The Cell

In human biology, we consider the smallest unit of protoplasm capable of independent existence to be the cell. The term was coined by Robert Hooke who discovered the compartmentalization of cork and christened each chamber as a cell. Examples of cells are bacteria, skin epithelial cells, blood cells, muscle cells and Goblet cells of the conjunctiva. Cells are organized to form tissues. Epithelial cells of the skin are organized with other cells to form the epidermis, a tissue. Muscle cells are grouped to form the tissue muscle. Goblet cells are organized with epithelial cells to form the tissue called conjunctiva. The tissues are organized together to form organs. The conjunctiva, cornea, iris, ciliary body, retina, choroid and optic nerve are all tissue organized to form the eye. The contents or protoplasm of a cell are divided into two compartments, the nucleus and the cytoplasm. Remember in H&E staining the nucleus stains blue (DNA) and the cytoplasm pink (protein). The cytoplasm of the cell contains a number of organelles instrumental in daily processes including the golgi complex, secretory granules, endoplasmic reticulum, centrioles, mitochrondria and cytoplasmic or plasma membranes. The nucleus, replete with DNA, contains a nucleolus or nucleolar organizer region, a nuclear envelope or membrane and cisternae near the membrane.
In pathology, we are mainly concerned with the alterations that occur in the organization of organs, tissues and cells and occasionally in altered organelles. Cells contain various pigment granules, glycogen, lipids depending on their phenotype. These features may be critical to a diagnosis. Nuclear abnormalities are paramount in cancers and are carefully assessed.