Thorax and chest wall

BIOMECHANICS
OF THORAX AND
CHEST WALL
- VIRESH V

Anterior View Posterior View
1st rib
Manubrium
Sternal Angle
Costochondral
Joint
Body of Sternum
Costal Cartilage
Xiphoid Process
Introduction: The Thorax consists of

GENERAL STRUCTURE AND FUNCTION
RIB CAGE  It is a closed chain Kinematics that involves many
muscles.
 Borders of the Rib cage:
Anterior – Sternum
Lateral – are the ribs
Posterior – Thoracic vertebrae
superior – Jugular notch of the
sternum, 1st costocartilage, 1st ribs and 1st
thoracic vertebrae
inferior – Xiphoid process, ribs 7 – 10,
inferior portions of 11th and 12th also.

STERNUM
The sternum is an osseous protective
plate for the heart and is composed of
the manubrium, body, and xiphoid
process .
The manubrium and the body form a
dorsally concave angle of
approximately 160 deg.

 There are 12 thoracic vertebrae that make up the posterior
aspect of the rib cage.
 One of the unique aspects of the typical thoracic vertebra is
that the vertebral body and transverse processes have six
costal articulating surfaces-
 four on the body - a superior and an inferior costal facet,
(or demifacet) on each side.
 one costal facet on each transverse process
 It also includes 12 pairs of ribs.
Thoracic
Vertebrae

The rib cage also includes 12 pairs of ribs. The ribs
are curved flat bones that gradually increase in
length from rib 1 to rib 7 and then decrease in
length again from rib 8 to rib 12.
The posteriorly located head of each rib articulates
with thoracic vertebral bodies; and the costal
tubercles of ribs 1 to 10 also articulate with the
transverse processes of a thoracic vertebra.

 Anteriorly, ribs 1 to 10 have a costal
cartilage that joins them either directly or
indirectly to the sternum.
 The first through the seventh ribs are
classified as vertebrosternal (or “true”) ribs
because each rib, through its costocartilage,
attaches directly to the sternum.
 The costocartilage of the 8th through 10th
ribs articulates with the costocartilages of
the superior rib, indirectly articulating with
the sternum through rib 7.
 These ribs are classified as vertebrochondral
(or “false”) ribs.
 The 11th and 12th ribs are called vertebral
(or “floating”) ribs because they have no
anterior attachment to the sternum.
T
R
U
E
ribs
F
A
L
S
E
ribs
FLOATING RIBS

Articulations of the Rib Cage
The articulations that join the bones of
the rib cage include the
1. Manubriosternal (MS) joint,
2. Xiphisternal (XS) joint,
3. Costovertebral (CV) joint,
4. Costotransverse (CT) joint,
5. Costochondral (CC) joint
6. Chondrosternal (CS) joint,
7. Interchondral joint.

MANUBRIOSTERNAL JOINT
The manubrium and the body of
the sternum articulate at the MS
joint .
This joint is also known as the
sternal angle or the angle of Louis
and is readily palpable.
The MS joint is a synchondrosis.
The Hyaline cartilage – covers the
articulating ends of the
manubrium and sternum.
The MS joint has a
fibrocartilaginous disk between
the articular surfaces.

XIPHISTERNAL JOINT
The Xiphoid process
joins the inferior
aspect of the sternal
body at the XS joint.
The XS joint is also a
synchondrosis that
tends to ossify by 40
to 50 years of age.

COSTOVERTEBRAL JOINTS
 The typical CV joint is a synovial
joint formed by the head of the
rib, two adjacent vertebral
bodies, and the interposed inter
vertebral disk.
 Ribs 2 to 9 have typical CV joints.
 The heads of these ribs each
have two articular facets, or so-
called demifacets (superior and
inferior costovertebral facets ).
 The demifacets are separated by
a ridge called the crest of the
head of the rib.

