Thoracic Wall Movements & Vasculature Worksheet

Describe the structure and content of a typical intercostal space.

Answer explanation

An intercostal space is the space between two adjacent ribs, containing intercostal muscles, nerves, and blood vessels. Structure (superficial to deep): Skin

• Subcutaneous tissue

• Muscles (from superficial to deep):

  • External intercostal muscle

  • Internal intercostal muscle

  • Innermost intercostal muscle (also called transversus thoracis in some regions)

• Endothoracic fascia

• Parietal pleura

Content:

Neurovascular bundle:

• Located in the costal groove at the inferior border of the rib above

• Comprises (from superior to inferior): a) Intercostal vein b) Intercostal artery c) Intercostal nerve

• Collateral branches:

  • Smaller branches of the neurovascular structures running near the superior border of the rib below

• Lymphatics

• Connective tissue

Describe the structures of the neurovascular bundle and the relation of these structures to each other.

Answer explanation

The neurovascular bundle comprises (from superior to inferior): a) Intercostal vein b) Intercostal artery c) Intercostal nerve that travel together in the costal groove. (VAN: Vein, Artery, Nerve)

Describe the course and branches of a typical intercostal nerve.

Answer explanation

Course:

1. Origin: Intercostal nerves originate as the ventral rami of thoracic spinal nerves T1-T11.

2. Initial path: Each nerve emerges from the intervertebral foramen and passes laterally.

3. Costal groove: The nerve then enters the costal groove on the inner surface of the corresponding rib, where it's part of the neurovascular bundle.

4. Intercostal space: It runs in the intercostal space between the internal and innermost intercostal muscles.

5. Anterior termination: The nerve continues anteriorly to the sternum, where it pierces the intercostal muscles and ends as a cutaneous branch.

Branches:

1. Posterior cutaneous branch:

   • Arises near the vertebral column

   • Supplies the skin of the back

2. Lateral cutaneous branch:

   • Emerges at the mid-axillary line

   • Divides into anterior and posterior branches

   • Supplies the skin of the lateral chest wall

3. Anterior cutaneous branch:

   • Terminal branch of the intercostal nerve

   • Supplies the skin of the anterior chest wall

4. Muscular branches:

   • Supply the intercostal muscles, serratus posterior superior and inferior, and levatores costarum

   • In the upper thorax, they also supply the upper parts of the thoracic diaphragm

5. Collateral branch:

   • Runs along the upper border of the rib below

   • Supplies similar areas as the main nerve but is smaller in distribution

6. Communicating branches:

   • Connect with the sympathetic trunk via rami communicantes

Special considerations:

• T1: Contributes to the brachial plexus

• T7-T11: Extend beyond the costal margin to supply the abdominal wall

• T12: Known as the subcostal nerve, it has a unique distribution in the abdominal wall

Explain the clinical importance of the neurovascular bundle during the insertion of an underwater drain in the pleural cavity.

Answer explanation

The neurovascular bundle is crucial to avoid injury to nerves and blood vessels during drain insertion, preventing complications.

Describe the arterial blood supply, venous drainage, and nerve supply of the thoracic wall.

Answer explanation

The thoracic wall is supplied by intercostal arteries, drained by azygos system, and innervated by intercostal nerves.

What are the actions of the external intercostal muscles?

Answer explanation

The external intercostal muscles elevate the ribs during inhalation to expand the chest cavity and assist in breathing.

What is the function of the pectoral fascia?

Answer explanation

Provide support and protection to the muscles and structures in the chest region.

What muscles are involved in normal breathing at rest?

Answer explanation

The diaphragm and intercostal muscles are involved in normal breathing at rest.

What muscles are involved in inspiration?

Answer explanation

The muscles involved in inspiration are the diaphragm and external intercostal muscles.

What muscles are involved in expiration?

Answer explanation

Expiration, particularly during quiet breathing, is primarily a passive process that relies on the elastic recoil of the lungs and thoracic wall. However, during active or forced expiration, several muscles are involved (Internal and innermost intercostals, abdominal muscles, transversus thoracis)