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The Musculoskeletal System
The human musculoskeletal system(also known as thelocomotor system) is an organ system that gives humans the
ability to move using their muscular and skeletal systems. The
musculoskeletal system provides form, support, stability, and
movement to the body.
It is made up of the bones of the skeleton, muscles, cartilage,
tendons, ligaments, joints, and other connective tissue that supports
and binds tissues and organs together.
Movements of different parts of the body require an interactionbetween bones and muscles.
To understand how muscles produce different movements, one
should learn where the muscles attach to individual bones and the
types of joints acted on by the contracting muscles.
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The Appendicular Skeleton
The appendicular skeleton consists of the bones of the upperand
lower limbs.
The upper and lower limbs are made up of bones that form the limb
girdles, and bones that form the free limbs.
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The Upper Limb
The upper limb is characterized by its mobility and its ability tograsp, strike, and conduct fine motor skills.
These characteristics are especially marked in the hand. Efficiency
of hand function results in a large part from the ability to place it inthe proper position by movements at the scapulothoracic, shoulder,elbow, radioulnar, and wrist joints.
Bones of the upper limb consist of the bones of the shoulder girdle,and those of thearm,theforearm,thewrist and thehand.
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Bones of the Shoulder Girdle
The bones of theshoulder (pectoral) girdle consist of the clavicle
and thescapula, which articulate with one another at theacromioclavicular joint.
The Clavicle (Collar Bone) /1
The clavicleis a long, slender bone that lies horizontally across the
root of the neck.
It articulates with the sternum and the first costal cartilage medially at
the sternoclavicular joint and with the acromion process of the
scapula laterally at the acromioclavicular joint.
The clavicle acts as a strut between the scapula and the sternum,
that holds the arm away from the trunk. It also transmits forces from
the upper limb to the axial skeleton and provides attachment for
muscles.
The clavicle is subcutaneous throughout its length;
its medial two thirds are convex forward and its lateral third is
concave forward.
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Clavicle (Collar Bone) /2
The acromial endof the clavicle is flat, whereas the sternal endismore robust and somewhat quadrangular in shape.
The inferior surface of the lateral third of the clavicle is roughconsisting of a tubercle medially, the conoid tubercleand, a lateral
roughening , the trapezoid linefor the attachment of thecoracoclavicular ligament.
The superior surface of the clavicle is smoother than the inferiorsurface
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The Scapula /1
The scapulais a flat triangular bone that lies on the posterolateralaspect of the thoracic cage between the second and the seventh
ribs. It connects the humerus with the clavicle.
It has two surfaces, three borders, three angles andthreeprocesses.
On its posterior surface, thespine of the scapula projectsbackward.
On the lateral end of the spine is theacromion process,whicharticulates with the clavicle at theacromioclavicular joint.
Thecoracoid processprojects upward and forward above theglenoid cavity and provides attachment for muscles and ligaments.
The superolateral angleof the scapula forms the pear-shapedglenoid cavity,or glenoidfossa, which articulates with the head ofthe humerus at the shoulder joint.
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The Scapula /2
The inferior angleof the scapula can be palpated easily in the livingsubject and marks the level of the seventh rib and the spine of theseventh thoracic vertebra.
Medial to the base of the coracoid process is thesuprascapularnotch.
The anterior surfaceof the scapula is concave and forms theshallow subscapular fossa.
The posterior surfaceof the scapula is divided by the spine into:
the smaller supraspinous fossaabove and the largerinfraspinous fossabelow.
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Bones of the Arm:
TheHumerus /1
The humerusis the bone of the arm. It articulates with the scapulaat the shoulder joint and with the radius and ulna at the elbow joint.
The upper end of the humerus has a head, which forms about one
third of a sphere and articulates with the glenoid cavity of thescapula.
Immediately below the head is a short, narrow constriction, theanatomical neck.
Below the neck are the greater andlesser tubercles, separatedfrom each other by the bicipital (intertubercular) groove orsulcus. These tubercles serve as attachment sites for the rotatorcuff muscles of the shoulder joint
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TheHumerus /2 The greater tubercle is lateral in position, whereas the lesser
tubercle is anterior in position.
Where the upper end of the humerus joins the shaft, there is anarrow surgical neck.
Because the surgical neck is weaker than the more proximal regions
of the humerus, it is one of the sites where the humerus commonlyfractures. A fracture in this area is most likely to cause damage tothe axillary nerve and posterior circumflex humeral artery. Damageto the axillary nerve affects function of the teres minor and deltoidmuscles
About halfway down the lateral aspect of the shaft is a roughenedelevation called the deltoid tuberosity.
On the posterior surface of the humerus is the spiral (radial)groove, which accommodates the radial nerve and the profunda
brachii artery.
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The Humerus/3
The body(shaft) of the humerus has an anterior, medial and lateralborders.
The lower end of the humerus possesses the medialand lateralepicondylesfor the attachment of muscles and ligaments, therounded capitulumfor articulation with the head of the radius, andthe pulley-shaped trochleafor articulation with the trochlearnotch ofthe ulna.
Above the capitulum is the radial fossa,which receives the head ofthe radius when the forearm is flexed.
