allison gong histology microscopy development i. histology
TRANSCRIPT
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
• 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)
The basement membrane
• Not usually visible with light microscope• Functions:
– “glue” - holds tissues together– Template for cell migration during development
• Separates epithelial and connective tissues:
connective tissue
basementmembrane
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 resolution!!