Pectoral Region & Breast Anatomy PDF

The Pectoral Region By Dr: Joseph Amin Ass. Prof. of anatomy & embryology Faculty of medicine-Zagazig university  The Pectoral Region The soft tissue overlying the anterior chest wall connecting the upper limb to the axial skeleton General arrang...

The Pectoral Region By Dr: Joseph Amin Ass. Prof. of anatomy & embryology Faculty of medicine-Zagazig university  The Pectoral Region The soft tissue overlying the anterior chest wall connecting the upper limb to the axial skeleton General arrangement  Skin  Superficial fascia (contains, cutaneous nerves ,superficial blood vessels & breast)  Pectoral fascia  Pectoralis major  - Pectoralis minor - Clavipectoral fascia - Subclavius  Serratus anterior* Cutaneous nerve supply  Supraclavicular nerves (C3,4)  Anterior cutaneous branches of intercostal nerves (T2-6)  Lateral cutaneous branches of intercostal nerves (T2-6) Pectoralis Major:  Pectoralis Major: Origin: it arises by Clavicular head: from the anterior surface of the medial 1/2 of the clavicle Sternoclavicular head: from upper 6 costal cartilages, the front of lateral sternal border and aponeurosis of external oblique Insertion: By bilaminar tendon into the lateral lip of the intertubercular groove Clavicular head …> anterior lamina Sternocostal head..> posterior lamina Nerve supply: Lateral and medial pectoral nerves N.B1. Deltopectoral groove: contains cephalic vein, deltoid branch of thoracoacromial artery and deltopectoral LN N.B2. The lower border of pectoralis major is rounded and form the anterior axillary fold Action:  Flexion  Adduction of the arm  Medial rotation (swinging of the arms during walking  Acting on the ribs: it helps deep inspiration  When the arm is fixed (gripping branch), it lifts the trunk upwards (pull-up, climbing)  It pulls the trunk forward during swimming  Pectoralis Minor: Origin: Front of (2nd ) 3rd , 4th and 5th ribs Insertion: Medial border of the coracoid process  Nerve supply: Medial pectoral nerve Action:  Protraction of the scapula  Depression of the scapula  Assists in deep inspiration  Poland syndrome: Underdeveloped pectoral muscles; usually on the right side  Subclavius: Origin: Junction of 1st rib and its costal cartilage Insertion: Subclavian groove (inferior surface of middle 1/3) Nerve supply: Nerve to subclavius Action:  Stabilizes the clavicle during movements at the shoulder joint  Clavipectoral fascia Costocoracoid membrane  Strong facial sheet stretched between subclavius above and pectoralis minor below  Structures piercing clavipectoral fascia C: cephalic vein A: acromiothoracic artery L: lateral pectoral nerve L: lymph vessels  Extension  Above, it splits to enclose subclavius muscle and attaches to clavicle  It is stretched between subclavius and the upper border of pectoralis minor  Then it splits again to enclose pectoralis minor and finally attached to axillary fascia in the floor of axilla N.B. Raising the arm causes hollowing of axilla  Serratus Anterior: Literally it is not one of the pectoral muscles Origin: By 8 digitations from the outer surfaces of upper 8 ribs (1st takes origin from 1st and 2nd ribs) Insertion: Anterior (costal) surface of the medial border of the scapula 1st, 2nd digitations …> superior angle 3rd digitation….> medial border 4th-8th digitations …> Inferior angle Nerve supply: Nerve to serratus anterior (long thoracic nerve) Action:  Main protractor of the scapula it is active in pushing & punching movements  With trapezius, lower 5 digitations laterally rotates the scapula to make abduction > 90 or raise the hand above the head  Assists in deep inspiration  trapezius serratus  Paralysis of serratus anterior:  Winging of the scapula: projection of the medial border and inferior angle of the scapula when the patients pushes against resistance Breast Definition: modified sweat gland Site: superficial fascia of pectoral region in both sexes Shape: conical, hemispherical. It has an apex (nipple & areola) and base Extension:  the base extends - from 2nd rib superiorly to 6th rib inferiorly - from sternal border medially to midaxillary line laterally  It’s upper lateral part extends below the lower border of pectoralis major, pierces the floor of axilla forming “ Axillary tail of Spence”  The nipple in nulliparous lies opposite 4th intercostal space Deep relations:  the base lies on: - pectoralis major - Serratus anterior Deep fascia - External oblique The breast is separated from the above structures by loose areolar C.T known as retromammary space Structure: Structure:  Mammary gland  Fibrofatty stroma  Skin, areola and nipple   The Mammary gland 15-20 lobes radiating from the nipple. Each lobe