Upper Extremity.docx

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Department
Anatomy and Cell Biology
Course
Anatomy and Cell Biology 3319
Professor
Kem Rogers
Semester
Fall

Description
Upper Extremity Pg. 186-194 & 298-314 Lab Notes: Pectoral Girdle • Shoulder girdle • Consists of clavicle (anteriorly) and scapula (posteriorly) • Paired pectoral girdles and their associated muscles form the shoulders • Girdle implies a belt completely circling the body – but these girdles do not satisfy this description: o Anteriorly –medial end of each clavicle joins to the sternum & first rib o Lateral ends of the clavicles join to the scapulae at the shoulder o Two scapulae fail to complete the ring posteriorly, because their medial borders do not join to each other or the axial skeleton • Attaches upper limb to trunk & provides attachment for many muscles that move the limb • Girdle is light & allows the upper limbs to be quite mobile • Mobility results from two factors o Because only clavicle attaches to axial skeleton, scapula can move quite freely across thorax, allowing the arm to move with it o Socket of shoulder joint – scapula’s glenoid cavity – is shallow so it does not restrict movement of humerus (arm bone) o Although arrangement is good for flexibility, it’s bad for stability: shoulder dislocations are common Clavicles • Collar bones • Slender, S-shaped bones that extend horizontally across the superior thorax on the anterior surface • Cone-shaped sternal end attaches to manubrium medially & flattened acromial end articulates with scapula laterally • Medial 2/3 of clavicle is convex anteriorly; can feel anterior protection when you palpate clavicle • Lateral third is concave anteriorly • Superior surface is almost smooth • Inferior surface is ridged & grooved for ligaments & muscles that attach clavicle to rib cage & scapula • Thick trapezoid line & conoid tubercle near acromial end - attachment for ligament that runs to scapula’s coracoid process • Rough area near sternal end is attachment site of costoclavicular ligament – connects clavicle to 1 rib • Functions: provide attachment for muscles, act as braces that hold scapulae & arms out laterally from thorax • Function becomes obvious when clavicle is fractured: entire shoulder collapses medially • Clavicles also transmit compression forces from upper limbs to axial skeleton (Ex. both arms pushes a car) • Fractures of the clavicle o Clavicles are not very strong and they often fracture o Can occur when person falls on lateral border of shoulder, is hit directly on clavicle in contact spot or uses outstretched arms to break a fall o Fractured clavicle is common injury in automobile accidents where occupants are wearing seat belts o Curves in clavicle ensure that it usually fractures anteriorly (outward) at its middle third o If it were to fracture posteriorly (inward), bone splinters would pierce main blood vessels to arm, subclavian vessels – lie just deep to clavicle Scapulae • Thin, triangular flat bones located on dorsal surface of the rib cage, between ribs 2 & 7 inferiorly • Each scapula has 3 borders: o Superior border  Shortest & sharpest o Medial border or vertebral border  Parallels the vertebral column o Thick lateral border or axillary border  Abuts the axilla (armpit) and ends superiorly in a shallow fossa: glenoid cavity  Cavity articulates with the humerus, forming the shoulder joint • Like all triangles – has three corners or angles o Glenoid cavity lies at lateral angle o Superior angle is where the superior & medial borders meet o Inferior angle is at the junction of the medial & lateral borders • Inferior angle moves as arm is raised & lowered – important landmark for studying scapular movements • Anterior or costal surface of the scapula is slightly concave & relatively featureless • Coracoid process o Projects anteriorly from lateral part of the superior scapular border o Root corac means like crow’s beak – but process looks like a bent finger o Attachment point for biceps of the arm o Strong ligaments also bind it to the clavicle • Just medial to coracoid process lies suprascapular notch (passageway for suprascapular nerve) • Lateral to coracoid process lies the glenoid cavity • Posterior surface bears a prominent spine that is easily felt through skin • Spine ends laterally in flat projection: acromium (apex of shoulder) –articulates with acromial end of clavicle • Several large fossae occur on both surfaces of scapula and are named according to location • Infraspinous fossae (below the spine) • Supraspinous fossae (above the spine) • Subscapular (under scapula) fossa is shallow concavity formed by entire anterior surface of scapula • Lying within Movements of Scapula these fossae are 1) Elevation (shrugging) & Depression muscles: 2) Protraction (punching) & Retraction (standing at attention) 3) Upward & Downward Rotation (moving arms over head & down again) infraspinatus, supraspinatus & subcapularis Posterior Thorax Levator Scapulae Trapezius Rhomboid (Major & Minor) Anterior Thorax Pectoralis Minor Serratus Anterior (Boxer’s Muscle) Subclavius  Stabilize and depress pectoral girdle  Extending from rib 1 to clavicle  O – costal cartilage of rib 1  I – groove