Muscles and Nerves of the Thoracic Region

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Questions and Answers

What is the primary role of the external intercostal muscles during respiration?

Protracting the sternum

Depressing the ribs

Elevating the ribs (correct)

Pulling the diaphragm upward

Which thoracic muscle is primarily responsible for decreasing the vertical diameter of the thoracic cavity?

Transversus thoracis

Diaphragm

Internal intercostals (correct)

External intercostals

How do the intercostal muscles assist during forced respiration?

By relaxing and allowing passive airflow

By actively depressing the abdominal wall

By aiding the diaphragm in lowering the rib cage

By preventing the thoracic cavity from collapsing (correct)

Which muscle is considered the major muscle of inspiration?

Diaphragm Signup and view all the answers

What movement occurs when the ribs are elevated during inspiration?

Bucket-handle movement Signup and view all the answers

Which of the following muscles are incorrectly paired with their function?

Diaphragm - Primary muscle of expiration Signup and view all the answers

Which action does the subcostales muscle perform?

Depresses the ribs Signup and view all the answers

Which intercostal muscles aid in quiet inspiration by raising the sternal ends of the ribs?

External intercostals Signup and view all the answers

What role do the scalenus muscles play during forced inspiration?

They elevate the first rib. Signup and view all the answers

Which muscles are actively involved in forced expiration?

Anterior abdominal wall and latissimus dorsi Signup and view all the answers

What distinguishes typical intercostal nerves from atypical ones?

Typical nerves run in the costal groove. Signup and view all the answers

During quiet expiration, which physiological process is primarily responsible?

Elastic recoil of the lungs Signup and view all the answers

Which statement correctly describes the relationship of the diaphragm during forced inspiration?

It exerts a powerful downward push. Signup and view all the answers

Which intercostal nerves are classified as atypical?

T1, T2, T7-T11 Signup and view all the answers

How does the quadratus lumborum affect the diaphragm's function during inspiration?

By fixing the 12th rib. Signup and view all the answers

What is the primary anatomical pathway of typical intercostal nerves?

They pass between the parietal pleura and posterior intercostal membrane. Signup and view all the answers

What is the primary function of the intercostal muscles during respiration?

Facilitate rib movement for expanding and contracting the thoracic cavity Signup and view all the answers

Which intercostal muscles are responsible for elevating the ribs during inhalation?

External intercostal muscles Signup and view all the answers

What anatomical structure separates the thoracic cavity from the abdominal cavity?

Diaphragm Signup and view all the answers

Which of the following describes the course of the intercostal nerves?

They originate from the thoracic spinal nerves and travel along the ribs Signup and view all the answers

What is the role of the azygos veins in the thoracic cavity?

Return blood from the thoracic wall to the systemic circulation Signup and view all the answers

Which group of muscles connects adjacent ribs and aids in forced expiration?

Internal intercostal muscles Signup and view all the answers

Which is a common clinical application of understanding intercostal nerves?

Administering thoracocentesis Signup and view all the answers

What is one of the typical functions of the thoracic cage?

Provide mechanical protection to vital organs Signup and view all the answers

Study Notes

Muscles connecting the ribs

External intercostal muscles: extend from the tubercle of the ribs posteriorly to the costochondral junction anteriorly.
Internal intercostal muscles: attach to the lower border of one rib and the upper border of the rib below.
Innermost intercostal muscles: form an incomplete inner layer with the subcostales and sternocostalis muscles, corresponding to the transversus abdominis muscle.

Muscles connecting the ribs to the sternum

Transversus thoracis (sternocostalis): draws down the costal cartilages to which it is attached.

Muscles connecting the ribs to vertebrae

Levatores costarum: 12 pairs of muscles connecting ribs to vertebrae.
Serratus posterior superior: connects ribs to vertebrae.
Serratus posterior inferior: connects ribs to vertebrae.

Intercostal Nerves

There are 12 pairs of thoracic spinal nerves that form the intercostal nerves (the upper eleven) and the subcostal nerve (the 12th).
Intercostal nerves are classified as typical (T3-T6) and atypical (T1, T2, and T7-T11).
Typical intercostal nerves run in the posterior part of the intercostal space between the parietal pleura and the posterior intercostal membrane.

Mechanics of Respiration

Respiration consists of inspiration and expiration, increasing and decreasing the capacity of the thoracic cavity, respectively.
The diaphragm is the major muscle of inspiration.
Quiet inspiration: All the diameters of the thoracic cavity increase
- Vertical diameter increased by contraction (descent) of the diaphragm.
- Anteroposterior diameter increased by contraction of intercostal muscles.
- Transverse diameter increased by contraction of intercostal muscles.
Forced inspiration: every muscle that can raise the ribs is brought into action.
Quiet expiration: passive and achieved by elastic recoil of the lungs and relaxation of the intercostal muscles and diaphragm.
Forced expiration: active process during which the muscles of the anterior abdominal wall and latissimus dorsi contract pushing the diaphragm upwards.

Intercostal Arteries

Intercostal arteries supply the intercostal spaces.
Divided into anterior and posterior arteries, which can be further classified as typical or atypical.

Intercostal Veins

Begin in the intercostal spaces, course along the lower border of the ribs, and terminate in the azygos veins or the superior vena cava.

Azygos Veins

drain blood from the posterior thoracic wall and abdominal wall.
Receive tributaries from the intercostal veins.

Clinical Importance of Intercostal Nerves

Intercostal nerve block is used to relieve pain in conditions affecting the chest wall.
Thoracentesis, a procedure to remove fluid from the pleural space, requires knowledge of the intercostal nerves to avoid damaging them.

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Description

Explore the anatomy of muscles that connect the ribs to the sternum and vertebrae, along with the intercostal nerves. This quiz covers details about external intercostal muscles, internal intercostal muscles, and the various muscles associated with the thoracic structures. Test your knowledge and understanding of thoracic muscle anatomy.