The Pectoral Girdle and Breast PDF

1. The Pectoral Girdle and Breast A: Anterior Pectoral Girdle 1. Clavicle: Connects upper limb to trunk Shaft of the clavicle has double curve (S-shaped) in the horizontal plane ! Medial " of shaft- convex anteriorly...

1. The Pectoral Girdle and Breast A: Anterior Pectoral Girdle 1. Clavicle: Connects upper limb to trunk Shaft of the clavicle has double curve (S-shaped) in the horizontal plane ! Medial " of shaft- convex anteriorly # Curvatures increase Lateral " concave anteriorly resilience of the clavicle Two ends: o Sternal end- enlarged and triangular where it articulates with the manubrium of the sternum at the sternoclavicular (SC) joint o Acromial end- flat where it articulates with the acromion of the scapula at the acromioclavicular (AC) joint Functions: o Serves as a moveable, crane-like strut from which the scapula and free limb are suspended, keeping them away from the trunk so that the limb has maximum freedom of motion o This strut is moveable and allows the scapula to move on the thoracic wall at the scapulothoracic joint (physiological joint) which increases the range of motion of the limb o Forms one of the bony boundaries of the cervico-axillary canal (passageway between the neck and the arm) which protects the neurovascular bundles supplying the upper limb o Transmits shocks from the upper limb to the axial skeleton Physiological joint: movement Long bone with no medullary (marrow) cavity occurs between musculoskeletal Consists of trabecular (spongy) bone with a shell of compact bone structures Anatomical joint: movement Superior surface: occurs between directly o Smooth articulating skeletal elements o Lies just deep to the skin and platysma muscle in the subcutaneous tissue Inferior surface: o Rough due to strong ligaments binding it to the first rib near its sternal end and suspend the scapula from its acromial end 1 Zaid Ganie  Landmarks: o Conoid tubercle Near the acromial end Attachment to conoid ligament (medial part of the coracoclavicular (CC) ligament) by which the remainder of the upper limb is passively suspended from the clavicle. o Trapezoid line Attachment of the trapezoid ligament (lateral part of the coracoclavicular ligament) o Subclavian groove In the medial third of the shaft of the clavicle Attachment of the subclavius muscle o Impression for the costoclavicular ligament More medial Rough, depressed oval area Gives attachment to the ligament binding the first rib to the clavicle which limits elevation of the shoulder 2. Scapula: Triangular, flat bone Lies in the posterolateral aspect of the thorax, overlying 2nd to 7th ribs Posterior surface: o Convex o Unevenly divided (by thick projecting ridge called spine of scapula) into small supraspinous fossa (1) and larger infraspinous fossa (2) Costal surface: o Concave o Forms large subscapular fossa (3) Surfaces of the 3 fossae provide attachment for fleshy muscles 2  Landmarks: o Body of scapula Thin, triangular Translucent superior and inferior to the spine of scapula Borders are thicker (especially lateral border) o Acromion Flat, expanded lateral continuation of the spine Forms the subcutaneous point of the shoulder Articulates with the acromial end of the clavicle o Deltoid tubercle Medial attachment of the deltoid muscle on the scapular spine o Spine of scapula Together with the acromion, serves as a lever for the trapezius muscle o Glenohumeral (shoulder) joint AC joint is placed lateral to the mass of the scapula and its attached muscles The shoulder joint on which these muscles operate is almost directly inferior to the AC joint The scapular mass is balanced by the free limb next to it The CC ligament is the balancing point lying between the two masses o Glenoid cavity Superolateral surface of scapula Receives and articulates with head of humerus at shoulder joint Shallow, concave, oval fossa Smaller than head of humerus for which it serves as a socket o Coracoid process Beak-like Superior to the glenoid cavity Projects anterolaterally Resembles a bent finger (bent towards the shoulder) "knuckle" provides inferior attachment of passively supporting CC ligament o Borders Medial, lateral