Introduction to Histology

Cell
is the functional unit of all tissues
is the structural unit of all living organisms
has the capacity to perform individually all the essential life functions

Cell structure
Two components:

• nucleus + nuclear membrane
• cytoplasm + phospholipid bilayer plasma membrane

            Both have subcellular elements called organelles

can be looked under :

• Light microscope
  • Resolving power ≈ 0.25 μm (250 nm)
• Electron microscope
  • Resolution of structures as small as 3.0 nm (30 Å)

Smaller structures seen by biochemical techniques (histochemistry) and immunological techniques (immunohistochemistry)

The cell nucleus
DNA < 20%
Some RNA: messenger, transfer and ribosomal RNA
Nucleoprotein associated with DNA:

• histones (bulk) involved in regulation of DNA activity

Chromatin: chromosomes in a different degree of coiling in nondividing nuclei or coiled strands of DNA bound to basic proteins (histones): The DNA is associated with proteins to form chromatin.
Nucleolus :spherical structure up to 1 mm in diameter, rich in rRNA and protein.
Basophilic on light microscope: H&E.
Large nucleoli present in cell proliferation, regeneration, in rapidly growing malignant tumors

- antihistones