Thoracic Wall Flashcards
Thoracic Wall
- Rigid but flexible
- Constantly in motion
Boundaries Forming the Thoracic Wall
- Skin
- Subcutaneous tissue
- Thoracic cage
- Ribs and costal cartilage
- Sternum
- Thoracic vertebrae and IVD
- Muscle (intercostals, pecs)
- Fascia
Thoracic Wall Function
- Protect thoracic and abdominal organs
- Respiration
- Muscle attachment
Thoracic Cavity
- Space enclosed by the thoracic cage, intercostal muscles and diaphragm
- Superior thoracic aperture
- Inferior thoracic aperture
Superior Thoracic Aperture
- Slopes antero-inferiorly
- Communication with neck and upper limb
Boundaries of Superior Thoracic Aperture
- Posterior: T1 body
- Lateral: rib 1 and cartilage
- Anterior: superior manubrium
Inferior Thoracic Aperture
- Posterior is more inferior than anterior
- Larger and enclosed by diaphragm
- Passageway to/from abdominal cavity pass
- Posterior or through diaphgram
Boundaries of Inferior Thoracic Aperture
- Body of T12 vertebra
- Rib 12 and distal end of rib 11
- Costal cartilage of ribs 7 – 10
- Xiphoid process
Infrasternal Angle (Subcostal Angle)
- Formed by costal margin and xiphisternal joint
Ribs
- Flat bones
- Active hematopoietic tissue (Red bone marrow)
True Ribs
- Vertebrosternal ribs (1-7)
False Ribs
- Vertebrochondral ribs (8-10)
False, Floating Ribs
- Free ribs (11, 12)
Typical Ribs
- Ribs 3-9
Atypical Ribs
- Ribs 1, 2, 10-12
Typical Ribs
- Head
- Neck
- Tubercle
- Body
Head of Typical Ribs
- 2 facets for articulating with 2 adjacent vertebrae and disc between
Tubercle of Typical Ribs
- Articular part that articulates with the TP of the corresponding vertebra, non-articular part
Body of Typical Ribs
- Costal angle and costal groove
1st Rib
- Morphology
- Single facet on the head (articulates with one vertebral body)
- Grooves for subclavian vessels
- Scalene tubercle
2nd Rib
- Noticeable tuberosity for serratus anterior
Ribs 10-12
- Single facet on the head (articulates with one vertebral body)
Ribs 11-12
- Single facet on the head (articulates with one vertebral body)
- Short and lack a neck and tubercle (no TP articulation
Costal Cartilages
- Provide flexibility
- Attach ribs to sternum
Costal Cartilage Attachments
- Directly: ribs 1-7
- Indirectly: ribs 8-10
- Forms costal margin
Intercostal Spaces
- Numbered based on the superior rib
- Filled by intercostal muscles and membranes
- 11 of them
Intercostal Spaces
- Each contains 2 sets of intercostal vessels and nerves
- Space changes dimensions with respiration
Subcostal Space
- Below rib 12
Thoracic Vertebrae (12)
- Bilateral costal facets on postero-lateral vertebral bodies
- Superior and inferior costal facets for rib head articulation
- Demifacets or full facets
Costal Facets on TP
- Articulation with rib tubercle
- T11 and 12 do not have costal face
Sternum
- Protects underlying viscera
- Rib attachment
Parts of the Sternum
- Manubrium
- Body
- Xiphoid process
Manubrium of Sternum
- Spans vertebral level T3-4)
- Jugular notch (vertebral level T2)
- Clavicular notches
- Synchondroses of 1st rib
Body of Sternum
- Spans vertebral level T5-9)
- Costal notches for ribs 3-7
- Transverse ridges (lines of fusion)
- Represents the fuses of 4 separate sternebrae
Xiphoid Process of Sternum
- Vertebral level T10
- Appearance varies
Manubrialsterno Joint (Sternal Angle)
- Part of the sternum
- Located T4/5
Xiphisternal Joint
- Located T9 in supine position
- Level of central tendon of diaphragm
- Inferior limit of heart, superior limit of liver
Costovertebral Joint
- Rib head and vertebral body
- Synovial joint
Costotransverse Joint
- Rib tubercle and TP
- Synovial joint
Costochondral
- Rib with costal cartilage
- Primary cartilaginous
Interchondral
- Between cartilages ribs 6-9
- Synovial joint
Sternocostal Joint
- Between costal cartilages and sternum
- Strengthened by radiate ** ligaments
- 1st is primary cartilaginous, synchondrosis
- 2-7 are synovial
Manubriosternal Joint
- Secondary cartilaginous (fibrocartilage)
Xiphisternal Joint
- Primary cartilaginous
Sternoclavicular Joint
- Upper extremity
Costovertebral and Costotransverse Joints
- Also considered joints of the vertebral column
Joints of the Thoracic Wall
- Costovertebral
- Costotransverse
- Costochondral
- Interchondral
- Sternocostal
- Manubriosternal
- Xiphisternal
- Sternoclavicular
Costovertebral Joints
- Articulates with costal facets on vertebral bodies
- Synovial joints, gliding
Head of Ribs 2-9
- Articulate with superior aspect of corresponding vertebra
the inferior aspect of the one above - Intervening IVD
- 2 joint cavities separated by intra-articular ligament
supported by radiate ligaments
Head of Ribs 1, 10-12
- Articulate with only its corresponding vertebral body
Costotransverse Joint
- Synovial joint, gliding joints
- Between rib tubercle and TPs of corresponding vertebra
- Supported by ** ligaments
- Shape of articulating surfaces of TPs differs between superior and inferior ribs