and superior borders Superior, lateral and inferior angles Thin medial border runs parallel to and lateral to the spinous processes of the thoracic vertebrae Lateral border § runs superolaterally from the inferior angle to toward the apex of the axilla (AKA axillary border). § Composed of a thick bar of bone preventing buckling of this stress-bearing region of the scapula. § Terminates in the truncated lateral angle which is the thickest part of the bone that bears the broadened head of scapula § Shallow constriction between the head and body is the neck of the scapula Superior border § Thinnest and shortest border ! # § Marked near the junction of medially and laterally by the suprascapular notch " " (where the superior border joins the base of the coracoid process) Function: o considerable movement on the thoracic wall at the physiological scapulothoracic joint, providing the base from which the upper limb operates and is able to move freely 3  Joints 1. Sternoclavicular (SC) joint: Saddle type synovial joint (functions as ball and socket) Articular disc divides joint into 2 compartments Disc is attached by o anterior and posterior sternoclavicular ligaments Disc attachments give o Thickenings of the fibrous layer of the joint capsule great strength to the joint o Interclavicular ligament Serves as a shock absorber of forces transmitted from upper limb Dislocation is rare (fracturing is more common) The only articulation between upper limb and axial skeleton Palpated easily since sternal end of clavicle is superior to manubrium of sternum Articular surfaces: o Sternal end clavicle articulates with Articular surfaces are o Manubrium and covered with fibrocartilage o 1st costal cartilage. Joint capsule of SC joint: o Surrounds the SC joint including epiphysis at the sternal end of the clavicle o Attached to the margins of the articular surfaces including the periphery of the articular disc o Synovial membrane lines the internal surface of the fibrous layer of the joint capsule extending to the edges of the articular surfaces Ligaments of the SC Joint: o Anterior and posterior sternoclavicular ligaments Reinforce the joint capsule anteriorly and posteriorly o Interclavicular ligament Strengthens the capsule superiorly In between, it is also attached to the superior border of the manubrium o Costoclavicular ligament 4  Anchors the inferior surface of the sternal end of the clavicle to the first rib and its costal cartilage Limits the elevation of the pectoral girdle Movement if the SC joint: o Able to be raised to approx. 600 when limb is fully elevated o When elevation is achieved via flexion, clavicle rotates along longitudinal axis o Movement anteriorly and posteriorly ranges between 250 and 300 o Circumduction is possible with the combination of the 2 movements Blood supply of SC joint: o Supplied by internal thoracic and suprascapular arteries Innervation of SC joint: o Branches of the medial supraclavicular nerve and the nerve to the subclavius supply SC joint 2. Acromioclavicular (AC) joint: Plane type synovial joint Articulation of the AC joint: o Acromial end of the clavicle articulates with the o Acromion of the scapula. o Articular surfaces are covered fibrocartilage and are separated by an incomplete wedge-shaped articular disc Joint capsule of AC joint: o Sleeve-like o Loose fibrous layer o Attached to the margins of the articular surfaces o Synovial membrane lines the fibrous layer o Although weak, capsule is strengthened superiorly by fibers of the trapezius Ligaments of AC joint: o Acromioclavicular ligament Acromion to clavicle Strengthens AC joint superiorly 5  o Coracoclavicular ligament Pair of bands uniting coracoid process of scapula to the clavicle Consists of 2 ligaments: conoid medially and trapezoid laterally Conoid: § Vertical cone with apex inferiorly where it attaches to the root of the coracoid process § Wide attachment (base of cone) to the conoid tubercle on the inferior surface of the clavicle Trapezoid: § Nearly horizontal § Attached to the superior surface of the coracoid process § Extends laterally to the trapezoid line on the inferior surface of the clavicle Blood supply of AC joint: