Comparison of Duct and Blood Vessels
This image contrasts three tubular structures, a duct, a small vein, and a small artery.
The lining of the duct is simple cuboidal epithelium.
Each cell is boxy, with a prominent round nucleus (white arrows in the thumbnail). Nuclei are clearly separated from the lumenal space by cytoplasm of the cuboidal cells.
The lining of the vein is simple squamous epithelium.
The lining of blood vessels is called endothelium. Each endothelial cell is thin and flat. As seen here edge-on, the flattened endothelial nuclei (white arrows in the thumbnail) appear to lie immediately adjacent to the vessel's lumen. The inconspicuous cytoplasm of each endothelial cell may appear as a very thin line extending out on either side of the nucleus.
The lining of the artery is also simple squamous epithelium.
As in the vein, above, the lining of this blood vessel is called endothelium. And, as in the vein, each endothelial cell is thin and flat. However, as a routine artifact of post-mortem contraction, smooth muscle in the arterial wall often causes lengthwise wrinkles in the vessel wall so that arterial endothelial nuclei often appear round (white arrows in the thumbnail). The nuclei of smooth muscle cells (black arrows) lie deep to the endothelial cells and are elongated in a direction encircling the vessel.
These three tubular structures are all surrounded by loose fibrous connective tissue, in which extracellular collagen is stained pink and nuclei of connective tissue cells (white arrows) are stained deep purple. Most of these cells are probably fibroblasts, but mast cells and macrophages may also be expected in this location.
[This image comes from the submucosa of the esophagus. The duct drains a submucosal mucous gland of the esophageal wall.]
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SIUC / School
of Medicine / Anatomy / David
Last updated: 31 July 2002 / dgk