The Pectoral Region Flashcards
What are the features of the clavicle?
Name its parts.
A subcutaneous and easily palpable bone.
Articulates medially with the manubrium of the sternum at the sternoclavicular joint.
Articulates laterally with the acromion of the scapula at the acromioclavicular joint.
There is also a coracoclavicular ligament which comes from the conoid tubercle and trapezoid ridge of the clavicle and goes to the coracoid process of the scapula.
Acts to attach the upper limb to the trunk, protect neurovascular structures, transmits force from upper limb to the axial skeleton.
Fall on the shoulder or outstretched hand may break the clavicle. The middle of the shaft is the weakest point.
What are the features of the scapula?
Name its parts.
Triangular flat bone.
Articulates with the humerus at the glenohumeral joint, and with the clavicle at the acromioclavicular joint.
The hook-like projection is called the coracoid process. The large inward depression is called the subscapular fossa.
The glenoid fossa articulates with the head of the humerus with the supraglenoid tubercle above and the infraglenoid tubercle below.
Posteriorly, the spine splits it into the supraspinatus fossa above and the infraspinatus fossa below.
What is winged scapula?
The serratus anterior is innervated by the long thoracic nerve and acts to hold the scapula against the rib cage. If this is damaged, and therefore paralysing the serratus anterior, the scapula is no longer held against the rib cage giving a ‘winged scapula’ - protruding out the back.
What are the features of the sternum?
Name its parts.
T-shaped bone in the midline of the thorax.
Superior portion is called the manubrium. The top of which is the suprasternal/jugular notch.
Fossa either side are the location for the sternoclavicular joints.
The manubrium joins the body to create the sternal angle, which marks the level of the 2nd costal cartilage.
The body has a number of facets that articulate with ribs 3-6.
Xiphoid process is located at the level of T10.
What are the features of the humerus?
Name its parts.
Articulates at the glenoid fossa of the scapula forming the glenohumeral joint.
At the elbow, the humerus articulates with the head of the radius and trochlear notch of the ulnar.
ANTERIORLY the humerus is made up of the head, the greater tubercle laterally (attachment site for most rotator cuff muscles) and the lesser tubercle medially (attachment site for subacpularis). The intertubercular groove houses the tendon of the long head of the biceps brachii.
On the shaft there is a roughened patch, where the deltoid muscle attaches, known as the deltoid tuberosity. The radial groove holds the radial nerve and profunda brachii artery. The coracobrachialis, deltoid, brachialis, brachioradialis and triceps brachii all attach to the shaft.
POSTERIORLY the lateral and medial borders of the humerus form supraepicondylar ridges. The projections of bone laterally and medial are known as the epicondyles and can be palpated at the elbow. The ulnar nerve passes in a groove on the posterior aspect of the medial epicondyle. The trochlea is located medially, and extends onto the posterior aspect of the bone. Lateral to the trochlea is the capitulum, which articulates with the radius.
Also located on the distal portion of the humerus are three depressions, known as the coronoid, radial and olecranon fossae. They accommodate the forearm bones during flexion or extension at the elbow.
How are typical and atypical ribs different?
Typical ribs consist of a head, neck and body. The head is made up of two articular facets, one that attaches to the numbered vertebrae and one that attaches to the vertebrae above. The neck contains a roughed tubercle where the transverse process of the corresponding vertebrae meets the rib. The body has a groove for neurovascular supply of the thorax.
Ribs 1, 2, 10, 11, 12 are atypical. Rib 1 is shorter and wider and contains only one articular facet, it also has grooves for subclavian vessels. Rib 2 is thinner and longer and has a roughened area for the attachment of the serratus anterior. Rib 10 only has one articular facet. Rib 11 and 12 have no neck and only have one articular facet.
How do different ribs articulate?
Ribs 1-7 attach directly to the sternum. Ribs 8-10 attach to the costal cartilages. Ribs 11 and 12 don’t attach anteriorly and are called ‘floating ribs’.
Each rib forms two joints with the vertebrae:
Costotransverse joint: Between the tubercle of the rib and the transverse costal facet of the vertebrae.
Costovertebral joint: Between the head of the rib, superior costal facet of the corresponding vertebrae, and the inferior costal facet of the vertebrae above.
What are the anatomical positions on the chest wall?
Midline: down the centre of the sternum
Mid-clavicular line: down the middle of the clavicle
Anterior axillary line: from the fold of muscle at the anterior of the axilla
Mid-axillary line: from the middle of the axilla and usually the widest part of the thorax
Posterior axillary line: from the fold of muscle at the posterior of the axilla
What are the features of the breast?
Extends from the 2nd to the 6th ribs. Mostly overlies the pectoralis major. May have an axillary tail and can be in the superficial fascia or deep with the lymph nodes.
There is fascia covering the pectoralis major (the pectoral fascia), then the retromammary space containing loose connective tissue, then the posterior capsule and then the breast itself.
What is the breast’s blood supply?
Supplied by branches from the axillary, internal mammary and intercostal arteries. The venous connection to the intercostal veins is a route by which malignancy can spread into the vertebrae as they drain into the vertebral venous plexus.
How is the breast drained by the lymph nodes?
Lymph drainage of the breast medial to the nipple passes through the intercostal spaces to lymph nodes within the thorax (the internal mammary/thoracic lymph nodes).
Lymph drainage of the lateral breast drains into lymph nodes in the axilla (75%).
How does breast cancer spread and removed?
Cancer of the breast develops in the cells of acini and ducts and spreads to the surrounding tissues as well as into the lymphatics and veins. Simple mastectomy (breast tissue), axillary clearance (dissection of the axilla), radical mastectomy (breast and pectoral muscles) may be performed. For a lymph node biopsy, a dye or radioactive tracer is injected into the area around the tumour, the path is followed and lymph nodes may be removed and histologically examined.
What is the pectoralis major?
Large and fan shaped and consists of a sternal (originates from the sternum, first 6 costal cartilages and external oblique aponeurosis) and clavicular head (originates from the mid clavicle). Both heads attach into the intertubercular groove of the humerus.
Pectoralis major is the most superficial.The underside of the pectoralis muscle is not attached to the chest wall, meaning that malignancies and infections can be present here.
Acts to adduct and medially rotate the upper limb. It draws the scapula anterioinferiorly. The clavicular head acts to flex the arm.
Supplied by the lateral and medial pectoral nerves.
What is the pectoralis minor?
It lies under the pectoralis major. Originates from the 3rd-5th ribs and inserts into the coracoid process of the scapula.
Acts to stabilise the scapula by drawing it anterioinferiorly against the thoracic wall.
Innervated by the medial pectoral nerve.
What is the serratus anterior?
Formed of several strips which originate from the lateral parts of ribs 1-8, they attach to the medial border of the scapula. Acts to rotate the scapula, allowing the arm to be raised over 90 degrees. Also holds the scapula against the rib cage.
Innervated by the long thoracic nerve. If this is damaged, therefore paralysing the serratus anterior, the scapula is no longer held against the rib cage giving a ‘winged scapula’.
