Thoracic Cage and Intercostal Spaces Flashcards
Components of thoracic wall: (3)
- Thoracic cage
- Muscles
- Fascia and skin
Compartments of thorax: (3)
- Mediastinum
- Right pleural cavity
- Left pleural cavity
Skeleton of the thoracic wall:
Components:
- 12 pairs of ribs and associated cartilages
- 12 thoracic vertebrae and the intervertebral discs between
What are the main characteristics of ribs? (2)
o Curved flat bones
o Each rib has spongy interior containing bone marrow which forms red blood cells
3 types of ribs:
- True (vertebrosternal) ribs
- 1st to 7th ribs
- Attach directly to sternum through their own costal cartilages - False (vertebrochondral) ribs
- 8th, 9th and usually 10th
- Cartilages are connected to the cartilages of the rib above them
- Indirect connection to the sternum - Floating (free vertebral) ribs
- 11th, 12th, sometimes 10th
- No connection to sternum
- End in the posterior abdominal musculature
2 classifications of ribs:
- Typical ribs (3rd to 9th)
- Atypical ribs
What are the characteristics of the head of the typical rib head?
Head: wedge shaped; 2 facets
(separated by crest of the head) for
articulation with numerically
corresponding vertebra and the
vertebra superior to it
What are the characteristics of the head of the typical rib neck?
connects head with body at
level of tubercle
What are the characteristics of the head of the typical rib tubercle? (2)
Tubercle: at junction of neck and
body. 2 parts:
* Smooth articular part with
corresponding transverse
process of vertebra
* Rough non-articular part
attaching costotransverse
ligament
What are the characteristics of the head of the typical rib body? (2)
Body: thin, flat and curved especially
at costal angle (where rib turns
anterolateral)
* Angle demarcates lateral limit
of attachment of the deep
back muscles
* Costal groove- on concave
interior surface- protects
vasculature
What are the characteristics of the head of the atypical first rib? (4)
- Broadest, shortest and most
sharply curved true rib - Single facet on head for
articulation with T1 only - 2 grooves transversely directed
for subclavian vessels - Scalene tubercle separates
grooves and serves as
attachment for anterior scalene
muscle
What are the characteristics of the head of the atypical second rib? (3)
- Thinner, longer and less curved
than 1st rib - Head has 2 facets for articulation
with bodies of T1 AND T2 - Tuberosity for serratus anterior is
a rough area on upper surface
What are the characteristics of the head of the atypical tenth to twelfth ribs? (2)
- Only one facet on head and
articulates with only one vertebra - 11th and 12th ribs are short with no
neck or tubercle
What are the characteristics of costal cartilage? (5)
- Provide attachment for anterior tips of ribs
- Increase in length through first 7 and then gradually decrease
- First 7 attach directly to the sternum
- The 8th to 10th articulate with the costal cartilage superior to them forming a
continuous costal margin - 11th and 12th form caps but don’t attach anywhere
What are the intercostal spaces? (2)
- Separate ribs and costal cartilages from one another
- Named according to the rib forming the superior border
What are the intercostal spaces occupied by? (4)
- Intercostal muscles
- Membranes
- Main intercostal vessels and nerves
- Collateral intercostal vessels and nerves
- Subcostal space- space below _____ rib
- Anterior ramus of spinal nerve T12 is the _____ nerve
- Spaces are widest _________ and widen during inspiration
12th
subcostal
anterolaterally
Typical components of the thoracic vertebrae: (3)
- Body
- Vertebral arch
- 7 processes for muscular and articular connections
Characteristic features of thoracic vertebrae: (4)
- Bilateral costal facets (demi facets) on vertebral bodies
- Usually occur in inferior and superior pairs for articulation with heads of ribs
- Usually on T2 to T9
- Flank interposed intervertebral discs
- Atypical vertebrae have whole facets in place of demi facets
- Costal facets on transverse processes
- Long, inferiorly slanting spinous processes
Flank interposed intervertebral discs:
Superior facet of inferior vertebra and inferior facet of superior vertebra together with posterolateral margin of intervertebral disc
between them form a single socket to receive head of the rib
o T1 has 1 whole _______ but a normal inferior demifacet
o T10 has 1 pair of whole facets partly on its body and partly on _____
o T11 and T12 have a _____ pair of whole facets on their pedicles
superior
pedicle
single
What is the function of costal facets on transverse processes? (2)
- For articulation with the tubercles of ribs
- Except inferior 2 or 3 thoracic vertebrae
What are the characteristics of the Long, inferiorly slanting spinous processes? (5)
- Slope inferiorly
- Project from vertebral arches
- Cover intervals between laminae of adjacent vertebrae
- Convex superior articular facets of superior articular processes face
