Anatomy of the Thoracic Wall Flashcards
The endothoracic fascia creates a natural cleavage plain between which two layers of the thoracic wall?
It separates the parietal pleura from its costal attachments.
Thoracic cage
Consists of 12 pairs of ribs and costal cartilages, sternum, 12 thoracic vertebrae and associated intervertebral discs.
Rib classification
_True ribs _(1-7) - articulate with sternum
False ribs (8-10) - articulate with the rib above
_Floating ribs _(11-12)
Also may be classified as:
Typical* *(3-9)
Atypical (1,2, 10-12)
Tubercle of typical rib
Facet for articulation with transverse process.
Abnormalities of ribs
Abnormalities of ribs are fiarly common:
- Extra ribs (cervical or lumbar: cervical rib relatively common (0.5-2%) and may affect the brachial plexus and/or subclavian vessels.
- Rudimentary 12th rib
- Congenitally fused ribs
Jugular notch
Level of vertebra T2
Sternal angle of Louis
Manubriosternal joint.
- Site of articulation of second costal cartilage.
- Level of T4/T5.
*
- Level of T4/T5.
Kyphosis
Anatomically used to describe the natural anteiror concavity of the thoracic spine.
Clinically is used to describe an excessive anterior concavity which may result from compression fractures of vertebral bodies.
Costovertebral joints
- Head of rib ‘x’ and thoracic vertebral bodies ‘x’ and ‘x-1’.
- Synovial plane joint.
- Ligament: mainly radiate ligament.
- Exceptions are irbs 1,11,12 (T1, T11, T12).
Costotransverse joint
- Tubercle of rib ‘x’ and transverse process of thoracic vertebra ‘x’.
- Synovial plane.
- Liagment: costotransverse ligament
Intervertebral T1-T12
- Symphysis (secondary cartilaginous) - vertebral bodies covered by hyaline cartilage united by fibrocartilage.
- Ligaments - anterior and posterior longitudinal.
Joints of the thoracic cage
- Costovertebral joint
- Costotransverse joint
- Intervertebral joints
Sternal joints
- Sternal angle of Louis/manubriosternal joint
- Sternoclavicular joint
- Sternocostal joints
- Costochondral junction
- Interchondral joint
Sternal angle of Louis
Manubriosternal joint.
- Symphysis - fibrocaritlage, often ossifies later in life.
Sternoclavicular joint
Synovial saddle
Sternocostal joints
Cartilages of ribs 1-7.
- First is primary cartilaginous (synchondrosis) usually ossifies in later life.
- Ribs 2-7 synovial plane.
Costochondral junction
Not really a joint. Degenerates with age so useful forensically.
Interchondral joint
- Between cartilages 6-7, 7-8, 8-9.
- Synovial plane.
- Ribs 9-10 fibrous.
Boundaries of thorax
- Superior thoracic aperture: rib 1, manubrium and T1.
- Inferiorly enclosed by diaphragm
Diaphragm
Most important muscle of respiration. It is a musculotendinous sheet which separates thoracic and abdominal cavities.
Central portion is tendinous (central tendon - dense fibrous CT), outer portions are muscular.
Diaphragm innervation
Phrenic nerve (C3-C5)
Diaphragm attachments
- Ribs 7-12
- Lumbar vertebrae
- Xiphoid process
- Crura (right and left crus)
- Arcuate ligaments
- Median
- Medial
- Lateral
Diaphragm openings
- IVC at T8
- Oesophagus and vagal trunks at T10
- Aorta and thoracic duct as T12
External intercostal membranes
External intercostal muscles do not continue all the way to the sternum.
Internal intercostal membrane
Internal intercostal muscles do not continue all the way to the thoracic spine
Subcostals
Similar to innermost intercostals except transverse more than one rib
Changes upon inspiration
During inspiration:
- The vertical, lateral and anteroposterior diameters of the thoracic cavity increase.
- The upper ribs have a ‘pump handle’ action which increases A-P diameter.
- The lower ribs have a ‘bucket handle’ action which increases the transverse diameter.
The external intercostals
Mainly inspiration
The internal intercostals
Mainly expiration - during normal respiration they mainly increase in tone and only during forced respiration do they create movement.
Innermost intercostals and subcostals actions
The innermost intercostals and subcostals probably act similar to internal intercostal muscles and transversus thoracis is probably active in forced expiration and is also involved in proprioception.
Levator costarum
Probably elevate the ribs in forced inspiration
Serratus posterior superior and inferior
Most likely only proprioceptive.
Accessory muscles of respiration
- Pectoralis minor and major
- Serratus anterior
- Scalene muscles
Forced expiration
During forced expiration the abdominals contract - increasing intra-abdominal pressure, forcing diaphragm superiorly.
Location of intercostal VAN
Located between internal and innermost intercostals, deep to the costal groove.
Smaller collateral branches are located above the rib below.
Posterior intercostal arteries
Arise from the superior intercostal a (rib 1,2) and from the thoracic aorta (rib 3-11).
Anterior intercostal arteries
Arise from the internal thoracic a (ribs 1-6) and musculophrenic artery (ribs 7-9).
Anastamoses exist between anterior and posterior intercostal aa.
Anterior intercostal veins
Drain to the musculophrenic and internal thoracic vein.
Posterior intercostal veins
- Right: 4-11 drain to the azygos v then to the SVC.
- Left: 4-11 drain to the hemiazygos vein and accessory hemiazygos vv then to the azygos vein.
- Superiorly the first intercostal vv drain into the right or left brachioephalic vv.
- The second and third (fourth) drain into the superior intercostal vv and then into the azygos v on the right or the brachiocephalic v on the left.
Intercostal nn
Arise form the ventral rami of spinal nerve T1-T12 (T12 = subcostal n), remember most of T1 goes to the brachial plexus.
T1-11 supply intercostal and abdominal mm and give off lateral and anterior cutaneous braches to skin of the trunk.
Base of breast surface anatomy
Overlies ribs 2-6, most of pectoralis major, part of serratus anterior.
Lateral mammary branches
From the lateral thoracic a, thoracoacromial a and posterior intercostal aa.
Medial mammary branches
Arise from the internal thoracic a.
Veins of the breast region
Veins drain mainly to the axillary v with some drainage to the internal thoracic v
Breast innervation
Intercostal nerves 2-6 (anteiror and lateral cutaneous branches).
Niiple and areola - T4 dermatome.
Breast lymphatic drainage
Breast cancer commonly spreads via lymphatics.
- Approximately 75% lymph drains to pectoral (anterior axillary) nodes, then to central axillary nodes and to apical axillary nodes.
- Approximately 20% of lymph to parasternal (internal thoracic) nodes
- 5% of lymph to interpectoral nodes, intercostal (posterior parietal) nodes, opposite breast and subdiaphragmatic nodes.
