Plate 5 Dense Regular Connective Tissue Tendons And Ligaments

Figure 1, tendon, longitudinal section, human, H&E x100.

This specimen includes the surrounding dense irregular connective tissue of the tendon, the epitendineum (Ept). The tendon fascicles (TF) that make up the tendon are surrounded by a less dense connective tissue than that associated with the epitendineum. In longitudinal sections such as this, the connective tissue that surrounds the individual fascicles, the endotendineum (Ent), seems to disappear at certain points, with the result that one fascicle appears to merge with a neighboring fascicle. This is due to an obliqueness in the plane of section rather than an actual merging of fascicles. The collagen that makes up the bulk of the tendon fascicle has a homogeneous appearance as a result of the orderly packing of the individual collagen fibrils. The nuclei of the tendon cells appear as elongate profiles arranged in linear rows. The cytoplasm of these cells blends in with the collagen, leaving only the nuclei as the representative feature of the cell.

Figure 2, tendon, longitudinal section, human, H&E x400.

This higher magnification micrograph shows the ordered single-file array of the tendon cell nuclei (TC) along with the intervening collagen. The latter has a homogeneous appearance. The cytoplasm of the cells is indistin-

Figure 3, tendon, cross section, human, H&E x400.

This specimen is well preserved, and the densely packed collagenous fibers appear as a homogeneous field, even though the fibers are viewed on their cut ends. The nuclei appear irregularly scattered, as opposed to their more uni-

guishable from the collagen, as is typical in H&E paraffin specimens. The variation in nuclear appearance is clue to the plane of section and the position of the nuclei within the thickness of the section. A small blood vessel (BV) coursing within the endotendineum is also present in the specimen.

form pattern in the longitudinal plane. This is explained by examining the clashed line in Figure 2, which is meant to represent an arbitrary cross-sectional cut of the tendon. Note the irregular spacing of the nuclei that are in the plane of the cut. Lastly, several small blood vessels (BV) are present within the endotendineum (Ent) within a fascicle.

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