Review of Key Concepts - Chapter 30

  1. Specialized cells express different genes. These cells aggregate and function together to form tissues. The four basic tissue types are epithelial tissue, connective tissues, nervous tissue, and muscle tissue.
  2. Epithelium is lining tissue. It may be simple (one layer), stratified (more than one layer), or pseudostratified (one layer appearing as more than one). Epithelial cells may be squamous (flat), cuboidal (cube-shaped), or columnar (tall). Keratin hardens squamous epithelium.
  3. Connective tissues consist of cells within a matrix. Fibroblasts secrete collagen and elastin. Loose connective tissue has loose collagen strands, whereas dense connective tissue has tightly packed collagen fibrils. Adipose tissue consists of adipocytes hugely swelled with lipid. The matrix of blood is plasma, which carries red blood cells, white blood cells, and platelets. Cartilage consists of chondrocytes in lacunae, in a collagen matrix. In bone, osteocytes communicate through canaliculi. Osteoclasts and osteoblasts tear down and rebuild bone tissue. Osteoprogenitor cells can become osteoblasts. Bone matrix consists of collagen and minerals.
  4. Neurons and neuroglia constitute nervous tissue. A neuron has a cell body, an axon, and dendrites and functions in communication. Neuroglia support neurons. Muscle tissue provides movement when filaments of actin and myosin slide past one another. Contractile cells include skeletal, cardiac, and smooth muscle cells and myoepithelial cells.
  5. The integument in many animals consists of an epidermis over a dermis, plus specialized structures, such as hairs, feathers, claws, and glands. In humans a basement membrane joins the epidermis to the dermis, and a subcutaneous layer underlies the dermis.
  6. Transplants, cell implants, and tissue engineering replace damaged tissue. An autograft transfers tissue within an individual. An isograft occurs between identical twins. An allograft uses tissue from the same species. A xenograft uses tissue from a different species. Controversial tissue sources include fetuses, newborns on the verge of death, and nonhuman animals.

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