histo lec finals

• Muscle


  One of the key tissues in the body that enables movement and other functions
• Basic types of muscles

  • Voluntary striated muscle
  • Involuntary smooth muscle
  • Striated cardiac muscle
• Voluntary striated muscle (skeletal muscle)


  • Movement can be voluntarily controlled
  • Composed of large elongated eosinophilic myofibers, with more than one peripheral nuclei, and contains striations or stripes that cross the fibers at right angle to their long axis
  • Each myofiber is in turn made up of thinned myofibrils separated by a well-developed system of mitochondria and sarcoplasmic reticulum
  • Contains an abundant store of glycogen that provides immediate source of energy
• Involuntary smooth muscle


  • Derived from mesenchymal tissue, and is composed of smaller tapered myofibers with eosinophilic cytoplasm containing glycogen
  • Myofiber contains bundles of myofilaments myofibrils
  • Nuclei are elongated, centrally located and show a pale staining cytoplasm with hematoxylin
  • Comprise the wall of gastrointestinal tract,urogenital tract and blood vessels, whose contractions cannot be controlled by will
• Striated cardiac muscle


  • Found in the heart, and is knowns the myocardium
  • Cytoplasm contains myofibrils and cytoplasm
  • Cells branch and anastomose frequently and contain "intercalated discs" or end-to-end junctions of adjacent muscle cells
  • Nuclei are centrally place and stained lightly with hematoxylin
• Types of muscle biopsy samples

  • Open muscle biopsies
  • Needle biopsy samples
• Open muscle biopsies


  1. Strips of skeletal muscle should be receive fresh or unfixed in the lab as soon as possible

  2. Transported from operating theater to laboratory wrapped in gauze soaked in normal saline, then squeezed till just damp, to minimize drying

  3. Muscle biopsy is cut into suitable block sized pieces (0.5 x 0.5 cm) and oriented so that transverse section will be cut

  4. Open muscle biopsies are divided into three parts: Small segment - glutaraldehyde for electron microscopy, Middle segment - frozen in cryostat for diagnostic enzyme histochemistry, Reimagining segment - buffered formaldehyde for light microscopy
• Needle biopsy samples


  Taken by a Bergstrom needle and can be quickly and easily obtained from the thigh under local anesthesia
• Stains for muscle


  • Trichrome stain
  • Masson's trichrome
  • Gomori's trichrome stain
  • Gomori trichrome stain for frozen muscle
  • Mallory's phosphotungstic acid hematoxylin (PTAH)
  • Periodic acid Schiff stain (PAS)
  • Sudan black stain
  • Oil red O
  • Heidenhain's iron hematoxylin method
• Trichrome stain


  "Three color" (Mallory's trichrome) which differentially colored erythrocytes orange, muscle red, and collagen tubes
• Masson's trichrome


  Most commonly used to differentiate muscle from collagen in fresh frozen muscle sections
• Gomori's trichrome stain


  Used for frozen sections in muscle biopsy
• Gomori trichrome stain for frozen muscle


  Very useful in detecting ragged fibers in mitochondrial myopathy
• Mallory's phosphotungstic acid hematoxylin (PTAH)


  Demonstrates striated muscle fibers and mitochondria, often without a counterstain, used to identify contraction bands
• Periodic acid Schiff stain (PAS)

  Used to detect glycogen storage, visualize the basement membrane of the capillaries
• Sudan black stain


  Intracellular lipid appears blue-black and is distributed throughout the intermyofibrilar network
• Oil red O


  Fat-soluble dye used for staining of neutral lipids and can be visualized by fluorescence or bright field microscopy
• Heidenhain's iron hematoxylin method

  Stains muscle striations, mitochondria, myelin, and chromatin grey-black
• Histochemical stains/enzyme histochemistry


  • Succinate dehydrogenase stain
  • NADH stain
  • Cytochrome oxidase stain
  • Alpha-glycerophosphate dehydrogenase
  • Myophosphorylase stain
  • Non-specific esterase
• Succinate dehydrogenase stain


  Used to distinguish between oxidative and less oxidative fibers
• NADH stain


  Stains mitochondria in the intermyofibrillar network
• Cytochrome oxidase stain


  Used to detect cytochrome oxidase deficiency
• Alpha-glycerophosphate dehydrogenase


  Used to distinguish among fibers based on their ability to generate ATP in the absence of oxygen (anaerobically)
• Myophosphorylase stain


  Phosphorylase acts on the substrate, glucose-1-phosphate and forms, in the presence of a glycogen primer, a polysaccharide composed of 1,4-glycosyl units
• Non-specific esterase


  Good stain to identify macrophages
• Types of bone tissue

  • Cortical/compact bone
  • Trabecular/cancellous/spongy bone
• Based on matrix arrangement (orientation of collagen type I), bone can be classified as

  • Woven bone
  • Lamellar bone
• Myophosphorylase


  Deficient in McArdle's disease, a primary phosphorylase deficiency
• Neuromuscular and myotendious junction

  • Positive for esterase
  • The neuromuscular junctions appear as small enzymatic reactive areas at the rim of the fibers
• Esterase staining


  • Excessively dark in denerved fiber but not in other atrophic fibers
  • Seen in muscle fibers undergoing necrosis
• Types of bone tissue

  • Cortical/compact
  • Trabecular/cancellous/spongy
• Cortical/compact bone


  • Solid, hard and immensely strong bone that forms the shafts of long bones and exterior surfaces of flat bones
• Trabecular/cancellous/spongy bone


  • Mesh of bony strands that look less solid than cortical bone, and is found in the diaphysis, epiphysis and marrow cavities of long bones, vertebrae and centers of flat bones
• Types of bone based on matrix arrangement

  • Woven bone/immature bone
  • Lamellar bone/mature bone
• Woven bone/immature bone


  • Develops in utero and during phases of rapid bone formation
  • Coarsely and haphazardly oriented collagen with thick and loosely packed collagen fibers
  • Mineral content and osteocyte density are high
  • Osteocytes and lacunae are larger than those of mature bone
  • Calcification is irregular
  • Weaker, less rigid, and more elastic than lamellar bone
• Lamellar bone/mature bone


  • Synthesized following birth
  • Collagen is present in successive layers with delicate and more closely packed fibers in the same direction to each other
  • Collagen bundles are organized in parallel layers or concentric layers/sheets called lamellae
  • Mineral content and osteocyte density are low and collagen density is high
  • Osteocytes and lacunae are smaller and organized
  • Firm with more tensile strength and less flexible than woven bone
• Bone cells


  • Osteoblasts
  • Osteocytes
  • Osteoclast
• Osteoblasts


  Fully differentiated cells, bone formation
• Osteocytes


  Terminally differentiated osteoblasts that incorporate into bone matrix
• Osteoclast


  Bone resorption