Pectoral Anatomy Flashcards
Costal margin
Costal cartilage of Ribs 7-10
passes to 11 and 12 inferiorly
Thoracic vertebrae features
Heart shaped body
Articular facets for ribs
Large articular facet on transverse process
Superior and inferior demi-facets on body
Identify the vertebra
Thoracic
Features of typical ribs
Atypical ribs
Atypical I 2 10 11 12 1 important clinically because of it close relationship to lower nerves of the brachial plexus and main vessels of arm
True, false and floating ribs
True ribs: 1 - 7
False ribs: 8 – 10
Floating ribs: 11, 12
All ribs articulate posteriorly with the thoracic vertebrae
Features of pectoral region
Located on the anterior chest wall
Contains muscles that exert force on the upper limb: Pectoralis major, Pectorails minor, Serratus anterior and Subclavius
Pectoralis major – most superficial
Pectoralis minor – deep to major
Serratus anterior – more laterally located, forming the medial border of the axillary region
Subclavius – small, located directly beneath the clavicle
– Offers some minor protection of neurovascular structures in cases of clavicular fracture
Innervation of pectoralis major
Lateral and medial pectoral nerves
Blood supply of pectoralis major
Pectoral branches of thoracoacromial artery, perforating branches of internal thoracic artery
Identify the muscle here
Pectoralis minor
Innervation of pectoralis minor
Medial pectoral nerve
Vasculature of pectoralis minor
thoracoacromial, superior thoracic and lateral throacic
Identify the nerves
Innervation of serratus anterior
Long thoracic nerve
Blood supply of serratus anterior
Superior and lateral thoracic
Identify the muscle
Serratus anterior
Innervation and blood supply of subclavius muscle
Nerve to subclavius
Vasculature: clavicular branch of thoracoacromial and suprascapular
Axilla
A pyramid-shaped region between the upper thoracic wall and the arm
Passageway for neurovascular and muscular structures to enter and leave the upper limb
Apex: open, also known as axillary inlet
4 walls: Lateral, Medial, Anterior and Posterior
Apex of axilla
Space between the cervicoaxillary canal between the 1st rib, clavicle and superior scapula
Base of axilla
Skin and fasciae (deep and superficial) at approximately level of 4th rib (shown as 5th rib on this diagram)
What is the cervicoaxillary canal?
TheCervicoaxillary canalis the passageway that extends between the neck and the upper limb through which the long thoracic nerve and other structures pass. Its structure is defined by being posteriorly bordered by the scapula, anteriorly by the clavicle, and medially by the first rib.
Axilla medial wall
1st to 4-5th ribs, intercostal muscles and serratus anterior muscle
Where does the axillary nerve originate and what branches does it have?
Axillary nerve origins from the posterior cord of the brachial plexus. It has cutaneous and muscular branches.
Axilla lateral wall
Lateral wall: Intertubercular groove of the humerus
The lateral wall of the axilla is constituted by the intertubercular groove of the humerus, where the Pectoralis major attaches
Axilla anterior wall
Anterior wall: Pectoralis major and minor (and associated fascia)
Axilla posterior wall
Posterior wall: Latissimus dorsi, teres major and subscapularis
Axillary artery begins and ends at…
The axillary artery begins at the lateral border of the 1st rib and ends at the inferior border of Teres major.
Pectoralis minor forms the boundary between the parts (1-2-3) of the axillary artery. Each part has branches that supply specific muscles.
After passing the inferior border of the Teres major, the axillary artery becomes the brachial artery.
Brachial artery is a continuation of what?
So the brachial artery is a continuation of the axillary artery and it runs along the medial aspect of the arm. It then bifurcates into the radial and ulnar arteries at about 1cm distal to the elbow joint.
Axillary vein
The axillary vein follows the same path of the axillary artery and its parts are divided following the same criteria.
After the boundary defined by the Teres major, the axillary vein becomes the basilic vein
The vein runs medially to the artery. After the teres major, the axillary vein becomes the basilic vein, which runs along the medial aspect of arm and forearm down to the dorsal hand.
What 5 groups are axillary lymph nodes divided into?
P= Pectoral (AKA anterior) H= Humeral (AKA lateral) S= Subscapular (AKA posterior) C= Central A= Apical (or infraclavicular)
Sc= Supraclavicular are not strictly considered
within the group of axillary lymph nodes but it
is where the axillary lymph nodes drain into.
What areas do each of the lymph nodes drain?
Humeral = upper limb, Subscapular = shoulder region, Pectoral = lateral breast.
These then drain into the central nodes -> apical nodes -> scapular nodes
lymph nodes a the top (Supraclavicular) then drain into the right lymphatic duct.
Thoracic duct is on the left side.
Axillary nerve
The Axillary nerve originates from the brachial plexus (posterior cord) and carries nerve fibres from C5-C6.
It provides motor innervation to the Deltoid and Teres minor muscles and carries sensory information from the shoulder joint.
What is the axillary sheath?
Is a layer of fascia that contains the:
- Axillary vein
- Axillary artery
- Cords and branches of the brachial plexus.
- It protects these structures from becoming trapped or damaged by the surrounding muscles during movements.
- The sheath is an extension of the deep cervical fascia, it enters the arm lateral to the base of the axilla.
Breast:
Overlies the 2nd–6th rib
Two-thirds of it rests on pectoralis major, one-third on serratus anterior
Lower medial edge just overlaps the upper part of the rectus sheath
Nipple located at level of 4th intercostal space in males and young females
Divided into quadrants
- Medial and lateral rather than ‘inner’ and ‘outer’
Suspensory ligaments of Cooper
strong fibrous processes running form dermis of skin to deep layer of superficial fascia and through the breast
Mammary gland
Modified sweat gland located in the superficial fascia
The axillary tail extends superolaterally into the axilla
It has 15-20 secretory lobules of glandular tissue, separated by fibrous septa that radiate from the nipple
Each lobule opens by a lactiferous duct onto the tip of the nipple, and each duct enlarges to form a lactiferous sinus, which serves as a reservoir for milk during lactation
Blood supply to breast
To the medial breast is via the internal thoracic artery (medial mammary and anterior perforating branches)
To the lateral part of the breast:
- Pectoral branches of the thoracoacromial
- Lateral mammary branches of the posterior intercostal arteries (spaces 2-4)
- Lateral mammary branches of lateral thoracic
Veins correspond, draining into the axillary vein and then the internal thoracic veins
Breast lymphatics
The distribution of lymph nodes follow a pattern
The largest lymph nodes are located where peripheral lymphatics connect with the trunk , such as the groin, axillae and base of the neck
Particular importance to the lymph nodes in the axilla
Frequent development of cancer in the mammary gland
Subsequent dissemination of the malignant cells along lymph vessels to the nodes
There are three groups of lymph nodes that receive lymph from breast tissue – the axillary nodes (75%), parasternal nodes (20%) and posterior intercostal nodes (5%).
Lymph nodes of axilla
Where in the breast does cancer occur?
Often occurs in the upper lateral quadrant
As it enlarges it can attach to the Cooper ligaments, producing shortening of the ligaments and causing dimpling of the overlying skin
Cancer may also attach to and shorten the lactiferous ducts, resulting in a retracted or inverted nipple
Cancer may also invade the deep fascia of the Pectoralis major muscle so that contraction of the muscle causes an upward movement of the entire breast
Metastasis commonly occurs through the lymph nodes. It is most likely to be the axillary lymph nodes that are involved.
They become stony hard and fixed.
Following this, the cancer can spread to secondary sites such as the liver, lungs, bones and ovary.
