Sternum Flashcards
What does the sternum do?
anchors the anterior ends of paired ribs 1-7 via costal cartilage and protects the cardiovascular organs
What are the 3 parts the sternum is composed of?
manubrium, mesosternum/body and xiphoid process
What is the sternum formed of?
Sternebrae (which can fuse with age and aid in estimating age)
State the shape of the anterior and posterior surfaces?
Anterior surface is convex and posterior surface is concave
Where does the sternum articulate and with what?
Articulates with clavicle at clavicular notch and with rib cartilage at costal notches
What is the name of the indentation on the superior surface of the manubrium? (Hint: ends in notch)
Jugular notch
What ridges run across the body of the sternum?
Transverse ridges
What is the name of the indentation on the sides of the manubrium?
Costal notches
What 2 muscles come from the manubrium?
Sternocleidomastoid and sternohyoid muscles
Where does the sternocleidomastoid muscle run from and to?
From the manubrium and clavicle to the mastoid process on the temporal bone
What movement/action does sternocleidomastoid produce?
Head rotation and flexion
Where does the sternohyoid muscle run from and to?
From posterior manubrium to the hyoid
What movement/action does sternohyoid produce?
depresses hyoid
What muscle comes from the manubrium AND the body/mesosternum?
Pectoralis major muscle
Where does pectoralis major run from and to?
From manubrium, mesosternum and clavicle sideways to proximal humerus
What movement/action does pectoralis major produce?
Adduction, medial rotation and flexion of arm
What percentage of individuals have a sternal foramen?
5-10%
Name the two kinds of synostosis related to the sternum
Matrical and sclerotic
Describe the 2 kinds of synostosis related to the sternum
Matrical is due to developmental anomaly resulting in the absence of fibrocartilaginous barrier between elements
Scelortic is due to age-related degeneration of the fibrocartilaginous pad in the joint
What percentage of adults have at least one foramen in the xiphoid process?
~30%
Describe pectus excavatum
failure of fusion of the sternal plates (associated with other connective tissue disorders including Marfan’s) and can cause compression of thoracic viscera
Is pectus excavatum more common in males or females?
Males (M3:F1)
Describe pectus carinatum
caused by overgrowth of costal cartilages which force sternal plates into a bowed arrangement and can cause difficulty in breathing
