Summer Session II; Anatomy; Lecture 18; Thorax Wall and Muscles of the Thorax
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Where is the thorax located?
The upper part of the trunk b/w the neck and abdomen
List (3) char. of the thoraic cage
- 12 thoracic vertaebrae posteriorly
- 12 pairs of ribs and costal cartilages
The thoracic vertabrae has facets on their bodies for what?
It also has facets on their transverse processes for what?
- For articulation of the heads of the ribs.
- For articulation with the rib tubercle.
How many pairs of true ribs are there? False ribs? Why are they called false ribs? How many floating ribs are there? Why are they called floating?
- 7 pairs of true ribs
- 3 pairs of false ribs; do not directly articulate with the sternum via their own costal cartilage
- 2 pairs of floating ribs- do not articulate with the sternum.
List 4 of the Rib articulations
describe the typical rib
- head w/ two articular facets
- body or shaft
- costal groove
List 2 synovial plane joints
Describe the articulation of the costovertebral joint; What ligament goes across it? Describe the ligament; What is the name of the ligament that attaches the head of the rib to the intervertebral disc?
Articulation of the head of the rib with the superior par tof the body of the corresponding throcacic vertebra, the inferior part of the body of the vertebra above and the intervertebral disc.
Radiate ligament- thickening of the anterior capsule surroinding the head of the rib and the two bodies of the vertebrae.
Describe the articulation of the Costotransverse joint.
How is it supported?
Articulation of the tubercle of the rib with the associated transverse process.
It is supported both superiorly and laterally by the superior and lateral costotransverse ligaments.
Describe the articulation of the costochondral joint. What type of joint is it?
Articulation of the sternal end of the ribs with the costal cartilages.
Primary cartilaginous joint
Describe the articulation of the sternocostal joints. What type of joint is the 1st rib? what about the 2nd to 7th? How are these sternocostal joints supported?
Articulation of the costal cartilages with the manubrium and sternum.
1st rib: primary cartilaginous joint
2nd to 7th: synovial plane joint
By anterior and posterior radiate sternocostal ligaments.
List 3 parts of the sternum
What does inspiration require of the thoracic cage? List the 3 steps of this process and describe.
requires that the volume of the thoracic cage be increased.
- 1. Vertical - diaphragm lowers during contraction
- 2. transverse- bucket handle movement of the ribs, primarily by ribs 8-10
- 3. Ant/Post - Pump handle movements of the ribs , primarily by ribs 1-7
List the 9 muscles of the thorax
- serratus anterior
- serratus posterior
- external intercostals
- internal intercostals
- innermost intercostals
- subcostal muscles
- transverse thoracis
- levatores costarum
How many pairs of external intercostals are there? Describe their direction of fibers. What do they become as they reach the costal cartilages?
- 11 pairs
- run obliquely from rib above to the rib below, in anterior inferior direction.
- external intercostal membrane
how many pairs of internal intercostals are there? Describe orientation and how they run. What do they form posteriorly?
deep to external intercostals, run obliquely at right angles to the external intercostals
internal intercostal membrane
How many pairs of innermost intercostals are there?
how do their fibers run?
How are they seperated by the internal intercostals?
What do they cover?
- 11 pairs, run similar to internal intercostals
- innercostal nerves and vessels
- middle 3/4 of the intercostal space
Describe the attachments of the "thin muscular slips" known as the subcostal muscles.
What do they cross?
How do their fibers run?
- extend from the angle of a rib on the internal surface to internal surface of rib below.
- two intercostal spaces
- in same direction as the internal intercostals.
How many transverse thoracis muscluar slips are there? How do they arise? How do they span?
- 4 or 5
- from the xiphod and body of the sternum
- superiorly and laterally to the 2nd to 6th costal cartilages
What shape is the lavatores costarum and how many are there? How do they arise? How do they insert?
- 12 fan shaped muschles.
- arise from the transverse process of C7 to T11
- inferiorly and laterally to insert on ribs below.
Give (2) char. of the intercostal nerves.
Ventral primary rami of the first eleven thoracic spinal nerves
The twelfth thoracic spinal nerve is called the subcostal nerve
What is each intercostal space supplied by (artery)?
What does the internal thoracic artery arise from?
- A large posterior intercostal artery arising from the aorta
- and a small anterior intercostal artery arising rom the internal thoraic artery.
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