Session 1.2c - Gray's Anatomy For Students - Thorax - Regional anatomy - Thoracic wall Flashcards
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How does the thoracic wall appear?
Segmental in design
What is the thoracic wall composed of?
Skeletal elements and muscles
Where is the thoracic wall bound to superiorly?
The superior thoracic aperture, bordered by vertebra TI, rib I, and the manubrium of the sternum
Where is the thoracic wall bound to inferiorly?
The inferior thoracic aperture, bordered by vertebra TXII, rib XII, the end of rib XI, the costal margin, and the xiphoid process of the sternum.
What are the skeletal elements of the thoracic wall?
The skeletal framework consists of the thoracic vertebrae, intervertebral discs, ribs and sternum
How many thoracic vertebrae are there?
Twelve THORACIC VERTEBRAE.
How are the 12 thoracic vertebrae characterised?
By articulations with ribs.
What is the shape of the body of a typical thoracic vertebra?
A typical thoracic vertebra has a heart-shaped VERTEBRAL BODY.
Describe the dimensions of the body of a typical thoracic vertebra.
Roughly equal dimensions in the transverse and anteroposterior directions (Fig. 3.18)
Describe the spinous process of a typical thoracic vertebra.
Long spinous processes (Fig. 3.18)
How do the vertebral foramen of the typical thoracic vertebra appear?
The VERTEBRAL FORAMEN is generally circular
How are the lamina of the vertebra?
The LAMINAE are broad and overlap with those of the vertebra below.
Describe the superior articular processes of a typical thoracic vertebra.
The SUPERIOR ARTICULAR PROCESSES are flat, with their articular surfaces facing almost directly posteriorly.
Describe the inferior articular processes of a typical thoracic vertebra.
The INFERIOR ARTICULAR PROCESSES project from the laminae and their articular facets face anteriorly.
Describe the transverse processes of a typical thoracic vertebra.
The TRANSVERSE PROCESSES are club shaped and project posterolaterally.
How do the vertebra articulate with the ribs?
A typical thoracic vertebra has three sites on each side for articulation with ribs.
What are demifacets?
i.e. partial facets
Where are the demifacets located?
On the superior and inferior aspects of the body
What do the demifacets articulate with?
Corresponding sites on the heads of adjacent ribs.
What does the superior facet articulate with?
The SUPERIOR COSTAL FACET articulates with part of the head of its own rib
What does the inferior costal facet articulate with?
The INFERIOR COSTAL FACET articulates with part of the head of the rib below.
What is the oval facet on the thoracic vertebra called?
TRANSVERSE COSTAL FACET
What shape is the transverse costal facet?
Oval
Where is the transverse costal facet?
At the end of the transverse process
What does the transverse costal facet articulate with?
The tubercle of its own rib
Not all vertebra articulate with ribs in a typical fashion. Which ones?
TI, TX, TXI and TXII (Fig. 3.19)
Describe the rib articulation of TI.
The superior costal facets on the body of vertebra TI are complete and articulate with a single facet on the head of its own rib - in other words, the head of rib I does not articulate with vertebra CVII.
Describe the rib articulation of TX.
Similar to TI, TX (and often TIX) articulates only with its own ribs and therefore lacks inferior demifacets on the body.
Describe the rib articulation of TXI and TXII.
These articulate only with the heads of their own ribs - they lack transverse costal facets and have only a single complete facet on each side of their bodies.
Which vertebra only articulate with their own ribs?
TI, TX (and often TIX), TXI and TXII.
Some vertebra only articulate with their own ribs. What is different about the costal facets of these?
TI - superior costal facet complete
(TIX) TX - lacks inferior demifacets
TXI and TXII - lack transverse costal facets and have a single complete facet on each side of their bodies
How many ribs are there?
Twelve pairs of ribs
What does each rib terminate as?
They terminate anteriorly in a costal cartilage (Fig. 3.20).
What do all ribs articulate with?
The vertebral column
What articulates with the sternum?
The costal cartilages of the upper seven ribs
Which are the true ribs?
