Thoracic+cage+WITH+NOTES

Learning Objectives

  • Identify surface landmarks used in the examination of the thoracic cage.

  • Name structures forming the skeleton of the thorax.

  • Describe the structure of the sternum and a typical rib.

  • Describe origin and course of intercostal nerves.

  • Describe origin and course of anterior and posterior intercostal arteries.

  • Describe the internal thoracic artery: origin, termination, course, and branches.

  • Name veins that drain the thoracic wall including their location and termination.

Features & Functions of Thoracic Cage

  • Features:

    • Light weight

    • Flexible

  • Functions:

    • Breathing: Facilitates respiratory movements.

    • Protection: Guards vital organs such as the heart and lungs.

    • Conduit: Serves as a passageway for structures such as blood vessels and nerves.

  • Components:

    • 12 thoracic vertebrae

    • Ribs and costal cartilage

    • Sternum

Surface Landmarks

  • Palpable bony landmarks:

    • Clavicle

    • Acromion

    • Sternoclavicular joint

    • Jugular or suprasternal notch

    • Sternal angle (angle of Louis)

    • Xiphoid process

    • Costal margin

    • Infrasternal angle

Surface Anatomy Lines

  • Anterior median (midsternal) line

  • Midclavicular lines (MCLs)

  • Anterior axillary line

  • Midaxillary line

  • Posterior axillary line

Surface Anatomy Structures

  • Axillary fossa

  • Lateral border of pectoralis major

  • Lateral border of latissimus dorsi

  • Digitations of serratus anterior

  • External oblique

  • Lower ribs (9 and 10)

  • Costal margins

Skeleton of the Thorax

  • Overview Components:

    • 12 thoracic vertebrae

    • 12 pairs of ribs (irregular bones)

    • Sternum (flat bone): includes manubrium, body, and xiphoid process

Thoracic Vertebrae

  • Anatomy of thoracic vertebrae and intervertebral discs (IVD) as viewed from various angles.

  • Important Ribs:

    • 1st thoracic vertebra

    • 12th thoracic vertebra (floating ribs 11 & 12)

Skeleton of the Thorax: Ribs

  • Types of Ribs:

    • True ribs (1-7)

    • False ribs (8-12)

    • Floating ribs (11 & 12)

Skeleton of the Thorax: Sternum

  • Components:

    • Manubrium

    • Body

    • Xiphoid process

  • Xiphoid process ossifies in the 40s and can be used for bone marrow biopsy

Thoracic Apertures

  • Superior Aperture:

    • Boundaries: T1 vertebra, 1st Rib, 1st costal cartilage, jugular notch of manubrium

    • Contents: Brachiocephalic veins, brachiocephalic trunk, left common carotid a., left subclavian a., internal thoracic a., trachea, esophagus, vagus n., phrenic n., recurrent laryngeal n., sympathetic trunk

  • Inferior Aperture:

    • Boundaries: T12 vertebra, 11th and 12th Rib, costal margin, and xiphisternal junction

    • Contents: Inferior vena cava (T8), esophagus (T10), descending thoracic aorta (T12), azygos vein, thoracic duct, vagus n.

Intercostal Nerves

  • Derived from thoracic spinal nerves:

    • Ventral rami of T1-T11 form intercostal nerves

    • Ventral ramus of T12 forms the subcostal nerve

    • Dermatomes: Bandlike skin areas each supplied by a single spinal nerve.

Vasculature of Thoracic Wall

  • Arterial Supply Sources:

    • Thoracic aorta

    • Subclavian artery

    • Axillary artery

  • Key arteries:

    • Posterior intercostal arteries

    • Internal thoracic artery and branches

Venous Drainage

  • Posterior Intercostal Veins:

    • Drain mostly into the azygos venous system

  • Anterior Intercostal Veins:

    • Drain into the internal thoracic vein

    • Anterior and posterior intercostal veins anastomose with each other.

Lymphatic Drainage

  • Lymphatic Plexuses:

    • Subareolar lymphatic plexus

  • Lymph Drainage Patterns:

    • 75% from lateral quadrants drain to axillary lymph nodes

    • Remaining lymph (medial quadrants) drains to parasternal nodes or opposite breast

    • Lymph from lower quadrants drains into inferior phrenic nodes

References

  1. Clinically Oriented Anatomy, by Moore & Dalley

  2. Gray's Anatomy for Students

  3. Basic & Clinical Anatomy of the Spine, Spinal Cord, and ANS

  4. Essentials of Clinical Neuroanatomy and Neurophysiology

  5. Atlas of Human Anatomy

  6. Clinical Anatomy By Systems