Morphohistological and surgical anatomy of the sinus interdigitalis in Egyptian native breeds of sheep

The current study aimed to characterize the gross and microscopic structures of the interdigital sinus in Egyptian native breeds of sheep and goats (Baladi sheep and goats) to aid in conducting farther studies on such sinus and its surgical importance. The study was carried out on the distal fore and hind limb specimens (below the fetlock joint) obtained from healthy mature ten Baladi sheep and ten Baladi goats of both sexes. For sheep, thirty specimens were subjected to gross anatomical investigation and the other ten specimens were used for histological examination. While, the forty goats fore and hind feet specimens were examined grossly. The results obtained revealed the presence of a well-developed interdigital sinus in Baladi sheep, but there was no evidence for the existence of this unique structure in all examined specimens of Baladi goats. Such sinus appeared grossly as a pipe-like, composed of two parts; body (corpus) and neck (column) which opened in the skin of the interdigital area with an external orifice. The body consisted of three distinct parts in the forefeet and a single part in the hind feet. Histologically, the wall in body and neck regions of the interdigital sinus composed of three distinct layers; epidermis, dermis and a fibrous capsule. Many sebaceous glands, hair follicles and sweat glands in addition to the glandular apocrine gland were distributed within the dermis. The secretory adenomers of the interdigital sinus arranged in different lobules and lined with cuboidal cells with bleb-like projections. It reacted positively with Periodic Acid Schiff (PAS), Sudan black and Sudan III stains, on the other hand it negatively reacted with Alcian blue stain (AB).