LECTURE -I. Intercostal Spaces & Its Content. BY Dr Farooq Khan Aurakzai. Date:

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1 LECTURE -I Intercostal Spaces & Its Content BY Dr Farooq Khan Aurakzai Date:

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3 Layers of IC space: Following are the layers of the thoracic region: Skin Subcutaneous CT External IC muscle and membrane Internal IC muscle and membrane IC v/a/n located in costal groove i.e: Inferior border of rib Innermost IC muscle. Endothoracic fascia Parietal wall of pleura

4 Costal cartilage The costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension. The first seven pairs are connected with the sternum. The next three are each articulated with the lower border of the cartilage of the preceding rib. The last two have pointed extremities, which end in the wall of the abdomen. They increase in length from the first to the seventh, then gradually decrease to the twelfth.

5 Introduction The intercostal space (ICS) is the anatomic space between the two ribs. Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it.i.e: The 4 th intercostal space is formed between the 4 th and 5 th ribs. The space below the 12 th rib does not lie between the ribs and thus called as subcostal space. Structures in intercostal space: Intercostal muscle Intercostal arteries and intercostal veins Intercostal lymph nodes Intercostal nerves

6 INTRODUCTION TO THORACIC muscles The muscles of the thoracic wall, together with the (axial Skelton) muscles extend from the thoracic cage to the bones of the upper limb (appendicular skeleton) and between the vertebrae and ribs posteriorly (i.e: levator costarum, serratus posterior superior and inferior muscles). They alter the position of the ribs and sternum and so change the volume during the breathing. The true muscles of the thoracic wall are the serratus posterior, levator costaurum, intercostal, subcostal and transverses thoracis.

7 Intercostal muscles con t As stated above, there are three layers of intercostal muscles: External intercostal muscle, Internal intercostal muscle, and Innermost intercostal muscle. The inner most is again divided into: Intercostalis intima. Subcostalis. Sternocostalis (Transversus thoracis)

8 External intercostal muscle The eleven pairs of external intercostal muscles forms the most superficial of the muscular layers of intercostal spaces. Its fibers are directed downward and forward from the inferior border of the rib above to the superior border of the rib below. This means that the origin of this muscle is from the lower border of a rib and is inserted into the upper border of the rib below. The muscle extends forward from the tubercle of the rib to the costochondral junction on the anterior aspect.

9 External intercostal muscle con t In front, after reaching the costochondral junction, the muscle is replaced by a membrane known as the anterior intercostal membrane. Sometimes also referred to as external intercostal membrane. The external intercostal muscles are most active in inspiration. They are thicker then the internal intercostal muscle. These muscles are continuous inferiorly with the external oblique muscles in the anterolateral abdominal wall.

10 Internal intercostal muscle It runs deep to the right angle of the External Intercostal Muscle. It forms the intermediate muscular layer of the intercostal spaces. Its fibers are directed downwards and backward in contrast to the fibers of external intercostal muscle. The muscle fibers originate from the subcostal groove of the rib above and are inserted into the upper border of the rib below.

11 Internal intercostal muscle con t The muscle extends backward from the sternum to the angle of the ribs. From here it is replaced by a membrane known as the posterior intercostal membrane or internal intercostal membrane. It is weaker then the external intercostal, and is more active during expiration. These muscles are continuous inferiorly with the external oblique muscles in the anterolateral abdominal wall.

12 Innermost intercostal muscle It forms the deepest muscular layer of intercostal spaces and correspond to the transversus abdominis muscle of the abdominal wall. It is a rather incomplete layer and crosses more than one intercostal spaces. It is related externally to intercostal nerves and vessels and internally to endothoracic fascia and parietal pleura. This muscle can be divided into three parts that are more or less separate from one another.

13 Innermost intercostal muscle.con t The names of the parts are: Subcostalis: It lies towards the posterior aspect. Transverses thoracis muscles. It lies in the anterior position

14 Also called as Infra costales. Subcostales It consist of muscular and aponeurotic fasciculi, which are usually well-developed only in the lower part of the thorax. Each originates from the inner surface of one rib, and is inserted into the inner surface of the second or third rib below, near its angle. Their fibers run in the same direction as those of the internal intercostals. The function of this muscle is unknown, but it is part of the innermost intercostal muscle group along with the transversus thoracis muscle which is known to be a synergist in aiding the internal intercostal muscles with forced exhalation.

15 Transversus thoracis muscle It lies internal to the thoracic cage, anteriorly. It is a thin plane of muscular and tendinous fibers, situated upon the inner surface of the front wall of the chest. It is in the same layer as the subcostal muscles and the innermost intercostal muscles. It arises on either side from the: From the lower third of the posterior surface of the body of the sternum, From the posterior surface of the xiphoid process, and from the sternal ends of the costal cartilages of the lower three or four true ribs. Its fibers diverge upward and lateralward, to be inserted by slips into the lower borders and inner surfaces of the costal cartilages of the second, third, fourth, fifth, and sixth ribs.

16 Levator Costarum It is an Accessory muscle. They are twelve in number on either side. They are small tendinous and fleshy bundles, which arise from the ends of the transverse processes of the seventh cervical and upper eleven thoracic vertebrae. They pass obliquely downward and laterally, like the fibers of the Intercostales externi. Other muscles are the serratus posterior superior and inferior.