Boundaries Of The Thoracic Cage

Question 1

Which bones form the boundaries of the thoracic inlet?

Answer 1

Vertebra T1, 1st ribs and manubrium

Question 2

Which bones/ costal cartilages form the boundaries of the thoracic outlet?

Answer 2

Vertebra T12, 11th and 12th ribs, costal cartilages of ribs 7-10 and xiphisternal joint

Question 3

Which bones/costal cartilages form the costal margin?

Answer 3

Ribs 7-10 and costal cartilages of 7-10 which come together and join at the xiphisternum

Question 4

Which costal cartilages are directly attached to the sternum?

Answer 4

1-7

Question 5

Which ribs are indirectly attached to the sternum (attached by costal cartilage)

Answer 5

8-10

Question 6

Why do new borns rely on the diaphragm as their main muscle for breathing?

Answer 6

Adults’ ribs lie obliquely and this allows the thoracic cavity to increase in volume during inspiration, however this isn’t the case in newborns as their ribs don’t lie obliquely. Therefore in newborns, contraction of the intercostal muscles doesn’t increase volume in the thoracic cavity.