4C.2: Thoracic wall + abdominal muscles

Posterior vs Anterior Rami

__**Posterior:**__

* Sensory from and motor to:
* *Zygapophyseal joints*
* *Muscles of the deep back*

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__**Anterior:**__

* Sensory from and motor to:
* everywhere else
* In thorax = intercostal nerve

Intercostal nerves

run from posterior to anterior

alongside intercostal artery and intercostal vein

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“VAN”

* Superior to Inferior
* vein, artery, nerve
* Travels in costal groove (inferior to rib) for protection
* Provides segmental innervation throughout the thorax

What is the peripheral nerve formed from the anterior rami of the spinal nerve called?

Intercostal nerve

Intercostal muscles

(in between the rib)

(another word for rib is costa)

__**External**__ - green

* Elevates ribs (inspiration)
* Superolateral to Inferomedial
* “hands in your pockets”

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__**Internal + Innermost**__ - purple + pink

* Depresses ribs (forced expiration, eg after exercise)
* Superomedial to Inferolateral
* “grab your collarbones”

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Innervation: Intercostal N

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Diaphragm

* separates thoracic cavity from abdominal cavity
* central tendon
* contraction lowers domes

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3 openings

* Caval Opening (vena cava)
* Esophageal hiatus
* Aortic hiatus
* ‘I ate 10 eggs at 12”

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Innervation = Phrenic nerve

Aorta

* very durable - ok to be squished a little bit
* Caval opening is in tendon NOT muscle (meaning it doesn’t get as squished)
* rigid backstop

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Blood can get through at 3 different spinal levels

* T9
* T10
* T12

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Thoracic muscle summary

Intercostal muscles

* external
* internal
* innermost

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Diaphragm

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Abdominal muscles

Innervation: Anterior Rami

Abdominal muscle Landmarks - Inguinal ligament

Inguinal ligament

* ligament that extends from anterior superior iliac spine to pubic symphysis
* divides abdominal region from lower limb

Linea alba

runs right down centre of abdomen

* Zyphoid process → pubic symphysis
* “6 pack line”

Linea Semilunaris

* ‘half moon’
* area where external and internal oblique muscles attach

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External and internal Oblique aponeurosis

* broad fascial layer
* Internal splits to form sheath of Posterior and Anterior

Arcuate line

* underneath rectus abdominis
* arcuate line is where you no longer have posterior and anterior sheath

Transversalis fascia

thin fascia layer that runs behind the abdominal muscles

Anterior body wall

Abdominal muscle summary

* external oblique
* Internal Oblique
* Rectus Abdominus
* Transverse Abdominus

Diastasis Recti

Separation of Fascia at Linea Alba (where the fascia layers fuse at the midline)

* increases with abdominal straining
* common during or following pregnancy
* carrying larger babies or multiples
* mom is of smaller structure
* age 35+
* Sometimes seen with newborns

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Treatment:

* stop all abdominal exercise during pregnancy - can worsen condition
* Post -pregnancy - exercise & physiotherapy can improve function
* sometimes surgery is needed

Muscles for breathing

* lungs are under tension
* anything that changes the volume of your thoracic cage will contribute to breathing

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* __**Inspiration (increase volume)**__
* Diaphragm, external Intercostals



* __**Active Expiration (decrease volume)**__
* Internal + innermost intercostals

Cadaveric specimen

Summary