Trunk Part #1

CLINICAL TRAINING: THE THORAX, PART I

Instructor: John Petrizzo, PT, DPT, CSCS

THE THORAX

• Definition:

  • The thorax is the superior part of the trunk located between the neck and abdomen.

• Thoracic Cavity:

  • Surrounded by the thoracic wall. Contains vital structures including:

  • Heart

  • Lungs

  • Thymus

  • Distal part of the trachea

  • Most of the esophagus

THE THORACIC WALL

• Components:

  • Composed of:

  • Skin

  • Fascia

  • Nerves

  • Blood vessels

  • Muscles

  • Cartilages

  • Bones

• Functions:

  • Protects thoracic and abdominal organs.

  • Resists negative internal pressures resulting from:

  • Elastic recoil of the lungs

  • Inspiratory movements

  • Provides attachment for muscles related to the upper limbs, neck, abdomen, back, and respiration.

SKELETON OF THORACIC WALL

• Description:

  • The thoracic skeleton forms the osteocartilaginous cage.

• Key Components:

  • Consists of:

  • 12 pairs of ribs and their costal cartilages

  • 12 thoracic vertebrae and intervertebral discs

  • Sternum

• Features:

  • Costal cartilages form the anterior continuation of the ribs.

  • Allow for flexible attachment at the articulation with the sternum.

  • Ribs and their cartilages are separated by intercostal spaces which are filled with:

  • Intercostal muscles

  • Blood vessels

  • Nerves

THORACIC APERTURES

• Superior Thoracic Aperture:

  • Communicates with the neck and upper limb.

  • Anatomical thoracic inlet.

  • Structures passing through include:

  • Trachea

  • Esophagus

  • Vessels

  • Nerves

  • Dimensions:

  • Approximately 6.5 cm anteroposteriorly

  • Approximately 11 cm transversely

  • Bounded:

  • Posteriorly by T1 vertebra

  • Laterally by first ribs and costal cartilages

  • Anteriorly by superior border of the manubrium

• Inferior Thoracic Aperture:

  • Connects thoracic cavity with the abdomen.

  • The diaphragm closes this aperture.

  • Structures passing through:

  • Inferior vena cava

  • Esophagus (through openings in the diaphragm)

  • Aorta (passes posterior to diaphragm)

  • Bounded:

  • Posteriorly by T12

  • Anterolaterally by costal cartilages of ribs 7-10

  • Anteriorly by xiphisternal joint

THE THORACIC SKELETON

Ribs

• Description:

  • Ribs are curved, flat bones forming most of the thoracic cage.

  • They are light but resilient and contain spongy interior with bone marrow for blood cell formation.

Types of Ribs:

• True Ribs (vertebrosternal):

  • 1st to 7th ribs

  • Attach directly to the sternum via their own costal cartilages.

• False Ribs (vertebrochondral):

  • 8th to 10th ribs

  • Connected to the sternum indirectly through the costal cartilages of the ribs superior to them.

• Floating Ribs (free):

  • 11th and 12th ribs, which do not attach to the sternum.

ANATOMICAL STRUCTURE OF RIBS

• Typical Ribs (3rd to 9th):

  • Parts includes:

  • Head:

    • Contains two facets that articulate with the vertebral body.

  • Neck:

    • Connects the head to the body.

  • Tubercle:

    • At the junction of the neck and body, articulates with the transverse process.

  • Body:

    • Shaft consisting of an angle, which is where the rib turns anterolaterally.

• Atypical Ribs (1st, 2nd, 10th - 12th):

  • 1st Rib:

  • Widest, shortest, and most sharply curved with only one facet.

  • 2nd Rib:

  • Thinner, more typical in shape.

  • 10th - 12th Ribs:

  • Have only one facet; 11th and 12th are short, lacking necks or tubercles.

• Costal Cartilages:

  • Extend the ribs anteriorly, enhancing the elasticity of the thoracic wall.

THORACIC VERTEBRAE

• Characteristic Features:

  • Presence of bilateral superior and inferior costal facets.

  • Costal facets located on their transverse processes.

  • Long spinous processes that slant inferiorly and overlap the intervertebral discs and vertebrae below.

COSTOVERTEBRAL ARTICULATIONS OF A TYPICAL RIB

• Joints involved in the articulation of the ribs include:

  • Costovertebral joints (joints of head of rib)

  • Costotransverse joints

  • Structure includes:

  • Body of vertebra superior to the rib, intervertebral disc, head of rib, tubercle of rib, and the transverse process of the vertebra of the same number as the rib.

STERNUM

• Parts of the Sternum:

  • Manubrium:

  • Superior part, lies at the level of T3 and T4.

  • Indented by the jugular notch centrally, with lateral clavicular notches.

  • 1st rib costal cartilage fuses with lateral border.

  • Forms sternal angle opposite the 2nd pair of costal cartilages at the level of the intervertebral disc between T4 and T5.

  • Body of the Sternum:

  • Extends from the T5 to T9 level; narrower and thinner than the manubrium.

