The Thoracic Wall

Question 1

What is the thorax?

Answer 1

The region of the body is between the neck and the diaphragm.

Question 2

What are the three parts of the sternum?

Answer 2

The manubrium, the body, and the xiphoid process

Question 3

Which rib lies at the sternal angle?

Answer 3

Rib 2 lies at this angle (also known as the manubriosternal joint)

Question 4

What is the jugular notch?

Answer 4

Also known as the suprasternal notch, is a concave center at the upper border of the manubrium

Question 5

What does the manubrium articulate with?

Answer 5

Articulates with the clavicles and the first and upper part of the 2nd rib

Question 6

What level of thoracic vertebrae does the manubrium lie?

Answer 6

3rd and 4th thoracic vertebrae

Question 7

What level of thoracic vertebrae does the xiphoid process lie at?

Answer 7

The 10th thoracic vertebrae

Question 8

What ribs does the body of the sternum articulate with?

Answer 8

Articulates with ribs 2-7

Question 9

Which rib lies at the xiphosternal joint lie at?

Answer 9

Rib 7

Question 10

How many pairs of ribs are there? How many are true ribs and how many are false ribs? What is another name for true ribs? What is another name for the false ribs (2 names)?

Answer 10

Twelve pairs; 7 true ribs and 5 false ribs
True ribs are also known as vertebrosternal ribs
False ribs (8, 9 and 10 are known as vertebrochondral ribs; 11 and 12 are known as floating ribs because of no anterior attachment)

Question 11

Which ribs are typical ribs?

Answer 11

Ribs 3-9

Question 12

What are the components of a typical rib?

Answer 12

Head, tubercle, neck, shaft/body, costal groove, angle

Question 13

What is the head of a rib? What is the tubercle of a rib?

Answer 13

The head has two facets for articulation with the corresponding vertebral bodies and the body above; the tubercle has a facet for the transverse process of the corresponding vertebrae

Question 14

What is the neck of a rib? What is the body of a rib? What is an angle of a rib?

Answer 14

The neck is a constriction between the head and tubercle; the body of the rib is thin and twisted and contains a costal groove along the inferior border; angle is where the shaft bends forward sharply

Question 15

What is contained in the costal groove of a typical rib, from most superior to most inferior?

Answer 15

Intercostal vein
Intercostal artery
Intercostal nerve (VAN)

Question 16

What are the atypical ribs?

Answer 16

Ribs 1, 2, 10, 11, and 12

Question 17

What unique tubercle is present on rib 1 that allows insertion of which muscle?

Answer 17

Rib 1 has a scalene tubercle that allows for the insertion of the scalenus anterior muscle

Question 18

What are the distinguishing features of rib 1 that make it atypical?

Answer 18

Shorter, smaller, wider (smaller) than the others
almost horizontal
Head has a single facet for the first vertebral body (others have two)
Has scalene tubercle

Question 19

What important structures (artery, vein, nerve) pass by the scalene tubercle either posteriorly or anteriorly?

Answer 19

The subclavian vein passes the first rib anterior to the scalene tubercle
The subclavian artery and the brachial plexus pass the first rib posterior to the scalene tubercle

Question 20

What are the three intercostal muscles of the thoracic wall?

Answer 20

External intercostal muscles, internal intercostal muscles, innermost intercostal muscles

Question 21

Describe the external intercostal muscles and the direction they move, their direction in relation to the thoracic wall and ribs, and what replaces the external intercostal anteriorly.

Answer 21

The external intercostal muscles pass downward and anteriorly from the rib above to the rib below (conform to external obliques of abdomen). They extend from rib tubercle posteriorly to the costochondral junction anteriorly. Replaced anteriorly by the external intercostal membrane.

Question 22

Describe the internal intercostal muscles and the direction they move, their direction in relation to the thoracic wall and ribs, and what replaces the internal intercostal posteriorly.

Answer 22

The internal intercostal muscles pass downward and posteriorly from rib above to rib below (conform to the internal obliques of abdomen). They extend from sternum anteriorly to the angles of ribs posteriorly. Replaced posteriorly by the internal intercostal membrane.

Question 23

What best distinguishes the innermost intercostal layer?

Answer 23

The innermost intercostal muscle layer is separated from the internal intercostal muscles by the neurovascular bundle

Question 24

What layers in the thoracic and abdominal walls does the neurovascular bundle separate? (high yield)

Answer 24

The neurovascular bundle lies between the middle and deepest layers of muscle.

