L13. Thoracic Walls Anatomy Flashcards
Define the borders of the breast
Horizontally between the lateral borders of the sternum and the mix axillary line.
Vertically between the level of second rib and the sixth rib
It is often divided into quadrants
Where in the breast do most carcinomas occur?
The upper lateral quadrants have an axillary tail of glandular tissue. The more glandular tissue present, the higher the risk of carcinoma development = suprolateral extension
What muscle do the breasts lie on?
The majority of the breast lies atop the pectoralis major muscle. Some part of the breast (up to 1/3) lies on the serratus anterior muscle
Where is and what function does the retromammary space/bursa play?
lies between the muscle and the actual glandular tissue of the breast. It is a small space for breast implants and allows for the breasts to move.
With what does the breast share its supply & drainage?
Shares supply with the thoracic cage and the upper limb:
Laterally = axillary artery and vein (shared with upper limb)
Medially = internal thoracic artery and vein into the azygous system
What lymph nodes drain the breasts?
Draining to the axillary lymph nodes and the intercostal lymph nodes and the parasternal nodes
What are the main components of the anterior cage (3)?
The ribs, the sternum and manubrium and costal cartilage
Classify the ribs
Ribs 1-7: True ribs articulating with costal cartilage onto the sternum
Ribs 8-10: false ribs which have costal cartilage articulating with the costal cartilage of the rib above (costal margin)
Ribs 11 and 12: floating ribs with costal cartilages that do not articulate at all
What are the main components of the posterior cage? (3)?
Ribs, vertebrae and associated IV discs
Describe the typical rib? (6) Define their articulations and/or functions
- Head with 2 facets: form the costovertebral joints on two consecutive vertebral bodies
- Neck
- Tubercle with medial facet that articulates with the transverse process and a lateral that forms a ligament attachment site
- Shaft or body
- Costal groove
- Sternal Edge which contains a groove for costal cartilage
Where to the neurovascular structures lie in the rib?
Through the costal groove: the internal aspect of the inferior costal groove
What are the main characteristics of the thoracic vertebra? (3)
- Long, almost vertical spinous processes
- Costal facets on the body
- Long transverse processes with facets
Where do the ribs articulate to the vertebrae? What are the joints called?
The heads of the rib articulate with the superior and inferior posteriolateral joints forming the costovertebral joints.
The tubercle has a medial facet articulating with the transverse process in the costotransversal joints.
What are the ligaments that form the joints between ribs and vertebrae?
Costovertebral ligament (radial ligament)
Costotransversal ligament
What structures enclose the superior and inferior aspects of the cage?
Inferiorly: diaphragm
Superiorly: the supralateral membrane (discontinuous due to the clavical)
What major functions does the diaphragm play? (2)
Respiratory muscle (inspiration) and physically and functionally separates the contents of the thorax from the abdomen.
What are the origins of the diaphragm? (4) inferiorly
What is the insertion of the diaphragm?
Xyphoid process anteriorly
Costal margin
Arcuate ligaments of the quadratus lumborum (laterally) and the psoas major (medially)
Tips of the floating ribs
Inserts into a club shaped central tendon
What are the crura and where do they extend?
Inferior extensions of the diaphragm on the posterior wall. The left extends down to the level of L1 while the right down to L1,2,3
What nerve supplies the diaphragm?
The phrenic nerve (from C3,4,5)
What are the hiatuses of the diaphragm and where are they? (3)
IVC passes through the caval orifice at the level of T8 to the right of the midline (Through the central tendon)
The oesoephagus at the level of T10 through a muscular part of the diaphragm through the left of midline
The aorta through T12 behind the diaphragm (between the crura)
How many layers of muscle are there and what are their names?
Three:
External intercostals
Internal intercostals
Innermost intercostals
How do the muscle fibre orientations and expansion affect respiration?
External intercostal muscles are front pocket orienting downwards and forwards while
- contraction pulls the muscles and the cage open
Internal and innermost is back pocket orientated (downwards and backwards)
- contraction pulls the ribs down (not as much)
What are the external and internal intercostal membranes?
The external intercostal membrane replaces the external muscles anteriorly while the internal membrane replaces the internal intercostals posteriorly
Through what muscles do the neurovascular bundles run in between?
Between the innermost and internal intercostal muscles
In what order do the components of the bundles run?
Vein
Artery
Nerve
(from up to down)
What do the intercostal arteries branch off?
The posterior intercostal and the anterior intercostal arteries meet and anastomose laterally.
They stem of the internal thoracic artery or one of its branches.
Where do the intercostal veins drain into?
Posterior and anterior veins mirror arteries and drain into the internal thoracic vein – the azygous system drainage
What is the nerve supply of the intercostal nerves?
ventral rami of the thoracic spinal nerve which becomes the intercostal nerve
What are the three dimensions of movement?
Antero-postero dimension
Vertical (elevation and depression)
Lateral
Explain each of the dimension changes that increase cavity volume
Elevation of the upper ribs forces the sternum to push up (physically attached) and changes the A-P dimension
Lower ribs don’t articulate with the sternum and so when they are pushed up (bucket handle) then they expand the lateral dimension
What is the consequence of an increased in cavity volume?
Decreasing negative pressure in the thorax and thus sucks pressure into the lungs