Adjacent thoracic vertebrae have facets corresponding to those
of the 9 ribs that articulates with them.
The head of each of the second through ninth ribs articulates with
an inferior facet on the superior of the two adjacent vertebrae
and with a superior facet on the inferior of the two adjacent
vertebrae.
The inferior and superior facets on the adjacent vertebrae
articulate, respectively, with the superior and inferior facets on the
head of the rib.
The 1st, 10th 11th, and 12th ribs are atypical ribs because they
articulate with only one vertebral body and are numbered by that
body.
A fibrous capsule surrounds the entire articulation of each CV
joint.

The typical CV joint is divided into two cavities
by the Interosseous or Intra - articular
ligament.
This ligament extends from the crest of the
head of the rib to attach to the Annulus fibrosus
of the intervertebral disk.

 The Radiate ligament is located within the capsule, with firm
attachments to the anterolateral portion of the capsule.
 The radiate ligament has three bands:
1. The superior band, which attaches to the superior vertebra;
2. The intermediate band, which attaches to the intervertebral disk
3. The inferior band, which attaches to the inferior vertebra.
 The atypical CV joints of ribs 1 and 10 through 12 are more mobile than
the typical CV joints because the rib head, articulates with only one
vertebra.
 The interosseous ligament is absent in these joints; therefore, they each
have only one cavity.
 The radiate ligament is present in these joints, with the superior band still
attaching to the superior vertebra.
 Both rotation and gliding motions occur at all of the CV joints

COSTOTRANSVERSE JOINTS
The CT joint is a synovial joint formed by the articulation of the
costal tubercle of the rib with a costal facet on the transverse
process of the corresponding vertebra.
There are 10 pairs of CT joints articulating vertebrae T1 through
T10 with the rib of the same number.
The CT joints on T1 through approximately T6 have slightly
concave costal facets on the transverse processes of the vertebrae
and slightly convex costal tubercles on the corresponding ribs.
At the CT joints of approximately T7 through T10, both articular
surfaces are flat and gliding motions predominate.
Ribs 11 and 12 do not articulate with their respective transverse
processes of T11 or T12.

 The CT joint is surrounded by a thin, fibrous
capsule.
 Three major ligaments support the CT joint
capsule - lateral costotransverse ligament,
the costotransverse ligament, and the
superior costotransverse ligament.
 The lateral costotransverse ligament is a
short, stout band located between the lateral
portion of the costal tubercle and the tip of
the corresponding transverse process.
 The costotransverse ligament is composed of
short fibers that run within the
costotransverse foramen between the neck of
the rib posteriorly and the transverse process
at the same level.
 The superior costotransverse ligament runs
from the crest of the neck of the rib to the
inferior border of the cranial transverse
process.

COSTOCHONDRAL JOINT
The CC joints are
synchondrosis.
The CC joints are
formed by the
articulation of the 1st
through 10th ribs
antero laterally with the
costal cartilages
The CC joints have no
ligamentous support.

CHONDROSTERNAL JOINTS
The CS joints are formed by the articulation of the costal cartilages
of ribs 1 to 7 anteriorly with the sternum
 Rib 1 attaches to the lateral facet of the manubrium,
 Rib 2 is attached via two demi facets at the manubriosternal
junction,
Ribs 3 through 7 articulate with the lateral facets of the sternal
body.
The CS joints of the first, sixth, and seventh ribs are synchondrosis.
The CS joints of ribs 2 to 5 are synovial joints.

The CS joints of the first through seventh ribs have
capsules that are continuous with the periosteum.
 Ligamentous support for the capsule includes :
1. Anterior and Posterior radiate Costosternal
ligaments.
2. Sternocostal ligament.
3. Costoxiphoid ligament.

The Sternocostal ligament is an intra-articular
ligament, that divides the two demi facets of the
second CS joint.
The Costoxiphoid ligament connects the anterior
and posterior surfaces of the seventh costal
cartilage to the front and back of the Xiphoid
process.

