I. Clavicle ( Atlas 1.8; Moore 6.1; Netter Atlas 395) - It is the first bone in the body to ossify. It develops from two ossification centers in the outer one third of the bone.

Functionally, the clavicles act as struts to hold the respective upper extremities away from the thorax which allows for a normal range of motion of the extremities. The clavicles also transmit compression forces from the upper limbs to the axial skeleton, as when someone reaches forward and pushes a car.

I. Scapula (Atlas 6.1 A,B; Netter Atlas 170,396,397) - The scapula is a mobile plate of bone completely encased in muscle. Fractures are therefore not only rare, but also require minimal treatment because of the prevention of displacement by the enclosing muscle. Its vertebral border covers the second to the seventh rib posteriorly.

This border is used in determining anatomical levels in magnetic resonance imaging(MRI) and computerized tomography(CT).

Projecting posteriorly from the body of the scapula is a large, easily palpable spine that bends sharply at its lateral border to become the acromion. The medial end of the spine of the scapula lies opposite the spine of the third thoracic vertebra. The glenoid fossa, a smooth pear-shaped area where the head of the humerus articulates, faces anteriorly and laterally. The humerus lies in a corresponding position, placing the upper limb in a position of apparent medial rotation. Adjacent to the glenoid fossa is the finger-like coracoid process, palpable 2.5 cm below the clavicle at the junction of its medial three-quarters and lateral quarter.

III. Humerus (Moore 6-49; Netter Atlas 396,397) At the proximal end of the humerus is the head which articulates poorly with the glenoid fossa. Adjacent to the head is the anatomical neck, site of the epiphyseal (growth) plate. Next to the anatomical neck are two large tubercles of tuberosities - the greater tubercle located laterally and the lesser tubercle located medially. The greater tubercle is responsible for the smooth contour of the shoulder.

Loss of this contour and its replacement with an indentation below the acromion are diagnostic of a dislocated shoulder joint, which is the most frequently dislocated large joint.

The bicipital or intertubercular groove for the tendon of the long head of biceps brachii separates the tubercles. This tendon is surrounded by a synovial sheath which may become worn or in some cases tear producing a common cause of a painful shoulder.

Below the tubercles, the humerus narrows into the surgical neck, so called because of the frequency of fractures at this level. Below this the shaft is cylindrical until the deltoid tuberosity, located halfway down the lateral surface.

If the surgical neck is damaged or the shoulder dislocated, then the axillary nerve or posterior humeral circumflex vessels in the quadrangular space are endangered. You will observe that the axillary nerve winds posteriorly from the brachial plexus to the deep side of the deltoid muscle. A damaged axillary nerve may result in a wasting of the deltoid with a square-shaped shoulder as well as a small sensory loss on the upper lateral part of the arm.

Before discussing the muscles of the shoulder and their nerve supply, the components of the sternoclavicular, acromioclavicular, and glenohumeral joints will be presented.

I. Sternoclavicular Joint (Moore 6-111,112,113; Netter Atlas 171, 395) - The sternoclavicular joint transmits nearly all the stress from the clavicle to the axial skeleton. This articulation has a thick cartilaginous intra-articular disc, which acts as a "shock absorber". This joint dislocates infrequently.

II. Acromioclavicular Joint (Moore 6-114; Netter Atlas 398) This joint is weak. Its dislocation is commonly seen in football and hockey players. Two ligaments are associated with this joint:

acromioclavicular ligament - connects lateral end of the clavicle to the acromion.

2. coracoclavicular (conoid and trapezoid parts) ligament - anchors lateral part of clavicle to coracoid process of scapula. It is the strongest of all the ligaments which hold the clavicle to the scapula.

Shoulder or glenohumeral Joint (Moore 6-115,116,117; Netter Atlas 398) - This joint, located between the glenoid cavity of the scapula and the head of the humerus, is a ball and socket joint which is a compromise between mobility and stability. Because the glenoid cavity of the scapula is shallow, it is deepened by a narrow rim of fibrocartilage, the glenoid labrum. The capsular ligament is fairly thin and is attached close to the margins of the articular surfaces. Inferiorly the capsular ligament attaches to the surgical neck of the humerus allowing freedom in abduction at the joint.

The many ligaments around the shoulder joint are mostly thickenings of the capsule. These include the glenohumeral ligaments located anteriorly and the coracohumeral ligament located superiorly. The most important of all the ligaments is the coracoacromial ligament. It prevents upward displacement of the humeral head. The head of the humerus and the greater tubercle have to move under this ligament and thus a subacromial bursa lies between them.

An important support of the shoulder joint is the tendon of the long head of the biceps brachii. It arises from the supraglenoid tubercle of the scapula, passes through the joint (outside the synovial membrane) and emerges at the upper end of the intertubercular sulcus carrying with it a prolongation of the synovial membrane to form a bursa.

The capsule of the shoulder is lax, so the intrinsic (glenohumeral) ligaments must also be lax and therefore ineffective in preventing dislocation. The major factor in maintaining stability of the shoulder is the tone of the muscles which act across it. These are the rotator cuff muscles which attach the humeral head to the scapula, and the long head of biceps brachii which acts as a strong strap-like support over the head of the humerus. These muscular supports are deficient inferiorly and it is in this direction that the humeral head usually dislocates, with only the tendon of the long head of triceps stabilizing the joint inferiorly in abduction.

As stated above, the real strength of the shoulder joint lies not in the shape of the participating bones or ligaments, but in the muscles which surround the joint. Before discussing these muscles, a review of the other muscles associated with the proximal part of the arm and shoulder joint will be given.

Trapezius (Atlas 4.47; Netter Atlas 160,399) - Arises from the medial third of the superior nuchal line, and from the ligamentum nuchae of the cervical region and the spines of the thoracic vertebrae. It is inserted into the spine of the scapula, the lateral surface of the acromion and the lateral third of the clavicle superior to the origin of the deltoid. Its motor supply is via the spinal part of the accessory nerve (CNXI). FUNCTION: Although it can extend the skull, acting in the opposite direction the muscle can shrug the shoulder (NOTE: a standard clinical test for the integrity of the spinal accessory nerve). Together the right and left muscles brace the shoulders back and fix the scapula when other muscles such as the deltoid act on the humerus. The trapezius also helps in rotating the scapula (glenoid fossa superiorly) during abduction of the upper limb.

Deltoid (Atlas 6.14, 6.39; Netter Atlas 160,399,407, 450) - Arises from the scapula and clavicle immediately inferior to the attachment of trapezius. It is inserted into the deltoid tuberosity of the humerus. The nerve supply is from the axillary nerve which encircles the surgical neck of the humerus. FUNCTION: The most important function of the deltoid is abduction of the upper limb at the shoulder joint. The deltoid cannot, however, initiate abduction since when the arm is by the side, its central (lateral) fibers are vertically oriented. All the muscle can do in this instance is pull the humerus superiorly. The initial movement of abduction is therefore carried out by supraspinatus. The anterior fibers of deltoid acting on their own are flexors of the shoulder and the posterior fibers are extensors.

Serratus Anterior (Atlas 6.28; Netter Atlas 177,232,240) - Arises from the upper eight ribs. It is inserted into the medial border of the scapula. The lower fibers of the muscle pull the inferior angle of the scapula forward and thus rotate the scapula which carries the humerus with it. Acting as a whole, the muscle will protract the scapula. The nerve supply is the long thoracic nerve (surgeons refer to this nerve as Bell’s nerve).

If the long thoracic nerve is damaged such as in a mastectomy, the trunk will fall forwards on the affected side when the weight is transferred to the arms. The scapula thus appears to be projecting backwards ("winged scapula"). In this case however, the scapula is in its correct position but the trunk has fallen forwards.

IV. Rhomboids (Atlas 4.48; Netter Atlas 399) and levator scapulae (Atlas 4.48; Netter Atlas 399) - Their location and structure were mentioned in the lecture on the back. FUNCTION: The rhomboids function to brace the scapula back while the levator scapulae elevates the scapula as in shrugging the shoulders. Nerve: They are both supplied by the dorsal scapular nerve.

Rotator Cuff Muscles (Atlas 6.29, 6.35, 6.37, 6.52; Netter Atlas 399,400,401) - Composed of four (SITS) muscles: Supraspinatus(S), Infraspinatus(I), Teres Minor(T), Subscapularis(S). These muscles are inserted into the joint capsule and the tuberosities by a musculotendinous insertion called the rotator cuff. Their function is to hold the head of the humerus firmly in the shallow pear-shaped glenoid fossa. The supraspinatus arises from the supraspinous fossa of the scapula. FUNCTION: The tendon of the supraspinatus passes across the superior aspect of the shoulder joint and therefore is a true abductor. Its nerve supply is from the suprascapular nerve. The supraspinatus initiates the movement of abduction (up to about 45 degrees), which is then continued by the much more powerful deltoid. The two muscles together can produce about 120 degrees of abduction.