on inferior surface of clavicle  Nerve to subclavius (C5 & C6) Rotator Cuff Muscles • 4 muscles that originate on the scapula and cross the shoulder joint to insert on the humerus • All encircle shoulder joint (cuff) & help to anchor head of humerus into glenoid cavity of shoulder joint • Some (3/4) act to rotate humerus (either medially or laterally); one (supraspinatus) acts to abduct arm • Supraspinatus, Teres Minor, Infraspinatus insert into greater tubercle of humerus • Subscapularis, inserts into lesser tubercle The Upper Limb • 30 bones form the skeleton of the upper limb - grouped into bones of the arm, forearm & hand Arm • Arm or brachium to designate part of the upper limb between shoulder & elbow only • Humerus is the only bone of the arm - largest and longest bone in the upper limb • Articulates with the scapula at the shoulder and with radius & ulna (forearm bones) at the elbow • At the proximal end of the humerus is hemispherical head – fits into glenoid cavity of scapula • Just inferior to head is a slight constriction, anatomical neck • Inferior to neck is lateral greater tubercle & more medial lesser tubercle separated by intertubercular sulcus or bicipital groove • Tubercles are sites of attachment for the rotator cuff muscles • Intertubercular sulcus guides at tendon of biceps to its attachment point at rim of glenoid cavity (supraglenoid tubercle) • Surgical neck of the humerus (most frequently fractured) is inferior to tubercles • About midway down the shaft on the lateral side, is the deltoid tuberosity o V-shaped roughened area is an attachment site for the deltoid muscle of the shoulder • Near deltoid tuberosity along posterior surface of shaft, radial groove descends obliquely – radial nerve • At the distal end of humerus are two condyles o Medial trochlea that articulates with the ulna – looks like an hourglass turned on its side o Lateral capitulum that articulates with the radius – looks like a half ball • Condyles are flanked by medial & lateral epicondyles - attachment sites for muscles of the forearm • Directly above epicondyles are medial & lateral supracondylar ridges • On posterior surface of the humerus directly proximal to trochlea is the deep olecranon fossa • Corresponding position on anterior surface is shallower coronoid fossa medially & radial fossa laterally • Fossae receive similarly named projections of the forearm bones during forearm movement Glenohumeral Joint: Shoulder Joint Dislocation of the Shoulder • Due to ill-fitted glenohumeral joint, shoulder is the most common form of dislocation accounting for about 85% of all dislocations • Most dislocations are in the anterior plane, but they can also occur posteriorly, or inferiorly Forearm • Forearm or antebrachium • 2 parallel long bones: radius & ulna • Articulate with humerus proximally and the bones of the wrist distally • Radius & ulna also articulate with each other both proximally and distally at the small radioulnar joints • Radius & ulna are interconnected along their entire length by flat ligament called interosseous membrane (between the bones) • In anatomical position, radius lies laterally (on the thumb side) and ulna medially • However, when palm faces posteriorly, distal end of radius crosses over ulna & two bones form an X Ulna • Slightly longer than the radius • Main bone forming the elbow joint with the humerus • Looks like a money wrench • At its proximal end are 2 prominent projections: olecranon (elbow) & coronoid (crown-shaped) process – separated by a deep concavity: trochlear notch • Together, 2 processes grip trochlea of humerus forming a hinge joint that allows forearm to bend upon arm (flex) and then straighten again (extend) • When forearm is fully extended – olecranon process “locks” into olecranon fossa of the humerus • When forearm is flexed, coronoid process of the ulna fits into the coronoid fossa of the humerus • On lateral side of coronoid process is smooth depression: radial notch – head of radius articulates with ulna • Distally, shaft of ulna narrows & ends in a knoblike head that articulates with the radius • Medial to this is ulnar styloid process – from which ligament runs to the wrist • Head of ulna is separated from wrist bones by disc of fibrocartilage & plays little/no role in hand movements Radius • Thin at its proximal end and widened at tis distal end – opposite of ulna • Proximal head is shaped like the end of a spool of thread • Superior surface is concave – articulates with the capitulum of humerus • Medially, head of radius articulates with radial notch of ulna – forming proximal radioulnar joint • Just distal to head, on anterior surface in anatomical position, is a rough bump: radial tuberosity o Site of attachment of the biceps • On distal end of radius – medial ulnar notch articulates with head of ulna – distal radioulnar joint • Lateral radial styloid process anchors a ligament that runs to the wrist • Distal articular surface is concave and articulates with carpal bones of the wrist • Whereas ulna contributes a lot to elbow joint – radius is primary forearm bone contributing to wrist joint • When the radius rotates – hand moves with it • Distal, knob-like radial & ulnar styloid processes