Above the trochlea anteriorly is the coronoid fossa, which duringthe same movement (flexion) receives the coronoid process of theulna.
Above the trochlea posteriorly is the olecranon fossa, whichreceives the olecranon process of the ulna when the forearm is
extended
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Bones of the Forearm
The bones of the forearm are the radius and the ulna.
The Radius/1
The radiusis the lateral bone of the forearm.
Its proximal endarticulates with the humerus at the elbow jointand with the ulna at the proximal radioulnar joint.
Its distal endarticulates with the scaphoid and lunate bones of the
wrist at the wrist jointand with the ulna at the distal radioulnarjoint.
At the proximal end of the radius is the small circular head.
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The Radius /2
The upper surface of the head is concave and articulates with theconvex capitulum of the humerus.
The circumference of the head articulates with the radial notch of theulna at the proximal radioulnar joint.
Below the head, the bone is constricted to form the neck.
Below the neck is the radial(bicipital)tuberosityfor the insertionof the biceps brachii muscle.
The shaftof the radius, in contradistinction to that of the ulna, iswider below than above.
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The Radius /3
The shaft of the radius has three borders (anterior, posteriorandinterosseous), and three surfaces (anterior, posteriorandlateral).
It has a sharp interosseous border medially for the attachment of theinterosseous membrane that binds the radius and ulna together.
The pronator tubercle, for the insertion of the pronator teresmuscle, lies halfway down on its lateral side.
At the distal end of the radius is the styloid process; this projectsdistally from its lateral margin.
On the medial surface of the distal end is the ulnar notch, whicharticulates with the head of the ulna at the distal radioulnar joint.
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The Radius /4
The inferior articular surface of the radius bone articulates with the
scaphoid and lunate carpal bones.
On the posterior aspect of the distal end is a small tubercle, the
dorsaltubercle, which acts as a pulley for the tendon of theextensor pollicis longus muscle.
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The Ulna /1
The ulnais the medial bone of the forearm.
Its proximal end articulates with the humerus at the elbow jointandwith the head of the radius at the proximal radioulnar joint.
Its distal end articulates with the radius at the distal radioulnar joint,but it is excluded from the wrist joint by the articular disc.
The proximal end of the ulna is large and is known as the olecranon
process; this forms the prominence of the elbow.
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The Ulna /2
The olecranon process has a notch on its anterior surface, the
trochlear notch,which articulates with the trochlea of the humerus.
Below the trochlear notch is the triangular coronoid process, whichhas on its lateral surface the radial notchfor articulation with thehead of the radius.
At the junction of the anterior surface of the coronoid process withthe front of the body is a rough eminence, the tuberosityof theulna or (ulnar tuberosity), which gives insertion to the brachialismuscle.
The shaftof the ulna tapers from above downard.
The ulna has three borders (anterior, posteriorand interosseous),and three surfaces (anterior, posteriorand medial).
It has a sharp interosseous borderlaterally for the attachment of
the interosseous membrane.
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The Ulna /3
The posterior borderis sharp and subcutaneous and can be easilypalpated throughout its length.
Below the radial notch is a depression, the supinator fossa, whichgives clearance for the movement of the radial tuberosity of the
radius.
The posterior border of the fossa is sharp and is known as thesupinator crest; it gives origin to the supinator muscle.
At the distal end of the ulna is the small rounded head, which has aprojection from its medial aspect, the styloid process.
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Bones of the Wrist & Hand /1
There are eight carpal bones, made up of two rows of four bones
each.
Theproximal rowconsists of (from lateral to medial) the
scaphoid, lunate, triquetrum,andpisiformbones.
Thedistal rowconsists of (from lateral to medial) thetrapezium,
trapezoid, capitate,andhamatebones.
Together, the bones of the carpuspresent on their anterior surfacea concavity (carpal arch), to the lateral and medial edges of which
is attached a strong membranous band called the flexor
retinaculum.
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Bones of the Wrist & Hand /2
In this manner, an osteofascial tunnel, the carpaltunnel, is formedfor the passage of the median nerve and the flexor tendons of the
digits.
The canal is narrow, and when any of the nine long flexor tendonspassing through it swell or degenerate, the narrowing of the canaloften results in the median nerve becoming entrapped orcompressed, a common medical condition known as carpal tunnel
syndrome.
There are five metacarpal bones, each of which has abase, ashaft,and ahead.
The first metacarpal bone of the thumb is the shortest and mostmobile. It does not lie in the same plane as the others but occupiesa more anterior position.
It is also rotated medially through a right angle so that its extensorsurface is directed laterally and not backward (posteriorly) as theother metacarpal bones do.
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Bones of the Hand /3
The basesof the metacarpal bones articulate with the distal row ofthe carpal bones at the carpo-metacarpal joints, whereas theheads, which form the knuckles, articulate with the proximalphalanges at the metacarpo-phalangeal joints.
The shaftof each metacarpal bone is slightly concave forward andis triangular in transverse section. Its surfaces are posterior, lateral,and medial.
There are three phalangesfor each of the fingers but only two forthe thumb.