o Supplied by the suprascapular and thoraco-acromial arteries Innervation: o Lateral pectoral and axillary nerves supply the AC joint (consistent with Hilton law) o Cutaneous lateral suprascapular nerve (since no muscles cut across the joint) 6  Muscles Anterior axio-appendicular muscles Muscle Origin Insertion Innervation Main Action Pectoralis 1. Clavicular head Lateral lip of Lateral and medial Adducts humerus major anterior surface of intertubercular sulcus pectoral nerves Medially rotates medial half of clavicle of humerus Clavicular head- humerus 2. Sternocostal head (C5, C6) Draws scapula anteriorly anterior surface of Sternocostal head- Draws scapula inferiorly sternum (C7, C8, T1) Clavicular head alone Superior 6 costal flexes humerus cartilages Sternocostal head alone Aponeurosis of extends humerus from external oblique flexed position muscle Pectoralis Upper margins and outer Medial border and Medial pectoral Stabilizes scapula by minor surfaces of 3rd-5th ribs near superior surface of nerve drawing it inferiorly and their costal cartilages coracoid process of (C8, T1) anteriorly against the scapula thoracic wall subclavius Junction of 1st rib and its costal Inferior surface of Nerve to Anchors and depresses cartilage middle third of subclavius clavicle clavicle (C5, C6) Serratus External surfaces of lateral Anterior surface of Long thoracic Protracts scapula anterior parts of 1st-8th ribs medial border of nerve (C5, C6, C7) Rotates scapula scapula (SALT) 7  Clavipectoral Fascia (costocoracoid membrane) Extent- clavicle superiorly to axillary fascia inferiorly Enclosed structures- subclavius and pectoralis minor Piercing structures- o Medial and lateral pectoral nerves o Pectoral branch of thoraco-acromial artery o Cephalic vein 8  B: Breast 1. Definition and function: Modified sweat gland Secretes milk Exists in both males and females o Rudimentary in males with no alveoli (component that secretes milk) and little supporting adipose tissue o In females- underdeveloped before puberty but undergoes growth after puberty and pregnancy 2. Position, shape and size: Shape o variable but base is fairly constant o Protuberant- hemispherical Position o Vertically- 2nd to 6th ribs o Horizontally- 4th intercostal cartilage from sternum to near midaxillary line o Superolateral part- breast prolonged upwards and laterally towards axilla (axillary tail of Spence) ! o " lies on pectoralis major # o " lies on serratus anterior and external oblique muscles 3. Components, borders and surfaces: Mammary papilla (Nipple) o Conical o 4th intercostal space in nulliparous females (female who has never given birth) o Variable in multiparous females o Pink or light brown in colour Areola o Base of nipple o Pigmented area of skin o Size increase and darkening with 1st pregnancy (3 months) and never returns to original colour o Contains areolar (sebaceous) glands of Montgomery which are tiny swellings (secretions are moistening and antibacterial) Structure of the breast o Entire gland in superficial fascia (retromammary space) o Lactiferous ducts give rise to buds that develop into 15-20 separate lobes of glandular tissue Tubulo-alveolar type Each separated from its neighbour by fibrous connective tissue Suspensory ligaments of cooper o Fibrous processes from deep fascia to skin and papilla Compartmentalizes the lobes of the breast Support glandular lobes Ligaments may become contracted by fibrosis in cancer of breast (pitting of the breast- looks like an orange) Lactiferous ducts o Each lobule is drained by a lactiferous duct that converge independently o lactiferous sinus- each duct has a dilated portion deep to the areola in which a small droplet of milk accumulates o Terminal ducts are larger near central end of each lobe and converge towards nipple 4. Arterial supply: Perforating branches of internal thoracic a. at 2nd to 4th interspaces (originating from subclavian artery) Perforating branches of 3rd to 5th intercostal aa. Pectoral branches of the thoraco-acromial artery (2nd part of axillary a.) Branches of lateral thoracic artery (2nd part of axillary a.) Branches of subscapular a. (3rd part of axillary a.) 9 5. Venous drainage: