Pectoral Region Flashcards
Surface Landmarks of Pectoral Region
- Clavicle : palpable throughout, acromioclavicular joint laterally, medially sternoclavicular joint (may be covered by sternocleidomastoid muscle), both joints palpable
- jugular notch: interclavicular notch, suprasternal notch - superior border of manubrium sterni
- Sternal angle (angle of louis): about 5 cms below the jugular notch - 2nd costal cartilage laterally - marks the manubriosternal joint
- Epigastric fossa: pit of stomach: overlies xiphoid process- infrasternal depression - 7th costal cartilage
- Nipple - variable position - male and immature female 4th intercostal space
- Midclavicular line: Middle of clavicle, tip of 9th cartilage and midinguinal point
- Infraclavicular fossa/ Deltopectoral triangle: Medially pectoralis major - laterally anterior fibres of deltoid - superiorly clavicle - below the junction of medial 2/3 and lateral 1/3 of clavicle
- Coracoid process: 2-3 cms below the clavicle - deep palpation- overlapped by the anterior fibres of the deltoid-lateral to infraclavicular fossa
- Acromion process: acromial angle - posterior surface of lateral border - acromioclavicular joint anterior surface of the medial border - subcutaneous
- Deltoid: triangular muscle- apex downwards- deltoid tuberosity (humerus) - acromion
- Axilla: Pyramidal space b/w arm and chest - abducted arm floor raised- anterior and posterior folds stand out - Anterior axillary fold, lower border of pectoralis major- Posterior axillary fold, tendon of latissimus dorsii winding round fleshy teres major- Medial wall, upper 4 ribs with serratus anterior muscle - Laterally by head of humerus covered by corocobrachialis and short head of biceps brachii
- Midaxillary line: vertically midway posterior and anterior folds of axilla
Contents of Superficial Fascia of Pectoral Region
- Cutaneous nerves derived from the cervical plexus and from the intercostal nerves
- Cutaneous branches from the internal thoracic and posterior intercostal arteries
- The platysma
- Mammary gland
Cutaneous nerves of the pectoral region
- Medial, Intermediate, Lateral Supraclavicular nerves - branches of the cervical plexus (C3,C4)- Supply the skin over the upper half of the deltoid and the from the clavicle down to the second rib
- The anterior(T2-T6) and lateral(T3-T6) cutaneous branches of the 2nd to 6th intercostal nerves- supply skin below the level of 2nd ribs
- Intercostabrachial nerve of the T2 supply the floor of the axilla and upper half of the medial side of the arm
Cutaneous vessels of the pectoral region
- Anterior cutaneous nerves are accompanied by the perforating branches of the internal thoracic artery (the 2nd, 3rd, 4th branches of this is larger in females to supply the breast)
- Lateral cutaneous nerves are accompanied by the lateral cutaneous branches of the posterior intercostal artery
what type of tissue is the breast
modified sweat glands which are rudimentary in males and immature females
Situation of the mammary gland
- Lies in the superficial fascia of the pectoral region
- Divided into four quadrants: upper medial, lower medial, upper lateral, lower lateral
- Axillary tail of spence: small extension of the upper lateral quadrant - pierces the deep fascia through an opening called foramen of langer and lies in the axilla
Extent of the mammary gland
Vertically - 2nd to 6th ribs
Laterally - Midaxillary line to the lateral border of the sternum
Deep relations of the mammary gland
- lies on the pectoral fascia (deep fascia) covering pectoralis major
- deeper to this lies three muscles - pectoralis minor, serratus anterior and external oblique
- Retro-mammary space: b/w Pectoral fascia and the breast, areolar tissue (reason for movement of the breast over the muscle pectoralis major)
Structure of the breast
Skin :
Nipple - conical projection below centre of breast at the 4th intercoastal space 10 cms from the midline - pierced by 15-20 lactiferous ducts - circular muscles ( stiffen) and longitudinal muscles(flatten) - rich in nerves with modified sweat glands and sebaceous glands
Areola - Pigmented circular area forming the base of the nipple- rich in modified sebaceous glands(at the outer margin especially)(become enlarged to form the tubercles of montgomery during pregnancy which lubricate and prevent cracking during lactation)- lactiferous sinus lies below the areola
Note: Skin of areola and nipple is devoid of hair and doesnt have fat subjacent to it
Parenchyma:
compound tubulo-alveolar gland which secretes milk
15-20 lobes, each lobe made of a cluster of alveoli and is drained by lactiferous ducts which all coverge towards the nipple
near termination, lactiferous duct has a termination called the lactiferous sinus
Alveolar epithelium —- Cuboidal in resting and columnar during lactation
note- in distended alveoli, cells may appear cuboidal due to stretching but are much larger than those in resting
Ducts - smaller by columnar, larger by 2 or more layer of cells and the terminal parts of the lactiferous ducts by stratified keratinised squamous epithelium
Myoepitheliocytes- B/w basement membrane and epithelium in alveoli and around the ducts
Stroma:
Partly fibrous and partly fatty
supports the breasts
fibrous stroma forms septa- suspensory ligaments of cooper ( from the superficial fascia) anchoring gland to the pectoral fascia
fatty stroma- main bulk of breast, absent under areola and nipple
Blood supply of the mammary gland
It is extremely vascular, posterior surface is relatively avascular
Present a anastomostic venous circle
Arteries
1. Internal thoracic artery (branch of subclavian) through its perforating branches
2. Lateral thoracic, Superior thoracic and acromiothoracic (thoracoacromial) branches of the axillary artery
3. Lateral branches of the posterior intercostal artery
Veins
1. Superficial veins - drain into the internal thoracic vein and into the superficial veins of the lower part of the neck
2. Deep veins - drain into the axillary and posterior intercostal veins