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Muscles of the Shoulder
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Muscles of the Shoulder
Theshoulder muscles can be described according to their locationand the areas of the skeleton to which they are attached into, the:
A.Anterior axioappendicular muscles (pectoralis major, pectoralis
minor, subclavius and serratus anterior.
B. Posterior axioappendicular muscles, of which there are three
subgroups:
1.superficial posterior axioappendicular muscles
(trapezius and latissimus dorsi)2 .deep posterior axioappendicular muscles (levator scapulae and
rhomboids)
3. Scapulohumeral muscles (deltoid, teres major, and the four
rotator cuff muscles : the supraspinatus, infraspinatus, teres minor, and
subscapularis.
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A.Anterior Axioappendicular Muscles /1
Fouranterior axioappendicular or pectoral musclesmove thepectoral girdle: these are the pectoralis major, pectoralis minor,subclavius, and serratus anterior.
The fan-shapedpectoralis majorcovers the superior part of theanterior aspect of the thorax. It hastwo heads of origin, aclavicular
headandasternocostal head,
The pectoralis major muscle is responsible for the muscular massthat forms most of the anterior wall of the axilla, with its inferiorborder forming the anterior axillary fold.
The pectoralis major and the adjacent deltoid muscle form thenarrow deltopectoral groove,in which the cephalic vein runs.However, the muscles diverge slightly from each other superiorlyand, along with the clavicle, form theclavipectoral triangle.
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A.Anterior Axioappendicular Muscles/2
The pectoralis major adducts, flexes, and medially rotates the arm.
The smaller triangularpectoralis minormusclelies in the anteriorwall of the axilla, where it is almost completely covered by thepectoralis major. The pectoralis minor muscle stabilizes the scapulaand is used when stretching the upper limb forward to touch anobject that is just out of reach.
With the coracoid process, the pectoralis minor forms a "bridge"under which vessels and nerves pass to the arm.
Thus the pectoralis minor is a useful anatomical and surgicallandmark for structures in the axilla (e.g., the axillary artery).
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A. Anterior Axioappendicular Muscles /3
Thesubclaviusmusclelies almost horizontally when the arm is in
the anatomical position. This small, round muscle is located inferior
to the clavicle and affords some protection to the subclavian vesselsand the superior trunk of the brachial plexus if the clavicle fractures.
Theserratus anterior muscleoverlies the lateral part of the thorax
and forms the medial wall of the axilla.
This broad sheet of thick muscle fibers was given its name because
of the saw tooth appearance of its fleshy slips or digitations (L.
serratus,a saw). By keeping the scapula closely applied to the
thoracic wall, the serratus anterior anchors this bone, enabling other
muscles to use it as a fixed bone for movements of the humerus.
The muscle is supplied by the long thoracic nerve. Paralysis of
serratus anterior muscle leads to a condition referred to as winging
of the scaula, in which the scapula protrudes from the back of theperson in an abnormal position.
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B. Posterior Axioappendicular &
Scapulohumeral Muscles
Theposterior axioappendicular musclesattach the upper limb to
the axial skeleton. The posterior shoulder muscles are divided into
three groups:
1. Superficial posterior axioappendicular muscles:trapezius andlatissimus dorsi.
2. Deep posterior axioappendicular muscles:levator scapulae and
rhomboids
3. Scapulohumeral muscles:deltoid, teres major, and the four
rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and
subscapularis).
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1. Superficial Posterior Axioappendicular Muscles /1
Thetrapezius muscleprovides a direct attachment of the pectoral
girdle to the trunk.
This large trapezoid muscle covers the posterior aspect of the neck andthe superior half of the back.
The trapezius attaches the pectoral girdle to the cranium and vertebral
column and assists in suspending the upper limb.
The fibers of the trapezius muscle are divided into three parts that havedifferent actions at the scapulothoracic joint between the scapula andthe thoracic wall:
Descending (superior) part elevates the scapula (e.g., when squaringshoulders).
Middle part retracts the scapula (i.e., pulls it posteriorly).
Ascending (inferior) fibers depressthe scapulaand lower the shoulder.
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The latissimus dorsiis a large, fan-shaped muscle that covers theinferior part of the back from the T6 vertebra to the iliac crest.
It passes from the trunk to the humerus and acts directly on the
shoulder joint and indirectly on the pectoral girdle (scapulothoracicjoint).
The latissimus dorsi muscle extends, adducts, and medially rotatesthe arm.
1. Superficial Posterior Axioappendicular Muscles /2
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2 D P t i A i di l M l
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2.Deep Posterior Axioappendicular Muscles
True to its name, the levator scapulae muscle acts with thesuperior part of trapezius to elevate the scapula.
The superior third of thelevator scapulaelies deep to thesternocleidomastoid muscle; the inferior third is deep to thetrapezius muscle..
Acting bilaterally, the levator scapulae muscles extend the neck;
acting unilaterally, the muscle contributes to lateral flexion of theneck.
The tworhomboids(rhomboid major and minor) lie deep to thetrapezius and form parallel bands that pass inferolaterally from thevertebrae to the medial border of the scapula.
The thin flatrhomboid majoris approximately two times wider thanthe thickerrhomboid minorlying superior to it.
