1. When a muscle is shortened to 30 – 50% of its resting length it is no longer capable of producing force. The contractile elements in the muscle (actin and myosin filaments) are maximally interlocked. When a muscle is maximally stretched it becomes incapable of generating force because the cross bridges between the contractile filaments are pulled apart. It offers passive resistance to being stretched out further. Muscle function: Fiber length and force production Multi-articulate muscles, e.g., the long finger flexors: - can’t shorten enough to produce maximum flexion at all joints they cross: active insufficiency - are stretched out and resist further stretching when all joints they cross are extended: passive insufficiency

2. 100 lb long muscle lever arm – small force short muscle lever arm – large force 100 lb Muscle function: lever arms To overcome the same resistance or load at a joint a muscle working on a short lever arm needs to generate more force. 100 lb

3. Calcaneal and olecranon processes increase the lever arms of the triceps surae and triceps brachii muscles, thereby allowing them to overcome the same resistance or load moment with less force/effort. In this module we will ask you to learn muscle attachment sites in greater detail. Whenever a visible “bump” is involved you will have to know its name, not just the bone’s name; e.g., olecranon process of ulna.

4. Joint types 1.Fibrous joints (sutures and syndesmoses) 2.Cartilaginous joints (symphyses)* 3.Synovial joints (* Synchondroses are the cartilaginous growth plates in the growing skeleton) Synovial joints have a capsule with a synovial lining. The joint surfaces are covered by smooth hyaline cartilage and lubricated by synovial fluid.

5. Functional Classification of Synovial Joints Hinge joint rotation around one principal axis Pivot joint rotation around one principal axis Planar joint sliding motion Ellipsoidal joint rotation around two principal axes Saddle Joint rotation around two principal axes Ball & Socket joint rotation around three principal axes - most mobile

6. Movements Flexion = movement out of the anatomical position movement in anterior direction movement that decreases the angle between adjacent segments Extension = movement into the anatomical position movement in posterior direction movement that increases the angle between adjacent segments These 3 criteria do not always apply simultaneously! Extension of the trunk decreases the angle between the upper and lower part of the trunk. Flexion of the lower limb joints from the knee down is a posterior movement. Flexion and extension are movements around transverse axes:

7. are movements away from the midline and towards the midline are movements around sagittal axes Circumduction is a combined movement that includes flexion/extension, ab/adduction and rotation Ab- and adduction: Rotation is movement around long axes of body segments

8. Movements can involve multiple joints elevation and depression of the shoulders (scapula and clavicle move together and ‘drag’ shoulder joint with it) lateral flexion of the trunk (multiple intervertebral joints) rotation of the trunk (multiple intervertebral joints)

9. Muscle function and muscle action What movements muscles are capable of producing depends upon where they cross a joint relative to the principal axes. These are called muscle actions and can be deduced by knowing the axes of rotation and the position of the muscle. Muscle functions describe how we actually use them. In most cases, muscle actions and functions are the same; i.e., learning the actions suffices. The muscles of the eyeball and the lower limb muscles during walking are important examples of muscles that we use differently from what their actions suggest. triceps extends the forearm or resists flexion of forearm and we use it to do just that (function = action) superior rectus can act to elevate, adduct and internally rotate the eyeball (actions) we use it to elevate the abducted eyeball (function)

10. Limbs Muscle origin: proximal (on the less mobile part) Muscle insertion: distal (on the more mobile part) In the trunk and neck Muscle origin: inferior Muscle insertion: superior In the head Muscle origin: on part that doesn’t move Muscle insertion: on part that moves Muscle origins and insertions Movement convention: with reference to the insertion segment Medial rotation at the knee is medial rotation of the lower leg, even if the foot is planted on the ground, the leg stationary, and the thigh rotates laterally on the stationary leg.

11. Glenohumeral (shoulder) joint – a ball and socket joint with three principal axes acromion clavicle glenoid fossa head of humerus Movements: Flexion and extension around a transverse axis Abduction and adduction around a sagittal axis Rotation of the humerus around its long axis

12. Shoulder girdle movements extend the range of movement of the upper limb, in particular abduction. Abduction of the arm beyond 90 degrees is a movement of the shoulder girdle. It elevates the glenoid fossa and makes it face superiorly. The scapula slides on the rib cage and moves in unison with the clavicle. Together, they form the shoulder girdle.

13. Muscles anterior to the shoulder joint are flexors: Pectoralis major and anterior part of deltoid What about pectoralis minor ? deltoid pectoralis major

14. Muscles posterior to the shoulder joint are extensors: posterior part of deltoid, latissimus dorsi, teres major What about trapezius ? teres major deltoid latissimus dorsi

15. Muscle superior to the shoulder joint are abductors: middle part of deltoid, supraspinatus supraspinatus deltoid

16. Muscles inferior to the shoulder joint are adductors: pectoralis major, latissimus dorsi, teres major

17. Muscles that approach the long axis of the humerus at an angle are rotators. Medial or internal rotators: subscapularis, pectoralis major, latissimus dorsi, teres major, anterior deltoid subscapularis teres major latissimus dorsi pectoralis major

18. Muscles that approach the long axis of the humerus at an angle are rotators. Lateral or external rotators: teres minor, infraspinatus, posterior deltoid teres minor infraspinatus posterior deltoid

19. Trapezius rotates the scapula. Its cranial fibers pull the acromion up Its caudal fibers pull the medial spine down. These two parts are synergistic* in their action. * Muscles or muscle parts that perform opposite movements are antagonistic in their actions, e.g., flexors and extensors. Shoulder girdle movements to enhance abduction

20. Serratus anterior protracts the scapula. Its caudal fibers pull inferior angle forward thereby rotating the glenoid upward (synergistic to trapezius). When doing push- ups it prevents the scapula from sliding backwards. What muscle is that?