INTERCHONDRAL JOINTS
The Interchondral joints are synovial joints and
are supported by a capsule and Interchondral
ligaments.
The 7th through the 10th costal cartilages
each articulate with the cartilage immediately
above them.
For the 8th through 10th ribs, this articulation
forms the only connection to the sternum

KINEMATICS OF THE
RIBS AND
MANUBRIOSTERNUM

The movement of the rib cage is an amazing
combination of complex geometrics governed by:
1. The types and angles of the articulations
2. The movement of the Manubriosternum
3. The elasticity of the costal cartilages.

 The anterior articulation of rib 1 is larger and thicker than that of any
other rib.
 The first costal cartilage is stiffer than the other costocartilages.
 Also, the first CS joint is cartilaginous (synchondrosis), not synovial,
and therefore is firmly attached to the manubrium.
 Finally, the first CS joint is just inferior and posterior to the
sternoclavicular joint.
 For these reasons, there is very little movement of the first rib at the
anterior CS joint.
 Posteriorly, the CV joint of the first rib has a single facet, which
increases the mobility at that joint.
 During inspiration, the CV joint moves superiorly and posteriorly,
elevating the first rib.

There is a single axis of motion for the 1st to 10th ribs
through the center of the CV and CT joints.
This axis for the upper ribs lies close to the frontal plane,
allowing thoracic motion predominantly in the sagittal plane.
The axis of motion for the lower ribs is nearly in the sagittal
plane, allowing for thoracic motion predominantly in the
frontal plane
 The axis of motion for the 11th and 12th ribs passes through
the CV joint only, because there is no CT joint present.
The axis of motion for these last two ribs also lies close to the
frontal plane.

The excursion of the Manubrium is less than that of the body of the
sternum because the first rib is the shortest, with the caudal ribs
increasing in length until rib 7.
The discrepancy in length causes movement at the MS joint.
The motion of the upper ribs and sternum has its greatest effect by
increasing the Anteroposterior (AP) diameter of the thorax.
This combined rib and Sternal motion that occurs in a
predominantly Sagittal plane has been termed the “Pump -
handle” motion of the thorax.

Elevation of the
upper ribs at the
CV and CT joints
results in anterior
and superior
movement of the
sternum there by
increasing AP
diameter is
referred to as the
“pump-handle”
motion of the
thorax.

 The lower ribs have a more angled shape (obliquity increases from rib
1 to rib 10) and an indirect attachment anteriorly to the sternum.
 These factors allow the lower ribs more motion at the lateral aspect of
the rib cage.
 The elevation of the lower ribs has its greatest effect by increasing
the transverse diameter of the lower thorax.
 This motion that occurs in a nearly frontal plane has been termed the
“Bucket - Handle” motion of the thorax.
 Elevation of the lower ribs at the CV and CT joints results in a lateral
motion of the rib cage and thereby increasing transverse diameter is
referred to as “Bucket Handle” motion of the thorax.

Let’s watch a video on
Pump - handle and
Bucket handle
movement

The 11th and 12th ribs each have only one
posterior articulation with a single vertebra
and no anterior articulation to the sternum;
therefore, they do not participate in the
closed-chain motion of the thorax.

The muscles that act on the rib cage are generally referred to as the
Ventilatory muscles.
The Ventilatory muscles are striated skeletal muscles that differ from
other skeletal muscles in a number of ways:
(1) The muscles of ventilation have increased fatigue resistance and
greater oxidative capacity;
(2) These muscles contract rhythmically throughout life rather than
episodically;
(3) The Ventilatory muscles work primarily against the elastic properties
of the lungs and airway resistance rather than against gravitational
forces;
(4) Neurologic control of these muscles is both voluntary and involuntary
(5) The actions of these muscles are life sustaining

Primary Muscles of Ventilation
The primary muscles are those recruited for quiet
ventilation.
These include the diaphragm, the Intercostal
muscles (particularly the parasternal muscles), and
the scalene muscles.
 These muscles all act on the rib cage to promote
inspiration