The rhomboids retract and rotate the scapula, depressing theglenoid cavity. They also assist the serratus anterior in holding the
scapula against the thoracic wall and fixing the scapula duringmovements of the upper limb.
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3. Scapulohumeral Muscles /1
The sixscapulohumeral muscles(the deltoid, teres major,supraspinatus, infraspinatus, subscapularis, and teres minor) arerelatively short muscles that pass from the scapula to the humerusand act on the shoulder joint.
Thedeltoidis a thick powerful muscle forming the rounded contourof the shoulder. The muscle is divided into clavicular (anterior),acromial (middle), and spinal (posterior) parts that can actseparately or as a whole.
When all three parts contract simultaneously, the arm is abducted.
The anterior (clavicular) fibers of deltoid muscle flex and mediallyrotate the arm; the posterior (spinal) fibers of the muscle extend andlaterally rotates the arm.
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3. Scapulohumeral Muscles /2
From the fully adducted position, abduction of the arm must be
initiated by the supraspinatus muscle. The deltoid becomes fully
effective as an abductor after the initial 15of abduction.
Theteres majoris a thick rounded muscle that lies on theinferolateral third of the scapula. It adducts and medially rotates the
arm, but along with the deltoid and rotator cuff muscles it is an
important stabilizer of the humeral head in the glenoid cavity during
movement.
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Rotator cuff muscles
Four of the scapulohumeral muscles supraspinatus,infraspinatus, teres minor,and subscapularisare called rotatorcuff musclesbecause they form a musculotendinous rotator cuffaround the glenohumeral joint.
The supraspinatus, besides being part of the rotator cuff muscles,
initiates the first 15or so of abduction movement of the arm.
The tendons of the rotator cuff muscles blend with the capsule of theshoulder joint, reinforcing it as the musculotendinous rotator cuff,which protects the joint and gives it stability.
Contraction of these muscles holds the relatively large head of thehumerus firmly against the small and shallow glenoid cavity duringarm movements.
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The Axilla (Arm pit) /1
The axilla orarm pit is the pyramidal shaped hollow space which islocated inferior to the shoulder and superior to the skin and axillaryfascia where your arm and body meet.
The shape and size of the axilla varies, depending on the position ofthe arm; it almost disappears when the arm is fully adducted.
The axilla provides a passageway for vessels and nerves going intoand out from the upper limb.
The axilla has an apex, base, and four walls, three of which aremuscular:
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The Axilla/2
The apex of the axilla is thecervicoaxillary canal,the passageway
between the neck and the axilla. It is bounded by the 1st rib,
clavicle, and superior edge of the scapula. Arteries, veins,
lymphatics, and nerves traverse this superior opening to pass into or
out from the arm.
The baseof the axilla is formed by the concave skin, subcutaneous
tissue, and axillary (deep) fascia extending from the arm to the
thoracic wall forming the axillary fossa.
The Axilla /3
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The Axilla/3
The anterior wallof theaxilla is formed by thepectoralis major and
minor muscles and thepectoral andclavipectoral fasciaassociated with them.
The clavipectoral
fascia is a sheet ofmembrane filling in thespace between clavicleand pectoralis minor,limited laterally by thecoracoid process.
Theanterior axillaryfoldis the inferiormostpart of the anterior wallof the axilla. It is formedby the inferior border ofpectolaris major muscle.
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The Axilla/4
The posterior wall of the axillais formed superiorly by the scapulaand the subscapularis muscle on its anterior surface and inferiorlyby the teres major and latissimus dorsi.
Theposterior axillary foldis the inferiormost part of the posteriorwall that may be grasped. It is formed by the teres major andlatissimus dorsi muscles.
The medial wall of the axilla is formed by the thoracic wall (1st-4thribs and intercostal muscles) and the overlying serratus anteriormuscle.
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The Axilla/5
The lateral wall of the axilla is the narrow bony wall formed by the
intertubercular groove of the humerus.
The axillacontains the axillary artery and its branches, the axillary
vein and its tributaries, nerves of the cords and branches of thebrachial plexus, lymphatic vessels, and several groups of axillary
lymph nodes,all embedded in axillary fat.
Proximally, the neurovascular structures in the axilla are ensheathed
in a sleeve-like extension of the cervical fascia, theaxillary sheath
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The Arm (Upper Arm, Brachium)
The arm proper (brachium), sometimes called the upper arm,theregion between the shoulder and the elbow, is composed of thehumerus with the elbow joint at its distal end.
The armextends from the shoulder to the elbow.
Two types of arm movement occur at the elbow joint: flexion-extension and pronation - supination.
The muscles performing these movements are clearly divided intoanterior(flexor)and posterior(extensor) groups.
The chief action of both groups of muscles is at the elbow joint, butsome muscles also act at the shoulder joint.
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Fascial Compartments of the Arm
The arm is enclosed in a sheath of deep fascia.
Two intermuscular fascial septa(the medial intermuscular andthe lateral intermuscular) extend from this sheath and are attachedto the medial and lateral borders of the humerus, respectively.
By this means, the arm is divided into an anteriorand a posteriorfascial compartment, with each compartment having its ownmuscles, nerves and blood vessels.