The effects of a partial or complete tear in the supraspinatus tendon is pain and spasm in the middle range of abduction (60 – 120 degrees). This is called the "painful arc syndrome". In a complete tear the patient cannot abduct the arm without shrugging the shoulder. Deltoid alone will not fully abduct the arm.

The infraspinatus arises from the infraspinous fossa of the scapula, passes posterior to the shoulder joint to insert on the posterior part of the greater tubercle. FUNCTIION: It is a lateral rotator. Its nerve supply is from the suprascapular nerve.

The teres minor arises from the lateral margin of the scapula. It inserts on the greater tubercle inferior to the infraspinatus. FUNCTION: It is a lateral rotator and weak adductor. Its nerve supply is from the axillary nerve.

The subscapularis arising from the subscapular fossa passes laterally to the lesser tubercle of the humerus. FUNCTION: Notice that based on its location it has to be a medial rotator. Its nerve supply is from the upper and lower subscapular nerves.

Two other muscles that are not located in the shoulder region but influence movement at the shoulder joint by causing a movement of the arm are the latissimus dorsi and teres major (Atlas 4.47,6.40,6.41; Netter Atlas 178,399). As you have seen in your study of the superficial back muscles the latissimus dorsi connects the trunk to the humerus. By attaching into the floor of the bicipital groove (intertubercular sulcus) its contraction causes adduction, medial rotation and extension of the humerus. If the arm is fixed, the muscle will pull the trunk nearer to the arm as in climbing. It is supplied by the thoracodorsal nerve.

Part of the origin of latissimus dorsi is on the iliac crest of the pelvis thus in paraplegic patients it can be used to elevate one side of the pelvis – so-called ("hip-hiking").

Teres major arises on the lateral border of the scapula and inserts into the medial lip of the bicipital groove of the humerus. FUNCTION: It is an adductor and medial rotator of the humerus. Its nerve supply is the lower subscapular nerve.

Muscles located in the pectoral region also influence the stability of the shoulder joint and its movements. These muscles include the pectoralis major and pectoralis minor.

Pectoralis Major (Atlas 1.2,1.3; Netter Atlas 174,399) - It is attached by two heads to the anterior chest. The clavicular head arises from the medial half of the clavicle while the sternocostal head is attached to the anterior surface of the sternum and to the upper six costal cartilages. The muscle fibers converge to be inserted into the lateral lip of the bicipital groove of the humerus. The upper (clavicular) fibers fold under the sternocostal fibers to form a thick bilaminar tendon. This produces the thickening in the anterior wall of the axilla. FUNCTION: It is a very powerful adductor and medial rotator of the arm. The clavicular fibers working alone can flex and the sternocostal fibers extend the arm at the shoulder joint. The entire pectoralis major can pull the trunk upwards if the arms are fixed above the head as in grasping a bar ("chinning" exercise). Its nerve supply is from the lateral and medial pectoral nerves.

Since the deltoid is attached to the lateral third of the clavicle and pectoralis major to the medial half, there is a small part of the clavicle to which neither muscle is attached. This forms the base of a triangular space (deltopectoral triangle) between the muscles. It contains some lymph nodes and the termination of the cephalic vein.

Pectoralis Minor (Atlas 1.5; Netter Atlas 403) - It is a small muscle that passes obliquely from the anterior ribs and costal cartilages to the coracoid process. FUNCTION: It can protract the scapula and depress the tip of the shoulder. Its nerve supply is the medial pectoral nerve.

Clavipectoral Fascia (Moore 6-11; Netter Atlas 403) - The clavipectoral fascia splits at its clavicular attachment to enclose the subclavius. It then proceeds inferiorly to enclose the pectoralis minor muscle. It is pierced by the thoracoacromial artery, lateral pectoral nerve, cephalic vein and important lymphatics from the breast. These lymphatics may carry cancer cells in breast cancer, but cannot be detected clinically because they lie deep to the thick pectoralis major.

The female breast (Atlas 1.3,1.4; Moore 1-11,1-12; Netter Atlas 167,168,169) consists of fat, fibrous and glandular tissue. The great bulk of the breast consists of fat through which fibrous septa(Cooper’s ligaments) pass to connect with the skin and nipple especially in the upper part of the breast. The glandular tissue is composed of 15-20 lobes and drained by 15-20 lactiferous ducts. These are slightly dilated to form lactiferous sinuses beneath the areola which ultimately open into the nipple. The breast rests mainly on pectoralis major but also overlaps its edges to lie on serratus anterior and the external abdominal oblique muscle. Part of the breast extends superiorly and laterally along the lower border of pectoralis major to form the axillary tail (tail of Spence). The blood supply to the breast is from branches of the axillary artery (lateral thoracic) and from the intercostal and internal thoracic(mammary) arteries.

Lymphatic drainage is mainly to the pectoral, subscapular and apical groups of axillary nodes. Some drainage also occurs to nodes in the infraclavicular fossa. From the medial side of the breast lymphatics pass to parasternal lymph nodes along the internal thoracic vessels, to the opposite breast, and inferiorly to lymph nodes within the rectus sheath of the abdomen.

In examining the breasts of a pregnant female there are classic features you should be aware of. The whole breast is enlarged, the axillary tail often being noticeable for the first time, and many dilated veins can be seen over the breast skin. The nipple and areola are well pigmented and normally there is a greatly increased number of areolar glands (sebaceous glands of Montgomery). These glands also increase in size.

Many of the above structures form the borders or are contained within the axilla and therefore the remainder of this lecture will deal with the location and contents of the axilla. The axilla is a pyramidal-shaped space between the upper limb and the chest wall. It contains the neurovascular trunks as they pass from the posterior triangle of the neck to the upper limb. It also contains large numbers of lymph nodes draining lymphatics from the upper limb and anterior and posterior chest, including the breast. All these structures are encased in varying amounts of fat.

The axilla (Moore 1-13,6-10; Netter Atlas 169,403,404) is a four sided pyramid with its apex consisting of the narrow gap between the first rib, clavicle, and scapula. As such, the axilla consists of four walls. You can grasp the anterior and posterior walls of the axilla between your fingers and thumb. The anterior wall consists of two muscles: pectoralis major and minor and the clavipectoral fascia. The posterior wall consists of the subscapularis, the teres major and the latissimus dorsi. You may confirm by palpation that the medial wall of the axilla consists of the upper part of the serratus anterior, the upper ribs and the intercostal muscles. The lateral wall is nearly nonexistent but is usually considered to be formed by the floor of the bicipital groove(intertubercular sulcus).

In the last lecture we outlined the contents of the axilla. In this lecture we will begin by discussing these structures in more detail.

The major axillary vessels and nerves are surrounded by an axillary sheath. The axillary sheath is an extension of the prevertebral fascia of the neck which is continued into the axilla as a covering for the axillary artery and vein, and cords of the brachial plexus. The sheath continues down the arm to the elbow joint where it fuses with the adventitia of the brachial artery.

I. Axillary Artery (Atlas 6.6,6.16,6.22,6.25; Moore 6-31) - It begins at the outer border of the first rib as a continuation of the subclavian artery. It ends by becoming the brachial artery at the lower border of teres major. It is divided into three parts by pectoralis minor, part two being located posterior to that muscle. The axillary vein is medial to the artery and the cords of the brachial plexus are arranged around the second part of the artery (lateral cord being lateral, medial cord medial and posterior cord behind the artery).

The first portion of the artery has one branch, the superior thoracic artery. It helps supply the first and second intercostal spaces. The second part of the artery has two branches namely the (1) thoracoacromial and (2) lateral thoracic arteries. The thoracoacromial artery(trunk) pierces the clavipectoral fascia and radiates into pectoral, acromial, deltoid and clavicular branches which supply these areas respectively. The lateral thoracic artery courses inferiorly lying along the lateral border of pectoralis minor and superficial to serratus anterior. It supplies the pectoral muscles and axillary lymph nodes.

The third part of the artery has three branches: the (1) subscapular, (2) anterior humeral circumflex and (3) posterior humeral circumflex. The subscapular artery, the largest branch of the axillary artery, descends along the lateral border of subscapularis and divides into the circumflex scapular and thoracodorsal arteries. The thoracodorsal artery supplies the latissimus dorsi while the circumflex scapular supplies muscles on the posterior aspect of the scapula (e.g. supraspinatus, infraspinatus, teres minor and major).

The humeral circumflex arteries form an arterial network around the surgical neck of the humerus by anastomosing with each other. The smaller anterior humeral circumflex artery supplies the shoulder. The larger posterior humeral circumflex artery supplies the deltoid and triceps brachii.

