Thoracic Wall (Anatomy II) 2024 PDF

(ANATOMY II) (1) THE THORAX Dr. Sara S. Elmegarhi Anatomy And Embryology Department Faculty Of Medicine University Of Tripoli Dr.Sara Elmegarh...

(ANATOMY II) (1) THE THORAX Dr. Sara S. Elmegarhi Anatomy And Embryology Department Faculty Of Medicine University Of Tripoli Dr.Sara Elmegarhi Anatomy & Embryology Department 1  THE THORAX IS THE PART OF THE BODY BETWEEN THE NECK AND ABDOMEN. Commonly the term chest is used to describe the thorax, but the chest is much more extensive than the thoracic wall and cavity contained within it. The chest is generally is the superior part of the trunk that is broadest superiorly owing to the presence of the pectoral (shoulder) girdle (clavicles and scapulae). Dr.Sara Elmegarhi Anatomy & Embryology Department 2 The thoracic cavity and its wall have the shape of a truncated cone, being narrowest superiorly, with the circumference increasing inferiorly, and reaching its maximum size at the junction with the abdominal portion of the trunk. The wall of the thoracic cavity is relatively thin, essentially as thick as its skeleton. The thoracic skeleton takes the form of a domed birdcage. The thoracic cage (rib cage), with the horizontal bars formed by ribs and costal cartilages, is also supported by the vertical sternum (breastbone) and thoracic vertebrae. The floor of the thoracic cavity (thoracic diaphragm) is deeply invaginated inferiorly (i.e., is pushed upward) by viscera of the abdominal cavity. Consequently, nearly the lower half of the thoracic wall surrounds and protects abdominal rather than thoracic viscera (e.g., liver). Thus the thorax and its cavity are much smaller than one might expect based on external appearances of the chest. Dr.Sara Elmegarhi Anatomy 3 The thorax includes the primary organs of the respiratory and cardiovascular systems. The thoracic cavity is divided into three major spaces: the central compartment or mediastinum that houses the thoracic viscera except for the lungs and, on each side, the right and left pulmonary cavities housing the lungs. The majority of the thoracic cavity is occupied by the lungs, Most of the remainder of the thoracic cavity is occupied by the heart and structures involved in conducting the air and blood to and from the lungs. Nutrients (food) traverse the thoracic cavity via the esophagus, passing from the site of entry in the head to the site of digestion and absorption in the abdomen. Dr.Sara Elmegarhi Anatomy 4  The Thoracic Wall  covered on outside by skin and muscles.  lined inside with parietal pleura. Boundries: 1)Posteriorly : thoracic part of vertebral column 2)Anteriorly :sternum and costal cartilages. 3)Laterally : ribs and intercostal spaces Superiorly suprapleural membrane 4)Inferiorly :diaphragm,(which separates The thoracic cavity from the abdominal cavity). Dr.Sara Elmegarhi Anatomy 53 Dr.Sara S.Elmegarhi /Anatomy &Embryology Dep. Facultyof Medicine/University of Tripoli  THORACIC WALL The True Thoracic Wall includes the thoracic cage and the muscles that extend between the ribs as well as the skin, subcutaneous structures, The mammary glands of the breasts lie within the subcutaneous tissue of the thoracic wall. The anterolateral axio-appendicular muscles, that overlie the thoracic cage and form the bed of the breast are encountered in the thoracic wall and may be considered part of it, but are distinctly upper limb muscles based on function and innervation. The Thoracic cage provides remarkable rigidity, given the light weight of its components, enabling it to: Protect vital thoracic and abdominal organs from external forces. Resist the negative (sub-atmospheric) internal pressures generated by the elastic recoil of the lungs and inspiratory movements. Provide attachment for and support the weight of the upper limbs. Provide the anchoring attachment (origin) of many of the muscles that move and maintain the position of the upper limbs relative to the trunk, as well as provide the attachments for muscles of the abdomen, neck, back, and respiration Dr.Sara Elmegarhi Anatomy 6 Dr.Sara Elmegarhi Anatomy 7  The osteocartilaginous thoracic cage protects the heart, lungs and great vessels. It is conical, with a narrow inlet superiorly and a wide outlet inferiorly, and is formed of:  Sternum anteriorly  12 pairs of ribs with costal cartilages laterally  12 thoracic