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Unit Two: Tissues

Ashley Gilly Inglés

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Unit Two: Tissues

Cells are organized into tissues
- Intercellular Junctions connect cells
  - Tight Junctions
    - Close space between cells by fusing cell membranes 
  - Desmosomes
    - Bind cells by forming "spot welds" between membranes 
  - Gap Junctions
    - Form tubular channels between cells to allow for the exhchange of substances 
Four major kinds
- Nervous
  - Conduct impulses for coordination, regulation (homeostasis), integration, and sensory reception
    - Found in the brain, spinal cord, and peripheral nerves
      - Neurons are highly specialized
        -sense changes in surroundings  -have dendrites, which receive sensory info and transmit the message as an electrical signal to the axon..sends message to the next neuron or to muscles or glands  -function: coordinate, regulate, and integrate 
  - Brain, spinal cord, nerves
  - Cells communicate with each other and other body parts
    - Neuroglia
      - Supporting cells of the nervous tissue
        Some bind and support nervous tissue, some carry phagocytosis
        Phagocytes protect nervous tissue by engulfing cellular debris, waste, and foreign material 
        Some connect neurons to blood vessels, and some are involved w/ cell-to-cell communication
- Muscular
  - Movement
  - Attached to bones, in hollow internal organs, heart
  - Able to contract in response to stimuli
    - Muscle cells are also called...
      - Cell fibers 
    - Skeletal muscle makes up....% of body weight and smooth and cardiac about...
      - 40%, 10%
      - Three types of muscle tissue
        Skeletal
        Function: move body parts, facial expressions, writing, talking, singing, chewing, swallowing, and breathing 
        Muscles that contain skeletal muscle tissue are usually attached to bones
        Each cell has many nuclei -> multinucleate
        voluntary muscle tissue
        Contract when stimulated by a nerve cell, then relaxed when it is no long stimulated
        The cells are long, threadlike
        About 40 mm in length and less than .1 mm in width 
        Contain striations
        Alternating light and dark cross-markings
        Smooth
        No striations
        Cells are short and spindle shaped
        Found in the walls of hollow internal organs
        Stomach, intestines, bladder, uterus, blood vessels 
        One central nucleus per cell
        Involuntary control
        Moves food through digestive tract, constricts blood vessels, and empties the bladder 
        Cardiac
        One nucleus per cell
        Involuntary control
        Pumps blood through the heart and into the blood vessels
        Cells are striated, branched, joined end-to-end and interconnected
        Specialized intercellular junction -> intercalated disc
        Connection b/w cardiac muscle cells 
        Function w/o nervous stim.
- Epithelial
  - Covers body surface, internal organs, and glands
    - Classified according to cell shape and the number of cell layers
      - Simple Squamous
        -One layer of flat cells -Diffusion, filtration, secretion  -alveoli of lungs, ithe kidney, the lining of the heart, blood vessels, and ventral cavities 
      - Simple Cuboidal
        -One layer of cuboidal cells -Secretion and absorption -Small glands, kidney tubules, and ovary surface
      - Simple Columnar
        -one layer of columnar cells -Non ciliated: absorption of digested food, secretion of mucus  -digestive track -Ciliated: secretion, moving mucus  -small bronchi, uterus
      - Pseudostraified Columnar
        -One layer of cells, all on basal membrane  -Secretion and propulsion of mucus -Nonciliated: male urethra and ducts of large glands -Ciliated: found on trachea, primary bronchi, and upper respiratory 
      - Stratified Squamous
        E-has several layers, with a surface of flat cells -protection..may contain keratin that repels bacteria  Keratinized: epidermis of skin Non-keratinized: lines wet surfaces, such as mouth, esophagus, tongue 
      - Stratified Cuboidal
        -Several layers, but the surface is cuboidal  -Protection  -largest ducts of sweat glands, mammary glands, salivary glands
      - Stratified Columnar
        -Several layers, with columnar surface -Protection and secretion -Very rare: lines parts of the urethra, large ducts of glands, conjunctiva of eye
      - Transitional
        -shape at surface us transitory..will look like stratified squamous when stretched, stratified cuboidal when not.  -distension of urinary organ  -on surface of stretchy organs, like the bladder and uterus. 
      - Glandular
  - Protection, secretion, absorption, excretion
  - Lacks blood vessels, cells readily divide, though are tightly packed
    - Basement membrane
      - Anchors epithelium to connective tissue
      - Cancer cells dissolve the membrane or produce fewer adhesion proteins
- Connective
  - Widely distributed throughout the body
    - Cell types
      - Fibroblasts
        Produce collagens and elastic fibers 
      - Macrophages
        Are phagocytes (eat cells)
      - Mast cells
        Release heparin and histamine 
    - Tissue fibers
      - Collagen
        Great tensile strength
      - Elastic
        Composed of elastin, are stretchy 
      - Reticular
        Fine collagen fibers 
  - Bind, support, protect, store fat, produce blood cells, protect against infection, and repair damaged tissue
    - Categories of Tissue
      - Loose
        Areolar
        Description: membranes between organs that bind them together  Location: Beneath skin and surrounds organs
        Adipose
        Function: stores fat, cushions, insulates Location: beneath skin, in certain abdominal membranes, and around kidneys, heart, and various joints
        Reticular
        Description: thin branched reticular fibers Function: supports the walls of the liver and spleen
      - Dense
        Regular
        Description: strong collagen fibers that bind structures as parts of tendons and ligaments 
        Irregular
        Description: thicker, randomly distributed collagen fibers  Location: found on dermis 
        Elastic
        Description: make up hollow internal organs  Location: line the lungs and blood vessels
      - Specialized
        Cartilage
        Description: provides support -fibers and a gel-like substance  -lacks direct blood supply, slow to heal Location: ends of various bones, in ear, in the larynx, in b/w spinal column, pelvic girdle, knees
        Bone
        -Matrix consists of mineral salts and collagen -Compact and spongy bones -Heals rapidly 
        Blood
        Description: composed of cells suspended in fluid Location: produced in tissue of hollow parts of certain bones 
  - Have a good blood supply, cells are farther apart, extra cellular mix in b/w
    - Consists of fibers and a ground substance (gel-like)