L13. Thoracic Walls Anatomy

Question 1

Define the borders of the breast

Answer 1

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

Question 2

Where in the breast do most carcinomas occur?

Answer 2

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

Question 3

What muscle do the breasts lie on?

Answer 3

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

Question 4

Where is and what function does the retromammary space/bursa play?

Answer 4

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.

Question 5

With what does the breast share its supply & drainage?

Answer 5

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

Question 6

What lymph nodes drain the breasts?

Answer 6

Draining to the axillary lymph nodes and the intercostal lymph nodes and the parasternal nodes

Question 7

What are the main components of the anterior cage (3)?

Answer 7

The ribs, the sternum and manubrium and costal cartilage

Question 8

Classify the ribs

Answer 8

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

Question 9

What are the main components of the posterior cage? (3)?

Answer 9

Ribs, vertebrae and associated IV discs

Question 10

Describe the typical rib? (6) Define their articulations and/or functions

Answer 10

1. Head with 2 facets: form the costovertebral joints on two consecutive vertebral bodies
2. Neck
3. Tubercle with medial facet that articulates with the transverse process and a lateral that forms a ligament attachment site
4. Shaft or body
5. Costal groove
6. Sternal Edge which contains a groove for costal cartilage

Question 11

Where to the neurovascular structures lie in the rib?

Answer 11

Through the costal groove: the internal aspect of the inferior costal groove

Question 12

What are the main characteristics of the thoracic vertebra? (3)

Answer 12

1. Long, almost vertical spinous processes
2. Costal facets on the body
3. Long transverse processes with facets

Question 13

Where do the ribs articulate to the vertebrae? What are the joints called?

Answer 13

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.

Question 14

What are the ligaments that form the joints between ribs and vertebrae?

Answer 14

Costovertebral ligament (radial ligament)

Costotransversal ligament

Question 15

What structures enclose the superior and inferior aspects of the cage?

Answer 15

Inferiorly: diaphragm
Superiorly: the supralateral membrane (discontinuous due to the clavical)

Question 16

What major functions does the diaphragm play? (2)

Answer 16

Respiratory muscle (inspiration)
and physically and functionally separates the contents of the thorax from the abdomen.

Question 17

What are the origins of the diaphragm? (4) inferiorly

What is the insertion of the diaphragm?

Answer 17

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

Question 18

What are the crura and where do they extend?

Answer 18

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

Question 19

What nerve supplies the diaphragm?

Answer 19

The phrenic nerve (from C3,4,5)

Question 20

What are the hiatuses of the diaphragm and where are they? (3)

Answer 20

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)

Question 21

How many layers of muscle are there and what are their names?

Answer 21

Three:
External intercostals
Internal intercostals
Innermost intercostals

Question 22

How do the muscle fibre orientations and expansion affect respiration?

Answer 22

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)

Question 23

What are the external and internal intercostal membranes?

Answer 23

The external intercostal membrane replaces the external muscles anteriorly while the internal membrane replaces the internal intercostals posteriorly

Question 24

Through what muscles do the neurovascular bundles run in between?

Answer 24

Between the innermost and internal intercostal muscles

Question 25

In what order do the components of the bundles run?

Answer 25

Vein
Artery
Nerve
(from up to down)

Question 26

What do the intercostal arteries branch off?

Answer 26

The posterior intercostal and the anterior intercostal arteries meet and anastomose laterally.
They stem of the internal thoracic artery or one of its branches.

Question 27

Where do the intercostal veins drain into?

Answer 27

Posterior and anterior veins mirror arteries and drain into the internal thoracic vein – the azygous system drainage

Question 28

What is the nerve supply of the intercostal nerves?

Answer 28

ventral rami of the thoracic spinal nerve which becomes the intercostal nerve

Question 29

What are the three dimensions of movement?

Answer 29

Antero-postero dimension
Vertical (elevation and depression)
Lateral

Question 30

Explain each of the dimension changes that increase cavity volume

Answer 30

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

Question 31

What is the consequence of an increased in cavity volume?

Answer 31

Decreasing negative pressure in the thorax and thus sucks pressure into the lungs