General Histology and General Pathology Notes

Pathological Investigations

  • Biopsy: Study of a specimen from a lesion during life.
  • Autopsy: Post-mortem examination of the cadaver.

NB:

  • Materials obtained are immediately placed in a fixative fluid to prevent autolysis.
  • The commonly used fixative fluid is 10% formalin.

Microscopic Slides Preparations

The workflow for preparing microscopic slides involves several steps:

  1. Fixing
  2. Processing
  3. Embedding
  4. Cutting
  5. Staining
  6. Microscopy

Microscope Parts

  • Eyepiece
  • Body Tube
  • Revolving Nosepiece
  • Objective Lens
  • Arm
  • Coarse Focus
  • Fine Focus
  • Stage
  • Stage Clips
  • Diaphragm
  • Light
  • Base

Magnification and Resolution

  • Magnification: Increase of an object’s apparent size.
  • Resolution: Power to show details clearly.
  • Both magnification and resolution are needed to see a clear image.

Power of Resolution (R.P.)

The Power of Resolution (R.P.) gives the minimal distance of two structural elements so that they can be imaged as two separate elements instead of one.

Paraffin Section Preparation and Staining

Tissue Processing Steps

  1. Obtain the specimen
  2. Fixation
  3. Dehydration
  4. Clearing
  5. Embedding
  6. Sectioning
  7. Sliding
  8. Staining
  9. Covering

Tissue Processing Details

  • Three to four changes of fresh wax are necessary during tissue processing.

H&E Staining

  1. Stain with Haematoxylin (2-5 mins)
  2. Stain with eosin (10 mins)

Microscopic Observations

  • Round, centrally-placed nuclei
  • Binucleate hepatocyte
  • Granular cytoplasm
  • Prominent nucleoli

Denervation Atrophy

  • Denervation atrophy: Some skeletal muscle fibers show atrophy compared to normal fibers.
  • The number of cells remains the same, but the size of some fibers is reduced.

Associated Diseases:

  • Peripheral nerve diseases
  • Neuromuscular junction diseases
  • Motor neuron diseases
  • Muscular Dystrophies
  • Myopathies other than Dystrophies
  • Ion channel diseases
  • Metabolic diseases of the muscle

Cerebral Atrophy

  • Cerebral atrophy observed in a patient with Alzheimer's disease.
  • The entire size of the brain is reduced, with some parts more affected than others.
  • Gyri are narrowed, and sulci are widened, most pronounced toward the frontal lobe region.

Cardiac Hypertrophy

  • Cardiac hypertrophy involving the left ventricle.
  • The number of myocardial fibers does not increase, but their size can increase in response to an increased workload.
  • Leads to the marked thickening of the left ventricle in patients with systemic hypertension.

Endometrial Hyperplasia

  • The prominent folds of the endometrium exemplify hyperplasia.
  • Cells forming both the endometrial glands and the stroma have increased in number.
  • As a result, the size of the endometrium has increased.
  • The cause is usually excess estrogenic stimulation.

ENDOMETRIUM:

  • It consists of two layers:
    1. Epithelium (Simple columnar)
    2. Lamina propria.

Squamous Metaplasia

  • Metaplasia of laryngeal respiratory epithelium in a smoker.
  • Chronic irritation has led to the exchanging of one type of epithelium (normal respiratory type) to another (abnormal type).

Cervical Dysplasia

  • Normal cervical squamous epithelium alongside dysplastic squamous epithelium.
  • Dysplastic epithelial cells are darker, smaller, and more crowded, without an orderly process of maturation.
  • Dysplasia is a disorderly growth of epithelium but is still confined to the epithelium and is potentially reversible.