The Chest Wall Anatomy

Vocabulary flashcards covering the osteology, arthrology, myology, and morphology of the chest wall.

Thorax

The anatomical region comprising the upper trunk situated between the neck above and the abdomen below, enclosed by a musculoskeletal wall and protecting major organs of the circulatory and respiratory systems.

External Configuration of the Thorax

Cylindrical in shape in the newborn, and conical, slightly flattened in the ventrodorsal direction at the lower base in adults.

Thoracoabdominal Diaphragm

The muscular partition that closes the inferior opening of the thorax, separating the thoracic cavity from the abdominal viscera.

Dimensions of the Thorax

Height measures $12\,\text{cm}$ anteriorly, $27\,\text{cm}$ posteriorly, and $33\,\text{cm}$ laterally; sagittal diameter is $5\,\text{cm}$ at the apex and $12\,\text{cm}$ at the base; transverse diameter is $11\,\text{cm}$ at the apex and $26\,\text{cm}$ at the base.

Endothoracic Fascia

The connective tissue membrane that lines the inner surface of the thoracic wall.

Sternum

A flat, median, unpaired, and symmetrical bone situated subcutaneously in the anterosuperior thoracic wall that participates in forming the shoulder girdle.

Manubrium

The thick, broad, trapezium-shaped superior segment of the sternum presenting the jugular notch, paired clavicular notches, the first costal notches, and demi-notches for the second costal cartilages.

Angle of Louis (Sternal Angle)

The junction formed between the manubrium and the body of the sternum, measuring on average $15^\circ$.

Body of the Sternum

The elongated central segment of the sternum displaying transverse striations from the fusion of six sternal elements, with lateral articular notches for costal cartilages two through seven.

Xiphoid Process

The cartilaginous and variably shaped inferior terminal segment of the sternum articulating superolaterally with the inferior half of the seventh costal cartilage.

True Ribs (Sternal Ribs)

The first seven pairs of ribs ($1^{\text{st}}$ to $7^{\text{th}}$) that connect directly to the sternum through individual costal cartilages at chondrosternal joints.

Floating Ribs

The eleventh and twelfth pairs of ribs ($11^{\text{th}}$ and $12^{\text{th}}$) whose anterior cartilaginous ends remain unattached and free anteriorly.

Asternal Ribs

The ribs from the eighth to twelfth pairs ($8^{\text{th}}$ to $12^{\text{th}}$) that do not attach directly to the sternum.

Typical Rib Anatomy

An elongated italic 'S'-shaped flat bone composed of a shaft with anterior and posterior angles, a costal groove on its thin inferior border, and dorsal and ventral extremities.

Costal Groove

The channel running along the internal aspect of the thin inferior border of a rib shaft that transmits the intercostal neurovascular pedicle.

Head of a Typical Rib

The dorsal articular extremity featuring upper and lower facets separated by a crest: the upper facet articulates with the vertebra above, and the lower facet articulates with the vertebra of the corresponding level.

Costal Tubercle

An elevation situated between the neck and shaft of a rib comprising an articular portion for the transverse process of the corresponding vertebra and a non-articular portion.

First Rib

The broadest and shortest rib, flattened craniocaudally, lacking a costal groove, and possessing a single articular facet on its head that articulates exclusively with T1.

Second Rib

An obliquely oriented rib intermediate in orientation between the first and third ribs that completely lacks a costal groove.

Tenth Rib

A rib characterized by having a solitary articular facet on its head that articulates solely with T10.

Eleventh and Twelfth Ribs

Ribs distinguished by the complete absence of a neck and costal tubercle, articulating solely with their correspondingly numbered thoracic vertebrae.

Morphology of a Typical Vertebra (Components 1–8)

Structural components of a vertebra: 1- Pedicles, 2- Superior articular process, 3- Laminae, 4- Vertebral foramen, 5- Spinous process, 6- Body, 7- Transverse process, 8- Inferior articular process.

Costocorporeal Joint

An arthrodial (plane synovial) joint connecting the head of a rib with two adjacent thoracic vertebral bodies and the intervertebral disc between them.

Costotransverse Joint

A trochoid (pivot) joint formed between the articular facet of the costal tubercle and the transverse process of the vertebra of the corresponding number.

Costochondral Joints

Syndesmotic fibrous joints formed between the anterior ends of the ribs and their corresponding costal cartilages.

Interchondral Joints

Synovial joints formed between the adjacent margins of the sixth, seventh, and eighth costal cartilages.

External Intercostal Muscles

Superficial muscles positioned between the ribs that elevate the ribs during active inhalation.

Medium Intercostal Muscles

Intercostal muscles situated deep to the external intercostals that act primarily during forced exhalation.

Internal Intercostal Muscles (Innermost Intercostals)

The deepest layer of the intercostal muscle group located within the intercostal spaces that is involved in the movements of the ribs.

Subcostal Muscles

Muscles located on the internal surface of the posterior thoracic wall that assist in depressing the ribs.

Transverse Thoracic Muscle

A muscle located on the posterior surface of the sternum connecting to the costal cartilages that plays a minor role in exhalation.