bio classes ucsc edu bio info content micro mi

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					 Allison Gong

• Histology
• Microscopy
• Development
I. Histology

• Histology = study of tissues
• Tissue = group of cells with similar structure
     and function
• Four types of human tissues:
  –   Nervous tissue
  –   Muscle
  –   Connective tissue
  –   Epithelial tissue
             Connective tissue

• Provides support (physical + metabolic) for
     other tissues
• Surrounds all other tissues
  – Provides structural framework
• Types of connective tissue:
  –   Bone
  –   Blood
  –   Cartilage
  –   Adipose tissue
  –   Tendons, ligaments
Connective tissue

        • Combination of:
           – Cells (type varies)
           – Extracellular materials; matrix
        • Cells far apart
        • Matrix holds H2O
           – Resists compression
           – Nutrients/wastes pass through
             (interstitial fluid)
        • Stretchy and strong
              Epithelial tissue

• Covers surfaces, lines tubes, forms glands
• Cells tightly packed, form sheets
• Functions:
  – Protection (e.g., skin)
  – Absorption (e.g., gut)
  – Secretion (e.g., gut, exocrine/endocrine glands)
                  Epithelial tissue

• Gland - group of epithelial cells, specialized
     to secrete specific substance(s)
• Types of glands:
   – Exocrine gland - ducts; to outside of body
      • e.g., sweat gland
   – Endocrine gland - ductless; hormones distributed
      via bloodstream
      • e.g., thyroid, pancreas
            Epithelial tissue

Epithelial tissues are categorized by number
             and type (shape) of cells
             Epithelial tissue

• 3 cell types:
   – Cuboidal
   – Columnar
   – Squamous
• Number of cells:
   – 1 layer thick - simple
      • Good for absorption (e.g., intestinal epithelium)
   – > 1 layer thick - stratified
      • Good for protection (e.g., skin)
Epithelial tissue - categories
      1. Simple cuboidal
Epithelial tissue - categories
     2. Simple columnar
Epithelial tissue - categories
     3. Simple squamous
Epithelial tissue -stratified epithelia

        Stratified cuboidal - sweat gland
Epithelial tissue -stratified epithelia

         Stratified columnar - duct
Epithelial tissue -stratified epithelia

        Stratified squamous - esophagus
        The basement membrane

• Separates epithelial and connective tissues:

                  connective tissue

• Not usually visible with light microscope
• Functions:
   – “glue” - holds tissues together
   – Template for cell migration during development
II. Microscopy
Parts of a light
  Requirements for a clear image

1. Magnification - make the image larger
     than life-size
2. Resolution - ability to distinguish two
     objects in close proximity
3. Contrast - make the image stand out
     against background
            1. Magnification

• Our scopes have four objective lenses:
  –   4X
  –   10X
  –   40X
  –   100X (oil immersion only)
• Ocular lenses are 10X
• Total magnification = (objective)(ocular)
  e.g., if using the 40X objective,
     total magnification = (40)(10) = 400X
              2. Resolution

i.e., How close can two objects be and still be
       seen as two objects?

                       well resolved

                       poorly resolved

                  **Note: Increasing magnification
                  does not help problems of
                    3. Contrast

• i.e., How well can you see the image against
  the background?
• Living cells have little contrast
• Use stains
   – Dyes that bind to certain functional groups in cells
   – Examples: hematoxylin, eosin
• But, most stains kill cells
   – Use phase contrast lighting instead

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