Thorax Flashcards
How many apertures does the thoracic cavity have and which are these?
Two - superior and inferior thoracic apertures
To which regions does the thorax communicate with through the superior thoracic aperture/thoracic inlet?
Neck and upper limb
How is the superior thoracic aperture shaped? Why is it shaped like this?
Slopes antero-inferiorly because of the obliquity of first pair of ribs
How is the superior thoracic aperture bounded?
- Posteriorly: T1 vertebra
- Laterally: first pair of ribs and their costal cartilages
- Anteriorly: superior border of manubrium
To which region does the thorax communicate with through the inferior thoracic aperture/thoracic outlet?
- Abdomen
How is the inferior thoracic aperture bounded?
- Posteriorly: T12 vertebra
- Posterolaterally: 11th and 12th pairs of ribs
- Anterolaterally: joined costal cartilage of 7-10 ribs (form costal margin)
- Anteriorly: xiphisternal joint
How many types of ribs are there and which are these?
Three.
True, false, and floating
Which are the true ribs and what characterizes them as such?
1-7th ribs
- Attach directly to sternum anteriorly through own costal cartilages
Which are the false ribs and what characterizes them as such?
8-10th ribs
- Have cartilages on their anterior ends that are joined to cartilage of the rib just superior to them; thus, their connection with the sternum is indirect
Which are the floating ribs and what characterizes them as such?
11th and 12th
- Have rudimentary cartilages on anterior ends that don’t connect to sternum; instead, they end in posterior abdominal musculature
Which are the typical ribs and what are the parts that compose these?
3rd to 9tn
Parts: head, neck, tubercle, body
How many facets does the head of a typical rib have and how do they articulate with the vertebra?
2 facets separated by the crest of the head
- The inferior one articulates with the body of the numerically corresponding vertebra (at superior facet) and the superior one with the superior vertebrae (at inferior facet)
What does the neck of a typical rib connect?
Head with body at the level of the tubercle
Where is the tubercle of a typical rib and which parts compose its articular cavity?
At the junction of neck and body
- It has a smooth articular part and a rough nonarticular part
What attaches to or articulates with the articular and nonarticular part of the tubercle of rib?
Articular: for articulating with corresponding transverse process (synovial)
Nonarticular: fibrous attachment to process through costotransverse ligament
What are the two structural features of the body of the rib?
Angle: where the rib begins to turn anterolaterally
Costal groove: concavity on the inferior edge that runs along the internal surface of the body
Which are the atypical ribs?
1st, 2nd, 10 - 12th
What are the characteristics of the 1º rib?
- Shortest and most sharply curved of true
- 2 shallow horizontal grooves crossing its superior surface; these are separated by the scalene tubercle and ridge
- Articulates with T1 only
What are the characteristics of the 2º rib?
- Thinner and more typical
- Formations for attachment of serratus anterior and posterior scalene muscles
- Almost twice length of 1st
Which ribs have only 1 facet on their heads?
10-12th and 1st
Which ribs have no necks or tubercles?
11th and 12th
What are the costal cartilages?
Bars of hyaline cartilage that prolong ribs anteriorly and contribute to elasticity of thoracic wall
What is the sternum?
Flat, vertically elongated bone that forms the middle of the anterior part of the thoracic cage
Which parts constitute the sternum?
Manubrium, body, and xiphoid process
What is the manubrium?
Superior part of sternum with a roughly trapezoidal shape
Where is the manubrium of the sternum?
Lies at the level of T3 and T4
What is the jugular notch?
Central indentation in superior border of the manubrium of the sternum
Where are the clavicular notches?
Indentations on each side of the jugular notch that articulate with sternal end of clavicle
What is the sternal angle and where is it located?
Located opposite to the second pair of cartilages at the level between T4 and 5, originated by the slight difference on the planes where the manubrium and body are located
What is the body of the sternum?
Inferior continuation of the manubrium; longer, narrower, and thinner than the manubrium, with a variable width
Where is the body of the sternum and what main structural feature does it have?
At the level of T5-9 vertebral level
-Costal notches: located on the lateral borders of the body for articulation with the costal cartilages
What is the xiphoid process?
Small elongated inferior projection of the body of the sternum
Where is the xiphoid process located?
At the level of T10
What is the thorax?
Superior part of the trunk between the neck and abdomen
What is the thoracic cavity?
