Dr. Kennedy Munisi, MD, MMed Muhas.

1. THE INTERCOSTAL MUSCLES
The intercostal muscles are a group of intrinsic rib
cage muscles that occupy the 11 intercostal spaces.
They are divided into three groups, going
from superficial to deep:
External intercostal muscles
Internal intercostal muscles
Innermost intercostal muscles
All three groups of muscles support the rib cage.
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They are all accessory respiratory muscles that
participate in the process of forced breathing.
Specifically, the external intercostals facilitate forced
inspiration, while the internal and innermost intercostals
aid forced expiration
There are five muscles that make up the thoracic cage
– the intercostals-(external, internal and internal),
subcostals and transversus thoracic. The muscles act
to change the thoracic volume during respiration.
However, there are others attached to thoracic wall
but do not constitute the intercostal muscle – pectoralis
major, P. minor, serratus anterior and the scalene
muscles

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Ext intercostal Mz–fibers run inferoanteriorly
Int intercostal Mz –fibers run inferoposteriorly

4. THE INTERCOSTAL MUSCLES
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5. TRANSVERSUS THORACIC AND
INNERMOST INTERCOSTAL
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THE EXTERNAL INTERCOSTAL
MUSCLES
The intercostal muscles lie in the intercostal spaces between
the ribs. They are organized into three layers external intcost.
muscle-there are 11 pairs of external Intercostal muscle
They run infero-anteriorly from the rib above to the rib below
and are continuous with external oblique of the abdomen
Attachment
Origin: the originated from at the lower border of the rib
inserting into the upper of the rib below.
Actions- elevate the ribs increasing the thoracic volume
Innervation- intercostal nerve T1- T11

7. THE INTERNAL INTERCOSTALS
These flat muscles lie deep to the external intercostals
Run from the rib above to the one below but in an opposite
direction, infero-posteriorly, they are continuous with the
internal oblique of the abdominal wall
Attachment
Originate from the lateral edge of the costal groove of the rib
and insert into the superior surface of the rib below
Actions: interosseous part reduces thoracic volume by
depressing the rib cage, the inter-chondral part elevates the
rib
Innervation- intercostal nerve T1- T11
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8. INNERMOST INTERCOSTALS
These muscles are the deepest of the intercostals, have a similar
structures to the internal intercostals
They are separated from the internal intercostal by the
intercostal neurovascular bundle and located in the most lateral
portion of the intercostal space
Attachment- originate from the medial edge of the costal
groove and insert into the superior surface of the rib below
Actions: interosseous part reduces thoracic volume by
depressing the rib cage, the inter-chondral part elevates the rib
Innervation- intercostal nerve T1- T11
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9. TRANSVERSUS THORACIC
These muscles are continuous with the transversus
thoracic of the abdomen.
Attachment- from the posterior surface of the
inferior sternum to the internal surfaces of costal
cartilages 2-6
Actions: weakly depress the ribs
Innervation: Intercostal nerves (T2-T6)
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10. SUBCOSTAL
Are found in the various portion of thoracic wall, comprise of
thin slips of muscle running from internal surface one rib to that
of 2nd-3rd rib below, direction of fibers is parallel to internal
intercostal
Attachment: this originate from the inf surf of lower rib near
the angle of rib and then attach to the sup border of ribs 2-3
below
Actions: same as internal intercostals
Innervation: intercostal nerves
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11. THE NEUROVASCULAR SPACE
The neurovascular space is the plane in which the
neurovascular bundle (intercostal vein, artery and nerve)
courses.
It lies between the internal intercostal and innermost
intercostal muscle layers.
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15. ARTERIES OF THORACIC WALL
The arterial supply to the thoracic wall. derives
from the:
Thoracic aorta,- via the posterior intercostal and
subcostal arteries.
Subclavian artery,- via through the internal
thoracic and supreme intercostal arteries.
Axillary artery, through the superior and lateral
thoracic arteries.
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17. VEINS OF THORACIC WALL
The intercostal veins accompany the intercostal arteries and
nerves and lie most superior in the costal grooves .
There are 11 posterior intercostal veins and one subcostal
vein on each side. The posterior intercostal veins anastomose
with the anterior intercostal veins (tributaries of internal
thoracic veins).
As they approach the vertebral column, the posterior
intercostal veins receive a posterior branch, which accompanies
the posterior ramus of the spinal nerve of that level, and an
intervertebral vein draining the vertebral venous plexuses
associated with the vertebral column.
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Most posterior intercostal veins (4–11) end in the
azygos/hemi-azygos venous system, which conveys
venous blood to the superior vena cava (SVC).
The posterior intercostal veins of the 1st intercostal space
usually enter directly into the right and left brachiocephalic
veins. The posterior intercostal veins of the 2nd and 3rd
(and occasionally 4th) intercostal spaces unite to form a
trunk, the superior intercostal vein