21. MuscleActionInnervationOriginInsertion Trapeziuselevate (upper part) retract (middle part) depress (lower part) rotate (upper and lower parts) CN XIoccipital bone ligamentum nuchae spines of thoracic vertebrae lateral clavicle acromion spine of scapula Rhomboidsretract elevate dorsal scapular n.spines of upper thoracic vertebrae medial border of scapula Levator scapulaeelevatedorsal scapula n.transverse processes of cervical vertebrae superior angle of scapula Serratus anteriorprotract rotate long thoracic n.upper nine ribsmedial border and inferior angle of scapula Pectoralis minorprotract depress medial pectoral n.ribs two to fivecoracoid process of scapula Muscles acting on scapula

22. MuscleActionInnervationOriginInsertion Deltoidabduct (middle part) flex (anterior part) extend (posterior part) axillary n.lateral clavicle acromion spine of scapula deltoid tuberosity on humerus Pectoralis majorflex adduct medially rotate medial and lateral pectoral nn. medial clavicle sternum costal cartilages of upper six ribs crest of greater tubercle of humerus Latissimus dorsiextend adduct medially rotate thoracodorsal or middle subscapular n. iliac crest, spinous processes of lumbar and lower thoracic vertebrae via thoracolumbar aponeurosis intertubercular sulcus of humerus Teres majorextend medially rotate adduct lower subscapular n. inferior angle of scapula crest of lesser tubercle of humerus Muscles acting on humerus I

23. MuscleActionInnervationOriginInsertion Subscapularismedially rotate adduct upper and lower subscapular nn. subscapular fossa of scapula lesser tubercle of humerus Supraspinatusabductsuprascapular n.supraspinous fossa of scapula greater tubercle of humerus Infraspinatuslaterally rotate adduct suprascapular n.infraspinous fossa of scapula greater tubercle of humerus Teres minorlaterally rotate adduct axillary n.lateral border of scapula greater tubercle of humerus Note that the biceps and triceps brachii have weak actions at the shoulder joint, the long head of triceps in extension, both heads of biceps in flexion. Their primary action is at the elbow joint. Muscles acting on humerus II: Rotator cuff muscles

24. Arteries of the shoulder I Branches of the subclavian a. suprascapular a. transverse cervical becomes dorsal scapular a. * Note: the dorsal scapular a. often comes off as an independent branch of the subclavian a. Via thyrocervical trunk: subclavian turns into axillary at inferior border of rib 1

25. 1 2 3 Arteries of the shoulder II Branches of the axillary a. subscapular a. with circumflex scapular and thoracodorsal branches thoracoacromial a. posterior circumflex humeral a. anterior circumflex humeral a. lateral thoracic a. superior thoracic a. (unimportant) This is a dorsal scapular a. coming off of the subclavian a.

26. 1. suprascapular a. with suprascapular n. through or over suprascapular notch (army … navy …) 2. posterior circumflex humeral a. with axillary nerve in quadrangular space 3. circumflex scapular a. in triangular space How the arteries and nerves of the shoulder, originating in the front, find their way back scapula and teres minor triceps long head teres major sup lat med inf humerus teres minor triceps long head teres major 4. profunda brachii a. and radial n. in triangular interval teres major triceps long head triceps lateral head

27. Collateral circulations: Even if a major artery to the arm is ligated or blocked, there is still blood flow into the arm and into the forearm suprascapular a. profunda brachii a. circumflex humeral aa. into brachial a. distal to ligation Ligation of brachial a. Ligation of axillary a. collateral aa. via recurrent aa. into radial and ulnar aa.

28. Superficial veins of upper limb (not accompanied by arteries) Superficial nerves of upper limb cephalic vein (watch out for it in the final.. ) basilic vein median cubital vein (venipuncture) medial cutaneous nerve of arm medial cutaneous nerve of forearm (runs with basilic vein into forearm)

29. superficial branch of radial nerve lateral cutaneous nerve of forearm (from musculocutaneous nerve) medial cutaneous nerve of forearm posterior cutaneous nerve of forearm (from radial nerve) cephalic vein and basilic vein form on dorsum of hand

30. Dissection today : Skin arm and forearm, but not hand Observe superficial veins and nerves Review pectoral region (front, already dissected) Dissect scapular region in prone position

31. List of ‘pinnable’ structures Skeleton: All structures pp 21 and 24 Bodies: Basilic vein, cephalic vein, median cubital vein, medial cutaneous nerves of arm and forearm, lateral cutaneous nerve of forearm, superficial branch of radial nerve (22 – 23) Deltoid, axillary nerve, posterior circumflex humeral artery, teres minor, quadrangular space, long head of triceps brachii, teres major, triangular space, circumflex scapular artery, supraspinatus, infraspinatus, suprascapular artery and nerve, superior transverse scapular ligament teres minor, teres major (24 – 26) Pectoralis major, cephalic vein, medial and lateral pectoral nerves, pectoralis minor, serratus anterior (29 - 30)