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Muscles of The Arm
Of the four arm muscles, three flexors (biceps brachii,brachialis,andcoracobrachialis) are in the anterior (flexor) compartment ofthe arm and are supplied by the musculocutaneous nerve, and oneextensor (triceps brachii) is in the posterior compartment of the
arm, supplied by the radial nerve.
In addition to the triceps muscle in the posterior compartment of thearm, there is a small triangular muscle the anconeus, covering theposterior aspect of the elbow.
Anterior compartment of the arm
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Anterior compartment of the arm
Biceps brachii muscle
Thebiceps brachiimuscle, as its name implies, has two heads : a
long headand ashort head.
A broad fascial band, the transverse humeral ligament,passesfrom the lesser to the greater tubercle of the humerus and convertsthe intertubercular groove into a canal for the tendon of the longhead of the biceps.
When the elbow is extended, the biceps is a simple flexor of theforearm; however, as the elbow flexion approaches 90and morepower is needed, the biceps with the forearm in supination producesflexion, but with the forearm in pronation the biceps is the prime
mover (most powerful) supinator of the forearm.
A triangular membranous band, thebicipital aponeurosis, runsfrom the biceps tendon across the cubital fossa and merges with theantebrachial (deep) fascia covering the flexor muscles in the medialside of the forearm.
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Brachialis & coracobrachialis muscles
The brachialisis a flattened fusiform muscle that lies posterior(deep) to the biceps brachii muscle.
It is the prime flexor muscle of the forearm, producing the greatestamount of flexion force. It flexes the forearm in all positions andduring slow and quick movements.
Thecoracobrachialis,an elongated muscle in the superomedialpart of the arm, is a useful landmark for locating other structures inthe arm.
The musculocutaneous nerve pierces it, and the distal part of its
attachment indicates the location of the nutrient foramen of thehumerus.
The coracobrachialis muscle helps flex and adduct the arm andstabilizes the shoulder joint.
Posterior compartment of the arm
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Posterior compartment of the arm
Triceps brachii muscle
The triceps brachii is a large fusiform muscle in the posteriorcompartment of the arm that arises by means of three heads, along, lateral, and medial.
The triceps is the main extensor muscle of the forearm at the elbow.
The anconeusis a small muscle located in the inferior aspect of thearm. It assists triceps in extending the forearm as well as stabilizingthe elbow joint.
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The Cubital fossa
The cubital fossa is the shallow triangular depression on theanterior surface of the elbow.
The boundaries of the cubital fossaare:
- The baseof the triangle is an imaginary line connecting the
medial and lateral epicondyles of the humerus.- Medially, the pronator teres muscle
- Laterally, the brachioradialis muscle
From medial to lateral, the cubital fossa contains the median nerve,
the bifurcation of the brachialartery into the ulnar and radialarteries, the tendon of biceps brachiimuscle, and the radial nerve.
Lying in the superficial fascia covering the fossa are the cephalicand the basilic veins and their tributaries.
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The Forearm
Theforearmlies between the elbow and the wrist and contains two
bones, the radius and ulna,which are joined by an interosseous
membrane.
The role of forearm movement, occurring at the elbow andradioulnar joints, is to assist the shoulder in the application of force
and in controlling the placement of the hand in space.
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Fascial compartments of the forearm
The forearm is enclosed in a sheath of deep fascia, which is
attached to the periosteum of the posterior subcutaneous border of
the ulna.
Together with the interosseous membrane and fibrous intermuscularsepta, this fascial sheath divides the forearm into several
compartments, with each compartment having its own muscles,
nerves and blood supply.
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Flexor & Extensor Retinacula
Retinaculaare bands of deep fascia that hold the long flexor andextensor tendons in position at the wrist.
The flexor retinaculumis attached medially to the pisiform boneand the hook of hamate and laterally to the tubercle of the scaphoid
and the trapezium bones.
The extensor retinaculumis attached medially to the pisiform boneand the hook of the hamate and laterally to the distal end of theradius.
The bones of the hand in the wrist region (carpal bones) and theflexor retinaculum form the carpal tunnel.
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Muscles of Forearm
The tendons of the forearm muscles pass through the distal part ofthe forearm and continue into the wrist, hand, and fingers.
The flexors and pronator muscles of the forearm are in the anteriorcompartment of the forearm and are served mainly by the median
nerve;the one and a half muscle exceptions are innervated by theulnar nerve.
The extensors and supinator muscles of the forearm are in theposterior compartment and are all innervated by the radial nerve.
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Flexor- Pronator Muscles of the Forearm /1
The flexor-pronator muscles are in the anterior compartment of theforearm.
The tendons of most flexor muscles pass across the anterior surfaceof the wrist and are held in place by the flexor retinaculum, athickening of the deep fascia of the forearm.
The flexor muscles are arranged in three layers:
1. A superficial layer of four muscles which are the pronatorteres, flexor carpi radialis, palmaris longus, and flexor carpi
ulnaris.
These muscles are all attached proximally to the medial epicondyleof the humerus, the common flexor origin.