II. Axillary vein (Atlas 6.4, 6.16; Moore 6-33) - It is the most superficial major structure in the axilla. It begins at the lower border of the teres major muscle with the confluence of veins accompanying the brachial artery. This vein then joins with the basilic vein and continues as the axillary vein. At the border of the first rib it becomes the subclavian vein. Draining into the superior portion of the axillary vein is the cephalic vein.

III. Brachial Plexus (Atlas 6.22,6.25,6.26,6.27) - You have already observed the location of the brachial plexus in the posterior triangle of the neck. In our discussion we will trace its course through the axilla into the arm (Moore 6-19). Recall that the brachial plexus is derived from the anterior primary rami of nerves C5-8 and T1 with occasional help from C4 and T2. Structurally the brachial plexus begins as roots(rami) from C5-T1. C5 and C6 form an upper trunk, C8 and T1 a lower trunk while C7 continues as the middle trunk. The trunks then split into anterior and posterior divisions. The posterior division will form the posterior cord. The anterior division splits to form the lateral cord and the medial cord of the brachial plexus. Arising from the cords are the majority of branches of the brachial plexus. NOTE: A pneumonic which is frequently used to remember the organization of the brachial plexus is:

Robert Taylor Drinks Cold Beer

(Roots) (Trunks) (Divisions) (Cords) (Branches)

The roots and trunks are located in the neck, the divisions behind the clavicle, and the cords are arranged around the axillary artery as their names indicate. In the laboratory you were given a diagram of the brachial plexus which you are to label. Our discussion will therefore focus on the major branches, their origin, distribution (Atlas 6.11A,B,C,D) and clinical presentation if injured.

(1) Branches from the Roots (2):

Dorsal Scapular Nerve - branch of C5; supplies rhomboid muscles.

Long Thoracic Nerve - arises from C5, C6, C7; supplies serratus anterior muscle.

(2) Branches from Trunks (1):

Suprascapular Nerve - arises from C5 and C6, supplies supraspinatus and infraspinatus muscles.

(3) Branches from Divisions (0): NONE

(4) Branches from Cords:

(Lateral Cord) (3)

Lateral Pectoral Nerve - to clavicular head of pectoralis major.

Musculocutaneous Nerve - supplies muscles in anterior compartment of arm (biceps brachii, brachialis, and coracobrachialis).

Lateral Root of Median Nerve - helps form median nerve.

(Medial Cord) (5)

Medial Pectoral Nerve - supplies sternocostal head of pectoralis major and all of pectoralis minor.

Medial Cutaneous Nerve of Arm - supplies skin on medial side of arm.

Medial Cutaneous Nerve of Forearm - supplies skin on medial side of forearm.

Ulnar Nerve - supplies muscles in forearm and hand and skin of hand.

Medial Root of Median Nerve - helps form median nerve. Median nerve supplies muscles in forearm and hand and skin of hand.

(Posterior Cord) (5)

Upper and Lower Subscapular Nerves - supplies

subscapularis(upper), subscapularis and teres major(lower).

Thoracodorsal Nerve - supplies latissimus dorsi.

Axillary Nerve - supplies deltoid and teres minor.

Radial Nerve - supplies muscles in posterior of arm and forearm and skin of hand.

The course of these nerves will be studied as we discuss the arm, forearm, and hand.

The arm is bounded superiorly by the lower border of the teres major and inferiorly by the lateral and medial epicondyles of the humerus. Between the epicondyles and deltoid tuberosity of the humerus a pair of intermuscular septa (lateral and medial) divide the arm into an anterior or flexor-supinator compartment and a posterior or extensor compartment.

Muscles of the Anterior Compartment:

I. Coracobrachalis Muscle (Atlas 6.22, 6.26) - A small muscle passing from the tip of the coracoid process to the medial side of the midshaft of the humerus. It is pierced and supplied by the musculocutaneous nerve. FUNCTION: Flexes and adducts arm.

II. Biceps Brachii (Atlas 6.25;Moore 6-51,6-56) - As its name implies it has two heads. The long head arising from above the supraglenoid tubercle, crosses the head of the humerus within the capsule of the shoulder joint and descends in the bicipital (intertubercular) groove of the humerus. The short head arises from the tip of the coracoid process. It inserts onto the tuberosity of the radius and fascia of the forearm via the bicipital aponeurosis. It is supplied by the musculocutaneous nerve. After passing through the coracobrachialis muscle, this nerve lies between the biceps brachii and brachialis muscle. FUNCTION: It is a powerful supinator of the forearm and when it is supine, flexes the forearm.

III. Brachialis (Moore 6-51) - Arises from the anterior aspect of the shaft of the humerus and passes inferiorly to insert onto the coronoid process and tuberosity of the ulna. It is supplied by the musculocutaneous nerve. FUNCTION: It is a powerful flexor of the forearm.

Also contained within the anterior compartment are the median, ulnar, medial brachial cutaneous, and medial cutaneous nerve of forearm.

NOTE: At the lateral border of the biceps brachii, the musculocutaneous nerve becomes the lateral cutaneous nerve of the forearm which supplies the skin of the lateral aspect of the forearm. Injury to the musculocutaneous nerve may arise following a penetrating wound.

Muscles of the Posterior Compartment:

I. Triceps Brachii (Atlas 6.40,6.41)- This is the main muscle in the posterior compartment of the arm. As its name implies it is composed of three heads: the long, lateral, and medial. The long head arises from the infraglenoid tubercle of the scapula. The lateral and medial heads arise from the posterior surface of the humerus. The three heads form a strong tendon which inserts onto the proximal end of the olecranon of the ulna. NOTE: As the long head of the triceps descends, it creates the triangular interval and quadrangular space. Through the quadrangular space pass the axillary nerve and posterior humoral circumflex vessels. Within the triangular interval is radial nerve and profunda brachii artery. The triceps brachii muscle is supplied by the radial nerve. NOTE: The radial nerve enters the arm and passes inferolaterally with the profunda brachii artery around the shaft of the humerus in the radial(spiral) groove. This groove is located inferior to the deltoid tuberosity in the shaft of the humerus.

The brachial artery (Moore 6-31,6-55) provides the main arterial supply to the arm. It begins at the lower border of teres major and ends immediately below the elbow joint by dividing into radial and ulnar arteries. The brachial artery is superficial and thus palpable throughout its course. At first it lies medial to the humerus but then passes anterior to it. As it passes inferiorly and laterally it accompanies the median nerve. In the cubital fossa the bicipital aponeurosis covers and protects the median nerve and brachial artery (Moore,6-56). This aponeurosis separates these neurovascular structures from the superficially located median cubital vein.

The largest branch of the brachial artery is the profunda brachii artery. As stated above, this artery accompanies the radial nerve in the radial groove on the humerus.

Although not involved with supplying muscles in the arm, the ulnar nerve should also be mentioned at this time. As the ulnar nerve descends from the axilla through the arm it passes posteriorly to course behind the medial epicondyle where it may be palpated (Moore, 6- 20B).

The cubital fossa lies anterior to the elbow joint and is triangular in shape (Moore,6- 48,6-56,6-57,6-58). NOTE: There are three important structures in the fossa you can palpate. The biceps tendon is thick and can be felt in the middle of the fossa. Immediately medial to the tendon feel the pulsation of the brachial artery. Medial to this the median nerve can be felt. Although not palpable, the proximal parts of the radial and ulnar arteries as well as part of the radial nerve are also found in the cubital fossa. Beneath the skin of the cubital fossa lies the median cubital vein. This vein forms a communication between the basilic and cephalic veins. NOTE: Because of the accessibility of veins in the cubital fossa, they are commonly used for venipuncture.

Forearm,Wrist

Before discussing the "soft tissues" of the forearm a review of the radius and ulna will be given.

I. Radius (Moore, 6-61) - This is the shorter of the two forearm bones. In the anatomical position it is located laterally. Its proximal end has a disc-shaped head, a cylindrical neck, and a tuberosity distal to the neck. The shaft of the radius increases in size from proximal to distal. Laterally the distal end of the radius tapers into a prominent styloid process.

II. Ulna (Moore, 6-61) - Unlike the radius, the head of the ulna is at its narrow distal end. Also at this distal end is a conical styloid process. Its proximal end is termed the olecranon. It fits into the olecranon fossa of the humerus. The dorsal surface of the olecranon, with its covering bursa, makes up the posterior projection of the elbow joint. The coronoid process of the ulna is located on the antero-superior surface of the bone. The trochlear notch, which articulates with the trochlea of the humerus, is the cavity formed by the junction of the olecranon with the coronoid process. Distal to the coronoid process is a triangular supinator fossa, which provides and attachment for the supinator muscle.

