Term
| How are the premuscle masses formed? |
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Definition
| Embryonic premuscle mass in each bud splits around the central skeletal axis to form two separate premuscle masses, one dorsal and one ventral |
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Term
| What nerves are present during differentiation of the muscle masses? |
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Definition
| Embryonic ventral primary rami of spinal nerves C5-T1 penetrate limb bud mesenchyme, intermingle to form the trunks of the brachial plexus, which then split into dorsal and ventral divisions. The divisions enter the differentiating dorsal and ventral muscle masses. |
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Term
| What forms out of the differentiating neuromuscular masses? |
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Definition
Individual muscles and nerves form out of these neuromuscular masses, and can be designated as dorsal or ventral limb muscles and dorsal or ventral nerves of the brachial plexus All parts (dorsal and ventral) of the brachial plexus are derived from ventral primary rami of spinal nerves |
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Term
| What are the characteristics of the ventral muscles? |
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Definition
Muscles derived from the embryonic ventral premuscle mass are located on the anterior (ventral) side of the adult upper limb Ventral limb muscles are innervated by ventral divisions/nerves of the brachial plexus (remember: the brachial plexus is formed by ventral primary rami of spinal nerves C5-T1) Ventral muscles act to flex and/or pronate |
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Term
| What are the characteristics of dorsal muscles? |
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Definition
Muscles derived from the embryonic dorsal premuscle mass are located on the posterior (dorsal) side of the upper limb. Dorsal limb muscles are innervated by dorsal divisions/nerves of the brachial plexus (remember: dorsal divisions/nerves of a plexus≠dorsal primary rami of spinal nerves) Dorsal muscles act to extend and/or supinate |
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Term
| What are the muscles that insert onto the clavicle/scapula unit and act upon the sternoclavicular and acromioclavicular joints? |
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Definition
trapezius levator scapulae rhomboid major and minor pectoralis minor serratus anterior subclavius |
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Term
| What are the muscles that insert onto the humerus or radius/ulna and act upon the glenohumeral joint? |
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Definition
Pectoralis major Latissimus dorsi Deltoid Supraspinatus Infraspinatus Teres major and minor subcscapularis biceps brachii coracobrachialis triceps brachii |
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Term
| What causes rotation of the scapula? |
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Definition
| Trapezius and serratus anterior cause upward and downward rotation of scapula |
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Term
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Definition
Innervation for serratus anterior is long thoracic nerve Blow to side wall of chest (stab, gun shot, radical mastectomy) can sever the long thoracic nerve Full abduction will be weakened and not completely disabled because other muscles are recruited to help -A patient will not be able to elevate arm above 90 degrees However, if try to do a push-up, the scapula will flare away from the chest wall = wing scapula The serratus anterior is what holds the scapula in place |
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Term
| Which muscles connect the shoulder to the vertebral column? |
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Definition
Trapezius levator scapulae rhomboid minor |
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Term
| Which muscles connect the shoulder to the thoracic wall? |
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Definition
Pectoralis minor serratus anterior subclavius |
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Term
| What are the muscles connecting the clavicle/scapula unit to the humerus or radius/ulna? |
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Definition
Pectoralis major deltoid supraspinatus (rotator cuff) infraspinatus (rotator cuff), teres major, teres minor (rotator cuff) subscapularis (rotator cuff), biceps brachii, coracobrachialis triceps brachii |
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Term
| Which shoulder muscle is not innervated by branches of the ventral primary rami of spinal nerves? |
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Definition
| Trapezius is innervated by the accessory nerve (cranial XI) |
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Term
| What is the function of the rotator cuff? |
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Definition
assist in holding the head of humerus in place assist in stabilizing the glenohumeral joint A group of four muscles that covers the glenohumeral joint on all side except inferior -Supraspinatus - DOES NOT ROTATE It initiates abduction. There is a 90 degree angle btw. scapula and humerus. This means you can not get abduction unless you change the angle, which is done by the suprospinatus. Once get to horizontal plane, all the deltoid fibers are horizontal and can only drive humerus into scapula. Need upward rotation of scapula by trap and serratus anterior -Infraspinatus -Teres Minor -Subscapularis |
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Term
| What's the innervation of the rotator cuff? |
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Definition
Innervation -Supraspinatus = suprascapular -Infraspinatus = suprascapular -Teres Minor = axillary nerve -Subscapularis = upper and lower subscapular |
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Term
| Explain the quadrangular space |
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Definition
Quadrangular ( = quadrilateral) space = lateral axillary hiatus Boundaries -Superior: teres minor -Inferior: teres major -Medial: long head of triceps -Laterally: surgical head of humerus Major contents -Axillary nerve -Posterior circumflex humeral artery |
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Term
| Explain the triangular space |
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Definition
Boundaries -Superior: teres minor -Inferior: teres major -Laterellay: long head of triceps Major contents - Circumflex scapular artery |
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Term
| What's the basic structure of the brachial plexus? |
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Definition
mnemonic - Robert Taylor Drinks Cold Beers R - Rami (ventral primary) - C5-T1 T - Trunks - Upper (C5,6), Middle (C7), Lower (C8,T1) D - Divisions - Anterior and Posterior C - Chords - Lateral, Medial, and Posterior B - Branches - major terminal branches |
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