The Rib Cage and Sternum

Total Ribs: There are $24$ ribs in total, consisting of $12$ pairs.
Sternum: The rib cage also includes the sternum, which adds support and stability.
Primary Function: The main job of the rib cage is to protect internal organs.
Muscle Involvement: Contains muscles that aid in breathing.
Spinal Support: Provides support to the spinal column. Injuries like slipped discs are less likely in the thoracic spine due to the extra support from the rib cage.
Attachment Site: Acts as an attachment site for the shoulder and arms.
Breathing Mechanism: Muscles pull on the rib cage, expanding the thoracic cavity, which helps draw air into the lungs. More detailed information will be covered in A&P $2$ (Respiratory System).

Overall Bone: The entire bone is known as the sternum, which stabilizes the rib cage.
Manubrium: The superior section at the top of the sternum.
Body: Makes up the majority of the sternum.
Xiphoid Process: A small, pointy bit at the inferior end of the sternum.
- Attachment: Abdominal muscles attach to the xiphoid process.
- Caution (CPR): It is crucial to avoid applying chest compressions directly on the xiphoid process during CPR. It can snap off easily, sending a sharp piece of bone into the abdominal or thoracic cavity, potentially causing severe harm. Hand placement for CPR must be securely on the body of the sternum, away from the xiphoid process.

There are $12$ pairs of ribs in total, categorized based on their attachment to the sternum:

True Ribs (Vertebrosternal Ribs):
- Number: Pairs $1$ through $7$ (total of $7$ pairs).
- Attachment: Each true rib has its own individual piece of costal cartilage that attaches directly to the sternum.
False Ribs:
- Number: Pairs $8$ through $12$ (total of $5$ pairs).
- Attachment: Do not attach directly to the sternum.
  - Vertebrochondral Ribs: Pairs $8$ , $9$ , and $10$ (some sources include $11$ but the speaker states $8-10$ ). These attach indirectly to the sternum by sharing costal cartilage with the superior ribs.
  - Floating Ribs: Pairs $11$ and $12$ . These do not attach to the sternum at all and lack costal cartilage connection to the sternum.
    - Note: While called "floating," they are still attached to the thoracic spine, unlike the truly floating hyoid bone.

Intercostal Spaces: The spaces between the ribs, shown in green in diagrams. These spaces house intercostal muscles (involved in breathing) and allow doctors to listen to heart and chest sounds without bone interference. They also provide access to the chest cavity for medical procedures.
Costal Cartilage: Represented in red in diagrams, it is composed of hyaline cartilage.
- Function: Provides flexibility to the rib cage, which is essential for breathing. If ribs were directly bone-to-sternum, breathing would be significantly harder due to reduced flexibility.

Each rib has distinct markings:

Head: The part that attaches to the vertebral body.
Tubercle: A pointy projection that attaches to the transverse process of the vertebra.
Costal Angle: The posterior curve of the rib, where it bends sharply forward.
Body: The main, shaft-like portion of the rib.
Costal Groove: A small indentation on the inferior aspect (bottom) of the rib. This groove protects blood vessels and nerves that run along the rib, as seen in cross-sections.

Purpose: A procedure to remove a buildup of fluid (e.g., blood) or air in the pleural space, which can press on the lungs, make breathing difficult, or cause lung collapse.
Procedure Safety: Chest tubes are inserted carefully to avoid damaging nerves and blood vessels located in the costal groove.
- Guidance: A physician uses a finger to guide the chest tube in place.
  - Protection: The finger protects the underlying blood vessels and nerves.
  - Accurate Placement: Sensory feedback from the fingertip helps ensure the tube passes through the outer pleural membrane into the correct space without puncturing the lung itself.