Structure surrounded by the thoracic wall; contains the heart, lungs, thymus, distal part of trachea, and most of esophagus
What are the functions of the thoracic wall?
- Protect thoracic and abdominal organs
- Resist negative internal pressure during inspiration
- Provide attachment for many muscles of upper limbs, neck, abdomen, and back and the muscles of respiration
What is the thoracic cage made out of?
- 12 pairs of ribs and costal cartilages
- 12 thoracic vertebrae + IV discs
- Sternum
What are the intercostal spaces?
Openings between ribs, that separate ribs and their costal cartilages from one another
- There are 11 of these
Where is the subcostal space?
Below 12th rib
How many intercostal nerves does the thoracic wall have and where are these?
11; located at the intercostal spaces (# intercostal nerve = # intercostal space)
What is the subcostal nerve?
Nerve located at the subcostal space, made of the anterior ramus of the spinal nerve T12
Name all the joints that can be found on the thoracic wall
- Intervertebral
- Costovertebral
- Costotransverse
- Sternocostal
- Sternoclavicular
- Costochondral
- Interchondral
- Manubriosternal
- Xiphisternal
Which structures articulate at the “intervertebral joints” of the thoracic wall?
Adjacent vertebral bodies bound together by an intervertebral disc
What type of joint are the “intervertebral joints” of the thoracic wall?
Symphysis (secondary cartilaginous joint)
Which ligaments are involved on the “intervertebral joints” of the thoracic wall and what is their function?
Anterior and posterior longitudinal ligaments
Function:
- ALL: limit extension
- PLL: limit flexion
Which structures articulate at the “costovertebral joints” of head of ribs of the thoracic wall?
Head of each rib with
- Superior demifacet or costal facet of corresponding vertebral body
- Inferior demifacet or costal facet of vertebral body superior to it
What type of joint are the “costovertebral joints” of head of ribs joints of the thoracic wall?
Synovial plane joint
Which ligaments are involved in the “costovertebral joints” of head of ribs of the thoracic wall and what are their functions?
Radiate and intra-articular ligaments
Function:
- Radiate: limits elevation and depression of ribs
- Intra-articular: stabilize head of the rib on the costal facet
Which structures articulate at the “costotransverse joints” of the thoracic wall?
Tubercle of the rib with transverse process of corresponding vertebra
What type of joint are the “costotransverse joints” of the thoracic wall?
Synovial plane joint
Which ligaments are involved in the “costotansverse joints” of the thoracic wall and what are their functions?
Lateral and superior costotransverse:
Which structures articulate at the “sternocostal joints” of the thoracic wall?
- Articulation of 1st costal cartilages w/manubrium of sternum
- Articulation of 2nd-7th pairs of costal cartilages w/sternum
What type of joints are the “sternocostal joints” of the thoracic wall?
1st: synchondroses (primary cartilaginous joint)
2nx-7th: synovial plane joints
Which ligaments are involved in the “sternocostal joints” of the thoracic wall and what are their functions?
Anterior and posterior radiate sternocostal:
Which structures articulate at the “sternoclavicular joints” of the thoracic wall?
Sternal end of clavicle with manubrium and 1st costal cartilage
What type of joint are the “sternoclavicular joints” of the thoracic wall?
Synovial saddle joint
Which ligaments are involved in the “sternoclavicular joints” of the thoracic wall and what are their functions?
- Anterior and posterior sternoclavicular ligaments
- Costoclavicular ligament
Which structures articulate at the “costochondral joints” of the thoracic wall?
Lateral end of costal cartilage with sternal end of rib
What type of joint are the “costochondral joints” of the thoracic wall?
Synchondroses (primary cartilaginous joint)
Which ligaments are involved in the “costochondral joints” of the thoracic wall and what are their functions?
Cartilage and bone; bound together by periosteum
Which structures articulate at the “interchondral joints” of the thoracic wall?
Between costal cartilages of the following ribs:
- 6th-7th
-7th-8th
- 8th-9th
Which ligaments are involved in the “interchondral joints” of the thoracic wall and what are their functions?
Interchondral ligaments
What type of joint are the “interchondral joints” of the thoracic wall?
Synovial plane joint
Which structures articulate at the “manubriosternal joint” of the thoracic wall?
Manubrium and body of sternum
What type of joint is the “manubriosternal joint” of the thoracic wall?