vertebrae and intervertebral (IV) discs between them posteriorly THE STERNUM Flat, elongated bone that forms the middle of the anterior part of the thoracic cage. overlies and gives protection for viscera in general and the heart in particular. The sternum consists of three parts: Manubrium, Body, And Xiphoid Process. In adolescents and young adults, the three parts are connected together by cartilaginous joints, that ossify during middle to late adulthood. Dr.Sara Elmegarhi Anatomy 8 Dr.Sara Elmegarhi Anatomy 9  The manubrium Roughly trapezoidal bone, widest and thickest of the three parts of the sternum. The easily palpated concave notch of the superior border of the manubrium is the jugular notch (suprasternal notch). Lateral toThe notch a small clavicular facets in the manubrium that receive clavicals, forming the sternoclavicular (SC) joints, followed laterally by facet for the costal cartilage of the 1st rib. And demifacet for 2nd rib. The manubrium and body of the sternum articulate in two different planes forming, the manubriosternal joint forms a projecting sternal angle (of Louis) at level of IVD T4&T5. The body of the sternum is longer, narrower, and thinner than the manubrium, and is located at the level of the T5–T9 vertebrae. Its width varies because of the scalloping of its lateral borders by the costal notches. In young people, four sternebrae (primordial segments of the sternum) are obvious. The sternebrae articulate with each other at primary cartilaginous joints. These joints begin to fuse from the inferior end between puberty and age 25. The nearly flat anterior surface of the body of the sternum is marked in adults by three variable transverse ridges, which represent the lines of fusion (synostosis) of its four originally separate sternebrae. The body articulate with 2nd -7th ribs. The xiphoid process The smallest, variable and thin part of the sternum. Its inferior end lies at the level of T10 vertebra. It is cartilaginous in young people but ossified in adults older than age 40. Gives attachment to the diaphragm and anterior abdominal wall muscles. The xiphisternal joint indicates the inferior limit of the central part of the thoracic cavity and the superior limit of abdominal cavity. The site of the infrasternal angle (subcostal angle) formed by the right and left costal margins. Dr.Sara Elmegarhi Anatomy 10 Dr.Sara Elmegarhi Anatomy 11 Dr.Sara Elmegarhi Anatomy 12  The ribs and costal cartilages form the largest part of the thoracic cage; both are identified numerically, from the most superior (1st rib or costal cartilage) to the most inferior (12th). RIBS, COSTAL CARTILAGES, AND INTERCOSTAL SPACES Ribs : are curved, flat bones that form most of the thoracic cage. They are remarkably light in weight yet highly resilient. Each rib has a spongy interior containing bone marrow (hematopoietic tissue), which forms blood cells. There are three types of ribs according to the sternocartiligenous attachment: 1. True (vertebrosternal) ribs (1st–7th ribs): They attach directly to the sternum through their own costal cartilages. 2. False (vertebrochondral) ribs (8th, 9th, and usually 10th ribs): Their cartilages are connected to the cartilage of the rib above them; thus their connection with the sternum is indirect. 3. Floating (vertebral, free) ribs (11th, 12th, and sometimes 10th ribs): The rudimentary cartilages of these ribs do not connect even indirectly with the sternum; instead they end in the posterior abdominal musculature. Dr.Sara Elmegarhi Anatomy 13 Dr.Sara Elmegarhi Anatomy 14  According to bony features and landmarks: Typical & Atypical ribs Typical ribs (3rd–9th) have the following components: 1) Head: wedge-shaped and has two facets, separated by the crest of the head; one facet for articulation with the numerically corresponding vertebra and one facet for the vertebra superior to it. 2) Neck: connects the head of the rib with the body at the level of the tubercle. 3) Tubercle: located at the junction of the neck and body; a smooth articular part articulates with the corresponding transverse process of the vertebra, and a rough non articular part provides attachment for the costotransverse ligament. 