Thorax Anatomy - Chest Wall Quiz

11 Questions

Where does the muscle originate from?

Inferior border of the lower ribs

At which rib does the muscle insert?

2nd rib below

What is the insertion point of the muscle?

Superior border of the 2nd rib below

Where does the muscle not originate from?

Superior border of the upper ribs

Which point marks the insertion site?

Superior border of the 3rd rib below

Which nerves pass into the abdominal wall between the 7th and 11th intercostal nerves?

Subcostal nerves

Where does the anterior ramus of the 12th thoracic nerve travel within the abdomen?

In the abdominal wall

Which nerve runs forward in the abdominal wall as the subcostal nerve?

12th thoracic nerve

What is the path of the subcostal nerve in relation to the intercostal nerves?

It runs alongside them

In what region do the 7th to 11th intercostal nerves enter the abdominal wall?

Abdominal region

Which nerve lies in the abdomen and does not pass into the abdominal wall?

12th thoracic nerve

Study Notes

The Chest Wall

Consists of skin, fascia, a skeletal framework, muscles, and a neurovascular bundle, all connected to form a strong, protective, and flexible cage.

Intercostal Spaces

Comprise of three layers of muscles: external, internal, and innermost.

External Intercostal Muscle

Forms the most superficial layer of the intercostal muscles.
Originates from the inferior border of the rib above.
Inserts at the superior border of the rib below.
Action: Elevates the ribs during inspiration.

Internal Intercostal Muscle

Forms the intermediate layer of the intercostal muscles.
Originates from the inferior border of the lower ribs.
Inserts at the superior border of the 2nd or 3rd rib below.
Anteriorly, it is replaced by an aponeurosis, the anterior (external) intercostal membrane.
Action: Decreases chest volume in expiration.

Innermost Intercostal Muscle

Is the deepest layer of the intercostal muscles.
Separated from the internal intercostals by the intercostal neurovascular bundle.
Found in the most lateral portion of the intercostal spaces.

Innervation and Blood Supply

Innervated by intercostal nerves (T1-T11).
Blood supply provided by intercostal vessels.

Intercostal Neurovascular Bundle

Contains the intercostal nerves, arteries, and veins.
Runs in the subcostal groove of the corresponding ribs.

Intercostal Nerves

Derived from the anterior rami of the first 11 thoracic spinal nerves.
First six intercostal nerves are distributed within their intercostal spaces.
7th to 11th intercostal nerves pass into the abdominal wall.
The anterior ramus of the 12th thoracic nerve lies in the abdomen and runs forward in the abdominal wall as the subcostal nerve.