can be palpated by grasping dorsal side of distal forearm adjacent to the wrist with the thumb and index finger of the opposite hand • In this position, thumb palpates radial styloid process & index finger palpates the ulnar styloid process • Radial styloid process lies about 1 cm (0.4 inch) distal to ulnar styloid process Clinical Application - Palpation of Colles’ Fracture • Cause: fallen on outstretched hand & wrist has curves that resemble a fork • Clinician palpates for the position of the styloid processes • If palpation reveals that styloid process of radius has moved proximally from its normal position • Impacted fracture in which the distal end of the radius is forced proximally into shaft of radius Hand • Skeleton of hand includes: bones of carpus (wrist), bones of metacarpus (palm) & phalanges (fingers) Carpus • True wrist or carpus is the proximal region of the heand, just distal to the wrist joint • Contains 8 marble-sized short bones or carpals – closely united by ligaments • Gliding movements occurs between carpals, making wrist rather flexible • Carpals are arranged in two irregular rows of four bones each • In proximal row, from lateral (thumb side) to medial: scaphoid (boat-shaped), lunate (moonlike), triquetrum (triangular), & pisiform (pea-shaped) bones • Only scaphoid and lunate bones articulate with radius to form the wrist joint • In distal row, from lateral to medial: trapezium (little table), trapezoid (four-sided), capitate (head- shaped) & hamate (hooked) bones Some Lovers Try Positions That They Can’t Handle • Scaphoid is the most frequently fractured – often result from falling on an outstretched hand • Impact bends the scaphoid, which then breaks at its narrow midregion Metacarpus • Five metacarpals radiate distally from the wrist to form the metacarpus or palm • Small long bones are not named individually but instead are numbered I to V from thumb to little finger • Bases of metacarpals articulate with carpals proximally & with each other on their lateral & medial sides • Distally, bulbous heads of the metacarpals articulate with the proximal phalanges to form the knuckles • Metacarpal I, associated with the thumb – is the shortest and most mobile Phalanges of the Fingers • Digits or fingers – numbered I to v beginning with the thumb or pollex • Fingers contain miniature long bones called phalanges (singular phalanx) • In post people – third finger is the longest • With the exception of the thumb – each finger has three phalanges: proximal, middle & distal • Thumb has no middle phalanx Clinical Application – Carpal Tunnel Syndrome • Flexor retinaculum (transverse carpal ligament) lies distal to radial joint, spans across carpal bones, forming tunnel through which flexor tendons & median nerve pass (innervates lateral ½ of hand including muscles of thumbs • Functionally, retinaculum prevents “bowstringing” of these tendons during contraction of flexors • Inflammation of anything in tunnel – ex. tendons swollen from overuse, can compress median nerve • Nerve impairment affects workers who repeatedly flex wrists & fingers • High risk: using vibrating tools for long time, assembly worker, workers in food processing & packaging • Nerve impairment causes skin of lateral part of hand to tingle or numb & thumb movements to weaken • Followed by dull pain in affected area – can spread up to shoulders & neck • Condition can be treated by resting hand in splint during sleep, anti-inflammatory drugs & surgery • Carpal tunnel syndrome is just one example of a repetitive stress injuries Muscles of Upper Limb: Shoulder & Arm Anterior Muscles of Arm Pectoralis Major • Origin: o Clavicular head: anterior surface of medial ½ of clavicle o Sternocostal head: anterior surface of sternum, superior 6 costal cartilages, aponeurosis of external oblique • Insertion: lateral lip of intertubercular groove of humerus • Action: flexion, adduction, medial rotation of shoulder • Innervation: lateral and medial pectoral nerves Coracobrachialis • Origin: tip of coracoid process of scapula • Insertion: middle 1/3 of medial humerus • Action: flexes and Adducts arm • Innervation: musculocutaneuos nerve (C5,C6,C7) ________________________________________________________________________________________ Posterior Muscles of Arm Teres Major • Origin: dorsal surface of inferior angle of scapula • Insertion: intertubercular groove of humerus • Action: Extends, adducts and medially rotates arm • Innervation: lower subscapular nerve (C6,C7) Latissimus Dorsi • Origin: spinous processes of inferior 6 thoracic vertebrae; thoracolumbar fascia, iliac crest & inferior 3-4 ribs • Insertion: intertubercular groove of humerus • Action: Extends, adducts and medially rotates shoulder • Innervation: thoracodorsal nerve (C6,C7, C8) ________________________________________________________________________________________ Deltoid • Origin: lateral 1/3 of clavicle, acromium & spine of scapula • Insertion: Deltoid tuberosity of humerus • Action: o Anterior fibers: flexes & medially rotates arm o Middle fibers: abducts arm o Posterior fibers: extends and laterally rotates arm • Innervation: axillary nerve (C5, C6) Compart
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