Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

At the end of the lecture you should know : • 1.Intercostal spaces • 2. • 3.Endothoracic fascia • 4.Intercostal neurovascular bundle • 5. Internal thoracic and its course and branches • 6. Muscles of *1. • It is the space between two . Since there are 12 ribs on each side, there are • 11 intercostal spaces. Each space contains: • 1. Intercostal muscles • 2. Intercostal neurovascular bundle • 3.Lymphatics • *2.Intercostal muscles Each intercostal space has three muscles: • *External Intercostal • *Internal Intercostal • *Innermost Intercostal • Supplied by corresponding •

1 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

* External intercostal muscles: Is the most superficial muscles .Its fibers directed downward & forward • Origin: from lower border of the above • Insertion: upper border of rib below • Extends from the rib tubercle behind to the costo-chondral junction in front and • replaced anteriorly by external (anterior) intercostal membrane. *Internal intercostal muscles Lies deep to external intercostal muscles .Its fibers directed downward & • backward, Origin: from subcostal groove of the rib above • Insertion: upper border of rib below • Extends from the sternum in front to the angle of the rib behind and it is • replaced posteriorly by internal (posterior) intercostal membrane .

* Innermost intercostal muscles: Is the deepest incomplete layer .It is divided into three portions and crosses • more than one intercostal space, Related externally to intercostal nerve and vessels, and internally to endothoracic • fascia.

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2 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

Action : When the intercostal muscles contract, they all tend to pull the ribs nearer to one another. If the 1st rib is fixed by the contraction of the muscles in the root of the neck, namely, the scaleni muscles, the intercostal muscles raise the 2nd to the 12th ribs toward the first rib, as in inspiration. If, conversely, the 12th rib is fixed by the quadratus lumborum muscle and the oblique muscles of the abdomen, the 1st to the 11th ribs will be lowered by the contraction of the intercostal muscles as in expiration. Endothoracic fascia: *lines the wall of the chest • *Located between the muscles and bones of the thoracic wall and the parietal • pleura. *Extends over the apex of the pleura as suprapleural membrane, and forms a thin layer between the diaphragm and the pleura.

3 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

Intercostal neurovascular bundles: *Lies between the innermost and the internal intercostal muscles • *Runs high in the intercostal space, related to subcostal groove of the rib above • Arrangement: -Artery-Nerve (VAN), from top to bottom • As the innermost intercostal muscle is not forming a complete layer, the bundle is • generally covered on the inside by the endothoracic fascia. • Intercostal nerves: • 11 pairs of intercostal nerves which are the anterior primary rami of the • thoracic spinal nerves. 1st -6th are distributed in the intercostal spaces supply the intercostal muscles , • from the 7th -11th supply the anterior abdominal wall Anterior ramus of 12ththoracic runs forward in the abdomen as the • subcostal nerve

Intercostal : Each intercostal space contains: • A single large posterior & Two small anterior . Each artery gives off branches to the muscles, skin, parietal pleura & . . . *Posterior intercostal arteries: • *In upper two spaces, arise from the superior intercostal artery (a branch of • of the ) *In the lower nine spaces, arise from the branches of thoracic . • The course and branching of the intercostal arteries follow the intercostal • nerves. *Anterior intercostal arteries: • In the upper six spaces, arise from the internal thoracic artery • In the lower five spaces arise from the musculophrenic artery (one of the • terminal branch of internal thoracic). Form anastomosis with the posterior intercostal arteries. • Intercostal : Accompany intercostal arteries and nerves • Each space has posterior & anterior • Eleven posterior intercostal and one subcostal vein • Lie deepest in the costal grooves • Contain valves which direct the blood posteriorly.

4 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

Posterior intercostal veins On right side: • The first space drains into the right brachiocephalic vein. • Rest of the intercostal spaces drain into the azygos vein. • On left side: • The upper three spaces drain into the left brachiocephalic vein. • Rest of the intercostal spaces drain into the hemiazygos and accessory • hemiazygos veins, which drain into the azygos vein. Anterior intercostal veins • The upper six spaces drain into the internal thoracic vein and then to subclavian • The lower five spaces drain into the musculophrenic vein (one of the tributary of • internal thoracic vein)

Lymph vessels: • Lymph vessels of the intercostal space follow arteries • Anteriorly drain into anterior intercostal nodes that lie along the internal • thoracic artery. Posteriorly drain into posterior intercostal nodes that lie in the posterior mediastinum.

Internal thoracic artery : *Arises from the subclavian artery near its origin. * Travels downward on the inside of the ribcage, approximately a centimeter from the sides of the sternum, and thus medial to the nipple. *Accompanied by the internal thoracic vein. *Runs deep to the external oblique, but superficial to the vagus nerve

5 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

Branches:  Mediastinal branches  Thymic branches  Pericardiacophrenic artery - travels with the phrenic nerve  Sternal branches  Perforating branches  Twelve anterior intercostal branches, two to each of the top six intercostal spaces After passing the sixth intercostal space, the internal thoracic artery splits into the following two terminal branches:  Musculophrenic artery - roughly follows the costal margin  Superior epigastric artery - continues the course of the internal thoracic artery, travelling downward into the abdominal wall

6 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

Other Muscles Of Thoracic Wall 1. Subcostalis : Thin bands of muscle fibers, mainly in lower 6 spaces and only in posterior part of spaces. Origin: Inner surface & lower border of rib above. Insertion: Upper border of 2nd or 3rd rib below

2.Sternocostalis : 4 to 5 slips which arise from inner surface of lower part of body of sternum and costal cartilages Inserted into inner surface of costal cartilages from 2 to 6

Subcostalis

Sternocostalis 3.Levator costarum: Twelve in number on either side, are small tendinous and fleshy bundles, which arise from the ends of the transverse processes of the seventh cervical and upper eleven thoracic vertebrae Flat triangular muscle , has an apex and base . •

7 Intercostal spaces

Tuesday 19/2/2018 By Dr: Hassna B. Jawad

The apex of the triangle is attached to the transverse process of the thoracic • vertebrae. The base is attached to the upper border of rib below. • The contraction of this muscle causes elevation of the ribs and this help in the • inspiration so it is inspiratory muscle . 4.Serratus posterior superior It arises by a thin and broad aponeurosis from the lower part of the ligamentum nuchae, from the spinous processes of the seventh cervical and upper two or three thoracic vertebrae and from the supraspinal ligament. Inclining downward and laterally it becomes muscular, and is inserted, into the upper borders of the second, third, fourth, and fifth rib. The function of serratus posterior superior is to elevate second to fifth ribs, which aids deep inspiration. 5.Serratus posterior inferior: It arises by a thin aponeurosis from the spinous processes of the lower two thoracic and upper two or three lumbar vertebrae, and from the supraspinal ligament. Passing obliquely upward and laterally, inserted into the inferior borders of the lower four ribs The serratus posterior inferior draws the lower ribs backward and downward to assist in rotation and extension of the trunk. This movement of the ribs also contributes to forced expiration of air from the .

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