MORPHOLOGICAL STUDIES ON THE FEMUR, TIBIOTARSUS AND FIBULA OF PEAHEN (Pavo cristatus)

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1 MORPHOLOGICAL STUDIES ON THE FEMUR, TIBIOTARSUS AND FIBULA OF PEAHEN (Pavo cristatus) A.R. Sreeranjini 1, N. Ashok, V. R. Indu, K. M. Lucy, S. Maya and K.V. Syam Department of Veterinary Anatomy and Histology College of Veterinary and Animal Sciences, Mannuthy, Thrissur, Kerala Received : Accepted : ABSTRACT A study was conducted on the femur, tibiotarsus and fibula of a peahen. The femur was extremely light compared to that of chicken and duck with curved shaft, two extremities and four surfaces. The proximal and distal extremities were almost of equal size with large number of pneumatic foramina. The proximal extremity presented distinct head and neck. Distal extremity contained a trochlea and two condyles. The condyles were separated by a wide intercondyloid groove. The lateral condyle was larger and was placed at a lower level. The caudolateral part of lateral condyle presented a facet for articulation with fibula. The femur of peacock presented all morphological features that were suited to make movements like protraction, retraction, abduction, adduction and rotation. The tibiotarsus was the largest of the leg bones and was twice longer than femur. It presented a long shaft and two extremities. Lateral surface of the shaft near the proximal extremity furnished an indistinct fibular crest. Near the distal extremity, dorsal aspect of the shaft presented the extensor canal. The proximal extremity contained larger medial and smaller lateral condyles. From the proximal articular surface, a short and stump cnemial crest extended ventrally and medially. The distal extremity of tibiotarsus presented large lateral and small medial condyle separated by intercondyloid fossa. The condyles continued caudally to constitute a wide grooved trochlea. The fibula was a reduced long bone with distinct head and rudimentary shaft. It terminated freely at about the middle of the shaft of tibiotarsus. The long tibiotarsus of peahen indicated adaptive features for bipedalism and running whereas, the highly reduced fibula and fusion of tibia with proximal row of tarsals to form tibiotarsus were indicative of adaptations for flight. Key words: Morphological study, femur, tibiotarsus, fibula, peahen 1. Corresponding author s Tamilnadu J. Veterinary & Animal Sciences 9 (4 ) , July - August 2013

2 INTRODUCTION Unlike in animals, hind limbs are the only structures for support and walking in birds. To combat the stresses involved in landing and taking off, in running and in hunting, many birds have relatively heavy and strong leg bones. Legs play an important role in determining the degree of mobility of the limbs in birds. The femur functions more like a forward extension of the hip bones and contributes little to the length of the bird s stride. This arrangement is very useful when the caudal part of the abdomen is swollen by the presence of a very large egg. The length of tibia is an indicator of a bird s habit, being the longest in wading birds, coming next in runners and well developed in swimming birds. The present study was conducted to assess the morphological features of the femur, tibiotarsus and fibula of an adult peahen. MATERIALS AND METHODS The present study was conducted on the femur, tibiotarsus and fibula of an adult peahen brought for post mortem to the Department of Pathology at College of Veterinary & Animal Sciences, Mannuthy, Thrissur. Muscles were separated by dissect and the bones were cleaned and examined for studying various morphological features. Femur RESULTS AND DISCUSSION The femur of peahen was a long bone having 10.5cm length with cylindrical but curved shaft and two extremities. The shaft was wider proximally and distally and presented medial, Morphological studies on the femur, tibiotarsus... lateral, cranial and caudal surfaces. The medial surface of the shaft was smooth and concave in its length (Fig.1). Most of the lateral surface of the shaft was smooth, but its proximal end was rough for muscular attachment and continued on to trochanter major. Muscular line on the cranial surface was indistinct, whereas the line on caudal surface was distinct and extended distally upto the medial condyle. Linea aspera seen on the caudal surface of the shaft in chicken and duck were indistinct. The proximal and distal extremities were almost of equal size with large number of pneumatic foramina which contributed to the light weight of the bone compared to that of chicken and duck. The proximal extremity presented a distinct, hemispherical head which contained a shallow fovea capitis compared to that of chicken. The head was separated from the shaft by a distinct neck. Similar to chicken and duck, the long axis of the neck was placed at right angles to the long axis of the shaft. Lesser trochanter was indistinct. Trochanter major extended above the level of the head and furnished a facet for articulation with the antitrochanter of ilium. Distal extremity furnished medial and lateral condyles and a trochlea that articulated with patella. The condyles were separated by a shallow intercondyloid groove and the larger lateral condyle was placed at a lower level similar to fowl (Nickel et al., 1977). The groove present on the lateral condyle in chicken and duck was not distinct. Caudolateral part of the lateral condyle presented a facet for articulation with fibula. As in chicken and duck, the lateral ridge of trochlea was larger. The femur of peahen presented all morphological features that were suited to make movements like protraction, retraction, abduction, adduction and rotation. Tamilnadu J. Veterinary & Animal Sciences 9 (4 ) , July - August