4) Body (shaft): thin, flat, and curved, most markedly at the costal angle where the rib turns anterolaterally. The concave internal surface of the body has a costal groove paralleling the inferior border of the rib, which provides some protection for the intercostal nerve and vessels. Dr.Sara Elmegarhi Anatomy 15 Dr.Sara Elmegarhi Anatomy 16 Dr.Sara Elmegarhi Anatomy 17  Atypical ribs (1st, 2nd, and 10th–12th) are dissimilar: 1) The 1st rib is the widest and nearly horizontal, shortest, and most sharply curved of the seven true ribs. It has a single facet on its head for articulation with the T1 vertebra only and two transversely directed grooves crossing its superior surface for the subclavian vessels; the grooves are separated by a scalene tubercle and ridge, to which the anterior scalene muscle is attached. 2) The 2nd rib is a thinner, less curved body and is substantially longer than the 1st rib. Its head has two facets for articulation with the bodies of the T1 and T2 vertebrae; its main atypical feature is a rough area on its upper surface, the tuberosity for serratus anterior, from which part of that muscle originates. 3) The 10th–12th ribs, like the 1st rib, have only one facet on their heads and articulate with a single vertebra. 4) The 11th and 12th ribs are short and have no neck or tubercle. Dr.Sara Elmegarhi Anatomy 18 The joints and the thinness and flexibility of the ribs allow it to absorb many external compressions without fracture and to change its shape for respiration. Because the most important structures within the thorax (heart, great vessels, lungs, and trachea), as well as its floor and walls, are constantly in motion, the thorax is one of the most dynamic regions of the body. With each breath, the muscles of the thoracic wall—working in concert with the diaphragm and muscles of the abdominal wall—vary the volume of the thoracic cavity, first by expanding the capacity of the cavity, thereby causing the lungs to expand and draw air in and then, due to lung elasticity and muscle relaxation, decreasing the volume of the cavity and causing them to expel air. Dr.Sara Elmegarhi Anatomy 19  Costal cartilages Costal cartilages prolong the ribs anteriorly and contribute to the elasticity of the thoracic wall, providing a flexible attachment for their anterior ends (tips). The cartilages increase in length through the first 7 and then gradually decrease. The first 7 costal cartilages attach directly and independently to the sternum; the 8th, 9th, and 10th articulate with the costal cartilages just superior to them, forming a continuous, articulated, cartilaginous costal margin (plate). The 11th and 12th costal cartilages form caps on the anterior ends of the corresponding ribs and do not reach or attach to any other bone or cartilage. The costal cartilages of ribs 1–10 clearly anchor the anterior end of the rib to the sternum, limiting its overall movement as the posterior end rotates around the transverse axis of the rib. Intercostal spaces The spaces are named according to the rib forming the superior border of the space—for example, the 4th intercostal space lies between ribs 4 and 5. There are 11 intercostal spaces and 11 intercostal nerves. Intercostal spaces are occupied by intercostal muscles and membranes, and two sets (main and collateral) of intercostal blood vessels and nerves, identified by the same number assigned to the space. The space below the 12th rib does not lie between ribs and thus is referred to as the subcostal space, and the anterior ramus (branch) of spinal nerve T12 is the subcostal nerve. The intercostal spaces are widest anterolaterally, and they widen further with inspiration. They can also be further widened by extension and/or lateral flexion of the thoracic vertebral Dr.Sara Elmegarhi Anatomy 120 column to the contralateral side. 5  Thoracic vertebra consists of: 1-a rounded body anteriorly 2-a vertebral arch posteriorly. They enclose a space called The vertebral foramen through which run the spinal cord and its coverings The vertebral arch gives rise to seven processes: a-One spinous b-Twotransverse c- Four articular  The spinous process is directed posteriorly from the junction of the two laminae.  