The radius and ulna are joined by an interosseous membrane (Atlas, 6.76C), a fibrous joint, whose fibers pass distally and medially from the radius to the ulna. This membrane also serves as an attachment site for certain forearm muscles and serves to divide the forearm into anterior and posterior compartments. The anterior compartment contains primarily flexor muscles of the wrist and hand. The posterior compartment contains primarily extensor muscles of the wrist and hand.

Muscles in Anterior Compartment of Forearm

The muscle groups in the anterior compartment of the forearm may be divided into three layers: superficial, intermediate, and deep (Atlas 6.80,6.82-87).

The superficial layer consists of muscles that arise from the medial epicondyle of the humerus. These include the pronator teres, flexor carpi radialis, palmaris longus, and the flexor carpi ulnaris. All but the Flexor Carpi Ulnaris are supplied by the median nerve. The Flexor Carpi Ulnaris receives its supply from the ulnar nerve.

The intermediate layer consists of the flexor digitorum superficialis. It is supplied by the median nerve.

The deep layer of muscles in the anterior compartment consists of the: flexor pollicis longus, flexor digitorum profundus, and the pronator quadratus. The median nerve supplies the flexor pollicis longus, pronator quadratus and the radial half of the flexor digitorum profundus. The ulnar half of the flexor digitorum profundus is supplied by the ulnar nerve.

Muscles in Posterior Compartment of Forearm

The posterior compartment contains both a superficial and deep muscle layer (Atlas 6.102,6.103, 6.109). The muscles of the superficial layer are the brachioradialis, extensor carpi radialis brevis, and extensor carpi radialis longus. All are supplied by the main trunk of the radial nerve. Other muscles of the superficial layer namely the extensor digitorum communis, extensor digiti minimi, and the extensor carpi ulnaris are supplied by the deep branch of the radial nerve.

The group of muscles comprising the deep layer of the posterior forearm muscles lie against the interosseous membrane. These are the supinator, abductor pollicis longus, and extensor indicis proprius. All are supplied by the deep branch of the radial nerve.

To give you some idea of the organization of these muscles, we will discuss them from a functional standpoint.

I. Supination - There are two supinators: a superficial, powerful, biceps brachii(discussed in the arm) and a deeper supinator muscle.

II. Pronation - Again there is a superficially located and more powerful pronator, the pronator teres, and a much weaker deep pronator, the pronator quadratus. The pronator teres is located proximally, by the elbow, while the pronator quadratus is found near the wrist.

III. Movements at the Wrist Joint - Muscles on both the radial and ulnar sides of the wrist joint can cause or prevent radial and ulnar deviation. These muscles, situated peripherally, act only on the wrist joint and thus insert no further than the carpus or proximal metacarpus. Anteriorly these muscles are the flexor carpi radialis and flexor carpi ulnaris. Posteriorly the muscles include the extensor carpi radialis (longus and brevis) and extensor carpi ulnaris. Notice that two extensor radial muscles are needed to offset the one flexor radial muscle. NOTE: The grip of the hand is strongest with the wrist in radial deviation.

IV. Movements of the Thumb and Fingers affecting the Wrist Joint - Between the peripheral muscles lie those tendons destined for the digits. On the flexor aspect there are tendons moving the metacarpophalangeal joints (MP joints), the proximal interphalangeal joints (PIP) and the distal interphalangeal joints (DIP joints). The palmaris longus enters the hand and becomes a very weak flexor of the wrist. It terminates in the hand as the triangular-shaped palmar aponeurosis.

The true flexors of the digits are the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. The tendons of the flexor digitorum superficialis insert on the middle phalanges while the tendons of the flexor digitorum profundus and flexor pollicis longus attach to the distal phalanges. NOTE: In order for the tendons of the flexor digitorum profundus to reach the distal phalanx they must split the flexor digitorum superficialis tendons. This allows the flexor digitorum profundus to flex both the metacarpohalangeal joints(MP) and both interphalangeal joints(PIP and DIP).

In the posterior or extensor compartment as stated above, the two radial and one ulnar carpi extensors are located peripherally. Spread your digits and then examine the dorsum of your hand. Notice the large space between your thumb and the remaining digits. Because of the large space, the muscles that move the thumb end in tendons that must course obliquely. From medial to lateral they are the extensor pollicis longus, extensor pollicis brevis and abductor pollicis longus. NOTE: The hollow between the extensor pollicis longus and the extensor pollicis brevis, best seen when the thumb is extended, is called the "anatomical snuffbox" (Atlas 6.115,6.116). Structures associated with the anatomical snuff-box are the subcutaneously located superficial branch of the radial nerve, the deeper radial artery, and the carpal bone in the floor of the box termed the scaphoid bone.

Although the brachioradialis is associated with the posterior compartment of the forearm and its nerve supply is from the radial nerve as are the other posterior compartment muscles, its function is to flex the wrist. The remaining muscles in the posterior compartment are destined for the four digits and therefore lie between the peripheral carpal extensors. NOTE: The second and fifth digits (besides the thumb) are the most mobile digits and therefore have extra muscles which control them. The tendons passing down the central aspect of the posterior forearm are the extensor digitorum communis for all four fingers, extensor indicis for the second finger, and the extensor digiti minimi for the fifth finger. Limiting the third and fourth fingers further are dorsal intertendinous bands that tether the tendons to each other.

NOTE: As the extensor digitorum communis, extensor indicis and extensor digiti minimi pass from the forearm to their insertion, they form an extension over the proximal phalanx. As you will see in the lecture on the hand, this dorsal expansion or ("extensor hood") is joined by the lumbrical and interosseous muscles from the hand (Atlas 6.109). The dorsal expansion continues distally as a central slip for the middle phalanx. Two lateral slips pass on either side of the central slip to join and insert into the distal phalanx.

Arteries Associated with Anterior and Posterior Compartments

From their origin in the cubital fossa, the radial and ulnar arteries (Moore 6-70) course with the radial and ulnar nerves. The radial artery courses deep to the brachioradialis while the ulnar artery is located deep to the flexor carpi ulnaris. At the distal end of the radius, near the styloid process, the radial artery courses superfically. NOTE: It is at this point where a pulse may be taken or a catheter inserted. It then passes posteriorly into the "anatomical snuff- box".

The ulnar artery also becomes superficial near the wrist where it is palpable lateral to the tendon of the flexor carpi ulnaris. It gives off the common interosseous which divides into the anterior and posterior interosseous arteries. These arteries help supply the anterior and posterior compartments of the forearm respectively.

Nerves Associated with the Forearm

Three nerves enter and supply the forearm: (1) the radial, (2) ulnar, and (3) median (Moore, 6-70).

(1) Radial - The radial nerve splits at the lateral epicondyle into the superficial radial nerve and the posterior interosseous (deep radial). The latter passes posteriorly through the supinator muscle which it supplies. It then enters the extensor compartment of the forearm. It supplies all of the muscles in the extensor compartment. The superficial radial nerve passes to the radial side of the dorsum of the hand and the back of the thumb, index and third fingers. Its specific distribution will be presented in the lecture on the hand.

(2) Ulnar - The ulnar nerve courses posterior to the medial epicondyle to enter the anterior compartment of the forearm. Passing between the flexor carpi ulnaris and flexor digitorum profundus, the ulnar nerve supplies the former and that half of the flexor digitorum profundus destined for the fourth and fifth digits.

(3) Median - As the name indicates, the median nerve courses in the midline. After entering the forearm it courses between the flexor digitorum superficialis and flexor digitorum profundus. At the wrist, the nerve lies between the palmaris longus and flexor carpi radialis tendons.

The median nerve, with its muscular branches, supplies all the muscles in the anterior compartment of the forearm not supplied by the ulnar nerve.

Before studying the hand, the wrist joint and carpal tunnel will be discussed. First learn the names and arrangements of the carpal bones (Moore, 6-71). There are eight small bones of the wrist called carpal bones. They are arranged in proximal and distal rows. Each contain four bones. The proximal row consists of the scaphoid, lunate, triquetrum, and pisiform. The distal row contains the trapezium, trapezoid, capitate, and hamate.

All the tendons in the anterior compartment, as well as the main vessels and nerves funnel down to the region of the wrist, where most, but not all of them, pass through the neck of a funnel termed the carpal tunnel (Moore, 6-72; Atlas 6.126). This is a rather narrow passage formed by the carpal bones posteriorly and the flexor retinaculum anteriorly. The carpal bones are shaped so as to form a curve and only those bones on the periphery can be palpated. These are the pisiform and hook of the hamate medially and the scaphoid and trapezium laterally. It is to these four bones that the flexor retinaculum attaches thus completing the tunnel. NOTE: If you are able to palpate these bones on your own hand you will notice that they are located in the very proximal part of the palm of the hand.

