Morphology of deep gland of the third eyelid in pig foetuses.

The morphological and histological examinations of the deep gland of the third eyelid were carried out on pig foetuses coming from the 35th, 50th, 63rd, 94th and 112th day of gestation. The morphological examinations were conducted using the method of macroscopic preparation with a forehead magnifying glass and binocular (magnification 1.5-5.0x). In order to make anatomical elements more visible, 60-80% absolute alcohol and 0.5-4% acetic acid solution were used for the examinations. For the histological examinations, the whole eyeball with developing accessory organs was collected from the pig foetuses on the 35th day of gestation. On the 50th, 63rd, 94th and 112th day of gestation only the deep gland of the third eyelid was collected. Staining with haematoxylin-eosin and Azan method was performed. It was found during the examinations that the process of the formation of the deep gland of the third eyelid starts on the 35th day of gestation. On the 50th day of gestation, the gland cells are evenly distributed in the connective tissue stroma. On the 63rd day of gestation, the connective tissue divides the gland parenchyma into indistinct lobes composed of 6-15 lobules. On the 94th day of gestation, the gland lobes become visible; the efferent ducts are situated in the central part of the lobe. On the 112th day of gestation, the lobes are composed of a high number of lobules composed of two kinds of excretory ducts. The first type of the excretory ducts is lined with the simple cuboid epithelium whose nuclei are situated at the base of the cell. The other type of the excretory ducts is lined with the simple cuboid epithelium whose nuclei are round and arranged less or more peripherally.

Morphology of the third eyelid and superficial gland of the third eyelid on pig fetuses.

The morphological and histological examinations of the third eyelid and superficial gland of the third eyelid were conducted in pig fetuses coming from the 20th, 24th, 27th, 30th, 35th, 50th, 63rd, 94th and 112th day of gestation. The morphological examinations were carried out by applying the method of macroscopic preparation with a forehead magnifying glass and binocular (magnification 1.5-5.0x). In order to make anatomical elements more visible, 60-80% absolute alcohol and 0.5-4% acetic acid solution were used for the examinations. On the 20th, 24th, 27th and 30th day of gestation, the whole fetuses were collected for the histological examinations. The whole eyeball with developing accessory organs was collected from the pig fetuses on the 35th day of gestation. On the 50th, 63rd, 94th and 112th day of gestation, only the superficial gland with the third eyelid was collected. Staining with haematoxylin-eosin (H-E) and Azan method was performed. On the 20th, 24th, 27th and 30th day of gestation, the primordia of the glandular epithelium were not found in the examined material. The process of the third eyelid and superficial gland formation starts on the 35th day of gestation. On the 50th and 63rd day of gestation, the gland surrounding the cartilage of the third eyelid is composed of the high amount of loose connective tissue and gland cells which give rise to excretory segments. On the 94th day of gestation, the gland lobes become visible, the efferent ducts form. On the 112th day, the cartilage of the third eyelid assumes the appearance of the mature hyaline cartilage. The excretory segments are composed of simple cuboid epithelium with a large, round nucleus arranged less or more peripherally. Their number increases 2- or even 3-fold at the end of gestation.