Thoracic Wall

Question 1

Where is the thorax located?

Answer 1

Inferior to the neck and superior to abdomen

Question 2

What is thoracic skeleton composed of?

Answer 2

12 thoracic vertebrae and associated intervertebral discs

12 pairs of ribs

Costal cartilages

Sternum

(All part of axial skeleton)

Question 3

Functions of the thoracic skeleton

Answer 3

Protect viscera within the thoracic cavity and abdominal cavity

Provide framework for attachemnt of muscles of respiration

Question 4

Anatomy of the 12 thoracic vertebrae

Answer 4

Vertebral body (anterior)
Spinous process (posterior)
Transverse process (lateral)
Costal facets (articulates with ribs to form synovial joints)

Question 5

Anatomy of ribs

Answer 5

12 ribs

Head - 2 facets for articulation with vertebral bodies, e.g. head of rib 4 articulates with T4 and T3

Tubercle - articulates with transverse process of vertebrae, e.g. tubercle of rib 4 articulates with T4

Body - interior border has costal groove which houses VAN

Angle - most commonly fractured

Question 6

Atypical ribs

Answer 6

Rib 1 - Flat, short, and tightly curved. Superior surface of body has 2 shallow grooves for subclavian artery and vein.

Ribs 11 and 12 - Floating ribs. Short with no neck and no tubercles.

Question 7

Costal cartilage

Answer 7

Hyaline cartilage

Contributes to elasticity of thoracic wall

Connects to body of rib - little movement at this joint

Connects to sternum via sternocostal joints (most are synovial)

Question 8

Costal margin

Answer 8

Formed by medial borders of costal cartilages 7-10

Question 9

Rib classificiation

Answer 9

True ribs 1-7 attach to sternum directly

False ribs 8-10 attach to sternum indirectly

Floating ribs 11-12 do not attach

Question 10

Manubrium of sternum

Answer 10

Jugular suprasternal notch on superior border

Articulates with clavicles at sternoclavicular joints

Articulates costal cartilages 1-2

Articulates with sternal body at sternal angle

Question 11

Sternal angle

Answer 11

Level with 2nd costal cartilage and T4 / T5

Question 12

Body of sternum

Answer 12

Articulates with costal cartilages 2-7

Question 13

Xiphoid process

Answer 13

Level of T10

Xiphisternal joint marks inferior limit of thoracic cavity and inferior border of heart

Xiphoid may ossify and fuse with sternum in adulthood

Question 14

Intercostal muscles

Answer 14

External, internal, and innermost muscles

Innervated by intercostal nerves (ventral rami of thoracic nerve spines)

Question 15

Intercostal neurovascular bundle

Answer 15

Superior to inferior - VAN (vein, artery, nerve)

Between internal and innermost muscles

Along costal groove

Question 16

Intercostal nerves

Answer 16

Intercostal nerves are the ventral rami of the thoracic spine nerves T1 - T11

Ventral ramus of T12 is called the subcostal nerve since it is inferior to rib 12

Intercostal nerves give off collateral branches that travel along the superior edge of the rib

Question 17

Fibers carried in intercostal nerves

Answer 17

Ventral rami convey both motor and sensory

• Somatic motor fibers to the skeletal muscle of thoracic wall
• Somatic sensory fibers from the skin (pain, temperature, touch), skeletal muscles, and tendons (proprioception)
• Sympathetic fibers to the sweat glands, arrector pili muscles, and blood vessels in the skin

Question 18

Dermatome

Answer 18

Area of skin supplied by a single spinal nerve

Terminal branches of intercostal nerves and sensory branches from corresponding dorsal rami create the segmental arrangement of dermatomes found in the torso

Question 19

Locating dermatomes

Answer 19

T4 at nipple

T10 at belly button

Question 20

Intercostal arteries

Answer 20

The primary blood supply of the thoracic wall is from the thoracic aorta and internal thoracic arteries (branches of the subclavian arteries)

Question 21

Posterior intercostal arteries

Answer 21

Majority arise from the thoracic aorta

Course with an intercostal nerve and vein (VAN)

Anastomose with anterior intercostal arteries

Question 22

Anterior intercostal arteries

Answer 22

Arise from internal thoracic arteries

There are usually 2 anterior intercostal arteries per intercostal space

Anastomose with posterior intercostal artery and collateral branch

Question 23

Intercostal veins

Answer 23

Anterior and posterior intercostal veins anastomose

Anteriorly, the anterior intercostal veins drain into the internal thoracic veins –> brachiocephalic veins –> SVC

Posteriorly, the posterior intercostal veins drain into the azygos system of veins –> SVC