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Flexor- Pronator Muscles of the Forearm/2
2. An Intermediate layer, consisting of one muscle, the flexordigitorum superficialis [FDS].
3. Adeep layer of three muscles: the flexor digitorum profundus[FDP], theflexor pollicis longus, andthepronator quadratus.
The five superficial muscles and the intermediate muscle cross theelbow joint; the three deep muscles do not.
Functionally, the brachioradialismuscle is a flexor of the forearm,but it is located in the posterior (posterolateral) or extensor
compartment and is thus supplied by the radial nerve. Therefore, thebrachioradialis is a major exception to the generalization that theradial nerve supplies only extensor muscles and that all flexors lie inthe anterior compartment.
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Flexor- Pronator Muscles of the Forearm /2
The long flexors of the digits (FDSand FDP) also flex the
metacarpophalangeal and wrist joints.
The FDPflexes the fingers in slow action; this action is reinforced by
the FDSwhen speed and flexion against resistance are required.
When the wrist is flexed at the same time the metacarpophalangeal
and interphalangeal joints are flexed, the long flexor muscles of the
fingers are operating over a shortened distance between
attachments, and the action resulting from their contraction isconsequently weaker.
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Flexor- Pronator Muscles of the Forearm /3
Extending the wrist increases their operating distance, and thus theircontraction is more efficient in producing a strong grip.
Tendons of the long flexors of fingers pass through the distal part ofthe forearm, wrist, and palm and continue to the medial four digits.
The FDSflexes the middle phalanges; the FDPflexes the distalphalanges.
The pronator quadratusmuscle is the prime mover for pronation.The pronator quadratus initiates pronation and is assisted by the
pronator tereswhen more speed and power are needed.
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Insertion of the long flexor tendons
Each tendon of the flexor digitorum superficialis is divided into twohalves that pass around the profundus tendon and meet on itsposterior surface.
The superficialis tendon, having united again, then divides into two
further slips, which are attached to the borders of the base of themiddle phalanx.
Each tendon of the flexor digitorum profundus, having passedthrough the superficialis tendon, is inserted into the base of the distalphalanx.
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Extensor Muscles of the Forearm /1
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Extensor Muscles of the Forearm /1
The extensor musclesare in the posterior compartment of theforearm, and all are innervated by branches of the radial nerve.These muscles are organized into three functional groups:
- Muscles thatextend andabduct oradduct the hand at the wristjoint(extensor carpi radialis longus, extensor carpi radialis
brevis, and extensor carpi ulnaris).
- Musclesthatextend the medial four digits (extensor digitorum,extensor indicis, and extensor digiti minimi).
- Muscles thatextend or abduct the thumb (abductor pollicis
longus[APL], extensor pollicis brevis[EPB], and extensorpollicis longus[EPL]).
Besides, there is the supinator musclelying between the lateralepicondyle of the humerus and the neck and shaft of radius, theaction of which is supination of the forearm.
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Extensor Muscles of the Forearm /2
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Extensor Muscles of the Forearm /2
The extensor tendons are held in place in the wrist region by theextensor retinaculum, which prevents bowstringing of the tendonswhen the hand is extended at the wrist joint.
As the tendons pass over the dorsum of the wrist, they are covered
with synovial tendon sheaths, which reduce friction for theextensor tendons as they traverse the osseofibrous tunnels formedby the attachment of the extensor retinaculum to the distal radiusand ulna.
The extensor muscles are organized anatomically into superficial
anddeep layers.
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Extensor Muscles of the Forearm /3
Four superficial extensors(extensor carpi radialis brevis,extensor digitorum,extensor digiti minimi,andextensor carpiulnaris) are attached proximally by a common extensor tendontothe lateralepicondyleof the humeus.
The proximal attachment of the other two superficial extensors
(brachioradialis and extensor carpi radialis longus) is to thelateral supracondylar ridge of the humerus.
The four flat tendons of the extensor digitorum pass deep to theextensor retinaculum to the medial four fingers.
Extensor Muscles of the Forearm /4
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Extensor Muscles of the Forearm /4
On the dorsum of the hand, the tendons of extensor digitorum
spread out as they run toward the fingers. Adjacent tendons are
linked proximal to the metacarpophalangeal joints by three oblique
intertendinous connectionsthat restrict independent extension of
the fingers.
Consequently, normally no finger can remain fully flexed as the
other ones are fully extended.
On the distal ends of the metacarpals and along the phalanges, the
four tendons of extensor digitorum flatten to formextensorexpansions.
E t M l f th F /5
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Extensor Muscles of the Forearm /5
The tendons of the interosseous and lumbrical muscles of the hand
join the lateral bands of the extensor expansion.
The deep extensor muscles of forearm, abductor pollicis longus(APL), extensor pollicis brevis(EPB), and extensor pollicislongus (EPL) act on the thumb.
The extensor indicis muscle confers independence to the indexfinger in that it may act alone or together with the extensordigitorum.
The tendons of the APLand EPBbound the triangularanatomical
snuffboxlaterally, and the tendon of the EPLbounds it medially.
The snuffbox is visible as a hollow on the lateral aspect of the wristwhen the thumb is extended fully.
