AGE RELATED ANATOMICAL CHANGES OF DIGITAL FLEXOR TENDONS OF FORELIMB IN THE BUFFALO BULL (Bubalus bubalis)

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Date
2019-04-26
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pvnrtvu
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Age Related Anatomical Changes of Digital Flexor Tendons of Fore Limb in the Buffalo Bull (Bubalus bubalis) was conducted to study these functionally important tendons. Eighteen apparently healthy intact post-natal specimens from the level of carpus to distal phalanx were procured from GHMC Abattoir, Hyderabad and were divided into three groups viz., groups I (1–3 yrs), group II (3–6 yrs) and group III (6 yrs & above). Gross features like structure and behaviour of tendons, their length and thickness were studied along with micro-anatomical studies for which tendon sections were stained with H & E, Masson’s trichrome, Verhoeff’s stain, PAS, PAS-Ab and Oil Red ‘O’ techniques. Gross anatomical features of SDFT and DDFT revealed that they are shiny white fibrous structures bound by tough, durable fibrous sheath the ‘flexor retinaculum’ on palmar aspect of manus in all three groups. Superficial part of SDFT was directed from lateral edge of carpus medially up to inter-digital space. SDFT in cross sections was flat elliptical in groups I and II at myo-tendinous junction and was oval in group III. At mid metacarpal region it was dorso-ventrally compressed and ring-shaped in digital region. Thickness increased in aged specimens at origin, mid metacarpus and at insertion point. xiv SDFT divided into two slips i.e., one each for abaxial and axial digits up to the vinculum (phalanx II). Lengths of the two slips of SDFT in buffalo gradually increased from inter digital space up to their insertion point from group I (9.1 ± 0.3 cm) to group II (10.2 ± 0.2 cm) and group III (11.3 ± 0.7 cm) respectively. DDFT was below SDFT in carpal tunnel on palmar aspect of manus. Its palmar surface was grooved to accommodate the deep part of SDFT. It was deeper and wider at the carpal level and it merged with thick fascia of metacarpus and superficial division of SDFT. The two slips of DDFT emerged from the tunnels of SDFT and were inserted to respective tubercles on phalanx III. Cross sectional profile of DDFT in mid metacarpus was flat elliptical in outline in all groups. At insertion it was flattened structure in first two groups. Under the muscular part of suspensory ligament distal vascular arch was seen from which fine branches emanated to DDFT. Thickness of the tendon steadily increased with age from group I to III i.e., it was 6.7 ± 0.6 and 7.7 ± 0.4 cm at the origin point respectively. At insertion the tendon significantly increased in mean thickness from 5.7 ± 0.1 cm in group I to 8.2 ± 1.7 cm group III. Length of DDFT from origin to its division and from division to insertion steadily increased from 16.4 ± 0.4 and 15.8 ± 0.3 cm to 18.3 ± 0.4 and 18.7 ± 0.2 cm in groups I and III respectively. Histological features revealed that both SDFT and DDFT at myo-tendinous junction comprised wavy bundles of collagen intermingled with muscle fibres oriented in different directions. SDFT was covered by epitenon below which numerous collagen bundles enveloped by paratenon were seen along with muscle fibres. Epitenon in all groups was made up of loose connective tissue with small blood vessels. Collagen fibres were wavy parallel bundles in group I with slender tenocyte nuclei in between them. Muscle fibres extended deep into myo-tendinous junction of SDFT in convergent manner. At the transitional zone collagen fibres and intermittently placed chondrocyte-like cells were seen whose number increased in tendons groups II and III. In mid metacarpus SDFT in all groups comprised closely packed tendon fascicles with small tenocytes wedged in between them. At insertion isolated clusters of chondrocyte-like cells along with scattered cells and adipose tissue were seen in groups II and III. Collagen fibre crimps were not appreciated at insertion point. Short elliptical tenocyte nuclei in between collagen fibres of group II were noticed at mid metacarpus. Collagen fibres were in random directions in the tendon. Loose fat tissue and chondrocytes were slightly more in insertion points of SDFT in later groups. xv Histological features of DDFT resembled in most aspects the SDFT. At myo-tendinous junction in all three groups these tendons were made up of collagen bundles arranged in compact masses and demarcated by connective tissue sheaths from group II onwards. Thick collagen covering was noticed in later groups. Elastic fibres were seen in internal elastic laminae of blood vessels. In group – III adipocytes and tissue spaces were seen in between collagen bundles of DDFT at origin, whereas in mid metacarpus long wavy bundles of collagen were arranged in parallel manner in all groups. Fat tissue in epitenon increased from group I to group III. Wavy nature of collagen fibres gradually decreased in the tendon from mid metacarpal to insertion in later groups. Adipocytes, collagen fibres with isolated chondrocyte like cells in between collagen fibres and scant elastic fibers were seen at insertion. Collagen crimps were barely noticeable. Histochemical features showed that PAS reaction was mild or negligible in collagen fibres in all groups of both SDFT and DDFT. It was moderate in linings of blood vessels which were located in connective tissue in all groups. Collagen fibres were inert to this reaction. PAS-Ab reaction was moderate in spaces between collagen bundles in both the digital flexor tendons in all groups. It was strong in chondrocyte-like cells and vascular elements in connective tissue of the tendon in all three groups. In this study lipids were localised in externally placed adipose tissue of epitenon and mesotenon of SDFT and DDFT tendons of group III. This feature was appreciable in group II and group III respectively. Presence of lipids was observed from mid metacarpal to insertion regions of both the digital flexors of forelimb in buffalo.
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D-629
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