Nine tendons and one nerve pass through the carpal tunnel. These are the median nerve and the tendons of the flexor pollicis longus, flexor digitorum superficialis and flexor digitorum profundus.

Hand

the hand is a remarkable part of the body that separates humans from all other animals. It is as strong as it is sensitive. The skin covering the hand differs on the palmar and dorsal surfaces. On the palmar surface it is thick, ridged, fairly immobile, hairless and possesses a number of sweat glands. The skin is bound to the underlying palmar aponeurosis.

The sensation of the skin of the hand is extraordinary and unmatched by skin anywhere else. It is the chief tactile "organ" of the body acting as an "eye" for a blind person, enabling him/her to read(Braille).

Bones of the Hand

The bony framework of the hand consists of five metacarpals and fourteen phalanges (Atlas 6.130). The 4 fingers have three phalanges while the thumb only two.

The metacarpals are numbered 1-5 starting from the radial side of the hand. The first metacarpal is the shortest and thickest of the five. It is positioned at a right angle to the palm of the hand. The second metacarpal is the longest of the metacarpals. At the distal end of each metacarpal bone is the head which contains a big condyle(knuckle). This articulates with a proximal phalanx.

Muscles and Tendons of Hand

The muscles are arranged in three groups. Two are associated with the first and the fifth metacarpals forming the (1) thenar and (2) hypothenar eminences respectively (Atlas 6.83,6.87,6.90,6.91). The third group is located deeper in the (3) central "hollow" of the palm.

(1) Thenar Muscles - Consist of three intrinsic muscles all supplied by the recurrent branch of the median nerve.

Abductor Pollicis Brevis - the most superficial of the thenar muscles. As its name implies, its abducts the thumb.

Flexor Pollicis Brevis - located medial to abductor pollicis brevis. It flexes the proximal phalanx of the thumb.

Opponens Pollicis - lies deep to abductor pollicis brevis. As its name implies it produces opposition of the thumb.

Although NOT part of the thenar muscles, the adductor pollicis is a fan-shaped muscle located deep to the thenar muscles. As its name implies, it is involved in adduction of the thumb. It is supplied by the deep branch of ulnar nerve.

(2) Hypothenar Muscles - consist of three short muscles all supplied by the deep branch of the ulnar nerve.

Abductor Digiti Minimi - is the most superficial of the three muscles. It abducts the fifth digit(little finger) and helps flex its proximal phalanx.

Flexor Digiti Minimi - lies lateral to the abductor digiti minimi. It flexes the proximal phalanx of the fifth digit.

Opponens Digiti Minimi - lies deep to both the abductor and flexor digiti minimi. As its name implies it is involved in opposition of the fifth digit.

(3) Centrally located deep muscles - These consist of the lumbricals and interosseous muscles (Atlas 6.95,6.99).

Lumbricals - These are four slender muscles which arise from the tendons of flexor digitorum profundus. Their tendons are inserted into the radial side of each of the proximal phalanges of the fingers and into the dorsal extensor expansion(hood). They flex the metacarpophalangeal (MP) joints and extend the interphalangeal joints. Lumbricals 1 and 2 are supplied by the median nerve while lumbricals 3 and 4 are supplied by the ulnar nerve.

Interosseous Muscles - These are divided into a palmar and dorsal group. The three palmar interossei arise from metacarpals. They insert into the proximal phalanx and the expansion of the extensor digitorum communis. Palmar interossei are adductors (PAD). The four dorsal interossei also arise from metacarpals. They insert into the proximal phalanges and the dorsal digital expansion(hood). Dorsal interossei are abductors(DAB). All of these interossei are supplied by the deep branch of the ulnar nerve.

Blood Supply of the Hand

The blood supply to the hand is via the radial and ulnar arteries (Atlas 6.95,6.96,6.97,6.98). The ulnar artery is palpable as it passes across the flexor retinaculum next to the pisiform bone. It is the major contributor to the superficial palmar arch, which lies immediately deep to the palmar aponeurosis. It supplies digital branches to the fingers. The arch is completed by a small branch of the radial artery before it passes to the dorsum of the hand. On the dorsum of the hand the radial artery lies in the "anatomical snuff-box" before it passes into the palm. Here it forms the deep palmar arch. This arch also gives rise to digital arteries.

Palmar Fascial Spaces of Hand

Between the palmar aponeurosis and the interossei are two potential spaces which are clinicaly important (Atlas 6.129). They are located between the flexor tendons and the fascia covering the interossei. The spaces are bounded medially and laterally by septa passing from the periphery of the palmar aponeurosis posteriorly to the metacarpal bones. A medial septum extends from the medial border of the palmar aponeurosis to the fifth metacarpal. A lateral septum extends from the lateral border of the palmar aponeurosis to the first metacarpal. From the middle of the palmar aponeurosis another septum passes posteiorly to the third metacarpal. These septa thus create two midpalmar spaces bounded anteriorly by the flexor tendons and lumbricals, posteriorly by the interossei, and laterally and medially by the respective septa.

Each of the eminences (thenar and hypothenar) as well as the central palmar area also contain potential spaces which may be the sites of infection.

Flexor and Synovial Sheaths (Atlas 6.93,6.105)

As the tendons of the long flexor and extensor muscles approach the hand and eventually terminate on the phalanges two things must occur. First, the flexor tendons must pass deep to the flexor retinaculum while the extensor tendons must pass under the and extensor retinaculum. On the palmar side the flexor tendons must then be anchored to the phalanges in such a way as to prevent "bow-stringing". This anchoring is performed by fibrous flexor sheaths. Now a second problem arises however. How do you prevent friction from occuring at those areas where the tendons come in contact with sheaths or retinacula? This is accomplished by synovial sheaths.

On the anterior surface of each digit, from the head of the metacarpal to the base of the distal phalanx, a strong fibrous flexor sheath is present. This serves as a tunnel for the flexor tendons of the digits.

In order to prevent friction from occuring here, synovial sheaths envelope the tendons. Synovial sheaths are first present at the retinaculae (flexor and extensor). On the palmar surface, the flexor pollicis longus tendon enters the osseofibrous tunnel of the thumb and is inserted into the base of the distal phalanx. On the thumb, the tendon is completely surrounded by a synovial sheath which extends into the forearm just proximal to the flexor retinaculum. The eight tendons of the flexor digitorum superficialis and profundus invaginate a common synovial sheath. This common sheath also extends into the forearm to a point just proximal to the flexor retinaculum. In the hand the sheath continues distally without interruption on the tendons of the little finger to the distal phalanx. The remainder of this sheath ends in the mid- palm. The distal ends of the index, middle, and ring fingers have digital synovial sheaths surrounding each of them. NOTE: In about 50% of the people the synovial sheath of the flexor pollicis longus communicates with the common synovial sheath of the superficialis and profundus tendons.

On the dorsum of the hand, synovial sheaths are present on each of the tendons deep to the extensor retinaculum. They extend from a point just proximal to the retinaculum to a point in the proximal 1/3 of the dorsum of the hand.

Nerves of the Hand

The ulnar, radial, and median nerves supply the hand (Moore 6-107,6-109; Atlas 6.111-6.113).

Ulnar Nerve - It exits the forearm by emerging from the tendon of flexor carpi ulnaris. It passes onto the flexor retinaculum lateral to the pisiform bone and medial to the ulnar artery. Both the ulnar nerve and artery are contained in a canal at this point called Guyon's canal. Immediately proximal to the wrist the ulnar nerve gives off a branch to supply skin on the medial side of the palm. It also gives off branches which supply the skin on the medial half of the dorsum of the hand, the fifth digit, and medial half of the fourth digit. Motor branches supply the hypothenar muscles, interossei, and the third and fourth lumbricals.

Radial Nerve - The superficial branch of the radial nerve supplies the skin over the lateral two- thirds of the dorsum of the hand, the dorsum of the thumb, and proximal parts of the lateral one and one-half digits. It has no motor branches in the hand.

Median Nerve - It passes through the carpal tunnel and enters the hand between the tendons of flexor digitorum superficialis and flexor carpi radialis. It supplies motor fibers for the thenar muscles and the first and second lumbricals. It sends sensory fibers to the entire palmar surface, the sides of the first three digits, the lateral half of the fourth digit, and dorsum of the distal halves of these digits.

Lymphatics of the Upper Extremity

Superficial lymphatic drainage from the lateral side of the hand(thumb, index finger, lateral half of middle finger), forearm and arm follow the cephalic vein to the infraclavicular group of nodes. Lymphatics from the medial side of the hand(medial half of middle finger, ring finger, fifth digit), forearm and arm first pass to the supratrochlear lymph node at the elbow and then follow the basilic vein to the lateral group of axillary nodes.

 Gluteal Region, Thigh,Knee

Before discussing the organization of the gluteal region, a review of the components of the hip bone or os coxae, upper portion of the femur, and the hip joint is necessary.