The upper seven ribs
Ribs I-VII are known as what, and articulate with what?
TRUE RIBS, articulate directly with the sternum
What are ribs VIII-XII known as?
The remaining five pairs of ribs are FALSE RIBS
How many true and false ribs are there?
7 true, 5 false
What do ribs VIII to X articulate with?
The costal cartilages articulate anteriorly with the costal cartilages of the ribs above.
What do ribs XI and XII articulate with?
These have no anterior connection with other ribs or with the sternum
What are ribs XI and XII often known as?
FLOATING RIBS
Which ribs are the floating ribs?
Ribs XI and XII
What does a typical rib consist of?
A curved shaft with anterior and posterior ends (Fig. 3.21).
What is the anterior end of the rib continuous with?
Its costal cartilage
What does the posterior end of the rib articulate with?
The vertebral column
How is the posterior end of the rib characterised?
By a head, neck and tubercle.
Describe the head of the rib.
The HEAD is somewhat expanded and typically presents two articular surfaces.
What are the two articular surfaces on the head separated by?
The HEAD presents two articular surfaces separated by a CREST.
Describe the relative sizes of the two articular surfaces of the head.
The superior surface is smaller than the larger inferior facet.
What does the superior surface on the head of the rib articulate with?
The inferior costal facet on the body of the vertebra above
What does the inferior surface (facet) on the head of the rib articulate with?
The superior costal facet of its own vertebra.
Describe the neck of the rib.
The NECK is a short flat region of bone that separates the head from the tubercle.
Describe the tubercle of the rib.
The TUBERCLE projects posteriorly from the junction of the neck with the shaft and cosistd of two regions, an articular part and a nonarticular part.
Describe the articular part of the tubercle of the rib.
The articular part is medial and has an oval facet for articulation with a corresponding facet on the transverse process of the associated vertebra.
Describe the nonarticular part of the tubercle of the rib.
The raises nonarticular part is roughened by ligament attachments.
Describe the shaft of the rib.
Generally thin and flat with internal and external surfaces.
Describe the superior margin of the rib.
Smooth and rounded
Describe the inferior margin of the rib.
Sharp
What is the relationship of the shaft to the tubercle?
The shaft bends forward just laterally to the tubercle at a site termed the ANGLE.
Where does the shaft face, and how?
It has a gentle twist around its longitudinal axis so that the external surface of the anterior part of the shaft faces somewhat superiorly relative to the posterior part.
How is the inferior margin of the internal surface marked?
By a distinct COSTAL GROOVE.
Which ribs have distinct features?
Upper and lower ribs
- Rib I, II, X, XI and XII (Fig. 3.22)
Describe the orientation of rib I.
RIB I is flat in the horizontal plane.
Describe the superior and inferior surfaces of rib I.
They are broad.
Describe the orientation of rib I from its articulation with vertebra TI.
It slopes inferiorly to its attachment to the manubrium of the sternum.
Describe the head of rib I.
The head articulates only with the body of vertebra TI and therefore has only one articular surface.
Describe the tubercle of rib I.
Like other ribs, the tubercle has a facet for articulation with the transverse process.
Describe the superior surface of rib I.
It is characterised by a distinct tubercle, the SCALENE TUBERCLE.
What does the scalene tubercle do?
Separates two smooth grooves that cross the rib approximately midway along the shaft.
What runs along the anterior groove of rib I?
The subclavian vein
What runs along the posterior groove of rib I?
The subclavian artery
Anterior and posterior to the grooves by the scalene tubercle (rib I), how does the shaft appear?
It is roughened by muscle and ligament attachments.
Describe rib II.
RIB II, like rib I, is flat but twice as long.
What does rib II articulate with?
The vertebral column in a way typical of most ribs.
Describe the head of rib X.
The head of RIB X has a single facet for articulation with its own vertebra.
Describe the structure and function of ribs XI and XII.
RIBS XI and XII articulate only with the bodies of their own vertebrae and have no tubercles or necks.
Describe the appearance of ribs XI and XII.
Both ribs are short, have little curve, and are pointed anteriorly.