The transverse processes are directed laterally from the junction of the laminae and the pedicles The articular processes are vertically arranged and consist of:  Two superior & Two inferior processes They arise from the junction of the laminae and the pedicles. Dr.Sara Elmegarhi Anatomy 21  The pedicles are notched on their upper and lower borders Forming the superior and inferior vertebral notches. On each side the superior notch of one vertebra and the inferior notch of an adjacent vertebra together form an intervertebral foramen. These foramina, in an articulated skeleton, serve to transmit the spinal nerves and blood vessels. Dr.Sara Elmegarhi Anatomy 22 Most thoracic vertebrae are TYPICAL with Characteristic features of include: Bilateral costal facets (demifacets) on the vertebral bodies, usually occurring in inferior and superior pairs, for articulation with the heads of ribs (two demifacets paired in this manner and the posterolateral margin of the IV disc between them form a single socket to receive the head of the rib of the same identifying number as the inferior vertebra (example: head of rib 6 with the superior costal facet of vertebra T6). ). Costal facets on the transverse processes for articulation with the tubercles of ribs. except for the inferior two or three thoracic vertebrae. spinous processes long and slope inferiorly, usually overlapping the vertebra below. thereby preventing sharp objects from entering the vertebral canal.. Atypical thoracic vertebrae : The superior costal facets of vertebra T1 are not demifacets because there are no demifacets on C7 vertebra above, but T1 has a typical inferior costal (demi)facet for rib 2. T10 has only one bilateral pair of costal facets, partly on its body and partly on its pedicle. T11 and T12 also have only a single pair of costal facets, located on their pedicles. Dr.Sara Elmegarhi Anatomy 23 Dr.Sara Elmegarhi Anatomy 24 Dr.Sara Elmegarhi Anatomy 25 Dr.Sara Elmegarhi Anatomy 26 17 Dr.Sara Elmegarhi Anatomy 27  Thoracic Apertures The thoracic cage is a complete wall, but it is open superiorly and inferiorly. The smaller superior opening (aperture) that allows communication with the neck and upper limbs as inlet. The larger inferior opening provides the ring-like origin of the diaphragm, which completely occludes the opening. The superior (Aperture) opening (thoracic inlet) Anatomists refer to the superior thoracic aperture as the thoracic inlet because non- circulating substances (air and food) enter the thorax through this opening. Nearly 10 cm wide and 5 cm anteroposteriorly, slopes downward and forwards and is bounded by: 1st thoracic vertebra posteriorly, upper border of the manubrium anteriorly first rib and costal cartilage. It transmits the oesophagus, the trachea and the great vessels of the head and neck, and on each side lies the cervical dome of the pleura. The inferior (Aperture) opening (thoracic outlet), bounded by: 12th thoracic vertebra posteriorly 11th and 12th ribs laterally The costal cartilages of 7th _ 10th ribs, which ascend to the sternum anteriorly. The diaphragm separates the thorax from the abdomen. Dr.Sara Elmegarhi Anatomy 28  Joints of Thoracic cage COSTOVERTEBRAL JOINTS Joints of Heads of Ribs: The head of the rib articulates with the superior costal facet of the corresponding vertebra, the inferior costal facet of the vertebra superior to it, and the adjacent intervertebral (IV) disc. For example (The head of the 6th rib articulates with the superior costal facet of the body of the T6 vertebra, the inferior costal facet of T5, and the IV disc between these vertebrae). The crest of the head of the rib attaches to the IV disc by an intra-articular ligament. only slight gliding movements occur at the facets. The 1st rib and 10,11,12 ribs have a single synovial joint with their corresponding vertebral body. The 2nd to 9th ribs, the head articulates by means of a synovial joint with the corresponding vertebral body and that of the vertebra above it. Costotransverse Joints: The tubercle of a rib articulates by synovial joint with the transverse process of the corresponding vertebra. (This joint is absent on the 11th and 12th ribs.) Costotransverse ligament passing from the neck of the rib to the transverse process lateral costotransverse ligament passing from the tubercle of the rib to the tip of transverse process. Superior costotransverse ligament joins the neck of the rib to the transverse process superior to itThe strong costotransverse ligaments binding these joints limit their movements to slight gliding. The articular surfaces on the tubercles of the superior 6 ribs are convex and fit into concavities on the transverse processes. so