Transcript - Nottingham SCRUBS

Osteology of anterior
thoracic wall
Beth
Learning Objectives
 Identify the ribs, sternum, costal cartilages, manubrium, clavicle and
thoracic vertebrae.
 Examine the important features of the relevant bones of the thorax.
 Identify important surface landmarks on the anterior thoracic wall and use
the sternal angle (of Louis) to accurately number the ribs on a living subject.
Case Study
 Luke was rushed to A&E, having been in a car crash.
 He has chest pain and shortness of breath.
 You notice part of his chest wall moves in on inspiration (meant to move
out).
 Chest X-Ray is ordered.
Bony Thoracic Wall
 Anterior: Sternum
 Lateral: 12 ribs
 Posterior: Thoracic
Vertebrae (T1-T12)
 Protects the internal
viscera (organs)
Sternum
 Manubrium
Articulates with the first rib, part of second rib, and
clavicle (sternoclavicular joint).
Superior depression is the Jugular Notch: T2/T3
 Body
Several cartilage lined depressions (articular facets)for
the costal cartilages of ribs 3-6.
 Xiphoid Process
Xiphisternal joint T9. Demifacet for 7th rib articulation.
Ribs
 Articulate with vertebrae posteriorly and terminate in costal cartilages
anteriorly.
 Role in protection and breathing.
 Ribs 1-6 are true, 7-10 false, and 11-12 floating
(see costal cartilages).
Typical Rib
Atypical Rib
3-9
1, 2, 10, 11, 12.
The head is wedge shaped, and has two
articular facets, one for the numerically
corresponding vertebrae, and the other
for the vertebrae above.
Rib 1 is shorter and wider than the other
ribs. It only has one facet on its head for
articulation with its corresponding
vertebrae (there isn’t a thoracic vertebrae
above it). The superior surface is marked
by two grooves, which make way for the
subclavian vessels.
The neck simply connects the head with
the body. A roughed tubercle, which
articulates with the transverse process of
the corresponding vertebrae.
Rib 2 is thinner and longer than rib 1, and
has two normal articular facets. It has a
roughened area on its upper surface,
where the serratus anterior muscle
attaches.
The body, or shaft of the rib is flat and
curved. The internal surface has a
groove protecting the neurovascular
supply of the thorax.
Rib 10 only has one facet – for
articulation with its numerically
corresponding vertebrae.
Ribs 11 and 12 have no neck, and only
one facet, which is for articulation with
their corresponding vertebrae.
No transverse process facets.
Costal Cartilages
 Hyaline cartilage
 Segments of cartilage connecting the sternum to
the ribs.
 Help to extend the ribs into a forward motion.
 Contributes to elasticity within the walls of the
thorax, allowing the chest to expand during
respiration.
Clavicle (Collarbone)
 S-shaped horizontal long bone.
 Sternoclavicular and Acromioclavicular joints at medial and lateral end,
respectively. Shaft is between.
 Supports the should, transmits physical impacts and protects the
neurovascular bundle supplying the upper limb.
 CLINICAL Relevance:
Mid-clavicular line is a useful landmark.
Fractures of the clavicle are most common in the midshift/at the junction
between the middle and lateral third.
Thoracic Vertebrae
 Thoracic spine consists of 12 vertebrae.
 Vertebral body is heart shaped.
 Costal facets on the sides of each vertebral body and transverse processes,
articulating with the head and tubercles of the ribs, respectively.
 The spinous processes are long and slant inferiorly.
Angle of Louis and Counting Ribs
 Angle of Louis = Sternal Angle.
 Palpable junction between manubrium and sternal body.
T4/T5 Important landmark for structures.
 Useful place to start counting ribs:
The angle of Louis is continuous with Rib 2.
Find the sternal notch, walk your fingers down the manubrium a few centimetres
until you feel a distinct bony ridge (the sternal angle).
Slide your finger down to localize the 2nd intercostal space, and go from there.
Case Study Revisited
Car crash caused a Flail Chest, which occurs when
a segment of the rib cage breaks under extreme
stress and becomes detached from the rest of the
chest wall.
It requires multiple adjacent ribs being broken in
multiple places, separating a segment, so a part of
the chest wall moves independently: paradoxical
breathing (due to pressure changes).
This also explains the chest pain and difficulty
breathing, as well as the movement expressed.
Clinical Relevance
 Cervical ribs – accessory rib articulating
with C7
 Can compress some of the nerves running
into the arm
Quiz!
 The Sternum is composed of the Manubrium, the Body and the
Zygapophyseal process.
False! It’s the Manubrium, Body and Xiphoid Process.
 The ninth rib is a false rib, because it’s costal cartilage joins to the cartilage
of the ribs above.
True!
 The Thoracic vertebrae articulate with the ribs by the body with the head
and transverse process with the neck tubercle.
True!
 The sternal angle is at T2/T3, and is continuous with the 2nd Rib.
False! The plane level for the sternal angle is T4/T5.
Take Home Messages
 Bony thoracic cavity comprises of Sternum, 12 ribs and 12 thoracic
vertebrae.
 Sternum is made up of Manubrium (superior is Jugular Notch and articulates
with the clavicles), Body and Xiphoid Process.
 Ribs 1-10 articulates with the sternum, directly or indirectly, via the costal
cartilages.
 Ribs articulate twice with the thoracic vertebrae, to the body and to the
transverse processes.
 Sternal angle/Angle of Louis is at T4/T5, and is continuous with the second
rib. Therefore, it can be used as a starting point for counting other ribs.
References
 Gray’s Anatomy
 Teach Me Anatomy Website
 Radiopaedia
 Google Images
Thanks For Listening!
Questions?
 [email protected]