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I ti f th l t t d /2
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Insertion of the long extensor tendons /2
Each extensor expansion is a triangular tendinous aponeurosis thatwraps around the dorsum and sides of a head of the metacarpal andthe base of the proximal phalanx.
Near the proximal interphalangeal joint, the extensor expansion then
splits into three bands: a central band, which is inserted into thebase of the middle phalanx, and two lateral bands, which pass tothe base of the distal phalanx.
The tendons of the interosseous and lumbrical muscles of the handjoin the lateral bands of the extensor expansion.
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The Hand
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The Hand
The palmar aspect of the handfeatures a central concavity thatseparates two eminences: a lateral more prominent thenareminenceproximal to the base of the thumb, and a medial, smallerhypothenar eminenceproximal to the base of the little finger.
The anterior surface of each finger from the metacarpal head to the
base of the distal phalanx is provided with a strong, fibrous sheathcalled the fibrous flexor sheaths, that is attached to the sides ofthe phalanges.
The sheath and the bones form a blind tunnel in which the long
flexor tendons of the finger lie.
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Synovial flexor sheaths
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In the hand, the tendons of the flexor digitorum superficialis and
profundus muscles invaginate a common synovial sheath.
The medial part of this common synovial sheath extends distallywithout interruption on the tendon of the little finger.
The lateral part of the sheath stops abruptly on the middle of the
palm, and the distal ends of the long flexor tendons of the index, themiddle, and the ring fingers acquire digital synovial sheaths asthey enter the finger.
The flexor pollicis longus tendon has its own synovial sheath thatpasses into the thumb.
These sheaths allow the long tendons to move smoothly, with aminimum of friction, beneath the flexor retinaculum and the fibrousflexor sheaths.
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Palmar apponeurosis
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Palmar apponeurosis
In the palm, the deep fascia is greatly thickened to protect theunderlying tendons, nerves, and blood vessels and is called thepalmar apponeurosis.
The palmar apponeurosis is continuous proximally with the palmarislongus tendon, and it is attached to the flexor retinaculum.
The distal end of the apponeurosis divides at the bases of thefingers into four slips that pass into the fingers forming the fibrousdigital sheaths.
The palmar apponeurosis is continuous also with the deep fasciacovering the thenar and hypothenar eminences.
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Muscles of Hand
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Muscles of Hand
The intrinsic muscles of the handare located in fivecompartments:
Thenar muscles in the thenar compartment: abductor pollicisbrevis, flexor pollicis brevis, and opponenes pollicis.
Hypothenar musclesin the hypothenar compartment: abductordigiti minimi, flexor digiti minimi brevis, and opponens digiti minimi.
Adductor pollicismusclein the Adductor compartment
The short muscles of the hand, the lumbricals, in thecentral
compartmenttogether with the long flexor muscles.
The interossei muscles in separateinterosseous compartmentsbetween the metacarpals.
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The Shoulder Joint /1
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The glenohumeral (shoulder)jointis a ball and socket synovialjoint that permits a wide range of movements; however, its mobilitymakes the joint relatively unstable.
Articulation and Joint capsule
The large humeral head articulates with the relatively shallow
glenoid cavity of the scapula, which is deepened slightly by the ring-like, fibrocartilaginousstructure the glenoid labrum.
Both articular surfaces are covered with hyaline cartilage.
The glenoid cavity accepts little more than a third of the humeralhead, which is held in the cavity by the tonus of themusculotendinous rotator cuff muscles (supraspinatus,infraspinatus, teres minor, and subscapularis).
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The Shoulder Joint /2
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The Shoulder Joint /2
The loose fibrous layerof the joint capsule surrounds theglenohumeral joint and is attached medially to the margin of theglenoid cavity and laterally to the anatomical neck of the humerus.
Superiorly, the fibrous layer encloses the proximal attachment of the
long head of biceps brachii to the supraglenoid tubercle of thescapula within the joint.
The inferior part of the joint capsule, the only part not reinforced bythe rotator cuff, muscles, is its weakest area. It is in this area that thecapsule is particularly lax and lies in folds when the arm is adducted;
however, it becomes taut when the arm is abducted
The Shoulder Joint /3
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The Shoulder Joint /3
The synovial membranelines the internal surface of the jointcapsule and reflects from it onto the glenoid labrum and thehumerus as far as the articular margin of the head.
The synovial membrane also forms a tubular sheath for the tendonof the long head of the biceps brachii.
Anteriorly, there is a communication between the subscapular bursaand the synovial cavity of the joint.
Nerve supply: The shoulder joint is supplied by the axillary and
suprascapular nerves.
Ligaments of the shoulder joint /1
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Ligaments of the shoulder joint /1
The glenohumeral ligaments,evident only on the internal aspect ofthe capsule, strengthen the anterior aspect of the capsule.
The glenohumeral ligaments are intrinsic ligaments that are part ofthe fibrous layer of the joint capsule.
Thecoracohumeral ligament,a strong band that passes from thebase of the coracoid process to the anterior aspect of the greatertubercle of the humerus, strengthens the capsule superiorly.
Thetransverse humeral ligamentis a broad fibrous band that runsfrom the greater to the lesser tubercles of the humerus, bridgingover the intertubercular groove and converting the groove into acanal for the tendon of the long head of biceps brachii and itssynovial sheath.