DIAPHRAGM
 The diaphragm is the primary muscle of inspiration during quiet
breathing.
 Origin : arise from the sternum, costocartilages, ribs, and vertebral
bodies.
 The fibers travel superiorly to insert into a central tendon.
 Functionally, the muscular portion of the diaphragm is divided into the
1. Costal portion, which arises from the sternum, costocartilage and
ribs.
2. Crural portion, which arises from the vertebral bodies
 The vertical fibers of the diaphragm, which lie close to the inner wall of
the lower rib cage, are termed as the zone of apposition.

The Crural portion of the diaphragm arises from the
anterolateral surfaces of the bodies and disks of L1 to L3 and
from the aponeurotic arcuate ligaments.
The medial arcuate ligament arches over the upper anterior
part of the psoas muscles and extends from the L1 or L2
vertebral body to the transverse process of L1, L2, orL3.
The lateral arcuate ligament covers the quadratus lumborum
muscles and extends from the transverse process of L1, L2, or
L3 to the 12th rib.

During tidal breathing, the fibers of the zone of
apposition of the diaphragm contract, causing a
descent of the diaphragm.
 As the dome descends, the abdominal contents
compress, increasing intra-abdominal pressure.
With a deeper breath, the abdomen, now compressed,
acts to stabilize the central tendon of the diaphragm.

With a continued contraction of the costal portion
of the diaphragm against the central tendon that is
stabilized by abdominal pressure, the lower ribs are
now lifted and rotated outwardly in the bucket-
handle motion.
Indirectly, the action of the crural portion results in
a descending of the central tendon, increasing
intra-abdominal pressure.
This increased pressure is transmitted across the
apposed diaphragm to help expand the lower rib
cage.

The resultant increase in thoracic size with
descent of the diaphragm results in the
decreased intrapulmonary pressure that is
responsible for inspiration.
Exhalation shows a decrease in thoracic size. As
the diaphragm returns to its domed shape, the
abdominal contents return to their starting
position.

Chronic hyperinflation of the lungs
results in a resting position of the
diaphragm that is lower (more flattened)
than normal.
Consequently, with more severe disease,
an active contraction of the diaphragm
pulls the lower ribs inwardly more than
pulling the diaphragm down.
With an active contraction of the
diaphragm in severe COPD, there is less
of a reduction in thoracic size and a
decreased inspiration.
Chronic obstructive pulmonary disease (COPD)

Compliance is a measurement of the distensibility of a
structure or system.
Compliance =
Compliance = Change in volume per unit of pressure
During diaphragm contraction, the abdomen becomes the fulcrum
for lateral expansion of the rib cage.
Therefore, compliance of the abdomen is a factor in the
inspiratory movement of the thorax.
▲Volume
▲ Pressure

Increased compliance of the abdomen, as in spinal cord
injury in which the abdominal musculature may not be
innervated, decreases lateral rib cage expansion as a result
the inability to stabilize the central tendon.
(Without stabilization of the central tendon, the costal fibers
the diaphragm cannot lift the lower ribs.)
Decreased compliance of the abdomen, as in pregnancy,
limits caudal diaphragmatic excursion and causes lateral and
upward motion of the rib cage to occur earlier in the
Ventilatory cycle.

INTERCOSTAL MUSCLES:
The External and Internal Intercostal
muscles are categorized as ventilatory
muscles.
The internal and external Intercostal
and the subcostalis muscles connect
adjacent ribs to one another.

The Internal Intercostal muscles arise
from a ridge on the inner surfaces of the
1st through 11th ribs, and each inserts into
the superior border of the rib below.
The fibers of the Internal Intercostal
muscles lie deep to the external intercostal
muscles and run caudally and posteriorly.
The internal intercostals begin Anteriorly
at the Chondrosternal junctions and
continue posteriorly to the angles of the
ribs, where they become an aponeurotic
layer called the posterior intercostal
membrane.
Internal intercostal muscles are also
called as Parasternal muscles

The External Intercostal fibers run caudally and
anteriorly, at an oblique angle to the Internal Intercostal
muscles.
The external intercostal muscles begin posteriorly at
the tubercles of the ribs and extend anteriorly to the
costochondral junctions, where they form the Anterior
Intercostal membrane.
Both internal and external inter costal muscles are
called as lateral inter costal muscles.

