Session 1: The Pectoral Region, Thoracic Cage and Lungs Flashcards
Where does the sternum lie?
The sternum lies anteriorly in the midline of the thoracic cage. It is composed of three parts.
- manubrium
- body
- xiphoid process/ xiphisternum
Identify these on a skeleton
Clavicle
Manubrium
Sternoclavicular joint
Suprasternal notch
Manubriosternal joint
Second rib
CostaL margin
What do the ribs form?
Twelve pairs of ribs form the anterior, lateral, and posterior walls of the thoracic cage.
What are ribs classed as?
Ribs are classed as typical or atypical. Typical ribs look similar and share common anatomical features. Atypical ribs look different to typical ribs and / or lack some of the features of typical ribs.
What are the thoracic vertebrae like?
Twelve thoracic vertebrae (T1 - T12) lie posteriorly in the midline of the thoracic cage.
The spinous processes of the thoracic vertebrae are palpable in the midline of the back.
What is the skin of the thoracic wall innervated by?
By spinal nerves T1 – T12.
What are the breasts like?
Also known as mammary glands
superficial to the muscles of the chest wall.
Breast tissue extends towards the anterior axilla (armpit) – this part of the breast is the axillary tail.
What does the breasts contain?
● Fat
● Glandular / secretory tissue arranged in lobules.
● Ducts which converge on the nipple. The areola is the region of pigmented skin that surrounds the nipple.
● Connective tissue and ligaments.
● Blood vessels and lymphatics.
What is the breast supplied by?
The breast is primarily supplied by branches from the:
● internal thoracic artery (which arises from the subclavian artery)
● axillary artery.
What artery’s are associated with the breast?
internal thoracic artery courses deep to the lateral edge of the sternum.
It gives rise to anterior intercostal arteries that supply the breast and the intercostal spaces.
Venous blood returns to the axillary and internal thoracic veins.
What is the lymphatic drainage of the breast?
Most lymph from the breast drains to lymph nodes in the axilla.
What are the five groups of lymph nodes in the axilla?
There are five groups of lymph nodes in the axilla: central, pectoral, humeral, subscapular, and apical.
What are the upper limb muscles?
● Pectoralis major is the most superficial muscle of the anterior chest wall.
● Pectoralis minor is a smaller muscle that lies deep to pectoralis major.
● Serratus anterior is a superficial muscle that sweeps around the lateral aspect of the thoracic cage.
What are rib fractures like ?
Rib fractures result from blunt trauma to the chest wall (falls, traffic accidents, assault). They are painful and the pain is typically worse on inspiration.
What are shingles?
Patients with shingles present with a red, painful, and itchy rash, typically over the chest or abdomen on one side of the body only. The rash typically appears in a strip-like distribution, as it affects dermatomes.
What is breast cancer like?
Because most lymph from the breast drains to the axillary lymph nodes, breast malignancy typically metastasizes (spreads) to these nodes first.
A malignant axillary node may be palpable as a lump in the armpit and noticed before a mass in the breast itself.
What do the intercostal spaces contain?
The spaces between the ribs are the intercostal spaces. They contain:
* three layers of intercostal muscles and their associated membranes
* an intercostal neurovascular bundle, comprising an intercostal nerve, an intercostal artery, and an intercostal vein.
What are intercostal muscles like?
The muscles in the intercostal spaces attach to the rib above and rib below. Their fibres run in different directions to each other and hence act on the ribs in different ways.
Where are the costal cartilages found?
- The anterior parts of the ribs are composed of costal cartilage.
- The ribs articulate with their costal cartilages at costochondral joints.
- The costal cartilages of ribs 1 - 7 articulate directly with the sternum at sternocostal joints – they are ‘true’ ribs.
- The costal cartilages of ribs 8 - 10 unite and join the seventh costal cartilage – they are ‘false’ ribs.
- The costal cartilages of ribs 7 - 10 form the costal margin, which is palpable.