rotation can occurs and results in elevation and depression movements of the sternal ends of the ribs and the sternum in the sagittal plane (pump-handle movement). Flat articular surfaces of tubercles and transverse processes of the 7th–10th ribs allow gliding, resulting in elevation and depression of the lateral-most portions of these ribs in the transverse plane (bucket-handle movement). STERNOCOSTAL JOINTS The 1st pair of costal cartilages articulates with the manubrium by means of a fibrocartilage. The 2nd–7th pairs of costal cartilages articulate with the sternum at synovial joints with fibrocartilaginous articular surfaces on both the chondral and sternal aspects, allowing movement during respiration Dr.Sara Elmegarhi Anatomy 29  Joints of the Chest Wall Cartilaginous joints – Manubriosternal joint – Xiphisternal joint – Joints of the Ribs and Costal Cartilages – 1st costal cartilages articulate with the manubrium Synovial joints – Joints of the Costal Cartilages with the Sternum (2nd to 7th) – Joints of the Heads of the Ribs Costovertebral joints – Joints of the Tubercles of the Ribs Costotransverse joints Dr.Sara Elmegarhi Anatomy 30  Surface Anatomy Of The Thorax Anterior Chest Wall : 1) The clavicles (collar bones) lie subcutaneously, forming bony ridges at the junction of the thorax and neck. The clavicles demarcate the superior division between zones of lymphatic drainage: above the clavicles, lymph flows ultimately to inferior jugular lymph nodes; below them, parietal lymph (that from the body wall and upper limbs) flows to the axillary lymph nodes. 2) The suprasternal notch is the superior margin of the manubrium sterni and is easily felt between the prominent medial ends of the clavicles in the midline.It lies opposite the lower border of the body of the 2nd thoracic vertebra. 3) The sternal angle (angle of Louis): is the angle made between the manubrium and the body of the sternum. It lies opposite the intervertebral disc between the 4th and 5th thoracic vertebrae. The position of the sternal angle can easily be felt and is often seen as a transverse ridge. The finger moved to the right or to the left will pass directly onto the 2nd costal cartilage and then the 2nd rib. All ribs may be counted from this point. Occasionally in a very muscular male, the ribs and intercostal spaces are often obscured by large pectoral muscles. In these cases, it may be easier to count up from the 12th rib. 4) The xiphisternal joint: is the joint between the xiphoid process of the sternum and the body of the sternum. It lies opposite the body of the ninth thoracic vertebra. 5) The subcostal angle: is situated at the inferior end of the sternum, between the sternal attachments of the 7th costal cartilages. The costal margin is the lower boundary of the thorax and is formed by the cartilages of the 7th, 8th, 9th, and 10th ribs and the ends of the 11th and 12th cartilages. The lowest part of the costal margin is formed by the 10th rib and lies at the level of the third lumbar vertebra. Dr.Sara Elmegarhi Anatomy 6) The clavicle: is subcutaneous throughout its entire length and can be easily palpated. 31 24 7) Diaphragm The central tendon of the diaphragm lies directly behind the xiphisternal joint. the right dome of the diaphragm arches upward as far as the upper border of the 5th rib in the midclavicular Line left dome only reaches as far as the lower border of the 5th rib. 8) Nipple In the male, in the fourth intercostal space about 4 in. (10 cm) from the midline. In the female, its position is not constant. 9)The apex beat is normally found in the fifth left intercostal space 3.5 in. (9 cm) from the midline. Should you have difficulty in finding the apex beat, have the patient lean forward in the sitting position. In a female with pendulous breasts, the examining fingers should gently raise the left breast from below as the intercostal spaces are palpated. 10) The anterior axillary fold is formed by the lower border of the pectoralis major muscle. 