anatomy of the thorax/ribs, sternum and musculature

what are the three components of ribs?

vertebral, body, sternal

what is the vertebral portion of the rib?

head, neck, tubercle

what does the sternal head articulate with?

the vertebral body

what does the sternal tubercle articulate with?

the transverse process of the same # vertebrae

• Non-articular area provides attachment of ligaments

what makes up the body of the rib?

• rib angle

• inferior costal groove

where is the rib angle?

it is just sternal to the articular facets

what is the inferior costal groove?

it houses the intercostal vessels

• VAN from superior to inferior

what are the true ribs?

• 1-7

• articulates directly with the costal cartilage, which then articulates directly with the sternum

what are the false ribs?

• 8-10

what do false ribs 9-10 articulate with?

the costal cartilage above

what do ribs 11 and 12 articulate with?

• they are free at the end

• this means they are floating ribs!

what does the first rib look like?

it is flat with no angle

what do ribs 1 & 10-12 have in common?

they have full facets at their vertebral end

what do ribs 2-9 look like?

they have two demifacts that articulate with the vertebrae

what is the 1st rib articulated with on the sternum?

fused with the manubrium as a synarthrosis

what is the 2nd rib articulated with on the sternum?

it articulates with the sternal angle as a synovial joint

what do the 3rd-7th ribs articulate with on the sternum?

They articulate with the body of the sternum as synovial joints

what do the 8-10 ribs articulate with on the sternum?

They articulate with the ribs above as synovial joints

do the 11 and 12 ribs articulate?

NOOOOO

what rib does the xiphoid process articulate with?

rib 7

what does the manibrium articulate with?

• rib 1

• rib 2

• clavicle

how is the sternal angle formed?

The inferior portion of the manubrium fuses to the superior portion of the body

how many segments does the body og the sternum have?

4

• they fuse between puberty and the 25th year

what is the origin of the external intercostals

the inferior border of rib above from tubercle to costochondral joint

what is the insertion of the external intercostals?

superior surface of rib below

what is the fiber direction of the external intercostals?

downward and forward

what is the action of the external intercostals?

elevates ribs by pulling them closer together

• muscle of inspiration

what is the muscle of inspiration?

external intercostals

what is the innervation and blood supply of the external intercostals?

adjacent intercostal nerves and vessels

what is the origin of the internal intercostals?

the inferior border of ribs at the sternum to the angle of the ribs

what is the insertion of the internal intercostals?

superior surface of rib below

what is the action of the internal intercostals?

• draws ribs together

• If supported from above, it elevates the ribs

• expiration

what is the innervation and blood supply of the internal intercostals?

adjacent intercostal nerves and vessels

what is the origin of the innermost intercostals?

close to the articulation of the rib with the transverse process

what is the insertion of the innermost intercostals?

extends just anterior to the membranous portion of the internal interrcostal muscles

what is the fiber direction of the innermost intercostals?

downward and posteriorly

what is the action of the innermost intercostals?

draws the ribs together, and if supported from above, to elevate the ribs

what is the innervation and blood supply of the innermost intercostals?

adjacent intercostal nerves and vessels

what is the origin of the diaphragm?

• posterior xiphoid process

• lower ribs

• bodies of lumbar vertebrae 1-2

what is the insertion of the diaphragm?

central tendon

what is the action of the diaphragm?

draws the central tendon down, increasing thoracic volume

what is the main muscle for inspiration, and what is it called?

diaphragm, quiet breathing

what is the innervation of the diaphragm?

phrenic nerve C3,4,5

C345 KEEPS THE DIAPHRAGM ALIVE

what is the blood supply from the diaphragm?

musculophrenic from internal thoracic and inferior phrenic from abdominal aorta

what organ sits on top of the diaphragm?

the heart

what is the origin of the transversus thoracis?

lower third of body of sternum (underside)

what is the insertion of the transversus thoracis?

lower border of ribs 2-6

what is the fiber direction of the transversus thoracis?

upward and outward

What is the action of the transversus thoracis?

draws ribs downward

what type of breathing does the transversus thoracis do?

forced expiration

what is the innervation and blood supply for the transversus thoracis?

adjacent intercostal nerves and vessels

how is quiet inspiration and expiration done?

contraction of the external intercostals of diaphragm

• BUCKET HANDLE MOVEMENT OF THE RIBS

how is forced inspiration done?

• The first two ribs are elevated by the contraction of the scalenes and sternocleidomastoid muscles.

• all intercostals muscles contract

how is forced expiration done?

• the quadratus lumborum pulls down last two ribs

• intercostals contract

• increased intrabdominal pressure, which pulls down on ribs and sternum and pushes upward on the diaphragm increasing pleural cavity pressure

what are the intercostal nerves?

the ventral rami of the 1st 11 pairs of thoracic nerves

what does each intercostal nerve break into?

• a lateral cutaneous branch at the mid axillary line

• an anterior cutaneous nerve lateral to the sternum