Symphysis (secondary cartilaginous joint)
Which structures articulate at the “xiphisternal joint” of the thoracic wall?
Xiphoid process and body of sternum
What type of joint is the xiphisternal joint of the thoracic wall?
Synchondrosis (primary cartilaginous joint)
Movements of the thoracic wall
Characteristics of the vertical dimension of the thoracic wall during inspiration
Increases, as the contracting diaphragm descends, compressing abdominal viscera
Characteristics of the anteroposterior dimension of the thoracic wall during inspiration
Increases considerably when intercostal muscles contract; movement of upper ribs at costovertebral joints, causes anterior ends of ribs and sternum (especially inferior end) to move anteriorly
Characteristics of the transverse dimension of the thoracic wall during inspiration
Increase slightly when intercostal muscles contract, raising the most lateral parts of the ribs (especially the most inferior ones)
Characteristics of the vertical dimension of the thoracic wall during expiration
Returns to neutral position, as the diaphragm ascends by decompressing the viscera
Characteristics of the anteriposterior dimension of the thoracic wall during expiration
Decreases when intercostal musclesrelax; movement of upper ribs at costovertebral joints, causes anterior ends of ribs and sternum (especially inferior end) to move posteriorly
Characteristics of the transverse dimension of the thoracic wall during expiration
Decreases slightly when intercostal muscles relax, depressing the most lateral parts of the ribs (especially the most inferior ones)
How does intrathoracic pressure change throughout respiration?
Inspiration: pressure decreases by increasing intrathoracic volume (diaphragm depresses), resulting in air being drawn into the lungs
Expiration: pressure increases by decreasing intrathoracic volume (diaphragm elevates), resulting in air being expelled
How many layers of muscle do the intercostal spaces contain? Which are these?
Three layers of intercostal muscles
Superficial: formed by “external intercostal” (fibers oriented infero-anteriorly)
Medial: formed by “internal intercostal” (fibers oriented inferoposteriorly)
Deep: “innermost intercostal” (only found at most lateral parts of intercostal spaces)
Anteriorly, the external intercostal muscles are replaced by…
External intercostal membranes
Posteriorly, the internal intercostal muscles are replaced by…
Internal intercostal membranes
What is the origin of the external, internal, and innermost intercostal muscles?
Inferior border of ribs
What is the insertion of the externa, internal, and innermost intercostal muscles?
Superior border of ribs below
What is the innervation of the external, internal, and innermost intercostal muscles?
Intercostal nerves
What is the main action of the external intercostal muscles?
During forced inspiration: elevate ribs
What is the main action of the internal intercostal muscles?
During forced inspiration
- Interosseous part: depresses ribs
- Interchondral part: elevates ribs
What is the origin of the transversus thoracis muscles?
Posterior surface of lower sternum
What is the insertion of the transversus thoracis muslces?
Internal surface of costal cartilages 2-6
What is the innervation of the transversus thoracis muscles
Intercostal nerves
What is the main function of transversus thoracis muscles?
Weakly depresses ribs
What is the origin of subcostal muscles?
Internal surface of lower ribs near their angles
What is the insertion of subcostal muscles?
Superior border of 2nd or 3rd ribs below
What is the innervation of subcostal muscles?
Intercostal nerves
What is the main action of subcostal muscles?
Probably acts in same manner as internal intercostal muscles
What is the origin of levatores costarum?
Transverse processes of C7-11
What is the insertion of levatores costarum?
Subadjacent ribs between tubercle and angle
What is the innervation of levatores costarum?
Posterior rami of C8-T11 nerves
What is the main action of levatores costarum?
Elevate ribs
What is the origin of serratus posterior superior?
Nuchal ligament, spinous processes of C7-T3
What is the insertion of the serratus posterior superior?
Superior borders of 2nd-4th ribs
What is the innervation of serratus posterior superior?
2nd-5th intercostal nerves
What is the main action of serratus posterior superior?
Elevate ribs
What is the origin of the serratus posterior inferior?
Inferior borders of 8th-12th ribs near their angles
What is the insertion of the serratus posterior inferior?
Spinous processes of T11-L2
What is the innervation of serratus posterior inferior?
9th-11th intercostal nerves, subcostal nerve
What is the main action of the serratus posterior inferior?
Depresses ribs
