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Anatomy I: Lesson 10 Myologia – Part I Objective: Students will examine the muscles of a canine in order to identify the musculature of the body. Practical Tasks 1) m. latissimus dorsi, m. trapezius, m. rhomboideus, m. serratus ventralis, mm. pectorales 2) extensors of the shoulder 3) flexors of the shoulder 4) extensors of the elbow 5) flexors of the elbow Practical Task 1 M. latissimus dorsi Origin: superficial layer of thoracolumbar fascia (from spinous processes of the last 7-8 thoracic and lumbar vertebrae); also muscular attachment proximally to the last few ribs Insertion: on teres major tuberosity (together with m. teres major) Action: draws free limb caudally; together with m. teres major flexes shoulder Musculature of the Pectoral Girdle Extrinsic = Superficial Musculature Origin by aponeurois from the Fascia thoracolumbalis 1) M. latissimus dorsi : one of the largest muscles of the body, flat, almost triangular in shape, on dorsal and lateral side of thorax. Insertion Tuberositas teres major resp. Crista tuberositas minoris (in Ca.) of the humerus Innervated by N. thoracodorsalis and Nn. pectorales caudales Actions antagonist to the M. brachiocephalicus. It retracts the free limb when shoulder is flexed; prevents arching of vertebral column when pulling a load; it also draws the trunk forward over the fixed limb Copyright, O.K. Anatomy School Musculature of the Pectoral Girdle Extrinsic = Superficial Musculature Origin mid-dorsal raphe and supraspinous ligament Insertion 1) M. trapezius : immediately under the skin on lateral surface of neck and withers region, triangular when seen from the side spine of the scapula Body two parts, cervical and thoracic separated by aponeurosis Innervated by dorsal branch of N. Accessorius Actions stabilize shoulders ◦ raises scapula against the trunk ◦ lift and advance the limb ◦ abduct the limb when sidestepping Copyright, O.K. Anatomy School Musculature of the Pectoral Girdle Intrinsic = Deep Musculature 4) M. serratus ventralis : covered entirely by M. trapezius and M. Insertion latissimus dorsi; the strongest and most important muscle of the „muscular dorsal part of medial cartilagenous sling“; all along fan shaped; surface of scapula → Facies serrata Body of two (2) parts: • (cranially): cervicis • (caudally): thoracis → most important weight bearing element of pectoral girdle Origin • • of pars cervicis: from transverse processes of the: 1st to 7th cervical vertebrae (Su) and 2nd3rd to 7th cervical vertebrae (Ca, Bo, Eq) of pars thoracis: from middle of thoracal ribs 1st to 7th (to max. 9-10th) Innervated by N. thoracis longus (→ M. ser.ventr.thoracis) and ventral branches of long thoracic nerve Actions supporting the weight of the trunk. At fixed limb the cervical part raises the neck whole the thoracic part lifts/propells the trunk forewards; aid also in forced inspiration when forelimbs are abducted; the thoracic part can move the unweighted limb forewards. Musculature of the Pectoral Girdle Intrinsic = Deep Musculature 4) M. serratus ventralis Musculature of the Pectoral Girdle Extrinsic = Superficial Musculature 5) Mm. pectorales superficiales : in domestic mammals less developed than the deep pectoral muscle. With 2 heads: cranially: M. pectoralis descendens more caudally: M. pectoralis transversus The superficial and deep pectoral muscles make a powerful ventral sling between ventral chest wall and the forelimbs. Musculature of the Pectoral Girdle Extrinsic = Superficial Musculature 5) Mm. pectorales superficiales : Origin • descendens → manubrium of sternum • transversus → ventrally from 1st to 3rd costal cartilages (in Ca) → from 1st to 6th costal cartilages (Eq, Bo, Su) Insertion • of descendens (cranial): Crista humeri distal to the deltoid tuberosity. • Of transverse (caudal): covers the elbow joint to insert on → the medial Fascia antebrachii (Ca), and → Crista humeri (Ungulates) Innervated by Nn. pectorales Actions ventral connection between thoracic limb and trunk; abduct the forelimb, pull limb either forwards or backwards (depending on position); pulls the trunk to the side when limb is fixed Musculature of the Pectoral Girdle Intrinsic = Deep Musculature Origin sternum and cartilages of true ribs, occasionally also xiphoid region, or deep fascia of trunk (Eq, Ca) Insertion (varies from species to species): → Ca: mainly to Tuberculum majus of the humerus → Su: only to Tuberculum minus → Eq: both to Tuberculi majus Actions and minus supporting trunk and retracting unsupported limb (→ synergist with latissimus dorsi); also extends and fixes shoulder joint, and pulls the trunk forward (when limb is advanced and fixed) 1) M. pectoralis profundus : In domestic mammals much better developed than the superficial ones. With variations of the insertions between species. Practical Task 2 Extensors of the Shoulder Muscles of the Shoulder Joint General considerations: There are four (4) muscles of the a) LATERAL group: 