19. NERVES OF THORACIC WALL
The 12 pairs of thoracic spinal nerves supply the thoracic wall. As soon
as they leave the IV foramina in which they are formed, the mixed
thoracic spinal nerves divide into anterior and posterior (primary) rami
or branches
The anterior rami of nerves T1–T11 form the intercostal nerves that run
along the extent of the intercostal spaces. The anterior ramus of nerve
T12, coursing inferior to the 12th rib, is the subcostal nerve.
The posterior rami of thoracic spinal nerves pass posteriorly,
immediately lateral to the articular processes of the vertebrae, to supply
the joints, deep back muscles, and skin of the back in the thoracic region.
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LYMPHATIC DRAINAGE OF THE THORAX
A. Sternal or Parasternal (Internal Thoracic) Nodes
-Are placed along the internal thoracic artery.
-Receive lymph from the medial portion of the breast, intercostal
spaces, diaphragm, and supraumbilical region of the abdominal wall.
Drain into the junction of the internal jugular and subclavian veins.
B. Intercostal Nodes
Lie near the heads of the ribs.
Receive lymph from the intercostal spaces and the pleura.
Drain into the cisterna chyli or the thoracic duct.
C. Phrenic Nodes
- Lie on the thoracic surface of the diaphragm.
-Receive lymph from the pericardium, diaphragm, and liver.
-Drain into the sternal and posterior mediastinal nodes-

21. APPLIED ANATOMY/CLINCAL CORRELATES
1. Chest Pain -Although chest pain can result from pulmonary
disease, it is probably the most important symptom of cardiac
disease (Swartz, 2009). However, chest pain may also occur in
intestinal, gallbladder, and musculoskeletal disorders. When
evaluating a patient with chest pain, the examination is largely
concerned with discriminating between serious conditions and
the many minor causes of pain. People who have had a heart
attack usually describe the associated pain as a “crushing” sub-
sternal pain (deep to the sternum) that does not disappear with
rest.
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Rib Fractures
The short, broad 1st rib, posteroinferior to the clavicle, is rarely
fractured because of its protected position (it cannot be
palpated). When it is broken, however, structures crossing its
superior aspect may be injured, including the brachial plexus of
nerves and subclavian vessels that serve the upper limb.
The middle ribs are most commonly fractured. Rib fractures
usually result from blows or crushing injuries. The weakest part of
a rib is just anterior to its angle; however, direct violence may
fracture a rib anywhere, and its broken end may injure internal
organs such as a lung and/or the spleen. Fractures of the lower
ribs may tear the diaphragm and result in a diaphragmatic
hernia.
Rib fractures are painful because the broken parts move during
respiration, coughing, laughing, and sneezing.

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Flail Chest
Multiple rib fractures may allow a sizable segment of the
anterior and/or lateral thoracic wall to move freely. The loose
segment of the wall moves paradoxically (inward on
inspiration and outward on expiration). Flail chest is an
extremely painful injury and impairs ventilation, thereby
affecting oxygenation of the blood. During treatment, the
loose segment may be fixed by hooks and/or wires so that it
cannot move.
Rib Excision
The surgical creation of an opening through the thoracic wall
to enter a pleural cavity is a thoracotomy. An anterior
thoracotomy may involve making H-shaped cuts through the
perichondrium of one or more costal cartilages and then
shelling out segments of costal cartilage to gain entrance to
the thoracic cavity.

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Supernumerary Ribs
People usually have 12 ribs on each side, but the number is
increased by the presence of cervical and/or lumbar ribs, or
decreased by failure of the 12th pair to form. Cervical ribs
are relatively common (0.5–2%) and may interfere with
neurovascular structures exiting the superior thoracic
aperture. Lumbar ribs are less common. Supernumerary
(extra) ribs also have clinical significance in that they may
confuse the identification of vertebral levels in radiographs
and other diagnostic images.

25. STERNAL ANGLE (ANGLE OF LOUIS)
■ Is the junction between the manubrium and the body of
the sternum.
■ Is located at the level where
(a) The second ribs articulate with the sternum.
(b) The aortic arch begins and ends.
(c) The trachea bifurcates into the right and left bronchi at
the carina.
(d) The inferior border of the superior mediastinum is
demarcated.
(e) A transverse plane can pass through the intervertebral
disk between T4 and T5.
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ASSIGNMENT
Identify the structures
No- 10, 11, 14, 16, 29
and 35
The part of the rib
protecting the vessels
and nerve is
………………
The part of rib where
fractures commonly
occur is……………....
Why is the first rib not
commonly fractured.
How is the rib counted
in surgery