I. Hip Bone(Os Coxae) - Although it appears to be one bone, the hip bone actually consists of three separate bones (Moore, 5.1). The three bones are the (1) upper fan-shaped ilium, (2) medially placed pubis, and (3) posteroinferiorly located ischium (Moore, 5-4). All three bones contribute to the formation of a cup-shaped acetabulum. The acetabulum as you will see is a socket for the head of the femur (Atlas, 5.43, 5.44). NOTE: Unlike its counterpart, the glenoid fossa, the acetabulum is deep. It has a smooth and cartilage covered articular area, as well as a rough area in the floor of the acetabulum, termed the acetabular fossa. In this fossa the bone is thin.

Two anatomical landmarks, the iliac crests and greater sciatic notch are associated with the ilium and will be discussed with the gluteal region. The lesser sciatic notch, ischial spine, and ischial tuberosity all components of the ischium are also important landmarks in the gluteal region. Landmarks associated with the pubis will be mentioned in our discussion of the anterior thigh.

II. Femur (Atlas, 5.1) - The femur is the longest and the sturdiest bone in the human body. It inclines medially and inferiorly so that the knee joint is at the center of gravity. Medial inclination of the femur is more pronounced in females than in males because of the greater width of the female pelvis. NOTE: The femur is the first of the long bones to ossify.

The superior segment of the femur consists of a head, a neck, and a greater and a lesser trochanter. The rounded femoral head is completely covered with cartilage except for its central area, the fovea capitis femoris, the site of attachment of the ligament to the head of the femur (Atlas, 5.46,5.48). The neck of the femur is triangular in shape. It connects the head to the shaft.

The greater trochanter arises from the superior end of the junction between the femoral neck and body. The lesser trochanter projects from the base of the femoral neck.

The shaft(body) of the femur is an almost cylindrical bowed bone which is wider both proximally and distally than it is centrally (Atlas 5.3). Along the posterior aspect of the shaft is a ridge of bone termed the linea aspera(Moore 5-3). As you will see, this is the attachment site for certain muscles composing the quadriceps femoris and all of the adductor muscles(longus, brevis, magnus).

Hip Joint - It is a ball-and-socket joint (Atlas 5.42AB,5.43,5.44,5.49). It is enclosed in a thick, strong articular capsule. The capsule is supported by three ligaments: (1) iliofemoral; (2) ischiofemoral; and (3) pubofemoral.

(1) iliofemoral - is an extremely strong Y-shaped ligament located anteriorly. Clinically it is referred to as the Y-ligament of Bigalow.

(2) ischiofemoral - arises from the ischium inferior and posterior to the acetabulum.

(3) pubofemoral - arises from the pubic bone.

The hip joint is involved in flexion, extension, adduction, abduction, rotation, and circumduction.

Gluteal Region

The musculature of the gluteal region is divided into three layers: (1) superficial, (2) intermediate, and (3) deep.

(1) Superficial Group - The superficial muscles of the gluteal region are the gluteus maximus and the tensor fascia lata (Atlas 5.27,5.31). The gluteus maximus is a thick muscle whose fibers pass inferiorly and laterally. It is important to note that it inserts onto the iliotibial band of the fascia lata of the thigh. FUNCTION: It is a strong extensor of the thigh. It is supplied by the inferior gluteal nerve.

The tensor fascia lata is a fusiform muscle located between the layers of the fascia lata. FUNCTION: It tenses the iliotibial band thereby allowing the gluteus maximus to act on the thigh. It is also an important stabilizer of the extended knee. It is supplied by the superior gluteal nerve.

(2) Intermediate Group - The middle layer of muscles consists of the gluteus medius and piriformis (Atlas 5.33). The gluteus medius lies deep to the gluteus maximus. It arises from the ilium just inferior to the iliac crest and inserts onto the greater trochanter. FUNCTION: It is a powerful abductor of the thigh. It also fixes the pelvis to the greater trochanter. Its nerve supply is via the superior gluteal nerve. The piriformis is a fan-shaped muscle passing from the sacrum to the greater trochanter. FUNCTION: Because of its direction, it is involved in abduction and lateral rotation of the thigh. It is supplied by sacral nerves.

(3) Deep Group - The deep layer is composed of the gluteus minimus, obturator internus, obturator externus, the superior and inferior gemelli, and the quadratus femoris muscles (Atlas 5.33,5.34). The gluteus minimus is a fan-shaped muscle located deep to the gluteus medius. It inserts on the greater trochanter of the femur. FUNCTION: It abducts the thigh and fixes the pelvis to the greater trochanter. Its nerve supply is via the superior gluteal nerve. Inferior to the piriformis are the remaining "short gluteal muscles" listed above. FUNCTION: All are lateral rotators of the thigh. All but one of these muscles shares its nerve supply. The superior gemellus is supplied by the nerve to the obturator internus, the inferior gemellus is supplied by the nerve to quadratus femoris. The obturator externus is supplied by the nerve to obturator externus.

Neurovascular Components of the Gluteal Region

The superior and inferior gluteal arteries furnish the main blood supply for this region (Atlas 5.36,5.37). They are both branches of the internal iliac artery. They are located superior and inferior to the piriformis respectively.

Located on the inferior border of the piriformis is the largest nerve in the body the sciatic nerve (Atlas 5.36-5.39). It emerges from the greater sciatic foramen just below the piriformis. It then courses vertically downward under cover of the gluteus maximus, lying on the "short gluteal muscles" midway between the greater trochanter and the ischial tuberosity. The sciatic nerve is so large that it has its own blood supply from a branch of the inferior gluteal artery.

Organization of the Thigh

The thigh is surrounded by an external investing layer of deep thigh fascia termed the fascia lata (Atlas 5.14). It surrounds the thigh like a stocking. Laterally, the fascia lata is thick and strong and forms the iliotibial band. Anteriorly and medially the fascia lata is quite thin.

The thigh is organized into three regions. These are the anterior extensor, medial adductor, and posteriorly located flexor region.

Posterior Region (Atlas 5.31-5.34) - Beneath the skin and fascia in the midline lies the posterior cutaneous nerve of the thigh. It supplies sensory branches to the skin of the posterior thigh, gluteal region and perineum(covered later in section on pelvis). The hamstring muscles lie deep to the nerve. They pass from the ischial tuberosity to the upper part of the tibia and fibula. The three hamstrings are the long head of biceps femoris, semitendinosus, and semimembranosus. From their ischial origin the muscles diverge, the long head of biceps femoris passing to the fibula, and the semitendinosus and semimembranosus passing to the tibia. The space between this diversion constitutes the upper part of the popliteal fossa. FUNCTION: The main function of the hamstring muscles is to flex the leg. They are supplied by the tibial component of the sciatic nerve.

The short head of the biceps femoris is not considered a hamstring because it does not arise from the ischial tuberosity and receives its nerve supply via the common peroneal component of the sciatic nerve. Beneath the hamstrings lies the posterior aspect of the adductor magnus muscle.

As stated above, the hamstring muscles are supplied by the components of the sciatic nerve. As this nerve passes inferiorly through the posterior thigh it splits. At about the junction of the middle and lower thirds of the thigh it divides into the common peroneal and tibial nerves. NOTE: Occasionally these two nerves emerge separately from under the gluteus maximus (Moore, 5-39). Both nerves are associated with the popliteal fossa.

Popliteal Fossa

The popliteal fossa(Moore 5-44,5-45) is a diamond-shaped area located posterior to the knee joint. It contains the popliteal artery and vein which are a continuation of the femoral artery and vein, nerves(tibial and common peroneal), some lymph nodes and a considerable amount of fat.

Muscles in the Anterior Region of the Thigh

Anterior Region(Moore 5-19) - Muscles in the anterior region of the thigh consist of a portion of the iliopsoas, sartorius, and the quadriceps femoris.

Iliopsoas (Moore 5-12, 5-19) - The iliospsoas is composed of the psoas major and iliacus muscles. The psoas major is a long, powerful muscle that passes from abdominal vertebrae to the lesser trochanter. The iliacus is a fan-shaped muscle which passes inferiorly from the ilium, joins the psoas major, and with it, inserts onto the lesser trochanter of the femur. It is supplied by branches from lumbar nerves. FUNCTION: It flexes the thigh at the hip joint.

Sartorius (Moore 5-12,5-19) - This is the longest muscle in the body. It passes from the pelvis to the tibia. It is the most superficial muscle in the anterior compartment of the thigh. It is called the "tailor's muscle" because it is used to cross the legs in the tailors position. It is supplied by a branch of the femoral nerve.

Quadriceps Femoris(Moore 5-13,5-19) - The quadriceps femoris is a group of four merging muscles. These muscles are the rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. One muscle (rectus femoris) arises from the pelvis. The remaining muscles arise from the femur (vastus lateralis and medialis from linea aspera, vastus intermedius from shaft of femur).

