Longitudinal section of a tendon, light micrograph. The tendon is made up of a connective tissue very rich in collagen fibres that are arranged in bundles (red bands stained with eosin). Few narrow and elongated nuclei are seen between these bundles, corresponding to a particular type of fibroblasts called tenocytes. At centre there is a band of nuclei that corresponds to a tendon envelope that encompasses the bundles of collagen bundles and is called the internal peritenon.