Functional anatomy of the papilla Vateri: biomechanical aspects and impact of difficult endoscopic intubation.

BACKGROUND: Problems with intubation of the ampulla Vateri during diagnostic and therapeutic endoscopic maneuvers are a well-known feature. The ampulla Vateri was analyzed three-dimensionally to determine whether these difficulties have a structural background. METHODS: Thirty-five human greater duodenal papillae were examined by light and scanning electron microscopy as well as immunohistochemically. RESULTS: Histologically, highly vascularized finger-like mucosal folds project far into the lumen of the ampulla Vateri. The excretory ducts of seromucous glands containing many lysozyme-secreting Paneth cells open close to the base of the mucosal folds. Scanning electron microscopy revealed large mucosal folds inside the ampulla that continued into the pancreatic and bile duct, comparable to valves arranged in a row. CONCLUSIONS: Mucosal folds form pocket-like valves in the lumen of the ampulla Vateri. They allow a unidirectional flow of secretions into the duodenum and prevent reflux from the duodenum into the ampulla Vateri. Subepithelial mucous gland secretions functionally clean the valvular crypts and protect the epithelium. The arrangement of pocket-like mucosal folds may explain endoscopic difficulties experienced when attempting to penetrate the papilla of Vater during endoscopic retrograde cholangiopancreaticographic procedures.

Blood supply of the peroneal tendons: injection and immunohistochemical studies of cadaver tendons.

We studied the vascular pattern of human peroneal tendons with injection techniques and immunohistochemically by using antibodies against laminin The main blood supply arises from the peroneal artery. The distal part of the peroneus longus tendon is supplied by branches of the medial tarsal artery. Blood vessels enter the peritenon of both tendons via a mesotenon from the posterior aspect. From the peritenon, the blood vessels penetrate the peroneus brevis and peroneus longus tendons and anastomose with a longitudinally-oriented intratendinous network. The amount of vessels in the tendon substance is consistently less than in the surrounding peritenon. The distribution of blood vessels in the peroneal tendons is not homogeneous. In the region where the peroneus brevis tendon passes through the fibular groove, the longitudinally-oriented intratendinous vascular network is interrupted and the tendon is almost avascular. In this region, the tendon is squeezed between the peroneus longus tendon and the bony slide bearing of the lateral malleolus. The peroneus longus tendon has two avascular zones. In the region where the peroneus longus tendon curves around the lateral malleolus and the peroneal trochlea of the calcaneus, the anterior part of the tendon which is directed towards the pulley is avascular. A second avascular zone is located more distally in the region where the tendon changes direction and wraps around the cuboid.

Structure of the human tibialis anterior tendon.

The structure and vascular pattern of the human tibialis anterior tendon was investigated using injection techniques, light and transmission electron microscopy and immunohistochemistry. From the well vascularised peritenon, blood vessels penetrate the tendon tissue and anastomose with a longitudinally oriented intratendinous network. The distribution of blood vessels within the tibialis anterior tendon was not homogenous. The posterior part of the tendon had a complete vascular network that extends from the musculotendinous junction to the insertion at the first metatarsal and medial cuneiform bones. In the anterior half, the tissue was avascular in a zone with a length of 45-67 mm. This zone was covered by a single layer (approximately 30 microm) of oval shaped cells. Transmission electron microscopy showed that these cells have the characteristics of chondroid cells. This region was stained by Alcian blue at pH 1 which indicates a high concentration of acid glycosaminoglycans and immunohistochemical staining for chondroitin-4-sulphate, chondroitin-6-sulphate and aggrecan was positive. However, immunostaining for the typical cartilage specific type II collagen within this zone was negative. The location of the avascular zone corresponds to the region where the tibialis anterior tendon wraps around the superior and inferior retinacula which serve as fibrous pulleys. This is the region where most spontaneous ruptures of the tibialis anterior tendon occur. The presence of fibrocartilage within gliding tendons is a functional adaptation to compressive and shearing forces. In contrast to reports from the literature about the structure of gliding tendons wrapping around a bony pulley, the gliding zone of the tibialis anterior tendon has only a narrow layer of chondroid cells and proof of type II collagen is lacking.