generates movement
  • Neuron: generates and sends electrical signals

  
• What is the function of connective tissue?

  To connect different tissues or give the body structure
• What do connective tissues consist of?

  Cells embedded in a non-cellular matrix with fibers
• What are the types of fibers found in connective tissue?

  Collagen, elastin, and reticular fibers

  
• What is the role of fibroblasts in connective tissue?

  They secrete extracellular matrix and fibers

  
• What do chondrocytes secrete?

  Extracellular matrix in cartilage
• What do osteocytes secrete?

  Extracellular matrix in bone
• What is the function of adipocytes?

  To store and metabolize fat
• What is the function of epithelial tissue?

  To form boundaries between different environments
• What are the characteristics of epithelial tissue?

  They have a top and bottom surface, rest on connective tissue, have no blood supply, and can regenerate
• How is epithelial tissue categorized?

  Based on the number of layers and shape of the cells

  
• What are the two classifications of epithelial tissue based on the number of layers?

  Simple (one layer) and stratified (multiple layers)

  
• What are the shapes of epithelial cells?

  Squamous, cuboidal, columnar, and transitional

  
• What is collagen known for in connective tissue?

  It is the most abundant protein in the human body
• What is the role of elastin in connective tissue?

  It provides stretch and elastic recoil

  
• What is the ground substance in connective tissue?

  A semi-fluid gel made of GAGs and water
• What is the principal GAG in loose supporting tissues?

  Hyaluronic acid
• Why are GAGs important in connective tissue?

  They are hydrophilic and attract a large volume of water
• What are the types of connective tissue?

  • Loose areolar
  • Dense fibrous
  • Cartilage
  • Bone
  • Adipose
  • Blood
• What are the three types of muscle tissue?

  Skeletal, smooth, and cardiac
• What characterizes skeletal muscle tissue?

  It has prominent striations and many nuclei at the periphery
• Where is smooth muscle tissue found?

  In visceral organs
• What characterizes cardiac muscle tissue?

  It is striated and has a single nucleus
• What is the composition of nervous tissue?

  It is made up of neurons and neuroglia
• What is the function of neurons?

  To generate, transmit, and receive impulses
• What are neuroglia specialized for?

  Supporting neurons