3 Tibiotarsus The tibiotarsus was the longest of the leg bones. It was almost twice longer (20.5cm) than the femur (Fig.2). This feature was similar to that of duck and goose and unlike that of fowl and pigeon, where the tibiotarsus is only one third longer than femur (Nickel et al., 1977). Gatesy (1991) observed that as total limb length increases, avian femora become relatively shorter. Short, robust femur resists bending to a far greater degree than the relatively longer, slimmer tibiotarsus. The tibiotarsus, formed by the fusion of tibia and proximal row of tarsals, presented a long shaft and two extremities. The shaft was straight in its proximal half and slightly curved in the distal half. Just below the proximal extremity, the lateral surface of the shaft furnished fibular crest for attachment of the fibula (Fig.2). However, the crest was not well developed as that of fowl and coturnix quail. Dorsal aspect of the shaft near its distal extremity showed extensor canal for the passage of the tendon of extensor muscles of the toes (Fig.4). The same was reported in fowl (Mc Lelland, 1990) and in coturnix quail (Fitzgerald, 1969). But, the groove seen proximal to the extensor canal was shallow in the peahen. Proximal to the extensor canal and on the bony bridge, a nutrient foramen was noticed. The proximal extremity was larger than the distal extremity as in fowl and coturnix quail. Similar to that of fowl, it contained larger medial and smaller lateral condyles separated by a ridge. The condyles articulated with menisci and condyles of femur. The lateral border of lateral condyle furnished a facet for articulation with the head of fibula. The convexities of the condyles along with menisci provide an Sreeranjini et al. extensive undulated area that permits some amount of rotation in addition to flexion and extension of the stifle (Fitzgerald, 1969). The cranial border of the articular surface presented a transverse ridge for attachment of the broad patellar ligament as in coturnix quail. From the centre of the ridge, the cnemial crest extended ventrally and medially (Fig.3). The crest was short and stump compared to that of the domestic fowl. Since it was located more towards the middle of the anterior aspect, the extensor groove was wider in the peahen. The cnemial crest provides attachment for the main extensor muscle of the knee joint (Mc Lelland, 1990). In fowl, the cnemial crest faded on the shaft, but in peahen it ended abruptly in the proximal extremity itself. In turkey, Al- Sadi (2012) reported the presence of two cnemial crests- cranial larger and caudal smaller. The distal extremity presented large lateral and small medial condyles separated by the intercondyloid fossa (Fig.4). The extensor canal was seen immediately proximal to the condyles. The condyles continued caudally to constitute a wide grooved trochlea. On the sides of the distal extremity, depressions for the attachments of collateral ligaments were present as in fowl (Getty, 1975). The extensive articular surface provided by condyles and trochlea permits great deal of movement of the hock joint (Fitzgerald, 1969). Fibula The fibula was a reduced long bone with distinct head and rudimentary shaft (Fig.2). The head articulated with the lateral condyle of tibia and femur. The shaft was distally tapering, thin and needle like. It terminated freely at about the middle of tibia as in coturnix 250 Tamilnadu J. Veterinary & Animal Sciences 9 (4 ) , July - August 2013

4 quail. But in fowl, the shaft of fibula extends up to the distal one third of the shaft of tibiotarsus. Proximal part of the shaft of the fibula showed attachment to the fibular crest of tibia. Morphological studies on the femur, tibiotarsus... The long tibiotarsus of peahen indicated adaptive features for bipedalism and running whereas, the highly reduced fibula and fusion of tibia with proximal row of tarsals to form tibiotarsus were indicative of adaptations for flight. Fig.1: Femur of peahen F- Pneumatic foramen, T-Trochanter major, H- Head, N-Neck, S-Shaft, TR-Trochlear ridges Fig. 2 : Tibiotarsus and fibula T-Tibiotarsus, F- Fibula, FC-fibular crest, D- Depressions for collateral ligaments Tamilnadu J. Veterinary & Animal Sciences 9 (4 ) , July - August

5 Fig.3: Proximal extremity of tibiotarsus dorsal view C-Cnemial crest, E-Extensor groove, T-transverse ridge Sreeranjini et al. Fig.4: Distal extremity of tibiotarsus dorsal view EC- Extensor canal, CO-Condyles, I-Intercondyloid fossa, N-Nutrient foramen REFERENCES Al- Sadi, S. (2012). Comparative morphometric study of shank bone in the tom (Meleagris gallopavo) and local cock (Gallus banikaval). Iraqi J. Vet. Sci., 26:57-64 Fitzgerald, T.C. (1969). The Coturnix Quail, Anatomy and Physiology. The Iowa State University Press, Ames, Iowa. pp : Gatesy, S. M. (1991). Hind limb scaling in birds and other theropods: implications for terrestrial locomotion. J. Morphol. 209: Getty, R. (1975). Sisson and Grossman s the Anatomy of the Domestic Animals. Vol. II, 5 th ed., The Macmillan Company of India Ltd, New Delhi. pp: Mc Lelland, J. (1990). A Colour Atlas of Avian Anatomy. Wolfe Publishing Ltd, England. pp: Nickel, R., Schummer, A. and Seiferle, E. (1977). Anatomy of the domestic birds. 2 nd ed., Verlag Paul Parey, Berlin, Hamburg. pp: Tamilnadu J. Veterinary & Animal Sciences 9 (4 ) , July - August 2013