Part 10: Osteology of Thorax

Question 1

What angle to ribs slope from vertebrae?

Answer 1

45’ anterior down. Anterior ends fall progressively short off midline - this is supplemented by longer costal cartilages

Question 2

Is Xiphoid process ossified?

Answer 2

No, may however sometimes ossify in later life

Question 3

What is unique to the 2nd sternocostal joint?

Answer 3

Has demifacet of costal cartilage - ie fibrocartilage disc bisects joint

Question 4

When does ossification of the sternum occur?

Answer 4

Variable centres appear in 5th foetal month -> fuse by 25 years

Question 5

When does ossification of the ribs occur?

Answer 5

Bony centres arise at week 8, neck remains cartilaginous until 15-25y

Question 6

Which ribs are atypical in regards to head?

Answer 6

1st, 11th, 12th and sometimes 10th

Each makes only a single synovial joint with its own vertebrae

Question 7

How many synovial joints does a typical rib have at its head?

Answer 7

2. One with own vertebrae and one with the above vertebrae

Question 8

Which ribs are atypical in regards to the tubercle?

Answer 8

11th and 12th rib.

They have no synovial joint here, only ligament

Question 9

Describe the joints of the tubercle of a typical rib

Answer 9

Medial facet - synovial joint with own vertebrae transverse process
Lateral facet - lateral costotransverse ligament to own vertebrae

Question 10

How does the 12th rib differ from typical ribs?

Answer 10

Only articulates with own vertebrae

No tubercle, no angle, no costal groove