1, supraspinatus, 2, infraspinatus, 3, deltoid, 4, teres minor and also four (4) of the b) MEDIAL group: 1, teres major, 2, articularis humeri, 3, subscapular, 4, coracobrachialis Muscles of the Shoulder Joint Lateral muscles 1) M. Supraspinatus: a strong muscle Origin fossa supraspinata of scapula Insertion Ca Su, Bo Eq Tuberculum majus of humeri (with one tendon) Tuberculum Medial and majus lateral humeri (with tuberosites branched humeri tendon); in Un. also onto Tuberculum minus Innervated by humeri N. suprascapularis Actions fix and extend shoulder joint, and helps in bearing weight of body Copyright, O.K. Anatomy School Muscles of the Shoulder Joint Lateral muscles 2) M. infraspinatus : also a strong muscle Origin infraspinous fossa of and spine of the scapula Insertion Tubercles majus of the humerus Innervated by N. suprascapularis of the brachial plexus Actions can act as contractile collateral ligament assist in flexion or extension (according to position of insertion points) in Ca: assists supination and abduction of humerus also a flexor when joint is fixed. Practical Task 3 Flexors of the Shoulder ◦ M. supraspinatus and M. Infraspinatus described in task 2 ◦ Act as both a flexor and extensor Muscles of the Shoulder Joint Lateral muscles 3) M. deltoideus : a flattened muscle directly under the skin Body of two (2) parts in Ca, Ru: • pars acromialis • pars scapularis ◦ in animals without distinct acromion (Eq, Su) the two parts are fused Origin (of pars acromialis): the spine and the caudal margin of the scapula Insertion deltoid tuberosity of the humerus Innervated by N. axillaris of the brachial plexus Actions flexor of shoulder joint and abducting the limb Muscles of the Shoulder Joint Lateral muscles 4) M. teres minor : a small muscle on caudolateral aspect of shoulder joint under the deltoid Origin distal third of caudal margin of the scapula Insertion just above deltoid tuberosity of humerus or on the tricipital line Innervated by humerus or on the tricipital line Actions to flex shoulder joint Muscles of the Shoulder Joint Medial muscles 1) M. teres major : a long, flattened, fleshy muscle Origin dorsal part of the caudal scapula Insertion Tuberositis teres majoris of humerus Innervated by N. axillaris of the brachial plexus Actions flex shoulder joint; to a small degree also adducting the limb Practical Task 4: Extensors of the Elbow ◦ M. triceps brachii Caput Caput Caput Caput longum laterale mediale accessorium ◦ M. tensor fasciae antebrachii ◦ M. anconeus Muscles of the Elbow Joint Extensors 1) M. triceps brachii : the strongest muscle of the thorcic limb; activates two joints Body : in all domestic mammals with four (4) heads except Eq, (3 heads) ◦ caput longum ◦ caput laterale ◦ caput mediale ◦ caput accesory (not in Eq) Origin ◦ of caput longum: → caudal border of scapula ◦ of caput laterale: → laterally from humerus near the deltoid tuberosity ◦ of caput mediale: → medial aspect of shaft of humerus near the teres tubercle ◦ of caput accessorium: → caudally near head of the Insertion on olecranon process of ulna (by all 4 heads) Innervated by N. radialis from the brachial plexus Actions extend the elbow joint; the long head also flexes the shoulder joint; in standing animal it greatly participates in the passive „stay apparatus“ by fixing the elbow. Muscles of the Elbow Joint Flexors 1) M. triceps brachii : the strongest muscle of the thoracic limb; activates two joints Muscles of the Elbow Joint Flexors 2) M. anconeus : a small, powerful muscle covered by triceps; could be viewed as part of triceps brachii Origin distal half of caudal border of humerus and lateral and medial epicondylesInsertion laterally on olecranon Innervated by N. radialis of the brachial plexus Actions extending the elbow joint Practical Task 4 Flexors of the Elbow ◦ M. Biceps brachii ◦ M. Brachialis Origin supraglenoid tuberosity of the scapula Insertion after the elbow joint its distal tendon dividing into two, inserting to medial tuberosity of both the proximal radius and adjacent ulna Innervated by N. musculocutaneus from the brachial plexus Actions flex elbow joint and also to extend the shoulder; in Eq: a long superficial tendin (→ lacertus fibrosus) joining the antebrachial fascia, eventually inserting on metacarpal tuberosity → transmitting action of biceps into carpal joint → functioning Muscles of the Elbow Joint Flexors 2) M. biceps brachii : a spindle-shaped muscle, acting on two (2) joints; its proximal tendon crosses the capsule of the shoulder joint (in: Ca, Su and sheep), resp. it is protected by large intertuberal bursa (in: goat, Bo, Eq) Muscles of the Elbow Joint Flexors 1) M. brachialis : fleshy, long-fibred muscle, winding over lateral surfce of humerus and crossing the biceps obliquely Origin caudally below the head of the humerus Insertion on both radius and ulna between M. biceps femoris and M. extensor carpi radialis Innervated by N. musculocutaneus of the brachial plexus Actions flex and lift elbow joint