The tendons of all four muscles surround the patella (knee cap) and form the patellar tendon which attaches to the tuberosity of the tibia. The quadriceps femoris is supplied by the femoral nerve. FUNCTION: It extends the leg at the knee.

Muscles in the Medial Region of the Thigh

Medial Region (Moore 5-19,5-22) - The muscles in the medial region of the thigh include pectineus, adductor longus, adductor brevis, adductor magnus, gracilis.

Pectineus(Moore 5-19) - Although this muscle helps form the floor of the femoral triangle(located anteriorly), it acts as an adductor of the thigh. It arises from the pubic bone and inserts onto the femur. It receives its nerve supply primarily from the femoral nerve (some nerve fibers from obturator).

Adductor Longus (Moore 5-19,5-22) - It is the most anterior muscle in the medial (or adductor) group. It arises from the pelvis and inserts onto the femur(linea aspera). It receives its nerve supply from the obturator. FUNCTION: It adducts the thigh.

Adductor Brevis(Moore 5-19, 5-22) - It is located in the medial region of the thigh between the adductor longus and adductor magnus. As does the adductor longus it arises from the pelvis and inserts onto the femur. It is supplied by the obturator nerve. FUNCTION: It adducts the thigh.

Adductor Magnus (Moore 5-19,5-22)- It is the largest of all the adductors. Arising from the pelvis it inserts onto the femur. It is supplied by the obturator nerve. FUNCTION: It's primary function is to adduct the thigh.

Gracilis (Moore 5-19,5-22)- This long, strap-like muscle passes from the pelvis to the tibia. It receives its nerve supply from the obturator. FUNCTION: It adducts the thigh.

"Femoral Triangle" and Neurovascular Components of Anterior and Medial Thigh

"Femoral Triangle" (Moore 5-9,5-14,5-15) - This trough-like triangle is bounded by the inguinal ligament(base), medial border of adductor longus, and the medial margin of sartorius. When the thigh is actively flexed, the triangle appears as a triangular depression in the proximal third of the thigh. It contains the femoral nerve, femoral artery, and femoral vein.

Immediately inferior to the inguinal ligament the contents of the femoral triangle are arranged in the following order from lateral to medial: femoral nerve(N), femoral artery(A), femoral vein(V), an empty or potential space(E), and numerous lymphatics(L) (Atlas 5.51). In this order it spells NAVEL.

The femoral artery is a continuation of the external iliac artery (Atlas 5.6A,B). It provides the main arterial supply to the lower limb. As this artery descends through the femoral triangle, it comes to lie immediately deep to the apex of the triangle. Within the femoral triangle the femoral artery gives off the profunda femoris. This is the chief artery of the thigh. The profunda femoris usually gives off the medial and lateral circumflex arteries which are the main supply to the proximal end of the femur. Of the two arteries, the medial femoral circumflex artery is the most important in that it supplies most of the blood to the head and neck of the femur.

The femoral vein (Atlas 5.14) passes deep to the inguinal ligament to become the external iliac vein. Its tributaries include the great saphenous vein (Atlas 5.4B). The importance of this vein will be presented in the last lecture on the extremities.

The femoral nerve (Atlas 5.8,5.24) likewise passes from the abdominopelvic cavity deep to the inguinal ligament enter the femoral triangle. Within the triangle it breaks up into its many muscular branches.

Leaving the area of the femoral triangle, the femoral vessels and branches of the femoral nerve enter the confines of the adductor(Hunter's) canal. This canal, located deep to the sartorius muscle, contains the femoral artery and vein, muscular branches of the femoral nerve and the saphenous nerve a cutaneous branch of the femoral nerve. The canal ends inferiorly at the popliteal fossa.

Knee Joint

The bones associated with the knee joint are the patella, femur, and proximal tibia. The main function of this joint is flexion and extension of the leg.

Proximal(Upper) Portion of the Tibia (Moore 5-2,5-3) - The surfaces of the two large condyles on the upper end of the tibia (tibial plateau) are almost flat and covered by articular cartilage. From the condyles, the tibia narrows down to a shaft. Anteriorly, at the beginning of the shaft is the tibial tuberosity. The epiphyseal line courses horizontally just below the tibial plateau.

Patella(Moore 5-2,5-91) - The patella is a triangular-shaped bone, embedded in the quadriceps femoris tendon. This tendon continues as the patellar tendon which inserts onto the tuberosity of the tibia.

Lower Portion of Femur (Moore 5-2,5-3) - The end of the femur consists of two large femoral condyles(lateral and medial) coated with articular(hyaline) cartilage. Keep in mind that the anteroposterior axis of the lateral condyle is straight while that of the medial condyle is curved and longer. Each condyle has outward projecting epicondyles(lateral and medial).

Ligaments (Moore 5-90,5-91) - The knee joint consists of the femoral condyles articulating with the patella anteriorly and inferiorly with the tibial condyles. The three bones that make up the knee joint are bound together by many ligaments. A capsular ligament loosely surrounds the joint. External to the capsular ligament is the patellar ligament mentioned above. Laterally and medially the knee joint is strengthened by the fibular (lateral) collateral ligament and tibial (medial) collateral ligament respectively. These ligaments connect the femur to their respective bones. In the center of the knee joint are two cruciate ligaments that cross in the fashion of the letter X. The anterior cruciate ligament passes from the anterior part of the intercondylar area and passes posterosuperiorly to the femur. NOTE: It is the weaker of the two cruciate ligaments. It prevents posterior displacement of the femur on the tibia. The posterior cruciate ligament arise from the posterior part of the intercondylar area and passes superiorly and anteriorly to the femur. NOTE: It is the stronger of the two cruciate ligaments. It prevents anterior displacement of the femur on the tibia.

Menisci (Moore 5-93B) - There are two menisci or fibrocartilages associated with the knee joint. The medial meniscus is "C" shaped while the lateral meniscus if shaped like an "O". Attaching to the medial meniscus is the medial(tibial) collateral ligament. The lateral meniscus is not adherent to any of the above ligaments. (This information will become important when we discuss damage to the knee joint.) FUNCTION: The menisci deepen the concavities of the tibial condyles to allow the femur to fit better and they act as buffers to diminish the pounding of the lower end of the femur on the tibia.

Bursae (Moore 5-90) - A bursa is a lubricating device consisting of a closed fibrous sac lined with a delicate smooth membrane. It is filled with viscous fluid. Bursae are found wherever tendons rub against bones, muscles, ligaments, or other tendons. They are commonly found close to joints where skin rubs against underlying bony structures.

There are numerous bursae related to the knee joint (total of 10). Based on the structure of the knee joint, you can see why. There are many tendons and ligaments associated with this joint. Time doesn't permit us to discuss the clinical significance of each of these bursae however, the patellar bursae (Moore 5-90) (e.g. prepatellar, infrapatellar) frequently become inflamed. The prepatellar bursa lies between the skin and patella. Because of its superficial and exposed position, this bursa may become inflamed after prolonged periods of weightbearing. Infrapatellar inflamation may be the result of a leakage of fluid from the synovial cavity.

The great saphenous vein, the major vein draining the superficial tissues of the foot, leg, and thigh, passes just posterior to the medial condyle of the femur. It then lies between the superficial and deep layers of the superficial thigh fascia. Just inferior to the inguinal ligament, it perforates the fascia lata. It then empties into the femoral vein within the femoral sheath (Atlas 5.10,5.11).

Anterior Body Wall

A. General Objectives

1. Identify the layers of soft tissue and skeletal elements which make up the anterior body

wall.

2. Examine the specialized attachments of the superficial fascia in the lower trunk.

Appreciate how the superficial veins make venous collateral circulation possible. Note

the course of superficial lymphatic drainage.

3. Appreciate that the muscles of thoracic and abdominal walls derive from the same basic

plan; understand that the primitive segmental organization of the body wall has not

veen fundamentally affected by absence of ribs over the lower part of the abdominal

cavity. Identify the most useful dermatome landmarks.

B. Specific Points:

1. Thoracic skeleton - forms a bony and cartilaginous cage which protects thoracic and

abdominal viscera and functions in respiration.

a. Thoracic vertebrae - bear unique articular facets on their bodies and transverse

processes for ribs (costovertebral joints and costotransverse joints respectively).

These are synovial joints.

b. Ribs

1. 12 pairs - ribs 1-10 articulate through separate costal cartilages with sternum.

Ribs 8-10 articulate with costal cartilages of upper ribs, ribs 11-12 have free

distal ends (floating ribs).

2. Features: head (articulates with vertebral body)

neck - section between head and tubercle body (shaft) flat, curved and

grooved (for intercostal vessels and n.)

