Ed dew claw dog11/24/2023 The hindlimb skeleton includes the pelvic girdle, consisting of the fused ilium, ischium, and pubis, and the bones of the hindlimb (see Figures 5-8 and 5-9). Those on the pad surface of the manus align the flexor tendons. The sesamoid bones at the dorsal surface of each metacarpophalangeal joint align the extensor tendons for optimal muscle action. Dogs are digitigrade animals and bear weight on digits II to V, with the main weight bearing occurring on digits III and IV. They allow for constant, biomechanically advantageous alignment of angles of insertion of tendons at their attachment sites, which helps relieve stress on the tendinous insertions for animals that walk on their digits. Sesamoid bones occur when there are significant changes in directions of pull on tendons in addition to the tensile forces produced during muscle contractions. Dogs have many sesamoid bones that are embedded in tendons or near them. The first metacarpal is short and nonfunctional. The radial carpal bone is analogous to the fused scaphoid and lunate. The anconeal process is needed for stability in weight bearing.Īt the carpus or wrist (see Figure 5-7), there are seven carpal bones. The dog has an anconeal process, which is near the attachment site of the anconeus muscle. It articulates distally with the ulnar carpal and accessory carpal bones by two distal facets and does not have an articular disk. The ulna is the longest bone of the canine body. The ulna is the lateral forearm bone and has a very prominent olecranon process, which allows secure attachment for the large triceps brachii muscle, needed as an antigravity muscle for weight bearing in dogs. The canine distal radius has distinct facets for articulation with carpal bones, providing stability in weight bearing. The proximal surface of the radius articulates with the humeral capitulum, which is not as prominent as in the human. The radius is the medial forearm bone and is the main weight-bearing bone of the antebrachium distally. Distally, there is an olecranon fossa and supratrochlear foramen for the secure positioning of the protruding anconeal process of the ulna for more stability in weight bearing. The canine humeral head is less rounded compared with the human head, to assist with weight bearing. The adult canine clavicle is mostly cartilage and is usually not visible on radiographs. It is a small oval plate often 1 cm or less in length and ⅓ cm wide, located at the tendinous intersection of the brachiocephalicus muscle. Dogs have an abbreviated clavicle that does not articulate with the rest of the skeleton. The canine scapula is positioned close to the sagittal plane. The forelimbs bear 60% of the dog’s weight. The size of forelimb bones varies a great deal, because of the greater variation in size for breeds of dogs. The forelimb skeleton consists of the thoracic or pectoral girdle and bones of the forelimb (see Figures 5-5 and 5-6). The word canine is an adjective and the word dog is a noun these terms are used in this consistent grammatical form throughout the chapter. The terms trunk, neck, and head refer to the same body segments in dogs and humans. Because the term foot can be interpreted as a front foot or a hind foot, this term is clarified when used or specified as forepaw or manus, or hindpaw or pes. The canine hindlimb is known also as the pelvic limb or rear limb, but we use the term hindlimb. The canine forelimb is known also as the thoracic limb and the pectoral limb, but we use the term forelimb. We have chosen to use some terms consistently throughout the chapter, rather than use equally acceptable synonyms. Comparative anatomy between dogs and humans has been described in other sources. These comparisons have been minimized, as this is a chapter about canine anatomy and not a chapter about comparative anatomy. To assist communication among human rehabilitation and veterinary colleagues, some anatomic terms used for dogs appear in regular print with the analogous terminology for humans in parentheses following the canine term. This text is intended for people who already possess knowledge of either veterinary or human anatomy.
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