  • Xiphoid Process:

  • Located at the T10 level and is the smallest part of the sternum.

  • Ossified in older adults (over 40 years).

  • Xiphisternal joint at T9 level serves as a midline marker for:

    • Superior level of the liver

    • Central tendon of diaphragm

    • Inferior border of the heart

JOINTS OF THE THORACIC WALL

• Movement Characteristics:

  • Joint movements are frequent, but the range of motion (ROM) is typically small.

  • Reduced mobility in these joints could impair respiration.

• Types of Joints:

  • Occur between the following structures:

  • Vertebrae (intervertebral joints)

  • Ribs and vertebrae (costovertebral and costotransverse joints)

  • Sternum and costal cartilages (sternocostal joints)

  • Sternum and clavicle (sternoclavicular joints)

  • Ribs and costal cartilages (costochondral joints)

  • Costal cartilages (interchondral joints)

  • Parts of the sternum (manubriosternal and xiphisternal joints)

MOVEMENTS OF THORACIC WALL

• During Inspiration:

  • Movements increase the intrathoracic diameters and volume of the thorax.

  • This creates pressure changes that draw air into lungs through the nose, mouth, larynx, and trachea.

• During Passive Expiration:

  • Relaxation of the diaphragm, intercostal muscles, and other muscles decrease intrathoracic volume and increase intrathoracic pressure, resulting in expelling air from the lungs.

  • Elastic tissue of the lungs recoils to push air out.

  • Concurrently, intra-abdominal pressure decreases, facilitating decompression of abdominal viscera.

• Vertical Dimension Changes:

  • During inspiration, the diaphragm descends, increasing the vertical dimension, which compresses abdominal viscera.

  • Volume returns to neutral during expiration.

• Anteroposterior Dimension Changes:

  • Increased by contraction of intercostal muscles.

  • Upper ribs movement at costovertebral joints alters the anterior end of the ribs and sternum anteriorly/posteriorly like a pendulum.

• Transverse Dimension Changes:

  • Slight increase during contraction of lower ribs via bucket-handle movement.

EXAMPLES OF MOVEMENTS DURING INSPIRATION

• Observed types of movements during breathing:

  • Bucket-handle Movement:

  • Upper ribs elevate, expanding AP diameter.

  • Pump-handle Movement:

  • Middle parts of lower ribs move laterally when elevated, increasing transverse diameter.

CLINICAL BOX: COSTAL CARTILAGES

• Role of Costal Cartilages:

  • They enhance the elasticity of the thoracic wall, preventing fractures with blows.

  • In elderly individuals, calcification occurs, reducing resilience.

• Rib Fractures:

  • The weakest point is typically anterior to the angle of the rib.

  • Commonly caused by direct or crushing injuries, with middle ribs being the most at risk.

  • Broken ends may injure internal organs such as lungs or spleen.

CLINICAL BOX: FLAIL CHEST

• Condition arises from multiple rib fractures, leading to a free segment of the thoracic wall.

  • Loose segment moves paradoxically, causing pain and impairing ventilation.

  • Oxygenation of blood may be affected, requiring internal fixation with plates or wires to stabilize movement.

CLINICAL BOX: SUPERNUMERARY RIBS

• A cervical rib presence in ~1% of the population.

  • Articulates with C7, potentially compressing spinal nerves C8 and T1 or the inferior trunk of the brachial plexus. - May result in tingling or numbness along the medial forearm and can compress the subclavian artery, leading to ischemic muscle pain.

  • Resection may be necessary.

CLINICAL BOX: THORACIC OUTLET SYNDROME

• Costoclavicular Syndrome:

  • Characterized by pallor and coldness of skin in the upper limb and diminished radial pulse due to compression of the subclavian artery between the clavicle and 1st rib, particularly when the neck-shoulder angle is increased.

CLINICAL BOX: DISLOCATION OF RIBS

• Refers to the displacement of costal cartilage from the sternum, causing severe pain during deep breaths.

  • May produce a lump at the site of the dislocation.

  • Complications can include pressure on or damage to surrounding nerves, vessels, and muscles.

CLINICAL BOX: SEPARATION OF RIBS

• Separation occurs at the costochondral junction between the rib and costal cartilage, with the rib sometimes moving superiorly and overriding the rib above, leading to pain.

CLINICAL BOX: PARALYSIS OF DIAPHRAGM

• Can be spotted through radiographic techniques showing paradoxical movement; domes are supplied independently by the left and right phrenic nerves.

• During inspiration, the paralyzed dome is pushed superiorly by compression from abdominal viscera, instead of descending.

  • The paralyzed dome will descend during expiration due to positive pressure from the lungs.

CLINICAL BOX: STERNAL FRACTURES

• Typically occur due to traumatic compression of the thoracic wall, such as in motor vehicle accidents (MVAs).

  • The main concern is possible injury to the heart and/or lung, with risks including myocardial contusion, cardiac rupture, and tamponade.

QUESTIONS?

• Questions about the thorax, its anatomy, and clinical conditions can be directed to the instructor.