Thoracic wall

Question 1

Describe the arrangement of the ribs.

Answer 1

Ribs 1-7 are true ribs - their costal cartilages articulate directly with the sternum
Ribs 8-10 are false ribs - their costal cartilages join onto the costal cartilages of the ribs above them before joining the sternum
Ribs 11 + 12 are floating ribs - they have costal cartilage but it doesn’t articulate with anything. There is not connection with the sternum.

Question 2

What do the ribs articulate with?

Answer 2

The costal cartilage anteriorly and the vertebral column via the head and tubercle of the rib

Question 3

Where does the first rib attach medially?

Answer 3

Manubrium - just inferior to the sternoclavicular joint

Question 4

What defines the thoracic inlet (superior thoracic aperture)?

Answer 4

1st rib and costal cartilage, 1st thoracic vertebra (T1) and the manubrium

Question 5

Describe the structure of the diaphragm.

Answer 5

The diaphragm has a central tendon and it is attached to the costal margin and vertebrae.

Question 6

What is the role of the intercostal muscles?

Answer 6

They stiffen the chest wall to improve the efficiency of breathing movements.

Question 7

How are the intercostal muscles arranged? State the directions of the muscle fibres.

Answer 7

External intercostal - inferomedially (like hands in pockets) - downwards and laterally from lower border of rib above to rib below. Replaced by anterior intercostal membrane at costo-chondral (rib-cartilage) junction

Internal Intercostal - attachments begin anteriorly at the sternum- from lower border of rib above to rib below - fibres directed at right angles to external intercostals.
Replaced by membrane posteriorly

Innermost intercostal

Question 8

How many intercostal nerves are there?

Answer 8

11 pairs (T1 - T11) and a subcostal nerve (T12) 
They involve a mix of motor and sensory nerves and supply the intercostal spaces

Question 9

Describe the branching of intercostal nerves

Answer 9

There is a lateral cutaneous branch (which splits into an anterior branch and a posterior branch)
There is an anterior cutaneous branch (which splits into a medial branch and a lateral branch)

Innervate the overlaying skin

Question 10

Where are the intercostal neurovascular bundles found?

Answer 10

Internal intercostal and innermost intercostal

Just below the bottom edge of a rib

Question 11

What implications does this have for putting a needle or chest drain through the thoracic wall?

Answer 11

As the neurovascular bundle is just below the bottom edge of a rib, you would want to insert the needle just above the superior edge of a rib to avoid piercing the neurovascular bundle
Vein, artery & nerve run just below rib deep to internal intercostal
VAN
Nerve is often not protected by the groove so is most at risk when upper aspect of intercostal space is perforated

Question 12

What are the borders for the safe area for inserting a chest drain?

Answer 12

Anterior border of the latissimus dorsi
Lateral border of pectoralis major
A line superior to the horizontal level of the nipple. 5th intercostal space
Apex below the axilla
In general - 4th intercostal space, anterior to the mid-axillary line

Question 13

What major artery do the intercostal arteries anastomose with?

Answer 13

Internal thoracic

Question 14

What do the internal thoracic arteries branch from?

Answer 14

Right and left subclavian arteries

Question 15

Which rib articulates with the sternum at the sternal angle?

Answer 15

Rib 2

Question 16

what to each rib attach to in the sternum?

Answer 16

1st costal cartilages attach to manubrium
2nd to manubriosternal joint
3rd – 7th to sternum
8th – 10th to cartilage above
11th & 12th - floating

Question 17

Describe the articulations of the ribs?

Answer 17

The vertebral column posteriorly via head and tubercle

Costal cartilages anteriorly with sternum

Question 18

describe the features of a rib?

Answer 18

Costal groove marks the inferior margin of the internal surface of the rib. The inferior edge is sharp as it is tapered to allow passage of some structures
Angle is at the superior of the rib

Crest separates the two articular surfaces of the head of the rib
Neck separates the head from the tubercle

Question 19

what is the landmark surface of the sternal angle?

What important things occur at this point?

Answer 19

Sternal angle – Manubrium and body of sternum articulate at T4/T5.

• trachea bifurcation into right and left main bronchi
• apex of aortic arch
• marks the position of the superior limit of the pericardium
• marks where the arch of the aorta begins and ends
• passes through the site where the superior vena cava penetrates the pericardium to enter the heart
• marks the superior limit of the pulmonary trunk

Question 20

describe the type of joints that the rib form with the sternum?

Answer 20

1. Rib 1 and Manubrium: not synovial and consists of a fibrocartilaginous connection between the manubrium and the costal cartilage
2. Rib 2 to Rib 7: synovial and have thin capsules reinforced by surrounding sternocostal ligaments
3. Rib 8 to Rib 10: bind to costal cartilage above (interchondral joints)

Question 21

what happens to the joint between the body of the sternum and xiphoid process?

Answer 21

becomes ossified with age.

Question 22

describe the inter vertebral joints?

Answer 22

1. Symphysis between vertebral bodies = Hyaline cartilage + Intervertebral disc
Intervertebral disc is made up of 
Anulus fibrosus (collagen – limits rotation)
Nucleus pulposus (gelatinous – absorbs compression forces)

2. Joints between vertebral arches (zygapophysial joints)
   Inferior Articular Process + Superior articular process

Question 23

How does the rib head articulate and the tubercle?

Answer 23

Superior costal facet: articulates with part of the head of its own rib

Inferior costal facet: articulates with part of hte head of the rib below.

Costotransverse joint = synovial joint between
Tubercle of rib and
Transverse process of its own vertebra

Question 24

what are the exceptions for rib articlations?

Answer 24

• SUPERIOR costal facets on the body of vertebra TI are COMPLETE and articulate with a single facet on the head of its own rib-in other words, the head of rib I does not articulate with vertebra CVII
  Rib 1 does not articulate with C7
  -vertebra TX (and often TIX) articulates only with its own ribs and therefore LACK INFERIOR demifacets on the body
  -vertebrae TXI and TXII articulate only with the heads of their own ribs-they lack TRANSVERSE costal facets and have only a single complete facet on each side of their bodies.

Question 25

Posterior intercostal arteries are branches of?

Anterior intercostal arteries are branches of ?

Answer 25

Posterior intercostal arteries are branches of the aorta (thoracic aorta)
Anterior intercostal arteries are branches of the internal thoracic artery (running down the chest wall)

Question 26

what is costo-vertebral joint and costo-transverse ligament?

Answer 26

When the 2 facets of the rib articulate with the vertebral above and below.

When the tubicle articles with the to of the transverse process.

Both are synovial joints