Anastomotic circle around nipples (circulus venosus) into axillary and internal thoracic vv. via intercostal vv. 6. Lymph drainage: Axillary group (drains 75%) o Lateral (humeral) nodes: Does not drain breast; only drains upper limb o Pectoral (anterior) nodes: found at inferior border of pectoralis minor, drains central and lateral breast o Subscapular (posterior) nodes: along subscapular vessels at axillary tail and along posterior axillary fold o Central: in axillary fat and nodes below o Apical (Behind clavicle): drains upper and peripheral parts along apex of the axilla, and the previous 4 nodes Ends in subclavian lymph trunk and ultimately into § Left- thoracic duct § Right- subclavian vein/right jugular trunk 10  Parasternal group (drains 20%) o Anterior ends of intercostal spaces along internal thoracic artery Drains medial quadrant and some aspects of lateral quadrant o Medial convexity o Carries cancer cells from one breast to another Intercostal group (drains 5%) o Intercostal vessels Sappey's plexus o Drains nipple and areolar Abdominal lymph nodes o Lymph from skin covering the breast 7. Nerve supply: Anterior and lateral cutaneous branches of 3rd to 6th intercostal nerves o Convey sympathetic fibers to blood vessels and smooth muscles Nervous plexus around nipple helps signaling suckling Nerves vulnerable during mastectomy: o Intercostal brachial n. o Medial brachial cutaneous n. o Long thoracic n. o Thoracodorsal n. o Medial pectoral n. 8. Applied anatomy: Lymph flow is important clinically o Since it is the primary route of metastasis of breast cancer and for performing and interpreting a node biopsy Cyst (galactocele) may develop with blockage of lactiferous ducts Peau D'orange Pits of hair follicles appear to be retracted beneath the level of surrounding skin Blockage of lymphatic drainage of skin leading to lymph stagnation and oedema Retraction of skin Invasion of ligaments of Cooper leading to dimpling Retraction of nipple Extension of growth along milk line ducts with subsequent retraction as fibrosis occurs leading to indrawn nipple Amastia Absence of one or both breasts Polymastia One or more extra mammae Polythelia One or more extra nipples Gynaecomastia Hypertrophy of male breast often after puberty from hormonal imbalance of oestrogens and androgens; may secrete milk 11  C: Shoulder Region and Back Bones 1. Humerus: Articulates with the scapula at the glenohumeral joint proximally, and with the radius and ulna at the elbow joint distally Proximal end of the humerus o Head- spherical, articulates with glenoid cavity of scapula o Anatomical neck- formed by the groove circumscribing the head and separating it from the greater and lesser tubercles (indicates the line of attachment of the glenohumeral joint capsule) o Surgical neck- narrow part distal to the head and tubercles (common site of fracture) Landmarks: o Junction of the head and neck with the shaft indicated by the greater and lesser tubercles provide attachment and leverage to some scapulohumeral muscles. o Greater tubercle lateral margin of humerus o Lesser tubercle projects anteriorly from the bone o Intertubercular sulcus (bicipital groove) Separates the tubercles and provides protected passage for the slender tendon of the long head of the biceps muscle o 2 prominent features of the shaft of humerus: Deltoid tuberosity § Lateral § For attachment of the deltoid muscle Oblique radial groove § Posterior § Groove for the radial nerve § Radial nerve and profunda brachii artery lie in the groove as they pass anterior to the long head and between the medial and lateral heads of the triceps brachii muscle Inferior end of the humeral shaft widens as the sharp medial and lateral supra- epicondylar ridges form and then the prominent medial epicondyle and lateral epicondyle providing for muscle attachment 12  Distal end of the humerus o Condyle of the humerus o 2 articular surfaces Capitulum § Lateral § For articulation with the head of the radius Trochlea § Medial § Spool-shaped and pulley-like § For articulation with the trochlear notch (proximal end) of the ulna o 2 Fossae (occur back to back superior to trochlea, making the condyle thin