posterolaterally - Concave inferior articular facets of inferior articular processes face
anteromedially
What is the sternum? (3)
o Flat elongated bone
o Protects mediastinal viscera
o 3 parts
- In adolescents/young adults- 3 parts are connected by cartilaginous joints (synchondroses) that ossify in middle to late adulthood
What are the characteristics of the manubrium? (4)
- Widest and thickest part
- Superior border of jugular notch deepened by clavicles
- Clavicular notches- for sternoclavicular joints
- Synchondrosis of first rib- inferolateral to clavicular notch where costal cartilage of first
rib attaches to lateral border of manubrium
What are the characteristics of the body of the sternum? (4)
- located at level T5 to T9 vertebrae
- Sternal angle of louis
- costal notches present on lateral borders
- transverse ridges on anterior surface represent lines of fusion of 4 separate sternebrae
o fusion occurs between puberty and age 25
Sternal angle of louis characteristics: (4)
o Junction of manubrium and body of sternum
o Created because they lie in slightly different planes
o Level of T4
o Most common site of sternal fracture in elderly
What are the characteristics of the Xiphoid process? (5)
- Smallest and most variable
- Thin and elongated
- Inferior end lies at the level of T10
- Cartilaginous in young people and ossifies at ~ age 40
- May fuse with the sternal body in elderly
The Xiphoid process is an important landmark in the median plane because: (3)
o Its junction with the sternal body indicates the inferior limit of the central part of
the thoracic cavity
o The junction is also the site of the infrasternal angle formed by right and left
costal margins
o It is the midline marker
What is the Xiphoid process the midline marker for? (3)
- Superior limit of the liver
- Central tendon of the diaphragm
- Inferior border of the heart
What are the thoracic apertures? (2)
- Superior thoracic aperture
- Inferior thoracic aperture
What is the Superior thoracic aperture bounded by? (3)
- T1 posteriorly
- 1st pair of ribs and their costal cartilages
- Superior border of manubrium anteriorly
What is the inferior thoracic aperture bounded by? (4)
- T12 posteriorly
- 11th and 12th ribs posterolaterally
- Costal margins anterolaterally
- Xiphisternal joint anteriorly
What are the characteristics of the inferior thoracic aperture bounded by? (2)
o Oblique due to posterior wall being much longer
than anterior wall
o Diaphragm separates thoracic and abdominal
cavities
Intervertebral joint:
Type
Articulation
Ligaments
Comments
Symphysis (secondary cartilaginous)
Adjacent vertebral bodies bound together by intervertebral disc
Anterior and posterior longitudinal
Movement limited to a small degree of rotation
Costovertebral:
Joints of head of rib
Type
Articulation
Ligaments
Comments
Synovial plane joint
Head of each rib with superior facet of vertebral body with the same number, and inferior facet of the superior vertebral body
Radiate and intra-articular ligaments of head of rib
Heads of 1st,11th and 12th ribs articulate only with vertebral body of same number
Costovertebral:
Costotransverse
Type
Articulation
Ligaments
Comments
Synovial plane joint
Tubercle of rib with transverse process of vertebra with the same number
Lateral and superior costotransverse
11th and 12th ribs do not articulate with transverse
processes of vertebrae with the same number
Costochondral
Type
Articulation
Ligaments
Comments
Primary (hyaline) cartilaginous
Lateral end of costal cartilage with sternal end of rib
Cartilage and bone bound together by periosteum
No movement
Interchondral
Type
Articulation
Ligaments
Comments
Synovial plane joint
Between costal cartilages of 6th and 7th, 7th and 8th, and 8th and 9th ribs
interchondral
Articulation between 9th and 10th ribs is fibrous
Sternocostal
Type
Articulation
Ligaments
Comments
Manubriosternal
Type
Articulation
Secondary cartilaginous joint (symphysis)
Between manubrium and body of sternum
Xiphisternal
Type
Articulation
Primary cartilaginous joint (synchondrosis)
Between xiphoid proves and body of sternum
Main action of: Serratus posterior superior (2)
Proprioception
Elevate ribs
Main action of: Serratus posterior inferior (2)
Proprioception
Depresses ribs
Main action of: Levator costarum
Elevates ribs
Main action of: External intercostal (2)
Elevate ribs during forced inspiration
Supports intercostal space
Main action of: Internal intercostal (3)
- Interosseous part depresses ribs during forced respiration
- Interchondral part elevates ribs during forced respiration
- Supports intercostal space
Main action of: Innermost intercostal (3)
- Interosseous part depresses ribs during forced respiration
- Interchondral part elevates ribs during forced respiration
- Supports intercostal space
Nerves of the thoracic wall: (2)
Intercostal nerves
Subcostal nerve
What is the Subcostal nerve?