The Subcostal muscles are also
inter costal muscles but are
generally found only in the lower
rib cage.
The Subcostal muscles are found at
the rib angles and may span more
than one Intercostal space before
inserting into the inner surface of a
caudal rib.
Their fiber direction and action are
similar to those of the internal
Intercostal muscles.

 External Intercostal muscles tend to raise the
lower rib up to the higher rib, which is an
Inspiratory motion.
 The internal Intercostal muscles tend to lower the
higher rib onto the lower rib, which is an
Expiratory motion.
 The external intercostal muscles are active
during inspiration and the internal intercostal
muscles are active during exhalation, both sets
of intercostal muscles may be active during both
phases of respiration as minute ventilation
increases.
 Minute ventilation is the amount of air that
is breathed in (or out) in one minute:
Minute ventilation (VE) = [TV] x [Respiratory rate (RR)]

The action of the Parasternal muscles appears to be a rotation of
the CS junctions, resulting in elevation of the ribs and anterior
movement of the sternum.
The primary function of the Parasternal muscles, however, appears
to be stabilization of the rib cage.
This stabilizing action of the Parasternal muscles opposes the
decreased intrapulmonary pressure generated during diaphragmatic
contraction, preventing a paradoxical, or inward, movement of the
upper chest wall during inspiration.
The function of the lateral (Internal and External) inter costal
muscles involves both ventilation and trunk rotation.

Scalene Muscles
 The scalene muscles are also
primary muscles of quiet
ventilation.
 The scalene muscles attach
on the transverse processes
of C3 to C7 and descend to
the upper borders of the first
rib (scalenus anterior and
scalenus medius) and second
rib (scalenus posterior).

Their action lifts the sternum and the first two ribs in the
pump-handle motion of the upper rib cage.
Activity of the scalene muscles begins at the onset of
inspiration and increases as inspiration gets closer to total lung
capacity.
The scalene muscles also function as stabilizers of the rib cage.
The scalene muscles, along with the Parasternal muscles,
counteract the paradoxical movement of the upper chest caused
by the decreased intrapulmonary pressure created by the
diaphragm’s contraction.

Accessory Muscles of Ventilation
The muscles that attach the rib cage to the shoulder girdle,
head, vertebral column, or pelvis may be classified as
Accessory muscles of ventilation.
They are :
Sternocleidomastoid, Pectoralis major , Pectoralis
minor,
Serratus posterior superior, Serratus posterior
inferior, abdominal muscles, Transverse Thoracis.
These muscles assist with inspiration or expiration in
situations of stress, such as increased activity or disease.

The accessory muscles of inspiration
increase the thoracic diameter by
moving the rib cage upward and
outward.
The accessory muscles of expiration
move the diaphragm upward and the
thorax downward and inward.

STERNOCLEIDOMASTOID
 Origin: Manubrium and superior
medial aspect of the clavicle .
 Insertion: mastoid process of the
temporal bone.
 Action :
1. Flexion of the cervical vertebrae.
2. With the help of the trapezius
muscle stabilizing the head, the
bilateral action of the
sternocleidomastoid muscles moves
the rib cage in the pump-handle
motion.

PECTORALIS MAJOR
 It has 2 portions: Sternocostal
head & Clavicular head.
 The Sternocostal portion of the
pectoralis major muscle can
elevate the upper rib cage when
the shoulders and the humerus
are stabilized.
 The Clavicular head of the
pectoralis major can be either
inspiratory or expiratory in action,
depending on the position of the
upper extremity.