between epicondyles) Coronoid fossa § Anterior § Receive coronoid process of the ulna during full flexion of the elbow Olecranon fossa § Accommodates the olecranon of the ulna during full extension of the elbow o Radial fossa Superior to the capitulum anteriorly Accommodates the edge of the head of the radius when the forearm is fully flexed 13  Joints 1. Glenohumeral joint: Ball and socket type synovial joint Multiaxial spheroidal Articulating surfaces: o Large round humeral head articulates with the shallow glenoid cavity of the scapula o Shallow glenoid cavity slightly deepened by the ring-like fibrocartilaginous glenoid labrum o Both articular surfaces covered with hyaline cartilage Joint capsule of glenohumeral joint: o Loose fibrous layer of the joint capsule surrounds the glenohumeral joint and is attached medially to the margin of the glenoid cavity and laterally to the anatomical neck of the humerus o Deficient inferiorly Only part not reinforced by rotator cuff muscles Capsule is lax when arm is adducted but taut when arm is abducted o Superiorly, the fibrous layer of the capsule encloses the proximal end of the long head of the biceps brachii to the supraglenoid tubercle of the scapula within the joint o Has 2 apertures- An opening between the tubercles of the humerus § For passage of the tendon of the long head of the biceps brachii An opening anteriorly and inferior to the coracoid process § Allows communication between the Subtendinous bursa of subscapularis and the synovial cavity of the joint 14  Ligaments: Glenoid cavity accepts a little more than a third of the o Glenohumeral humeral head and is held in the 3 fibrous bands cavity by the rotator cuff Evident on the internal aspect of the capsule muscles (SITS) Reinforce the anterior aspect of the joint capsule Radiate laterally and inferiorly from the glenoid labrum at the supraglenoid tubercle Attaches to the anatomical neck of the humerus o Coracohumeral Strong broad band Passes from the base of the coracoid process to the anterior aspect of the greater tubercle of the humerus o Transverse humeral ligament Broad fibrous band that runs obliquely from the greater to the lesser tubercle of the humerus Bridges over the intertubercular sulcus Converts the groove into a canal which holds the synovial sheath and tendon of the biceps brachii in place during movement of the GH joint o Coracoacromial ligament Spans between the inferior surface of the acromion and the lateral border of coracoid process Forms a protective arch that overlies the humeral head, preventing its superior displacement from the glenoid cavity Very strong Bursae: o Subtendinous bursa of subscapularis Located between tendon of subscapularis and neck of scapula Protects the tendon o Subacromial (subdeltoid) Large Located under coracoacromial ligament and deltoid muscle Blood supply o Anterior and posterior circumflex humeral arteries o Branches of the suprascapular artery Innervation o Suprascapular, axillary and lateral pectoral nerves supply the glenohumeral joint 15  Muscles involved in movement of the joint: Movement Prime movers (synergists) Abduction Deltoid, (supraspinatus initiates movement) Adduction Pectoralis major, latissimus dorsi, (teres major, long head of triceps brachii) Flexion Clavicular head of pectoralis major, anterior deltoid , (coracobrachialis) Extension Posterior deltoid, (teres major, latissimus dorsi, long head of triceps brachii) Medial rotation Subscapularis, (pectoralis major, deltoid, latissimus dorsi, teres major) Lateral rotation Infraspinatus, (teres minor, deltoid) Factors for stability: o Glenoid labrum- increases concavity o Coracoacromial arch- prevents upward dislocation o Tendon of long head of biceps- superior support o Long head of triceps- inferior support during abduction o Ligaments o Rotator cuff muscles- strong lateral stability, stabilizes head of humerus in glenoid cavity Supraspinatus Infraspinatus Teres minor Subscapularis Applied anatomy: o Most frequently dislocated joint o Dislocation occurs inferiorly since inferior aspect is devoid of muscles o Axillary nerve Prone to tear at surgical neck of humerus Close relation to inferior aspect