The volume of the carotid body and periadventitial type 1 and type 2 cells in the carotid bifurcation regions of the pregnant and lactating cat.

The bilateral distribution of carotid body type 1 cells was investigated in 2 pregnant cats at 95% full term and two lactating cats (2 and 4 d after parturition). Carotid body type 1 and 2 cells occurred bilaterally in close proximity to the occipital artery or one of its branches in a division of connective tissue with defineable but irregular borders. This combination of connective tissue and type 1 and 2 cells constituted the principal mass of the carotid body, which received its blood from the occipital and/or the ascending pharyngeal arteries. Using an interactive image analysis system, the area of the carotid body in each serial section was measured by accurately contouring its perimeter. The volume of the carotid body was calculated by multiplying the sum of the contoured areas of the serial sections by the thickness of the section. The volumes for the carotid bodies in pregnant cats ranged between 0.186 and 0.278 mm3 while the values in lactating animals lay between 0.287 and 0.356 mm3. Caudally and separate from the carotid body, isolated groups of periadventitial type 1 and 2 cells were found in 5 out of 8 specimens around the occipitoascending pharyngeal trunk, origin of the occipital artery, external carotid artery and rostral part of the common carotid artery. The volumes of the periadventitial type 1 and 2 cells were variable in pregnant and lactating cats.