Thoracic Nerves (Intercostal + Subcostal) | Anatomy

Summary

This video covers the anatomy of the thoracic nerves, specifically the intercostal and subcostal nerves. It explains their course, branches, and function in both motor and sensory innervation of the thoracic and abdominal walls. The intercostal nerves are classified as typical and atypical, with differences in their pathways and areas of innervation. The subcostal nerve, the largest of the thoracic nerves, provides sensory and motor functions to the lower abdominal wall and diaphragm. The video also discusses the clinical importance of understanding these nerves, especially in procedures like thoracocentesis.

Takeaways

• 😀 The thoracic nerves originate from T1 to T12 and are responsible for motor and sensory innervation to the thoracic and abdominal walls.
• 😀 There are 11 intercostal spaces in the thoracic wall, each associated with an intercostal nerve that runs beneath each rib.
• 😀 Intercostal nerves provide motor innervation to the intercostal muscles and sensory innervation to the skin of the thorax and abdomen.
• 😀 The thoracic nerves can be classified as 'typical' (T3–T6) and 'atypical' (T1, T2, T7–T11) based on their course and function.
• 😀 The first intercostal nerve is unique in that it joins the brachial plexus via a superior branch and sends an inferior branch to the first intercostal space.
• 😀 The second intercostal nerve gives rise to the 'intercostobrachial nerve', which provides sensation to the skin of the axilla (armpit).
• 😀 The typical intercostal nerves (T3–T6) stay within their respective intercostal spaces, innervating the thoracic and abdominal walls.
• 😀 Atypical intercostal nerves, such as T1 and T2, have additional functions, like joining other plexuses or innervating structures outside the thoracic wall.
• 😀 The subcostal nerve (T12) is the last thoracic nerve and innervates the abdominal muscles and skin, including the lower abdomen and inguinal regions.
• 😀 Clinical procedures like thoracocentesis (pleural tap) require careful knowledge of the neurovascular bundle (Vein, Artery, Nerve) to avoid damaging nerves during needle insertion.

Q & A

What are the thoracic nerves, and where are they located?

The thoracic nerves are nerves that emerge from the thoracic spine (T1 to T12). They are located between the ribs, and they run in the intercostal spaces between the ribs, supplying both motor and sensory innervation to the thoracic and abdominal walls.

How many intercostal spaces exist, and what are they numbered by?

There are 11 intercostal spaces on each side of the thorax. These spaces are numbered according to the rib above them, with the 1st intercostal space being located beneath the 1st rib, the 2nd under the 2nd rib, and so on up to the 11th intercostal space.

What is the difference between typical and atypical intercostal nerves?

Typical intercostal nerves (T3 to T6) course solely within their intercostal spaces, while atypical intercostal nerves (T1, T2, T7-11, and the subcostal nerve) extend beyond the thoracic wall to supply other areas such as the abdominal wall or upper limb.

What is the function of the intercostal nerves in terms of motor and sensory innervation?

The motor branches of intercostal nerves supply muscles such as the intercostals, subcostals, and others that aid in respiration and trunk movement. The sensory branches (lateral and anterior cutaneous branches) supply the skin of the thoracic and abdominal walls, and the sensory innervation follows specific dermatome patterns.

What is the neurovascular bundle, and why is it important?

The neurovascular bundle is a structure that runs in the costal groove underneath each rib. It consists of a vein, artery, and nerve (VAN) arranged from superior to inferior. It is crucial to avoid damaging these structures during procedures like thoracocentesis (pleural tap), which requires precise needle placement.

What role does the second intercostal nerve play, and why is it unique?

The second intercostal nerve is unique because its lateral cutaneous branch, called the intercostobrachial nerve, is longer and provides sensory innervation to the axilla. This nerve is also commonly known as the 'tickle' nerve.

What is the significance of the dermatome map in clinical practice?

The dermatome map is useful for localizing lesions or injuries to specific spinal nerves. By testing sensations in different dermatomes, clinicians can identify which spinal nerve may have been damaged, assisting in diagnosis.

What are the collateral branches of intercostal nerves, and what do they innervate?

Collateral branches of intercostal nerves arise near the angles of the ribs and course along the superior border of the inferior rib. These branches innervate the intercostal muscles, parietal pleura, and periosteum of the ribs.

How does the first intercostal nerve differ from the others?

The first intercostal nerve is special because it bifurcates into two branches: a superior branch that joins the brachial plexus and an inferior branch that becomes the first intercostal nerve, running within the first intercostal space.

What is the role of the subcostal nerve, and how does it differ from the other thoracic nerves?

The subcostal nerve is the last and largest of the thoracic nerves. It runs beneath the 12th rib and supplies the abdominal wall muscles and skin, as well as the parietal peritoneum. It also communicates with the iliohypogastric nerve to contribute to the lumbar plexus.