o Primary anterior ramus of T12 spinal nerve
What are Dermatomes? (2)
o T2-T12 spinal nerves provide cutaneous innervation to thorax and back
o Since these spinal nerves are not involved in any plexus formation, there is no difference between the zones of peripheral nerve distribution
Primary anterior rami of spinal thoracic nerves ________.
T1-T11
T3 to T6 are typical intercostal nerves having: (5)
- Rami communicantes (communicating branches) connecting each intercostal nerve
to the ipsilateral sympathetic trunk - Collateral branches arising near the angles of the ribs supplying intercostal muscles
and parietal pleura - Lateral cutaneous branches arising near the midaxillary line branching into anterior
and posterior branches - Anterior cutaneous branches branching into medial and lateral branches
- Muscular branches
First intercostal nerve no ______ cutaneous branch.
anterior
Second intercostal nerve gives rise to a large _______ cutaneous branch- intercostobrachial nerve
lateral
Lateral cutaneous nerve of third often gives rise to a second _______ nerve.
intercostobrachial
What do the 7th to 11th intercostal nerves become?
7th to 11th become thoraco-abdominal nerve of anterior abdominal wall after giving rise to
lateral cutaneous branches
Posterior intercostals artery:
Origin
Course
Distribution
1st 2 intercostal spaces: Superior thoracic a. Remaining spaces: Thoracic aorta
Pass between internal and innermost intercostal mm.
Intercostal muscles, skin and parietal pleura
Anterior intercostals artery:
Origin
Course
Distribution
1st 6 intercostal spaces: Internal thoracic
Spaces 7-9: Musculophrenic a.
Pass between internal and innermost intercostal mm. Occur in ipsilateral pairs
Intercostal muscles, skin and parietal pleura
Internal thoracic artery:
Origin
Course
Distribution
Subclavian a.
Passes inferiorly and laterally to sternum between costal cartilages and transversus thoracis to divide into superior epigastric and musculophrenic aa.
Through branches
Subcostal artery:
Origin
Course
Distribution
Thoracic aorta
Courses along inferior border of 12th rib
Muscles of anterolateral abdominal wall
Anterior intercostal veins: (5)
- 2 in each space
- 7th -9th join the vein accompanying
musculophrenic a. - 4th -6th join the vein accompanying
internal thoracic a. - 1st to 3rd join internal thoracic v.
- Internal thoracic v. drains into
brachiocephalic v.
Posterior intercostal veins on the right hand side: (3)
- 1st drains into brachiocephalic v.
- 2nd and 3rd unite to form right
superior intercostal v. draining into azygous v. - 4th to 11th and subcostal vv. drain into azygous v.
Posterior intercostal veins on the left hand side: (4)
- 1st drains into left brachiocephalic v.
- 2nd and 3rd unite to form left superior intercostal v. draining into left brachiocephalic v.
- 4th to 8th form superior hemiazygos v. to azygous v,
- 9th to 11th and subcostal form inferior hemiazygos v. to azygous v.
