Anatomy of the Thoracic Cavity Quiz

Thoracic Wall Structure and Function

• Thorax: Also known as the chest or breastplate, it's the region between the neck and abdomen. The thoracic cage is a bony framework of the thorax. It's flat anteriorly and posteriorly, but rounded laterally.
• Boundaries: The thorax is bordered anteriorly by the sternum and costal cartilages, posteriorly by the thoracic vertebrae, and laterally by the intercostal spaces. It communicates superiorly with the neck. The superior thoracic aperture is defined by T1, the first rib, and the manubrium. The inferior border is separated from the abdomen by the diaphragm.
• Functions: The thorax houses and protects the heart and lungs. It also acts as a conduit for structures passing between the neck and abdomen. It plays a crucial role in breathing and supports the upper limbs (UE).
• Lines of Orientation: Critical for anatomical references, these lines include midsagittal, midclavicular, anterior and posterior axillary, midaxillary, vertebral, and scapular lines.
• Spaces: Anteriorly, there are infraclavicular, supraclavicular, precardiac, and Traube's spaces. Posteriorly, there are interscapular, suprascapular, and intrascapular spaces.

Osteology of the Thoracic Cage

• Framework: Formed by the thoracic vertebrae, ribs, intercostal spaces, sternum, and costal cartilages. It's divided into the mediastinum (central) and the pleurae and lungs (lateral).
• Visceral Pleura: Thin membrane covering the lungs.
• Parietal Pleura: Inner surface of the chest wall.
• Pleural Cavity: Space between the visceral and parietal pleurae.

Osteology of the Sternum

• Structure: Flat bone with three parts: manubrium, body, and xiphoid process.
• Manubrium: Articulates with the clavicle and first and upper costal cartilages. Located opposite T3-T4 (thoracic vertebra 3 and 4).
• Body: Articulates with costal cartilages 2-7.
• Xiphoid: Hyaline cartilage that ossifies in adulthood.
• Sternal Angle: A noticeable landmark. Opposite the intervertebral disc of T4-T5. Rib 2 is attached at this point.

Osteology of the Ribs

• Structure: 12 pairs of ribs attached posteriorly to the thoracic vertebrae.
• Types:
  • True Ribs (1-7): Attach directly to the sternum.
  • False Ribs (8-10): Attach to the costal cartilage of the 7th rib, not directly to the sternum.
  • Floating Ribs (11-12): Have no attachment to the sternum.
• Parts: Head (posterior vertebral end), neck, tubercle (prominence for articulation with transverse process), shaft (body), and angle.
• Costal Groove: Located on the inferior aspect of the rib. Passageway that contains intercostal vessels and nerves.

Osteology of the Thoracic Vertebrae

• Structure: 12 thoracic vertebrae are found in the main facet (superior facet) region. Heart-shaped; they have costal facets for articulation with ribs, which are critical for attachment points.

Atypical Ribs

• 1st Rib: Flat, short, connects to T1 only, and features a subclavian groove instead of a typical tubercle for muscle attachment.
• 2nd Rib: Flat but longer than the first rib. Atypical articulation.
• 10th, 11th, and 12th Ribs: Have reduced articulation (head only).

Costal Cartilages

• Structure: Hyaline cartilage connecting ribs 1-7 to the sternum and ribs 8-10 to the 7th costal cartilage. Provide elasticity and mobility.

Joints

• Sternal Joints: Manubriosternal and xiphisternal joints are primarily cartilaginous.
• Costovertebral Joints: Synovial plane joints (two joints in most cases) between ribs and vertebrae.
• Rib-Costal Cartilage Joints: Cartilaginous joints (1st rib-sternum is cartilaginous, rest are synovial plane).

Thoracic Openings

• Superior Thoracic Aperture: Communicates with the root of the neck. Defined by T1, rib 1, and the manubrium sterni.
• Inferior Thoracic Aperture: Large, expandable opening communicating with the abdomen. Closed by the diaphragm. This opening is crucial for passing structures such as esophagus, major blood vessels, and nerves.

Clinical Notes (Thoracic Outlet Syndrome)

• Thoracic outlet syndrome is a condition involving compression of brachial plexus nerves (C5-T1), subclavian artery, and vein.
  • Symptoms: Vascular (swelling, bluish discolouration, heaviness, pulsating lump, fatigue, pain) and neurologic (paresthesia, muscle weakness, atrophy, cramps, pain)
  • Causes: Cervical rib, scalene syndrome, costoclavicular syndrome, hyperabduction syndrome.
  • Tests: Allen test, Adson's test, costoclavicular maneuver.

Respiratory Muscles

• Intercostal Muscles: Located between ribs, these muscles (external, internal, innermost) are critical for inspiration and expiration. They stabilize the rib cage and vary in function based on their position in relation to the other intercostal muscles and their positioning relative to other ribs on the rib cage.
• Diaphragm: Dome-shaped muscle that separates the thorax and abdomen.
  • Attachments: Xiphoid process, costal margin, ribs (11 and 12), lumbar vertebrae.
  • Sections: Sternal, costal, vertebral parts.
  • Crura (Right and Left): Parts of the diaphragm, attaching to the lumbar vertebrae.
  • Central Tendon: Point of convergence for the diaphragm's muscles. Located in alignment with the xiphisternal junction.
  • Openings: Caval (vena cava), esophageal, aortic openings.
  • Nerve Supply: Phrenic nerve (C3-C5), critical because impingement will damage breathing functions.
  • Action: Primary muscle of inspiration; also involved in increasing intra-abdominal pressure for actions like straining.

Neurovascular Bundle

• Organization: Vein, artery, and nerve occur in a triad-like or bundle structure. Crucial for placement and avoiding injury during procedures.

Intercostal Nerves

• Origin: Anterior rami of T1-T11 spinal nerves; T12 is the subcostal nerve.
• Function: Somatic motor innervation to the thoracic wall, sensory innervation to skin and parietal pleura, and postganglionic sympathetic fibers.
• Relationship: Anterior rami of T1 contribute to the brachial plexus; lower intercostal nerves innervate abdominal wall.

Arteries and Veins

• Intercostal Arteries: Supply the intercostal spaces.
• Intercostal Veins: Drain the intercostal spaces.

Test your knowledge about the anatomy and functions of the thoracic cavity. This quiz covers key concepts related to the diaphragm, intercostal muscles, and pleura. Perfect for students studying anatomy or related fields!