Pay attention to the following details:
The cell nuclei of the epithelium, are clearly visible. The acidophilic (pink) areas around each nucleus are the cytoplasm of the epithelial cells. There is almost no space between the cells because they are closely attached to their neighbors.
The nuclei in the connective tissue are apart from each other. The cytoplasm of the cells that contain these nuclei seems thin and is often barely visible. The areas between the cells are spaces filled by extracellular matrix – there are many pink collagen fibers of different sizes and thicknesses – and, in addition, “empty” spaces that probably result from technical artifacts due to the histological techniques and that resulted is a retraction of components of the extracellular matrix.
There are no blood vessels in the epithelium but there is one in the connective tissue.
The layer of connective tissue underlying the epithelia that cover the inner cavities of the digestive, respiratory and urinary systems is also called lamina propria.
The combinationn of an epithelium + its lamina propria that cover the moist surfaces of the inner cavities of internal organs, is called a mucous membrane, very often simplified to mucosa (as in: oral mucosa, gastric mucosa).
The epithelial layer that surrounds the outer surfaces of the organs placed inside the large inner cavities of the body (cardiac, toracic and abdominal cavities) is called mesothelium. The epithelium that covers the inner surface of blood vessels is called endothelium.
Check the