of articular capsule 16  Muscles Posterior axio-appendicular muscles 1. Superficial posterior extrinsic shoulder muscles: Muscle Origin Insertion Innervation Action Trapezius Medial third of Lateral third of Spinal accessory Descending part superior nuchal line clavicle nerve (CN XI) elevates External occipital Acromion and (motor fibres) Ascending part protuberance spine of scapula C3, C4 (pain and depresses nuchal ligament proprioceptive All parts retract Spinous processes of fibres) scapula C7-T12 vertebrae Ascending and descending rotate glenoid cavity superiorly Latissimus Spinous processes of Floor of the Thoracodorsal nerve Extends, adducts, dorsi inferior 6 thoracic intertubercular sulcus (C6,C7,C8) medially rotates vertebrae of the humerus humerus Thoracolumbar fascia Raises the body Iliac crest towards arms during Inferior 3/4 ribs climbing 17 2. Deep posterior extrinsic shoulder muscles: Muscle Origin Insertion Innervation Action Levator Posterior tubercles of Medial border of scapular Dorsal Elevates scapulae transverse processes of C1- superior to root of scapular scapula C4 vertebrae scapular spine nerves (C4,C5) Rotates Cervical nerves glenoid cavity (C3,C4) inferiorly Rhomboid Minor: Minor: Dorsal scapular Retract minor and Nuchal ligament Smooth triangular nerve (C4,C5) scapula and major Spinous processes of area at medial end rotates glenoid C7&T1 vertebrae of scapular spine cavity inferiorly Major: Major: Fix scapula to Spinous processes of Medial border of thoracic wall T2-T5 vertebrae scapula from level of spine to inferior angle 3. Scapulohumeral (intrinsic shoulder) muscles: 18 Muscle Origin Insertion Innervation Muscle action Deltoid Lateral third of clavicle Deltoid tuberosity Axillary nerve Clavicular (anterior) Acromion and spine of of humerus (C5,C6) part: scapula Flexes & medially rotates arm Acromial (middle) part: Abducts arm Spinal (posterior) part: Extends and laterally rotates arm Supraspinatus Supraspinatus fossa of Superior facet of Suprascapular Initiates and assists -RC scapula greater tubercle of nerve deltoid in abduction of humerus (C4,C5,C6) arm Acts with rotator cuff muscles Infraspinatus Infraspinatus fossa of Middle facet of greater Suprascapular Laterally rotates arm -RC scapula tubercle of humerus nerve (C5,C6) Acts with rotator cuff muscles Teres Minor Middle part of lateral Inferior facet of Axillary nerve Laterally rotates arm -RC border of scapula greater tubercle of (C5,C6) Acts with rotator cuff humerus muscles Teres Major Posterior surface of Medial lip of Lower Adducts arm inferior angle of scapula intertubercular sulcus subscapular Medially rotates arm of humerus nerve (C5,C6) Subscapularis Subscapular fossa (most Lesser tubercle of Upper and Medially rotates arm -RC of the anterior surface of humerus lower Helps hold the head of scapula) subscapular the humerus in glenoid nerves cavity (C5,C6,C7) RC- rotator cuff muscles o SITS muscles have the primary function of holding the humeral head in the glenoid cavity of the scapula 19  Triangle of auscultation o Superior horizontal border of latissimus dorsi o Medial border of scapula o Inferolateral border of trapezius Anastomosis of arteries of scapula o Transverse cervical artery from thyrocervical trunk of subclavian artery Gives off dorsal scapular artery o Suprascapular artery From thyrocervical trunk o Subscapular artery from axillary artery Divides into circumflex scapular artery and Thoracodorsal artery Anastomosis: connection of two or more vessels, usually between multiple branches of an artery; provide numerous potential detours if the pathway is obstructed 20  Quadrangular space o Boundaries Superior: teres minor Inferior: teres major Lateral: surgical neck of humerus Medial: long head of triceps o Contents Axillary nerve Posterior circumflex humeral artery Triangular space (upper) o Boundaries Superior: teres minor Inferior: teres major Lateral: long head of triceps o Contents Circumflex scapular artery Triangular interval (lower) o Boundaries Superior: subscapularis (anteriorly) and teres major (posteriorly) Medial: long head of triceps Lateral: humerus o Contents Radial nerve Profunda brachii vessels 21