The carotid body of the mini-pig.

The bilateral distribution of carotid body type 1 and 11 cells was investigated in 3 mini-pigs by serially sectioning the carotid bifurcation regions. The majority of type 1 and 11 cells occurred bilaterally in close proximity to the wall of the occipital artery or one of its small proximal branches, the internal carotid artery and the common arterial trunk. A division of connective tissue surrounded the type 1 and 11 cells with defineable but very irregular borders and this combination of connective tissue and cells constituted the principal mass of the carotid body. In the majority of specimens the cells were diffusely arranged giving a fragmented appearance to the organ but in 2 specimens part of the carotid body was discrete, adopting an ovoid or crescent-shaped appearance over a limited rostral-caudal part of its extent. Arteries to the carotid body originated from the occipital arterial tree in the vicinity of the division of the common arterial trunk and less commonly from the common arterial trunk itself. A supplementary blood supply came from unidentified connective tissue arterioles. In 2 out of 6 specimens type 1 and 11 cells were associated with cervical nerve trunks. Periadvential type 1 and 11 cells were observed in one out of 6 specimens lying dorsal to the common arterial trunk. From our data on 6 specimens, three dimensional reconstructions were made of ventral views of the distribution of carotid body type 1 and 11 cells. On account of the diffuse arrangement of the mini-pig carotid body, morphometric analysis of the organ volume was not feasible.