When the arm is positioned on the side of
trunk ,the Clavicular portion acts as an
expiratory muscle by pulling the Manubrium
and upper ribs down.
 When the arm is raised, the muscle
becomes an Inspiratory muscle, pulling the
manubrium and upper ribs up and out.

PECTORALIS MINOR
The Pectoralis
minor can help
elevate the
third, fourth, and
fifth ribs during
a forced
inspiration.

SUBCLAVIUS
A muscle between
the clavicle and the
first rib, can also
assist in raising the
upper chest for
inspiration.

SERRATUS POSTERIOR
Serratus posterior
superior (SPS) & Serratus
posterior inferior (SPI)
have been assumed to be
accessory muscles of
respiration.
The presumed actions
would be elevation the
ribs by the SPS (
inspiration).
and lowering of the ribs
and stabilizing the
diaphragm by the SPI
(expiration).

ABDOMINAL MUSCLES
They are :
1.Transversus Abdominis,
2. Internal Oblique Abdominis.
3. External Oblique Abdominis.
4. Rectus Abdominis
Action :
 Expiratory muscles , help in forced expiration.
 Trunk flexors and rotators.
 By increasing intra-abdominal pressure, the abdominal muscles
can push the diaphragm upward into the thoracic cage.

BUT DURING INSPIRATION:
First, the increased intra-abdominal pressure
created by the active abdominal muscles
during forced exhalation pushes the
diaphragm cranially and exerts a passive
stretch on the costal fibers of the diaphragm.
These changes prepare the respiratory system
for the next inspiration by optimizing the
length tension relationship of the muscle
fibers of the diaphragm.

Second, the increased abdominal pressure
created by lowering of the diaphragm in
inspiration must be countered by tension in
the abdominal musculature.
Without sufficient compliance in the
abdominal muscles, the central tendon of the
diaphragm cannot be effectively stabilized so
that lateral chest wall expansion occurs.

TRANSVERSUS THORACIS
(TRIANGULARIS STERNI) MUSCLES
 These are a flat layer of muscle that runs
deep to the Parasternal muscles.
 Origin: from the posterior surface of the
caudal half of the sternum and run
cranially and laterally,
 Insertion: into the inner surface of the
costal cartilages of the third through
seventh ribs.
 Action: These muscles are recruited for
ventilation along with the abdominal
muscles to pull the rib cage caudally.
(force expiration)

Gravity acts as an accessory to ventilation in the supine
position. Gravity, acting on the abdominal viscera, performs the
same function as the abdominal musculature in stabilizing the
central tendon of the diaphragm.

SCOLIOSIS
Increase in lateral curvature of spine.
On the side of the convexity, with sufficient
curvature, the Intercostal space is widened and
the Intercostal muscles are elongated.
On the side of the concavity, the ribs are
approximated and the Intercostal muscles are
adaptively shortened.
Lung volumes and capacities are reduced.

 The newborn has a cartilaginous, and therefore extremely compliant (travel through
the birth canal).
 Due to increased compliance, there is thoracic instability.
 The infant’s chest wall muscles must act as stabilizers, rather than mobilizers.
 Complete ossification of the ribs does not occur for several months after birth.
 Rib cage of an infant shows a more horizontal alignment of the ribs, with the angle of
insertion of the costal fibers of the diaphragm also more horizontal than those of the
adult.
 There is an increased tendency for these fibers to pull the lower ribs inward.
 Only 20% of the muscle fibers of the diaphragm are fatigue-resistant fibers in the
healthy newborn. (diaphragmatic fatigue)

Until infants can stabilize their upper extremities, head, and spine, it
is difficult for the accessory muscles of ventilation to produce the
action needed to be helpful during increased ventilatory demands.
As the infant ages and the rib cage ossifies, muscles can begin to
mobilize rather than stabilize the thorax.
As the infant gains head control, he is also gaining accessory muscle
use for increased ventilation.
As the toddler assumes the upright position of sitting and standing,
gravitation forces and postural changes allow for the anterior rib
cage to angle obliquely downward allowing a greater bucket handle
motion of the rib cage.

