1. Ribs & Sternum Flashcards
What is the function of the sternum?
Anchors anterior ends of ribs 1-7
Protects cardiorespiratory organs
What are the 3 parts of the sternum?
Manubrium
Mesosternum
Xiphoid process
Where does the clavicle articulate with the sternum?
Clavicular notch
Where do the ribs articulate with the sternum?
Costal notches
What is the sternal angle?
Joint formed by articulation of the manubrium and mesosternum
What are the transverse processes?
Raised ridges running laterally across mesosternum between costal notches
What muscles attach to the manubrium?
Sternoclediomastoid (goes to temporal bone)
Sternohyoid (goes to hyoid bone)
Action of SCM?
head rotation and flexion
Action of sternohyoid?
Depression of hyoid
What muscles connects to the manubrium and the mesosternum?
Pectoralis major (goes to the humerus)
Action of pec major?
Adduction, medial rotation and flexion of arm
Examples of non-metric traits of the sternum?
Sternal foramen
Synostosis
Bifid/trifid xiphoid process
What is pectus excavatum?
Failure in fusion of sternal plates
Causes compression of thoracic viscera
More common in males than females (3:1)
Indent of the chest
What is pectus carinatum?
Overgrowth of costal cartilages which force sternal plates into bowed arrangement
Can cause difficulties in breathing
Outgrowth of the chest
Which ribs are false ribs and why?
8-10
articulate with the costal margin
Which ribs are floating ribs and why?
11-12
do not connect to sternum or costal cartilages
end in abdominal musculature
Which ribs are true ribs and why?
1-7
Articulate directly with sternum via costal cartilages
What is the pattern of length of ribs?
Increase 1-7, decrease 7-12
What vertebrae do ribs articulate with?
Thoracic vertebrae
Characteristics of Rib 1?
Rougher superior (grooves for vascular structures - subclavian vein and artery)
Scalene tubercle for anterior scalene msucle
Oriented in transverse plane, no angle
Single whole articular facet on head
Characteristics of Rib 2?
Starts to deviate inferiorly
Ridge for posterior scalene muscle
Characteristics of Rib 11?
Singular articular facet on head
Lacks tubercle
Slight angle
Shallow costal groove
Characteristics of Rib 12?
Similar to rib 11 but shorter with no angle
Shaft tapers to point
Examples of non-metric traits of ribs?
Extra cervical and lumbar ribs
Bifid ribs - sternal end may be congenitally split
What are costal cartilages?
Persistent, unossified extensions of cartilaginous models that preceded the fully ossified ribs
Flat bars of hyaline cartilage
What do costal cartilages contribute to?
Mobility and elasticity of the thorax
What is the costochondral junction?
Where rib and cartilage merge together with convex tip of cartilage being received by concave end of rib
No movement across joint
Properties of 1st costosternal joint?
Between costal cartilage 1 and manubrium
Primary cartilaginous
Potential to synostose with age
What type of joints are costosternal joints 2-7/8?
Synovial
What type of joints are costosternal joints 9&10?
Rarely synovial
Joint cavity may be absent
How does ossification in a ventral direction occur?
Morphological alteration of ventral/sternal rib end
OR
Direct ossification of the costal cartilages
What problems does the Iscan et al (1984) method suffer from?
Depends on preservation and positive identification of 4th rib
Criteria used for method do not allow consistent application between examiners
Separate standards for race and sex
Estimated age ranges provided do not equate to 2SD as normally expected
What 3 age related changes did Iscal et al (1984) describe?
Pit depth
Pit shape
Rim and wall configuration
…at the end of the 4th rib