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Ligaments of the shoulder joint /2
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Ligaments of the shoulder joint /2
Thecoracoacromial archis an extrinsic, protective structureformed by the smooth inferior aspect of the acromion and coracoidprocess of the scapula, with thecoracoacromial ligamentspanning between them.
The coracoacromial arch overlies the head of the humerus,preventing its superior displacement from the glenoid cavity.
The arch is so strong that a forceful superior thrust of the humeruswill not fracture it; the shaft of the humerus or clavicle fractures first.
Movements at the shoulder joint /1
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The shoulder joint has more freedom of movement than any other joint
in the body. This freedom results from the laxity of its joint capsule andthe large size of the humeral head compared with the small size of theglenoid cavity.
The shoulder joint allows movements around the three axes andpermits flexion-extension, abduction-adduction and rotation (medial
and lateral) of the humerus, and circumduction.
Flexion: Normal flexion is about 90
Extension: Normal extension is about 45
Abduction: Abduction of the upper limb occurs both at the shoulderjoint and between the scapula and the thoracic wall. The middle fibersof deltoid, assisted by the supraspinatus are involved.
Movements at the shoulder joint /2
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Movements at the shoulder joint /2
Adduction: Normally, the upper limb can be swinged 45across thefront of the chest.
Lateral rotation: Normal lateral rotation is 40to 45.
Medial rotation: Normal medial rotation is about 55.
Circumduction: This is not an independent movement but rather acombination of the above movements.
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The Elbow Joint /1
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The elbow joint, a hinge type of synovial joint, is located 2-3 cm
inferior to the humeral epicondyles.
Articulation and joint capsule
The spool-shaped trochleaand spheroidal capitulumof the humerus
articulate with the trochlear notchof the ulna and the slightlyconcave superior aspect of the head of radius, respectively;therefore, there are humero-ulnar andhumero-radial articulations.
The fibrous layerof the joint capsule surrounding the joint isattached to the humerus at the margins of the lateral and medial
ends of the articular surfaces of the capitulum and trochlea.Anteriorly and posteriorly, it is carried superiorly, proximal to thecoronoid and olecranon fossae.
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The Elbow Joint /2
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The synovial membranelines the internal surface of the fibrous
layer of the joint capsule.
It is continuous inferiorly with the synovial membrane of the proximal
radioulnar joint.
Thejoint capsuleis weak anteriorly and posteriorly but is
strengthened on each side by ligaments.
Ligaments of elbow joint /1
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g j
The collateral ligamentsof the elbow joint are strong triangularbands that are medial and lateral thickenings of the fibrous layer ofthe joint capsule.
The lateral, fanlikeradial collateral ligamentextends from the
lateral epicondyle of the humerus and blends distally with theanularligament of the radius.
This ligament (the anular ligament) encircles and holds the head ofthe radius in the radial notch of the ulna, forming the proximalradioulnar jointand permitting pronation and supination of the
forearm.
Ligaments of elbow joint /2
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g j
The medial, triangularulnar collateral ligamentextends from the
medial epicondyle of the humerus to the coronoid process and
olecranon process of the ulna.
It consists of three bands:(1) the anterior cord-like band is the strongest,
(2) the posterior fan-like. band is the weakest, and,
(3) the slender oblique band deepens the socket for the trochlea of
the humerus.
Movements at the elbow joint
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j
Flexionand extensionmovements occur at the elbow joint
The long axis of the fully extended ulna makes an angle ofapproximately 170with the long axis of the humerus.
This angle is called thecarrying angleand is named for the waythe forearm angles away from the body when something is carried,such as a pail of water.
The obliquity of the angle is more pronounced in women than inmen.
The elbow joint is supplied by articular branches arising from themusculocutaneous, median, radial, and ulnar nerves.
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The Wrist Joint /1
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The wrist jointis an ellipsoidal synovial jointbetween the distalend of radius and the articular disc overlying the distal end of ulnaproximally, and the scaphoid, lunate and triquetral bones distally.
The proximal articular surface forms an ellipsoid concave surface,which is adapted to the distal ellipsoid convex carpal surface.
Because the radial styloid process extends further distally than doesthe ulnar styloid process, the hand can be adducted to a greaterdegree than it can be abducted.
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The Wrist Joint /2
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Thejoint capsuleencloses the joint and is attached above to thedistal ends of radius and ulna and below to the proximal row ofcarpal bones.
The synovial membranelines the capsule and is attached to themargins of the articular surfaces.
The joint cavity does not communicate with that of the distalradioulnar joint or with the joint cavities of the intercarpal joints.
There are anterior and posterior ligamentsstrengthening thecapsule, as well as amedial ligament attached to the styloidprocess of the ulna and to the triquetral bone, and a lateralligament between the styloid process of the radius and thescaphoid bone.
The Wrist Joint /3
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The following movements are possible at the wrist joint: flexion,
extension, abduction, adductionand circumduction.
Rotation is not possible because the articular surfaces are ellipsoid
shaped.
The wrist joint is innervated by the anterior interosseous nerve and
the deep branch of ulnar nerve.