Fine structure of the ultimobranchial body of the pheasant (Phasianus colchicus L.).

The pheasant's ultimobranchial body is characterized by the presence, in the connective tissue stroma, of epithelial cells between which two types of granulated cells comprising the main part of the glandular portion of the body are formed. Type I is characterized chiefly by the presence of nonrounded electron-dense secretory granules measuring 65-240 nm in the cytoplasm and by a very well-developed Golgi apparatus. The cytoplasm of type II cells also contains dark secretory granules, but somewhat smaller (50-150 nm). This type is very frequently in close contact with specific and often branching tubular structures from whose cells microvilli project into the lumen. The dark cytoplasm of the cells lining these structures contains a relatively large number of mitochondria and dense bodies, but no secretory granules.