What does the adult sternum consist of?
The adult STERNUM consists of three major elements: - manubrium - body - xiphoid process (Fig. 3.23)
Describe the manubrium of the sternum.
Broad and superiorly positioned (Fig. 3.23)
Describe the body of the sternum.
Narrow and longitudinally oriented (Fig. 3.23)
Describe the xiphoid process of the sternum.
Small and inferiorly positioned (Fig. 3.23)
What does the manubrium of the sternum form?
Part of the bony framework of the neck and the htorax.
What occurs on the superior surface of the manubrium?
It is expanded laterally
What is found on the superior surface of the manubrium?
A distinct and palpable notch: the JUGULAR NOTCH (SUPRASTERNAL NOTCH), in the midline.
What is found either side of the jugular notch?
A large oval fossa for articulation with the clavicle.
What is found immediately inferior to the fossa, either side of the jugular notch?
Immediately inferior, on each lateral surface of the manubrium, is a facet for the attachment of the first costal cartilage.
What is found at the lower end of the lateral border of the facet that attaches to the first costal cartilage?
A demifacet for articulation with the upper half of the anterior end of the second costal cartilage.
Describe the body of the sternum.
It is flat.
What is the anterior surface of the body of the sternum marked by?
Often marked by transverse ridges
What do the transverse ridges on the body of the sternum represent?
Lines of fusion between the segmental elements called sternebrae
Where does the body of the sternum arise embryologically?
From the sternebrae (transverse ridges on sternum)
What is found on the lateral margins of the body of the sternum?
Articular facets for costal cartilages.
What does the body of the sternum have superiorly?
Each lateral margin has a demifacet for articulation with the inferior aspect of the second costal cartilage.
How many facets are there on the body of the sternum, inferior to the first demifacet?
Four facets
What do the facets of the body of the sternum articulate with?
The costal cartilages of ribs III to VI.
What is found at the inferior end of the body of the sternum?
A demifacet for articulation with the upper demifacet on the seventh costal cartilage.
What is the inferior end of the body of the sternum attached to?
The xiphoid process.
Which is the smallest part of the sternum?
The XIPHOID PROCESS.
Describe the shape of the xiphoid process.
Its shape is variable: it may be wide, thin, pointed, bifid, curved or perforated.
How does the xiphoid process begin and mature.
It begins as a cartilaginous structure, which becomes ossified in the adult.
What is found on the upper lateral margin of the xiphoid process, on each side?
A demifacet for articulation with the inferior end of the seventh costal cartilage.
What does a typical rib articulate with?
The bodies of adjacent vertebrae and the transverse process of its related vertebra.
What do the bodies of adjacent vertebrae articulate wth on the rib?
They form a joint with the head of the rib
What is the joint between a typical rib and the transverse process of its related vertebra known as?
A COSTOTRANSVERSE JOINT (Fig. 3.24)
What do the costovertebral joints and related ligaments do?
They allow the necks of the ribs either to rotate around their longitudinal axes, or to ascend and descend relative to the vertebral column.
Where do the costovertebral joints allow the necks of the ribs to rotate around their longitudinal axes?
Mainly in the upper ribs
Where do the costovertebral joints allow the necks of the ribs to ascend and descend relative to the vertebral column?
Mainly in the lower ribs.
How do the ribs aid breathing?
The combined movement of all of the ribs on the vertebral column are essential for altering the volume of the thoracic cavity during breathing.
What do the two facets on the head of the rib articulate with?
The superior facet on the body of its own vertebra and the inferior facet on the body of the vertebra above.
How is the joint between the head of the rib and the vertebra divided?
Into two synovial compartments by an intra-articular ligament
How does the intra-articular ligament of the rib/vertebral joint occur?
It attaches the crest to the adjacent intervertebral disc and separates the two articular surfaces on the head of the rib.
What are the two synovial compartments and the intervening ligament surrounded by?
A single joint capsule
What is the joint capsule around the two synovial compartments and intra-articular ligament of the rib attached to?
The outer margins of the combined articular surfaces of the head and vertebral column.