The Thoracic Cavity
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How many ribs are there total?
What are "true" ribs?
True ribs (also known as vertebrocostal) are ribs that attach directly to the sternum through their own costal cartilage. Ribs 1-7 are true ribs and attach directly, both anteriorly and posteriorly
What are "false" ribs?
False ribs (also known as vertebrochondral) are ribs that have cartilages that join with rib just superior and thus connect with the sternum indirectly. Ribs 8-10 are false ribs and attach to sternum via common cartilage
What are "floating" ribs?
Floating ribs (also known as free) are ribs that have rudimentary cartilage and do not connect even indirectly with the sternum. Ribs 11-12 are free ribs and have no anterior articulation (connection)
The ____ ____ on rib number attach to ____ and ____.
A rib is most commonly injured...
Just anterior to its angle, where it is weakest; middle ribs (5-9) are most commonly injured because they are not protected and are the longest
Are ribs 1-4 commonly injured?
No; ribs 1-4 are rarely injured because they are fairly short and protected by the clavicle
- Sharpest curve
- Broadest (the broader the rib is, the more muscles can attach)
2 facets; one attaches to T1 and the other attachs to the 1st rib
Articulate (attach) with corresponding vertebra and the one superior (above). Example:Rib 3 articulates with T3 and T2
- Short with one facet
- No neck or tubercles (because they do not attach at the anterior aspect)
12 thoracic vertebrae
- Long vertebral spinous processes that slant inferiorly
- Thin intervertebral discs (very thin in order to limit movement; recall the slice of bread and textbook example)
What features of the thoracic vertebrae limit movement?
- The inferior sloping of spinous processes (makes it so that bone sits on bone and therefore cannot easily move)
- Thin intervertebral discs
- Articulation of ribs (limits movement in the transverse plane)
What are the "bumps" you feel along your back?
What are the parts of the sternum?
- Xiphoid process
What is the manubrium?
The superior part of the sternum which articulates with the 1st and 2nd ribs; it's roughly trapezoidal in shape and contains the jugular notch land marking
What is the "body"?
The part of the sternum just inferior to the manubrium, which is longer, narrower, and thinner than the manubrium; the body's width varies due to costal notches
What is the xiphoid process?
The smallest and most variable part of the sternum; it is cartilaginous in young people, but more or less ossified in older people (composed of hyaline cartilage until individuals are roughly 40 years old)
What is costocartilage?
Cartilage that prolong ribs anteriorly; it contributes to the elasticity of the thoracic wall
Meaning "between ribs"; contains intercostal muscles, vessels (arteries/veins), and nerves
What is the pleura?
- Thin double layer membrane
- Contains fluid between layers
- Enables lungs to move freely
- Protects heart and lungs
- Fluid also helps to absorb shock
What is a costovertebral joint?
A synovial plane joint where a rib articulates with a vertebra; contains 2 ligaments: the radiate (stabilizes at external aspect) and intra-articular (stabilizes at internal)
What is a costotransverse joint?
A joint where a rib articulates with a transverse process of the corresponding vertebra; contains the lateral and superior costotransverse ligaments
What is a manubriosternal joint?
A cartilaginous joint where the manubrium articulates with the body of the sternum
What is a xiphisternal joint?
A cartilaginous joint where the ziphoid process articulates witht he body of the sternum
What is a costochondral joint?
A cartilaginous joint where the sternal end of a rib articulates with lateral costal cartilage; the rib and cartilage are binded together by periosteum
What is a interchondral joint?
A synovial plane joint responsible for the articulation between ribs 6/7, 7/8, and 8/9
What is a sternochondral joint?
A joint responsible for the articulation between the sternum and costal cartilage; contains the anterior and posterior radiate sternocostal ligaments
External Intercostal muscle
- Origin: Inferior border of rib above (superior)
- Insertion: Superior border or rib below (inferior)
- Action: Elevation of ribs during inspiration
Internal Intercostal muscle
- Origin: Superior border of rib below
- Insertion: Inferior border of rib above
- Action: Depression or ribs during expiration
*Runs at right angle to External Intercostal muscle*
Innermost Intercostal muscle
*Deepest / most internal*
- Origin:Inferior border of rib above
- Insertion:Superior border of rib below
- Action:Elevate ribs during inspiration
*Innermost Intercostal muscle runs primarily on the lateral
aspect because we need more power
to raise ribs there because the ribs get longer
Transverse Thoracis muscle
*Runs more in the horizontal plane*
- Origin: Posterior surface of lower sternum
- Insertion: Internal surface of ribs 2-6 costal cartilage
- Action: Rib depression
What is pleurisy?
An infection of the fluid of the pleura
What occurs during rib separation?
The rib separates from the costal cartilage that attaches it to the sternum
Name the joints listed 1-6 in the picture above
- 1. Costovertebral joint
- 2. Costotransverse joint
- 3/4. Sternocostal joint
- 5. Costochondral joint
- 6. Manubriosternal joint
Structures of the thoracic cage
Structures of the thoracic vertebrae
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