This study determines the micromorphometric parameters of the main structural elements of the paranal sinus in male (n = 20) and female (n = 8) mongrel dogs of different ages. Pieces of about 1 cm3 were obtained from different parts of the organ and put in 10% neutral formalin. The tissue samples were further used for the preparation of paraffin sections that were stained with hematoxylin-eosin for light microscopy measurements. In the sinus wall, the thickness of the epithelium was measured, as was that of the subepithelial and subglandular connective tissue layers, the zona with the apocrine glands, and the entire sinus wall. The outer and inner diameters of the apocrine tubular glands and the height and number of glandular epithelial cells in the apocrine glands were also measured. Statistical data processing was done using Data Analysis tool and t-test by means of the StatMost for Windows software. For the period from the 1st month to the 2nd year, the thickness of the epithelial layer of the sinus wall remained almost identical (from 40.83 ± 9.37 µm during the 1st month to 47.79 ± 3.67 µm in the 2nd year). After the 2nd year, the thickness of the epithelial layer decreased. In the 8th year its thickness reached 35.72 ± 5.89 µm and in the 12th year it was 28.92 ± 6.53 µm. We measured the thickness of the subepithelial and subglandular connective tissue layers of the wall of the sinus, forming the organ's stroma. It was found that the thickness of these layers increased 3-fold for the period from the 1st month to the 12th year. Their thickness increased most intensively until the 5th month, followed by the period from the 5th month to the 2nd year, then from the 2nd to the 8th year, and changed the least up to the 12th year. Therefore, the increase in the thickness of the sinus wall (without its excretory duct) with age was due to the increase of the thickness of the subepithelial and subglandular connective tissue layers in particular. The results of the present study demonstrate that the period featuring the most active weight increase and growth of sinus macromorphometric parameters coincided with the period of increase in the number of cells and the active growth of the main structural elements of the organ.

This study determines the micromorphometric parameters of the main structural elements of the paranal sinus in male (n = 20) and female (n = 8) mongrel dogs of different ages. Pieces of about 1 cm3 were obtained from different parts of the organ and put in 10% neutral formalin. The tissue samples were further used for the preparation of paraffin sections that were stained with hematoxylin-eosin for light microscopy measurements. In the sinus wall, the thickness of the epithelium was measured, as was that of the subepithelial and subglandular connective tissue layers, the zona with the apocrine glands, and the entire sinus wall. The outer and inner diameters of the apocrine tubular glands and the height and number of glandular epithelial cells in the apocrine glands were also measured. Statistical data processing was done using Data Analysis tool and t-test by means of the StatMost for Windows software. For the period from the 1st month to the 2nd year, the thickness of the epithelial layer of the sinus wall remained almost identical (from 40.83 ± 9.37 µm during the 1st month to 47.79 ± 3.67 µm in the 2nd year). After the 2nd year, the thickness of the epithelial layer decreased. In the 8th year its thickness reached 35.72 ± 5.89 µm and in the 12th year it was 28.92 ± 6.53 µm. We measured the thickness of the subepithelial and subglandular connective tissue layers of the wall of the sinus, forming the organ's stroma. It was found that the thickness of these layers increased 3-fold for the period from the 1st month to the 12th year. Their thickness increased most intensively until the 5th month, followed by the period from the 5th month to the 2nd year, then from the 2nd to the 8th year, and changed the least up to the 12th year. Therefore, the increase in the thickness of the sinus wall (without its excretory duct) with age was due to the increase of the thickness of the subepithelial and subglandular connective tissue layers in particular. The results of the present study demonstrate that the period featuring the most active weight increase and growth of sinus macromorphometric parameters coincided with the period of increase in the number of cells and the active growth of the main structural elements of the organ.