Thoracic Walls and Diaphragm

Question 1

Name the three parts of the sternum.

Answer 1

Manubrium, body of sternum, xiphoid process.

Question 2

How many pairs of ribs and costal cartilages are there?

Answer 2

12 pairs of ribs and 12 pairs of costal cartilages.

Question 3

How many thoracic vertebra and intervertebral discs are there?

Answer 3

12 thoracic vertebra and IV discs.

Question 4

Which ribs comprise the “costal margin”?

Answer 4

Ribs 7-10.

Question 5

Which ribs directly articulate with the sternum anteriorly?

Answer 5

Ribs 1-7.

Question 6

Ribs 8-10 articulate with what?

Answer 6

The costal cartilage of the rib above.

Question 7

Which ribs are considered “floating” ribs and can increase the volume of the thoracic cage?

Answer 7

Ribs 11 and 12.

Question 8

Which ribs are considered “typical” middle ribs?

Answer 8

Ribs 3-9. (1-2 and 10-12 are “atypical”).

Question 9

Which end of a rib is anterior and associated with cartilage?

Answer 9

The sternal end.

Question 10

Which end of a rib is posterior?

Answer 10

The vertebral end, where the head of the rib is found.

Question 11

At the head of a rib, which structures articulate with the associated thoracic vertebra?

Answer 11

The two demifacets.

Question 12

Outline the two sections of a tubercle of a rib.

Answer 12

A tubercle has an articular facet (a smooth impression that contributes to a joint), and a rough part which attaches to a ligament or a muscle.

Question 13

What runs around the internal surface of the body (near the inferior border) of a rib?

Answer 13

The costal groove.

Question 14

Discuss the costal facets of thoracic vertebrae.

Answer 14

Thoracic vertebrae have 3 costal facets on each side: an inferior costal facet and a superior costal facet on their body and a transverse costal facet on their transverse process.

Question 15

Thoracic vertebrae have what type of spinous process?

Answer 15

A long, vertical spinous process.

Question 16

Discuss costovertebral joints.

Answer 16

The head of a typical rib articulates with the inferior facet of the vertebra above it, the associated intervertebral disc and the superior facet of its own vertebra. Strong reinforcing ligaments limit the joint’s movement.

Question 17

Discuss costotransverse joints.

Answer 17

Costotransverse joints are between a rib tubercle and a vertebral transverse process. Strong reinforcing ligaments provide strength and limit the joint’s movement.

Question 18

Where is the superior aperture located and what is its defining feature?

Answer 18

The superior aperture is located at T1 and it is partially closed off by the suprapleural membrane. It is smaller than the inferior aperture.

Question 19

Where is the inferior aperture located?

Answer 19

The inferior aperture is located at T12 and runs along the costal margin. It is much bigger than the superior aperture.

Question 20

The muscular part of the diaphragm has what type of attachments and insertion?

Answer 20

The muscular part of the diaphragm has circumferential attachments and inserts into the central tendon.

Question 21

The central tendon has what type of attachments?

Answer 21

Peripheral attachments. It has no bony attachments.

Question 22

Which dome of the diaphragm is higher?

Answer 22

The right dome is higher than the left.

Question 23

Discuss the 3 hiatuses of the diaphragm that you have learnt.

Answer 23

There is a large hiatus for the inferior vena cava (IVC) that passes through the diaphragm at T8. There is a smaller hiatus for the esophagus that passes through at T10. There is a hiatus for the aorta to pass behind the diaphragm and infront of the vertebral column at T12.

Question 24

Which nerves complete motor innervation of the diaphragm?

Answer 24

The left and right phrenic nerves. Damage to the phrenic nerves can lead to paralysis of the diaphragm.

Question 25

Discuss the external intercostal muscles.

Answer 25

The external intercostal muscles are inferomedial or “front pocket” muscles - they sit forward and downward toward the sternum. Anteriorly, they are replaced by external intercostal membrane. The external intercostal muscles are most active in inspiration.

Question 26

Discuss the internal intercostal muscles.

Answer 26

Posteriorly, the internal intercostal muscles are replaced by internal intercostal membrane. They sit backwards and downwards and play the biggest role in expiration.

Question 27

Discuss the innermost intercostal muscles.

Answer 27

The innermost intercostal muscles are discontinuous.

Question 28

Where is the origin of the intercostal nerves?

Answer 28

Intercostal nerves originate at the anterior rami of the spinal nerves (T1-T11).

Question 29

Where are the intercostal nerves located?

Answer 29

Between the internal and the innermost intercostal muscles.

Question 30

Discuss the intercostal arteries.

Answer 30

Posterior intercostal arteries originate from the aorta. Anterior intercostal arteries originate from internal thoracic arteries. Intercostal arteries run between the internal and the innermost intercostal muscles.

Question 31

How is the volume of the thorax in the vertical dimension changed?

Answer 31

By movement of the diaphragm.

Question 32

How is the volume of the thorax in the anteroposterior (AP) dimension changed?

Answer 32

By movement of the upper ribs. (Pump handle movement).

Question 33

How is the volume of the thorax in the lateral (transverse) dimension changed?

Answer 33

By movement of the lower ribs. (Bucket handle movement).