consists of group of acini which collects into a lactiferous duct. Lactiferous ducts (15-20) open separately on the nipple. Before they end the ducts have dilate to form lactiferous sinus. Radial incisions are preferred in breast  Fibrofatty stroma The lobes are separated by 15-20 fibrous septa called suspensory ligaments of breast or ligaments of Cooper. Each septum extends between the skin and pectoral fascia. Fat fills the space between lobes giving the breast the smooth rounded contour and softness   Covering - Nipple: conical projection which receives the openings of lactiferous ducts. In nulliparous in lies opposite 4th intercostal space. - Areola: circular pigmented area around the nipple it contains sebaceous gland which in pregnancy enlarges forming Montgomery tubercles. The color of areola is pink in nulliparous and becomes brown after pregnancy. Blood supply:  Arterial blood supply - Perforating branches of internal mammary (thoracic) artery. - Superior thoracic - Acromiothoracic (pectoral branch) - Lateral thoracic - Lateral branches of Intercostal arteries  Venous drainage - Internal thoracic vein - Axillary vein - Posterior intercostal veins Lymph Drainage: Lymph Drainage: 75% of lymph drains into axillary LN Subareolar plexus 20% of Lymph drains into Internal mammary LN Sucutaneous plexus 5% of Lymph drains into other LN Submammary plexus  upper part drain in apical group of axillary LN lateral part medial part drains drains in pectoral in parasternal group of axillary (internal mammary) LN, LN. it can reach other breast Lower medial part can reach LN in rectus sheath  Applied anatomy In breast carcinoma:  Invasion of lactiferous duct ….> retraction of the nipple and blood discharge from the nipple  Invasion of suspensory ligaments …..> skin dimpling  Invasion of subcutaneous lymphatics….> peau d’ orange  Invasion of retromammary space…..> fixation of the breast Gynecomastia (enlarged male breast): Muscles of the Back Cutaneous nerve supply  Cutaneous branches of the dorsal rami of T1-T12  Muscles Trapezius levator scapula Rhomboid minor Rhomboid major latissimus dorsi  Muscles of the back  Muscles Trapezius - Trapezius 1st layer - latissimus dorsi Latissimus dorsi - levator scapula - Rhomboid major 2nd layer - Rhomboid minor Trapezius:  Trapezius: Origin: Medial 1/3 of superior nuchal line External occipital protuberance Ligamentum nuchae Spine of C7 Spines of T1-T12  Insertion:  Upper fibers…> posterior border of the lateral 1/3 of the clavicle  Middle fibers ….> medial border of the acromion  Lower fibers…> upper lip of the spine of the scapula Nerve supply: Spinal accessory (11th cranial nerve) N.B. Trapezius is the only muscle of upper limb is not supplied by brachial plexus Action:  Upper fibers…> Eelevation of the scapula, lateral flexion of the neck  Middle fibers ….> Retraction of the scapula  Lower fibers…> Depression of the scapula  With lower 5 digitations of serratus it rotates the scapula to raise the hand above the head Latissimus dorsi:  Latissimus dorsi Origin: Spines of T6-T12 Thoracolumbar fascia Outer lip of the posterior 1/3 of iliac crest Lower 3 ribs Posterior surface of the inferior angle of the scapula Insertion:  Floor of the intertubercular groove Nerve supply: Nerve to Latissimus dorsi (Thoraco-dorsal nerve) Action:  Extension, adduction and medial rotation of the arm  Draws the trunk upward in climbing  Expulsive expiratory acts (sneezing, coughing) N.B. The lower border of latissimus dorsi forms the posterior axillary fold  Levator scapulae  Origin: Transverse processes of C1-C4  Insertion: Dorsal surface of the medial border of the scapula form the superior angle till the spine  Nerve supply: Dorsal scapular nerve ( N to rhomboids)  Action: Elevation of the scapula Fixation of the scapula  Rhomboideus minor  Origin: Lower part of ligamentum nuchae, C7 & T1 spines  Insertion: Dorsal surface of the medial border of the scapula opposite the the spine  Nerve supply: Dorsal scapular nerve ( N to rhomboids)  Action: Retraction of the scapula Fixation of the scapula  Rhomboideus major  Origin: T2-T5 spines  Insertion: Dorsal surface of the medial border from the the spine till the inferior angle  Nerve supply: Dorsal scapular nerve ( N to rhomboids)  Action: Retraction of the scapula Fixation of the scapula Before Puberty & in males: breast is small due to minimal fat and glandular tissue which does not extend beyond the areola Puberty: breast enlarges due to increase in fat more than growth of ducts Early Pregnancy: breast enlarges due to Increase in the length and branching of ducts and development of alveoli Late Pregnancy and lactation : alveoli are distended with milk.