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EQUINE VETERINARY EDUCATION / AE / july 2022
a) MC
b) MC CB
c)
NSC 1000 µm d) e) 1000 µm f) 1000 µm
O 100 µm 100 µm
100 µm
Fig 6: Sutura internasalis, HE stain. a,d) 1-day-old foal (b,e) 2-year-old horse (c,f) 9-year-old horse. a,b,c) 253 magnification, (d,e,f) 1003 magnification of the region of interest shown in the low magnification photomicrograph. Woven bone with medullary cavities (MC) can be seen on either side of the suture in both the 1-day-old and 2-year-old samples. The higher magnification reveals a highly cellular connective tissue inside the suture as well as numerous blood vessels (arrows). At the bottom of (a), the nasal septal cartilage (NSC) is prominent. The sample from the 9-year-old horse reveals cancellous bone (CB) with osteons (O) visible in the higher magnification. The connective tissue is dense, and blood vessels are identifiable (arrows).
a) b)
50 µm
100 µm
Fig 7: a) Sutura maxillolacrimalis 1-day-old foal, HE stain. Note the row of walled in osteoblasts along the outer border of the suture (box). The high density of fibrocytes and fibroblasts can be seen in the suture along with blood vessels. b) Sutura nasofrontalis 9-year- old horse, HE stain. The border of the suture is lined by fibrocytes (arrows), which can also be found in the connective tissue of the suture along with blood vessels.
juxtaposition of the internasal sutures of the 1-day-old foal and the 2- and 9-year-old horses, which clearly shows the change in density of the connective tissue and cellularity as well as the maturation of the adjacent bone from woven to cancellous. In fact, newborn foals have wide sutures with a high degree of highly cellular loose connective tissue and a high level of vascularisation, surrounded by woven bone. As the horse matures, there is a clear reduction in the number of cells present in the suture and osteoblasts become rare. Interpretation of width measurements in this study is
prone to error because of the limited number of values obtained in each location and the width appeared to be
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influenced by the plane of sample transection, which appeared in some samples inconsistent. Despite this, we feel that in the samples examined from individual horses there was subjectively, a slight narrowing of overall suture width from all locations with increasing horse age. This could be made more objective by using larger sample numbers, ensuring that all samples were extracted from the same anatomical location (i.e. relative location to gross landmarks irrespective of gross identification of the suture) and taking more measurements. Additionally, analysing sutures along a larger portion of their length, as well as at comparable levels of depth, would provide additional information as to whether sutures tighten at similar or
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