11) The posterior axillary fold is formed by the tendon of the latissimus dorsi muscle as it passes around the lower border of the teres major muscle. Dr.Sara Elmegarhi Anatomy 32 25 Dr.Sara Elmegarhi Anatomy 33 Dr.Sara Elmegarhi Anatomy 34 Dr.Sara Elmegarhi Anatomy 35  Posterior Chest Wall 1) The spinous processes of the thoracic vertebrae can be palpated in the midline posteriorly.The index finger should be placed on the skin in the midline on the posterior surface of the neck and drawn downward in the nuchal groove. The first spinous process to be felt is that of the seventh cervical vertebrae (vertebra prominens). Below this level are the overlapping spines of the thoracic vertebrae. The spines of C1 to 6 vertebrae are covered by a large ligament, the ligamentum nuchae. The tip of a spinous process of a thoracic vertebra lies posterior to the body of the next vertebra below. 2) The scapula (shoulder blade) is flat and triangular in shape and is located on the upper part of the posterior surface of the thorax. The superior angle lies opposite the spine of the second thoracic vertebra The spine of the scapula is subcutaneous The root of the spine lies on a level with the spine of the third thoracic vertebra. The inferior angle lies on a level with the spine of the seventh thoracic vertebra. Lines of Orientation Several imaginary lines are sometimes used to describe surface locations on the anterior and posterior chest walls. 1) Midsternal line: Lies in the median plane over the sternum 2) Midclavicular line: Runs vertically downward from the midpoint of the clavicle 3) Anterior axillary line: Runs vertically downward from the anterior axillary fold 4) Posterior axillary line: Runs vertically downward from the posterior axillary fold 5) Midaxillary line: Runs vertically downward from a point situated midway between the anterior and posterior axillary folds 6) Scapular line: Runs vertically downward on the posterior wall of the thorax passing through Dr.Sara the inferior angle of the scapula (armsElmegarhi at the sides)Anatomy 36 29 Anatomic and Physiologic Changes in the Thorax with Aging Certain anatomic and physiologic changes take place in the thorax with advancing years: The rib cage becomes more rigid and loses its elasticity as the result of calcification and even ossification of the costal cartilages; this also alters their usual radiographic appearance. The stooped posture (kyphosis), so often seen in the old because of degeneration of the intervertebral discs, decreases the chest capacity. Dr.Sara Elmegarhi Anatomy 37  Sternal Anomalies The sternum develops through the fusion of bilateral, vertical condensations of precartilaginous tissue, sternal bands or bars. 1) The halves of the sternum of the fetus may not fuse. Complete sternal cleft is an uncommon anomaly through which the heart may protrude (ectopia cordis). 2) Partial clefts involving the manubrium and superior half of the body are V- or U-shaped and can be repaired during infancy by direct apposition and fixation of the sternal halves. 3) sternal foramen Sometimes a perforation, remains in the sternal body because of incomplete fusion. It is not clinically significant; however, one should be aware of its possible presence so that it will not be misinterpreted in chest X-ray, as a being an unhealed bullet wound for example. 4) A receding (pectus excavatum, or funnel chest) or projecting (pectus cavinatum, or pigeon breast) sternum are anomalous variations that may become evident or more pronounced during childhood. 5) Sternal fractures have become commen (less common with seatbelts) can lead to Pericardial, cardiac or aortic damage may then follow 6) Collection of sternal bone marrow:The subcutaneous position of the sternum makes it possible to place a needle through the hard outer cortex into the internal bone marrow. And it can be aspirated. Evaluation of this material under the microscope helps clinicians diagnose certain blood diseases such as leukemia. 7) The xiphoid process is commonly perforated in elderly persons because of age- related changes; this perforation is also not clinically significant. Similarly, an anteriorly-protruding xiphoid process in neonates is not unusual; when it occurs, it does not usually require correction. 8) later life the xiphoid calcifies Dr.Sara Elmegarhi Anatomy 38  Clinical Notes 1) A flail chest may also result from multiple rib fractures, when a whole section of the chest, wall moves paradoxically during respiration 1) Supernumerary Ribs  The presence of extra cervical and/or lumbar ribs, or decreased by absence of the 12th.  Cervical ribs are relatively common (2%) and may interfere with neurovascular Structures in the superior thoracic aperture.  