3. Costal cartilages - lend elasticity and mobility to rib cage (hyaline cartilage).

Present distally on all ribs. Costal cartilages from the 10th ribs form costal

margins on either side. Costal margins together form the costal arch. Except

for 1st rib, costal cartilages are joined to sternum by synovial joints.

c. Sternum - 3 parts manubrium, body, (formed by 4 embryonic sternebrae), xiphoid

process.

a. Sternoclavicular joint - with two synovial cavities and an articular disc

b. Sternocostal joints - 1st rib cartilage fused (synchondrosis) remaining

sternocostal joints (ribs 2-7) are synovial joints

c. Manubriosternal joint - a symphysis involving fibrocartilage; produces sternal

angle

d. Xiphisternal junction - xiphoid process begins as cartilage, later ossifies and

frequently fuses with body of sternum.

2. Surface and bony landmarks (all but one are palpable from the surface).

a. Sternum (Atlas 1-11; 1-8)

1. Suprasternal (jugular) notch

2. Sternal angle (of Louis) between manubrium and body; landmark for second rib

3. Xiphisternal junction; boundary between thoracic and abdominal cavities in

midline (the diaphragm is dome-shaped; many abdominal viscera are protected

within the rib cage); region of rectus abdominis m. attachment

b. Costal margin (costal arch)

1. Costal cartilage of ribs 7-10

2. Ribs 8-10 articulate with sternum only indirectly; their costal cartilages attach to

those of the rib above

3. Last 2 ribs (floating ribs) do not articulate with sternum at all; stabilized by

muscles

c. Abdominal wall (Atlas 1-1)

1. Linea semilunaris; lateral border of rectus abdominis m.

2. Linea alba; the aponeurotic line connecting the fascial sheaths (rectus sheaths)

which enclose the rectus abdominis mm.

3. Tendinous intersections of rectus abdominis mm.; reflect the fact that these

longitudinal muscle columns were originally segmented

4. Umbilicus; scar where umbilical cord attached until birth. A weak spot,

particularly in young babies while it is still scarring over; site of umbilical

hernia

d. Pelvic region (Atlas 2-1a)

1. Pubic symphysis (fibrocartilage) and pubic crest; rectus abdominis m. attaches

here

2. Pubic tubercle; inguinal ligament attaches

3. Inguinal ligament; deep to the anterior skin crease (inguinal crease) where thigh

joins body

4. Anterior superior iliac spine; inguinal ligament attaches

5. Iliac crest and its tubercle; the flat muscles of the ant. abdominal wall have

attachments here

6. Pubic arch; where adductor mm. of thigh attach. The important superficial

perineal pouch lies in the interval between the arches

7. Pectineal line of pubis (Atlas 5-42) surmounted by pectineal ligament (too deep

to palpate)

8. Femoral artery (Atlas 2-1c). Note: it enters the thigh below the inguinal

ligament

9. Inferior epigastric artery; not palpable at surface (except inside inguinal canal),

but its pulsations are important for orientation during surgery

3. Layers of wall

a. Integument

1. skin

2. superficial fascia

b. Investing layer of deep fascia; on superficial surface of:

c. Bones and/or muscles

d. Fascia covering internal surfaces of bone/muscle layer:

1. an (areolar connective tissue) endothoracic fascia in the thorax

2. a (denser connective tissue) endoabdominal fascia in the abdominal cavity; most

of it is called transversalis fascia

e. Serous membranes

1. (parietal) pleura in thorax

2. (parietal) peritoneum in abdomen (fat often found between it and transversalis

fascia)

4. Features of superficial fascia

a. Superficial lymphatic drainage of the body (below the neck; Moore, 1-24)

1. Four quadrants of the body:

a. to left and right of midline

b. above and below umbilicus

c. include front and back, and limbs

2. Upper quadrants drain into respective axillary nodes

3. Lower quadrants drain into respective inguinal nodes

4. Drain into deep lymphatics; all lymph finally retuned to veins in root of neck

b. Superficial epigastric vv. (Atlas 2-5) can develop large anastomoses around

umbilicus with branches of lateral thoracic vv. to detour blood around obstructions

in deep vv. which retard return of blood from lower body to heart (no valves

interfere)

c. Below umbilicus, superficial fascia usually divisible into:

1. Superficial fatty layer (Camper's fascia)

a. contains the large superficial vessels

b. continues uninterrupted into thigh

2. Deeper, more membranous layer (Scarpa's fascia)

a. thickened in midline into fundiform ligament which helps suspend penis

(clitoris)

b. fused to fascia lata (deep fascia of thigh) just inferior to infuinal crease

5. Muscles of wall (Atlas 2-3)

A. Basic Plan - Three flat muscles on each side:

i. In thorax (Atlas 1-20):

a. external intercostal

b. internal intercostal

c. innermost intercostal/transversus thoracis

Note: the muscles, or their membranes, are anchored to the sternum.

ii. In abdomen

a. external oblique

b. internal oblique

c. transversus abdominis

Note: Anteriorly the aponeuroses of these muscles form a fascial supporting sheath (rectus sheath) around each rectus abdominis muscle. The linea alba connects the sheaths across the midline.

iii. Ventrally (originally segmented) muscles combine into a pair of longitudinal

columns:

a. replaced by bone (sternum) in thorax; sometimes a small remnant, the

sternalis muscle persist. Continued to the chin as strap muscles eg.

omohyoid

b. in abdomen: rectus abdominis

B. Further details on thoracic muscles:

i. external intercostals represented by membrane anteriorly

ii. deeper muscles represented only by internal intercostal membrane posteriorly

iii. external intercostal fibers (Atlas 1-15) pass down and forward (hand in outside

pocket) - similar to external abdominal oblique

iv. internal intercostal fibers (Atlas 1-16) pass up and forward (hand in inside

pocket; so do innermost intercostals) - similar to internal abdominal oblique

C. Abdominal muscles; further comments

i. Transversus abdominis attaches inside rib cage, above costal arch

ii. External oblique (Atlas 2-5):

a. Attaches outside rib cage, well above costal arch

b. Is the only muscle available to contribute to the highest part of rectus sheath

(anterior lamina)

c. Is represented only by an aponeurosis anteroinferiorly

iii. Internal oblique (Atlas 2-6):

a. Attaches at costal margin

b. Aponeurosis splits above arcuate line:

- Internal and external obliques form anterior lamella of rectus sheath

- Internal oblique and transversus abdominis form posterior lamella of rectus

sheath

iv. Below arcuate line:

a. All flat muscle aponeuroses pass anterior to rectus m. therefore:

b. There is no rectus sheath below arcuate line; rectus m. lies directly on

transversalis fascia

c. Inferior epigastric a. enters rectus sheath at arcuate line

v. Other attachments of flat muscles:

a. All three on iliac crest

b. The inner two (Atlas 4-55) to the lumbar aponeurosis; its anterior and posterior lamellae are in fact formed by splitting of the posterior aponeurosis

of transversus abdominis

vi. Actions of abdominal wall muscles:

a. Most important: protect abdominal viscera where no bony protection exists

(Note: many lower animals, like fish, keep all their ribs to protect all their

viscera)

6. Vessels and nerves; basic plan

a. The segmental vessels and nerves which supply these muscles:

1. Are the 12 thoracic aa. and nn. (intercostals and subcostal); lower 6 continue

into abdomen to supply almost all abdominal wall mm.; small contribution to flat

mm. from L1.

2. They run between the two inner muscle layers

3. Useful dermatome landmarks:

a. T4 - male nipple

b. T10 - umbilicus

c. L1 - inguinal crease

b. Longitudinal vessels are associated with the ventral supporting structures:

1. Internal thoracic (internal mammary) aa., from subclavian provide:

a. Arteries to accompany anterior cutaneous nn.

b. Anterior intercostals to anastomose with posterior intercostals (from aorta) in

upper 6 interspaces

c. Musculophrenic, on deep surface of costal arch, for some of diaphragm and

some lower interspaces; internal thoracic then becomes:

2. Superior epigastric:

a. Continues inferiorly to supply upper rectus abdominis

b. Anastomoses with:

3. Inferior epigastric (from external iliac, which becomes femoral in thigh)

4. Internal thoracic, superior and inferior epigastrics can provide collateral arterial

circulation to lower body from subclavians if obstruction develops in deeper

vessels (e.g., aorta)

7. Case Studies: Appreciate the following:

a. Hernias: A hernia is a place where any structure (usually gut) has been pushed into

some place where it is not supposed to be e.g., umbilical hernia, (Moore 132, 184),

femoral hernia (Moore 405), inguinal hernia (Moore 147-149) etc.

b. Cervical rib (Moore, 524)

c. Coarctation of aorta (Moore, 110)

d. Caput medusa (Moore, 210)