Many of the articulations of the chest wall undergo fibrosis with
advancing age.
The Interchondral and Costochondral joints can fibrose, and the
Chondrosternal joints may be obliterated.
The Xiphosternal junction usually ossifies after age 40.
The chest wall articulations that are true synovial joints may
undergo morphologic changes associated with aging, which
results in reduced mobility.
The costal cartilages ossify, which interferes with their axial
rotation.
Overall, chest wall compliance is significantly reduced with age.

Aging also brings anatomical changes to the lung tissue that affect
the function of the lungs.
The airways narrow, the alveolar duct diameters increase, and there
are shallower alveolar sacs.
There is a reorientation and decrease of the elastic fibers.
Overall, there is a decrease in the elastic recoil which allows the
thorax to rest with an increased A-P diameter.
An increased kyphosis is often observed in older individuals, which
decreases the mobility.
Decreased compliance of the bony rib cage, an increased
compliance of the lung tissue, and an overall decreased compliance
of the respiratory system as a result of the effects of aging.

Skeletal muscles of ventilation of the elderly
person have a documented loss of strength,
fewer muscle fibers, a lower oxidative
capacity.
The resting position of the diaphragm
becomes less domed, with a decrease in
abdominal tone in aging

CHRONIC OBSTRUCTIVE PULMONARY DISEASE
The major manifestation of COPD is damage to the airways and
destruction of the alveolar walls.
Pathophysiology :
As tissue destruction occurs with disease, the elastic recoil property
of the lung tissue is diminished and becomes ineffective in removing
air from the thorax.
Air trapping and hyperinflation occur.
The static position of the thorax changes as more air is now housed
within the lungs at the end of exhalation.
This affects the lung volume and ventilatory capacities

In COPD, there is an imbalance in these two opposing forces. (between the
elastic recoil properties of the lungs pulling inward and the normal outward
spring of the rib cage)
As elasticity decreases, an increase in the A-P diameter (more of a barrel
shape) of the hyperinflated thorax is apparent, along with flattening of the
diaphragm at rest.
The range of motion of the thorax is limited.
The basic problem in COPD is an inability to exhale.
Due to hyperinflation, the fibers of the diaphragm are shortened.
Contraction of this very flattened diaphragm will pull the lower rib cage
inward, actually working against lung inflation.
The diaphragm has a limited ability to laterally expand the rib cage, and so
Inspiratory motion must occur within the upper rib cage.

In a forceful contraction of the functioning Inspiratory muscles
of the upper rib cage, the diaphragm and the abdominal
contents actually may be pulled upward.
This is a Paradoxical thoracoabdominal breathing
pattern because the abdomen is pulled inward and upward
during inspiration and is pushed back out and down during
exhalation.
the work of breathing, in COPD is markedly increased.

SOME IMPORTANT QUESTIONS FROM THE CHAPTER:
(FROM PREVIOUS YEARS QUESTION PAPERS)
1. Name any four accessory muscles involved in Ventilation. (2)
2. Name the muscles involved in Normal Breathing. (2)
3. Name the muscles of Ventilation. (2)
4. Scoliosis (2)
5. Movements of Rib – cage during breathing. Add a note on muscles of breathing. (5)
6. Explain the movements occurring during breathing. (5)
7. Mention in detail about muscles responsible for normal ventilation. (5)
8. Explain in brief the kinematics of ribs and Manubriosternum. (5)
9. Describe the biomechanics of respiration. (5)
10. Explain Chest wall motions during normal breathing. (5)
11. Explain the kinematics of Chest wall. (5)
12. Pump Handle and Bucket handle movement. (5)
13. Describe the mechanical of Normal breathing. (10)
14. Explain chest movements associated with Ventilation. (10)

Thorax and chest wall

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