Dog Thoracic Limb Skeletal System PDF

The Thoracic Limb Lecture Notes #5 Learning Objectives Identify Identify Identify Identify the bones Identify the Identify the action of the shoulder, different parts of that can be brachium, the bones of the produced when antebrachium,...

The Thoracic Limb Lecture Notes #5 Learning Objectives Identify Identify Identify Identify the bones Identify the Identify the action of the shoulder, different parts of that can be brachium, the bones of the produced when antebrachium, thoracic limb these bones move and manus Other terms of Thoracic Limb Pectoral limb Forelimb I. Shoulder Clavicle (collarbone) A vestigial bone not articulated with the skeleton Located near the medial end of the clavicular tendon of the brachiocephalicus muscle Clavicle of the dog does not usually appear on radiographs Scapula Large , flat bone of the shoulder Imperfect triangle: 2 surfaces, 3 borders, 3 angles  Lateral surface ▫ Spine - most prominent feature of the lateral surface of the scapula  Acromnion – distal end of the spine ▫ Supraspinous fossa – supraspinatus m. ▫ Infraspinous fossa – infraspinatus m. Medial or costal surface ▫ Subscapular fossa – subscapularis m. ▫ Serrated face  Cranial border ▫ Scapular notch – rhomboideus m. Dorsal border ▫ Base of the scapula in between the cranial and caudal angles Caudal border ▫ Bears the infraglenoid tubercle Supraglenoid tuberosity ▫ Largest tuberosity of the scapula ▫ It is where biceps brachii m. arise Coracoid process ▫ It is where coracobrachialis m. arise Shoulder Design in Dogs Rudimentary collarbone Scapula Humerus Why is the shoulder design of dogs different from human beings? Dogs being cursorial species, they don’t have a need to lift, push or pull objects or swing their arms as we do Crafted for the need of predators: speed and agility To increase stride length Provides muscle stability and protects the nerves and blood vessels that supply the front legs II. Brachium Humerus connects the shoulder and the elbow a S-shaped bone with a twist Main bone of the brachium Humerus 2 extremities – proximal & distal 4 surfaces - medial, lateral, cranial and caudal Proximal extremity Head Greater tubercle Lesser tubercle Intertubercular groove  Deltoid tuberosity- most prominent feature of the lateral surface ▫ insertion of the deltoideus Brachial groove or musculospinal groove ▫ origin of the brachialis Distal extremity Capitulum (lateral) Trochlea (medial) ▫ + trochlear notch = elbow joint Lateral epicondyle - extensor epicondyle of the humerus (smaller) Medial condyle – flexor epicondyle of the humerus  Olecranon fossa – receives the anconeal process of the ulna and anconeus m. Radial fossa Supratrochlear foramen – maybe absent when the humerus is small III. Antebrachium BONES OF THE ANTEBRACHIUM RADIUS and ULNA cross each other obliquely so that the proximal end of the ulna is medial and the distal end of the ulna is lateral to the radius Radius is SHORTER than the ulna. RADIUS Cranial surface – convex, attachment for supinator muscle Caudal surface – concave, presents interosseous border Interosseous ligament unites the radius and ulna proximally ULNA Articulation ▫ Proximal  humerus (trochlear notch)  radius (radial notch) ▫ Distal  radius (ulnar notch)  ulnar carpal and acc. carpal bones  Proximal extremity ▫ Olecranon - serves as lever arm or tension process for the powerful extensor muscles of the elbow joint ▫ Trochlear notch/semilunar notch IV. MANUS or FOREPAW FOREPAW or MANUS FOREPAW or MANUS  CARPUS = “wrist” ▫ Proximal – radial, ulnar, accessory  Radial CB is the largest among the 7 CB ; also called intermedioradial CB  Ulnar CB is lateral  Accessory CB is at the palmar side of the ulnar CB ▫ Distal row – 1st, 2nd, 3rd, 4th  1st CB is the smallest  4th CB is the largest Deep ligaments of the right forepaw, palmar aspect. (CA, Accessory carpal; I to V, metacarpals.) (From Evans HE, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, 2013, Saunders/Elsevier.)  METACARPUS ▫ 1st MCB – atypical and vestigial; usually present in the forelimb PHALANGES OR DIGITAL SKELETON ▫ Proximal, middle , distal phalanx ▫ 2 palmar sesamoid bones at the metacarpophalangeal joints  Ungual crest ▫ Thin shelf of bone that overlaps the claw forming a band that surrounds the root of claw Ungual process ▫ Curved extension of the distal phalanx into the claw Ligaments of forepaw, lateral aspect. CA, Accessory carpal; V, metacarpal V. (From Evans HE, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, 2013, Saunders/Elsevier.)