Question 25

What are the three specific muscles of the innermost intercostal muscle layer?

Answer 25

Intercostalis intimi (innermost intercostal muscles), very similar to internal intercostal muscles and runs mid-axillary line
Subcostal muscles pass from the inside angle of one rib to rib two levels inferior to it (pass two intercostal spaces)
Transversus thoracis, where four or five slips of muscle fan out from inferior part of sternum to costal cartilages 2 through 6

Question 26

What branch of the spinal nerve gives rise to the intercostal nerves?

Answer 26

They are also known as the ventral rami of the first 11 thoracic nerves (the dorsal ramus of a spinal nerve is much smaller); the 12th thoracic nerve runs below the 12th rib and is called the subcostal nerve

Question 27

What space does each intercostal nerve enter?

Answer 27

Enters space between parietal pleura and the internal intercostal membrane then continues between the internal intercostal muscle and the innermost intercostal muscle (neurovascular plane)

Question 28

What are the atypical spinal nerves?

Answer 28

First intercostal nerve, second intercostal nerve, the 7th-11th intercostal nerves, and the subcostal nerve (below T12)

Question 29

What does the major part of the ramus of the first intercostal nerve join?

Answer 29

Brachial plexus (high yield)

Question 30

What is the intercostobrachial nerve? What nerve does it join, and what area does it supply?

Answer 30

It is the lateral cutaneous branch of the second intercostal nerve, it joins the medial cutaneous nerve of the arm, supplies skin of axilla and upper medial arm

Question 31

Where is pain referred along in coronary artery disease?

Answer 31

The intercostobrachial nerve (lateral cutaneous branch of the 2nd/3rd intercostal nerve) carries referred pan to the medial side of the arm

Question 32

What makes the 7-11th intercostal nerves atypical?

Answer 32

They leave the intercostal spaces and continue into the abdominal wall

Question 33

What plane does the 7-11th intercostal nerve travel in once reaching the abdominal wall?

Answer 33

They travel in the same plane between the internal oblique and the transversus abdominus muscles (i.e., in the neurovascular plane between the middle and deepest layers of muscles)

Question 34

What is unique about the 12th thoracic intercostal nerve?

Answer 34

It lies below the 12th rib and is termed the subcostal nerve. It follows the course of the 7th - 11th itnercostal nerves.

Question 35

Where do the posterior intercostal arteries arise in each of the 11 intercostal spaces?

Answer 35

The first two spaces originate from the subclavian -> costocervical trunk -> supreme intercostal artery -> first 2 intercostal arteries
The lower 9 spaces are direct branches from the thoracic aorta

Question 36

Where do the anterior intercostal arteries arise in each of the 11 intercostal spaces (3 groups)?

Answer 36

Upper 6 spaces: they are branches of the internal thoracic (internal mammary arteries) and anastomose laterally with the posterior intercostal arteries
Lower (7-9th) spaces: branches off of the musculophrenic artery (which is a terminal branch of the internal thoracic artery)
Absent in the lower two intercostal spaces (10 and 11)

Question 37

Which anterior intercostal arteries are supplied by branches of the internal thoracic artery (internal mammary artery)

Answer 37

Intercostal arteries 1-6

Question 38

Does the internal thoracic artery (internal mammary artery) lie anterior or posterior to transversus thoracis muscle?

Answer 38

Anterior to it

Question 39

Where does the internal thoracic artery divide and into which 2 terminal branches?

Answer 39

Divides just below the 6th costal cartilage into the superior epigastric artery and the musculophrenic artery

Question 40

What are the 3 types of branches that the internal thoracic artery can give rise to?

Answer 40

1. The upper six anterior intercostal arteries
2. The pericardiophrenic artery (which runs with the phrenic nerve)
3. The perforating branches (which perforate wall, pass to skin with anterior cutaneous branches of intercostal nerves, and are the main blood supply of the medial part of breast; enlarged in lactating women)

Question 41

What does the pericardiophrenic artery branch of the internal thoracic artery supply?

Answer 41

Pericardium, diaphragm, and part of the pleura

Question 42

What veins do the posterior intercostal veins empty into?

Answer 42

The azygous and hemiazygous veins (depending on if it is from the left or the right)

Question 43

What veins do the anterior intercostal veins drain into?

Answer 43

The internal thoracic vein or the musculophrenic vein

Question 44

What does the internal thoracic vein drain into?

Answer 44

Drains into the branchiocephalic vein (which empties into the superior vena cava)