Morphometric development of sheep (Ovis aries) lymph nodes in fetal period

Immune system plays crucial role in body and lymph nodes are essential parts of this system for combating pathogens. However, no study has ever been conducted on morphometric development of sheep lymph nodes in fetal period. Thus, this study attempted to examine the morphometric characteristics of a number of important lymph nodes of some lymphocenters of sheep during fetal period. To this end, 60 pieces of sheep fetuses collected from Ahvaz slaughterhouse were fixated in 10% formalin and then divided into four categories based on crown-rump length (CRL) following gender and weight determinations. Mandibular, caudal superficial cervical (prescapular), caudal mediastinum, jejunal mesenteric and popliteal lymph nodes were evaluated in five lymphocenters of head, neck, thoracic cavity, abdominal viscera and pelvic limbs, respectively. In each sample, nodes formation was visually checked and in cases of nodes formation, they were measured in terms of weight, length, width and thickness and collected data were statistically analyzed. The longest and shortest fetal CRLs were found to be 48.50 cm and 3.50 cm, respectively. Gender had no effect on study parameters in 32 male and 28 female fetuses. Study of sheep fetuses' lymph nodes revealed no macroscopic lymph node development by day 45, while all nodes were observable after the day 59. The shortest lymph node was mandibular node and the longest one was caudal mediastinum. Based on the results, it seemed that although the size of lymph nodes grows by age, this increase is not the same for all nodes and groups.