Thorax: The Pectoral Region Flashcards
Name two parts (and constituents) of the pectoral region.
•Superficial compartment constitutes the breast, superficial fascia and skin.
•Deep compartment constitutes the muscles and associated structures.
What do we mean when we say the muscles of the pectoral region are axio-appendicular?
-They extend from the thoracic cage to the bones of the upper limb.
Name and briefly describe the three subcutaneous nerves of the pectoral region.
•Supraclavicular nerves
-They extend from the cervical plexus in the neck.
-They supply skin over upper thoracic wall.
•Lateral cutaneous nerves
-Branch from the intercostal nerves.
-Supply skin over lateral thoracic and abdominal walls.
•Anterior cutaneous nerves
-Branch from the intercostal nerves.
-Supply skin over the anterior thoracic and abdominal walls.
Dermatomes for:
A. Nipple
B. Xiphoid process
C. Umbiculus
A. T4
B. T6
C. T10
What are the three branches of the intercostal nerves?
-Lateral cutaneous
-Anterior cutaneous
-Small collateral
What are the three blood vessels of the pectorial region and their branches?
•Descending thoracic aorta
-Posterior intercostal and subcostal branches.
•Subclavian artery
-Internal thoracic branches
-Supreme intercostal branches
•Axillary artery
-Superior thoracic branches
-Lateral thoracic branches
-Thoraco-acromial branches
Name the four pectoral muscles
-Pectoralis major muscle
-Pectoralis minor muscle
-Subclavius muscle
-Serratus anterior
What is the origin, insertion, innervation and action of the pectoralis minor muscle?
ORIGIN
-Anterior surface of rib 3-5.
-Deep fascia over intercostal spaces 3-5.
INSERTION
-Coracoid process of scapula.
INNERVATION
-Medial pectoral nerve
ACTION
-Depression of the tip of the shoulder.
-Protraction of scapula.
What is the origin, insertion, innervation and action of the serratus anterior?
ORIGIN
-Lateral surface of upper 8-9 ribs.
-Deep fascia overlying related intercostal spaces.
INSERTION
-Medial border of scapula.
INNERVATION
-Long thoracic nerve
ACTION
-Protraction and rotation of scapula.
-Keeps the medial border and inferior angle of the scapula against the thoracic wall.
What is the origin, insertion, innervation and action of the pectoralis major muscle?
ORIGIN
-Clavicular head, abdominal head and sternal head.
INSERTION
-Lateral lip of the intertubercular sulcus (humerus).
INNERVATION
-Medial and lateral pectoral nerves
ACTION
-Adduction
-Medial rotation and flexion of humerus.
What is the origin, insertion, innervation and action of the subclavius muscle?
ORIGIN
-Rib 1 @ junction btwn the rib and costal cartilage.
INSERTION
-Groove on inferior surface of middle 1/3 of clavicle.
INNERVATION
-Nerve to subclavius.
ACTION
-Depression of the tip of the shoulder.
-Pulls the clavicle medially to stabilise the sternoclavicular joint.
What are the two extrathoracic muscles?
External oblique muscle
Ructus abdominis muscle
What is the origin, insertion, innervation and action of the rectus abdominis muscle?
ORIGIN
-Pubic crest and tubercle
-Pubic symphysis
INSERTION
-Costal cartilages of ribs 5-12
-Xiphoid process
INNERVATION
-Anterior rami of lower 6 thoracic spinal nerves.
ACTION
-Compresses abdominal contents
-Tenses abdominal wall
-Flexes vertebral column
What is the origin, insertion, innervation and action of the external oblique muscle?
ORIGIN
-Muscle slips of outer surface of lower 8 ribs.
INSERTION
-Aponeurosis ending at linea alba.
-Lateral lip of pubic crest.
INNERVATION
-Anterior rami of lower 6 thoracic spinal nerves.
ACTION
-Compresses abdominal contents.
Fascia found in the pectoral region?
Clavicopectoral fascia
What does the clavicopectoral fascia enclose?
-Partially encloses the subclavius muscle, completely encloses the pectoralis minor muscle.
Structures that passes through the clavicopectoral fascia (4)
-Cephalic vein
-Lymphatics
-Thoraco-acromial artery
-Lateral pectoral nerve
Between which two ribs do breast lie? (Generally)
2nd and 6th ribs
Where does the nipple generally lie?
Lies over the 4th intercostal space
What do we call the superolateral extension around the pectoralis major muscle?
Axillary tail/ process
Lobules converge to form which structure?
Lactiferous ducts
Circular pigmented area that surrounds the nipple.
Areola
More abundant component in non-lactating female?
Fat
Most abundant component in lactating females?
Glandular tissue
Layer of loose connective tissue which separates the breast from the deep fascia?
Retromammary space
Explain the arterial supply of the breast (5)
- Axillary artery
-Superior thoracic artery
-Lateral thoracic artery
-Subscapular artery
-Thoraci-acromial artery - 2nd to 4th posterior intercostal arteries
- Internal thoracic arteries
Venous drainage of the breast? (3)
-Axillary vein
-Internal thoracic vein
-Posterior intercostal veins
Nerve supply of the breast
-2nd to 6th intercostal nerves with the nipple being specifically innervated by the 4th intercostal nerve.
Lymphatic drainage of the breast
-Most drain into the axillary lymph nodes.
-Most of the remaining into the parasternal nodes.
-Some into the intercostal nodes.
Five groups of the axillary lymph nodes
-Apical
-Central
-Anterior (pectoral)
-Posterior (subscapular)
-Lateral (humeral)
Where do apical nodes drain into?
-The subclavian trunks
Where does the parasternal nodes drain into?
-Bronchomediastinal trunks
Where does the intercostal nodes drain into? (2)
-Bronchomediastinal trunks and thoracic duct.