- Ribs 11 and 12 do not articulate with TP therefore they do not have a tubercle
Rib Fracture
- Usually as a result of blunt trauma to thorax
- 4-9 most commonly injured
- Can result in injury to underlying organs
- Pulmonary laceration, hemothorax, pneumothorax
Flail Chest
- Life-threatening condition
- Fracture of 3 or more adjacent ribs at 2 locations
Flail Chest
- Creates a free segment
- Paradoxical movement of the free segment with respiration
- Indicative of more serious underlying injuries (pulmonary contusion, cardiac tamponade)
- Leading to respiratory compromise causing hypoxia
Intercostal Muscles
- Span the intercostal space, attached to the ribs
- Superior border of rib below, inferior border of rib above
External Intercostal Muscles
- Most superficial
- Located from rib tubercle to costochondral junction
- ** membrane spans the gap to the sternum
- Anteromedial muscle fiber direction
- Elevate rib during inspiration
Internal Intercostal Muscles
- Deep to external intercostals
- Muscle fibers run postero-inferior (90⁰ angle to the externals)
- Located from rib angle to sternum
- ** membrane spans the gap to about rib neck
- Depress the ribs during forced expiration
- Interchondral part (anteriorly) elevates the ribs
Innermost Intercostals
- Deep to internal intercostals, attached to inner part of rib
- Only found in the lateral part of the intercostal space
- Function similar to internal intercostals
Transversus Thoracis Muscles
- Originates from the inner surface of sternum
- Inserts onto the costal cartilages (ribs) of 2-6
- Function: depress ribs
Subcostal Muscles
- Internal aspect of posterior thoracic wall
- Span multiple ribs
- Function: similar to internal intercostals
Inspiration
- Increase volume –> decrease pressure, air flows in
Expiration
- Decrease volume –> increase pressure, air flow out
Inspiration
- Muscle contraction increases volume of thoracic cavity
- Diaphragm contraction increases vertical dimensions
- Pump handle movement increases AP diameter
- Bucket handle movement increases transverse diameter
Additional Muscles Recruited when Needed for More Inspiration
- External intercostals
- SCM
- Scalenes
- Anterior axio-appendicular muscles
Expiration
- Muscle relaxation and natural elasticity of tissue decreases volume of thoracic cavity
Forced Expiration
- Recruitment of additional muscles
- Abdominals
- Internal intercostals
Layers of the Thoracic Wall
- Skin
- Superficial fascia
- Deep fascia
- Serratus anterior or some other muscle (depends on the - - Region of the thoracic wall)
- External intercostal
- Internal intercostal
- Innermost intercostal
- Endothoracic fascia
- Parietal pleura
Thoracic Spinal Nerve Branches
- Posterior ramus
- Anterior ramus (intercostal nerve)
Posterior Ramus
- Innervates skin over back
Anterior Ramus (Intercostal Nerve)
- Branches have segmental distribution
- Anterior and lateral cutaneous branches
- Branches to intercostal muscles
- Connection with rami communicantes
Lateral Cutaneous Branch of the 2nd and/or 3rd Thoracic Spinal Nerve
- Give rise to the intercostobrachial nerve
Intercostobrachial Nerve
- Supplies axilla, communicates with branches of brachial plexus
- 7th – 11th intercostal nerves also supply the abdominal wall
C4/5 Dermatome
- Dermatome to clavicles
T4 Dermatome
- Dermatome to nipples
T10 Dermatome
- Dermatome to umbilicus
Posterior Intercostal Arteries
- 1 and 2 (1st and 2nd intercostal space)
- Arises from superior intercostal artery (costocervical trunk)
- 3 – 11 arise from thoracic aorta
Subcostal Artery
- A branch off thoracic aorta
Anterior Intercostal Arteries
- 1 - 6 arise from internal thoracic artery
- 7 - 9 arise from musculophrenic artery
- Space 10 and 11 lack these arteries
Superior and Lateral Thoracic Arteries
- Branch off axillary artery
Internal Thoracic Arteries (Internal Mammary)
- Branches of the subclavian arteries
- Descends lateral to sternum on interior aspect of thoracic wall
Branches of Internal Thoracic Arteries
- Pericardiophrenic
- Anterior intercostal arteries (1st 6 spaces)
- Superior epigastric and musculophrenic (terminal branches)
Musculophrenic Artery
- Gives off anterior intercostal arteries to spaces 7-9
Intercostal Neurovascular Bundle
- Found between the internal and innermost intercostal muscles
- In the costal groove
- Intercostal Nerves
- Posterior/Anterior intercostal arteries and veins
Intercostal Neurovascular Bundle
- Collateral branches run on the super aspect of the inferior rib
- VAN: Vein (closest to the rib), Artery, Nerve
- Below rib 12 are the subcostal nerve and vessels
Below the 12th Rib
- Subcostal nerve and vessels
Venous Drainage of Thoracic Wall
- 11 posterior intercostal veins and the subcostal vein drain into the azygos venous system
- Anterior intercostal veins drain into internal thoracic and musculophrenic veins
11 Posterior Intercostal Veins and Subcostal Vein
- Drain into the azygos venous system
Anterior Intercostal Veins
- Drain into internal thoracic and musculophrenic veins
