Thoracic Wall Flashcards
Where is the thorax located?
Inferior to the neck and superior to abdomen
What is thoracic skeleton composed of?
12 thoracic vertebrae and associated intervertebral discs
12 pairs of ribs
Costal cartilages
Sternum
(All part of axial skeleton)
Functions of the thoracic skeleton
Protect viscera within the thoracic cavity and abdominal cavity
Provide framework for attachemnt of muscles of respiration
Anatomy of the 12 thoracic vertebrae
Vertebral body (anterior) Spinous process (posterior) Transverse process (lateral) Costal facets (articulates with ribs to form synovial joints)
Anatomy of ribs
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
Atypical ribs
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.
Costal cartilage
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)
Costal margin
Formed by medial borders of costal cartilages 7-10
Rib classificiation
True ribs 1-7 attach to sternum directly
False ribs 8-10 attach to sternum indirectly
Floating ribs 11-12 do not attach
Manubrium of sternum
Jugular suprasternal notch on superior border
Articulates with clavicles at sternoclavicular joints
Articulates costal cartilages 1-2
Articulates with sternal body at sternal angle
Sternal angle
Level with 2nd costal cartilage and T4 / T5
Body of sternum
Articulates with costal cartilages 2-7
Xiphoid process
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
Intercostal muscles
External, internal, and innermost muscles
Innervated by intercostal nerves (ventral rami of thoracic nerve spines)
Intercostal neurovascular bundle
Superior to inferior - VAN (vein, artery, nerve)
Between internal and innermost muscles
Along costal groove
Intercostal nerves
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
Fibers carried in intercostal nerves
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
Dermatome
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
Locating dermatomes
T4 at nipple
T10 at belly button
Intercostal arteries
The primary blood supply of the thoracic wall is from the thoracic aorta and internal thoracic arteries (branches of the subclavian arteries)
Posterior intercostal arteries
Majority arise from the thoracic aorta
Course with an intercostal nerve and vein (VAN)
Anastomose with anterior intercostal arteries
Anterior intercostal arteries
Arise from internal thoracic arteries
There are usually 2 anterior intercostal arteries per intercostal space
Anastomose with posterior intercostal artery and collateral branch
Intercostal veins
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