How are ribs 11 and 12 different?
- Ribs 11 and 12 are short and do not articulate with the sternum – they are ‘floating’ ribs.
- The ribs articulate posteriorly with the thoracic vertebrae at costovertebral joints.
- Adjacent ribs are connected to each other by intercostal muscles, which lie in the intercostal spaces.
Describe the manubrium
The manubrium is the superior part of the sternum:
● the superior border has a notch in it – the suprasternal (jugular) notch.
● laterally, it articulates with the clavicle (collarbone) at the sternoclavicular joint, and with the first rib.
● inferiorly, it articulates with the body of the sternum at the manubriosternal joint, also known as the sternal angle (or the ‘angle of Louis’).
Describe the body of the sternum
● it articulates with ribs 2 – 7.
● the second rib articulates with the sternum at the sternal angle
Describe the xiphoid process of the sternum
● small and variable in shape.
● the seventh rib articulates with the inferior part of the body of the sternum and the superior part of the xiphoid process.
Which ribs are typical?
- Ribs 3 - 9 are typical ribs. They have a head, neck, tubercle, and body (shaft).
Which ribs are atypical?
- Ribs 1 - 2 and 10 - 12 are atypical, for various reasons. For example, ribs 1, 11 and 12 are much shorter than typical ribs.
What forms the superior thoracic aperture?
The manubrium, the first ribs and the first thoracic vertebra
This the ‘passageway’ through which structures pass between the neck and the thorax.
What do the thoracic vertebrae articulate with?
articulates with the posterior parts of the ribs at costovertebral joints.
- the head of the rib articulates with the vertebral body
- tubercle of the rib articulates with the transverse process of the vertebra
How do you describe a specific location on the chest wall?
Using two sets of coordinates:
1. Ribs
2. Series of vertical lines
At what level is the second rib?
Sternal angle
What imaginary vertical lines must you know? (Show them)
- Midsternal line
● Midclavicular line
● Anterior axillary line
● Mid-axillary line
● Posterior axillary line
● Scapular line
● Midvertebral line
How does sensation from the skin of the thoracic wall reach our conscious perception?
via somatic sensory fibres in the spinal nerves
What is a dermatome?
A dermatome is an area of skin innervated by a single spinal nerve. Each pair of thoracic spinal nerves supplies a ‘strip’ of skin around the chest wall.
What Innervates the skeletal muscles of the thoracic walls?
Somatic motor fibres in spinal nerves T1 -12
When does the breast grow?
during puberty and pregnancy.
After menopause, the breast atrophies
What nerves supply the breasts?
somatic nerves and sympathetic fibres via the intercostal nerves
Somatic sensory fibres innervate the skin of the breast. Sympathetic fibres innervate smooth muscle in the blood vessel walls and nipple.
What do the lymph nodes do?
● They drain the breast, upper limb, chest wall, scapular region, and the abdominal wall.
● The apical nodes (in the apex of the axilla) receive lymph from all other lymph nodes in the axilla.
What are the functions of the upper limb muscles?
prime function - move the upper limb pectoralis major adducts the humerus; pectoralis minor and serratus anterior protract the scapula
However, they can also function as accessory muscles of breathing because they attach to the ribs and hence can move the ribs if the humerus and scapula are fixed. In patients, use of these muscles is a sign of respiratory distress.
What are the intercostal muscles?
Within each intercostal space, there are three layers of muscles:
• External intercostal is most superficial.
• Internal intercostal lies deep to the external intercostal.
• Innermost intercostal lies deep to the internal intercostal.
What is the function of the intercostal muscles?
Collectively they move the ribs and alter the dimensions of the thoracic cavity with inspiration (breathing in) and expiration (breathing out).
How can you investigate a rib fracture?
If there is concern about multiple rib fractures or a pneumothorax, a chest X-ray or CT scan may be required to assess the extent of the injury.