Epithelial tissue is composed of cells laid together in sheets with the cells tightly connected to one another. Epithelial layers are avascular, but innervated.
Epithelial cells have two surfaces that differ in both structure and function.
The epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue. One side of the epithelial cell is oriented towards the surface of the tissue, body cavity, or external environment and the other surface is joined to a basement membrane. The basement layer is non-cellular in nature and helps to cement the epithelial tissue to the underlying structures.
Prokaryotic cells have a cell wall surrounding their cell membrane .The Prokaryotic cells don't have a well defined nucleus .The genetic material of the cell is basically naked and not enveloped by the Nuclear membrane .
Eukaryotic cells don't have a cell wall surrounding their cell membrane. The Eukaryotic cells have a well organised nucleus .The genetic material of the cell is surrounded by nuclear membrane or nuclear envelope.
Both Eukaryotic and prokaryotic cells have DNA.Both have a plasma membrane or cell membrane.
The Pathway • air enters the nostrils •passes through the nasopharynx •the oral pharynx •through the glottis • into the trachea • into the right and left bronchi, with branches and rebranches into • bronchioles each of which terminates in a cluster • alveoli