Lumbar ribs are less common.  Supernumerary (extra) ribs also have clinical significance in that they may confuse The identification of vertebral levels in radiographs and other diagnostic images. 3) Rib excision is commonly performed by thoracic surgeons wishing to gain entrance to the thoracic cavity. A longitudinal incision is made through the periosteum on the outer surface of the rib, and a segment of the rib is removed. A second longitudinal incision is then made through the bed of the rib, which is the inner covering of periosteum. After the operation, the rib regenerates from the osteogenetic layer of the periosteum. 4) Rib and Costal Cartilage Identification When one is examining the chest from in front, the sternal angle is an important landmark. Its position can easily be felt and often be seen by the presence of a transverse ridge. Dr.Sara Elmegarhi Anatomy 39  Muscles of Thoracic Wall Some muscles attached to and covering the thoracic cage are primarily involved in serving other regions. The axio-appendicular muscles act primarily on the upper limbs. But several of them, including the pectoralis major and pectoralis minor and the inferior part of the serratus anterior, may also function as accessory muscles of respiration, helping elevate the ribs to expand the thoracic cavity when inspiration is deep and forceful. The scalene muscles of the neck, serve as accessory respiratory muscles by fixing the 1st and 2nd ribs. The True Muscles Of The Thoracic Wall The Serratus Posterior, Levatores Costarum, Intercostal, Subcostal, And Transversus Thoracis. The serratus posterior muscles The Serratus posterior superior Originate from Lower portion of ligamentum nuchae, spinous processes of C7 to T3 and supraspinous ligaments, Inserted into Upper border of ribs 2 to 5. It elevate the superior four ribs, thus increasing the AP diameter of thorax. The Serratus posterior inferior Originate from spinous processes of T11 to L3 and supraspinous ligaments, Inserted into Lower border of ribs 9 to 12. it depress the inferior ribs. The levatores costarum muscles are 12 fan-shaped muscles, Originate from tip of the transverse process of C7 and T1 to T11. And Inserted into the rib below. it elevate the ribs. Dr.Sara Elmegarhi Anatomy 40 34  Intercostals muscles The external intercostal muscles (11 pairs) from the tubercles of the ribs posteriorly to the costochondral junctions anteriorly. Anteriorly, the muscle fibers are replaced by the external intercostal membranes. These muscles run infero- anteriorly from the rib above to the rib below. most active during inspiration. The internal intercostal muscles (11 pairs) run deep to and at right angles to the external intercostals. Their fibers run inferoposteriorly from the floors of the costal grooves to the superior borders of the ribs inferior to them. posteriorly, medial to the angles, the internal intercostals are replaced by the internal intercostal membranes. most active during expiration. The innermost intercostal muscles are similar to the internal intercostals. But it is deeper and separated from the internal intercostals by intercostal nerves and vessels. The subcostal muscles are variable in size and shape, run in the same direction as the internal intercostals and blend with them. The transversus thoracis muscles consist of four or five slips that radiate superolaterally from the posterior aspect of the inferior sternum. it has a weak expiratory function and may also provide proprioceptive information. The diaphragm is the primary muscle of inspiration. Expiration is passive unless one is exhaling against resistance (e.g., inflating a balloon) or trying to expel air more rapidly than usual (e.g., coughing, sneezing, blowing one’s nose, or shouting). Dr.Sara Elmegarhi Anatomy 41 35  Diaphragm Thin muscular and tendinous septum – Right dome: upper border of the 5th rib – Left dome: lower border of the 5th rib – Central tendon: level of xiphisternal joint Origin: – Sternal part: posterior surface of the xiphoid process – Costal part: lower six ribs and their costal cartilages – Vertebral part: vertical columns (crura )and arcuate ligaments Insertion: central tendon Dr. Sara S.Elmegarhi /Anatomy &Embryology Dep. Faculty of Dr.Sara Elmegarhi Medicine/University of Tripoli Anatomy 40 42  Right crus: bodies of the first three lumbar vertebrae and the intervertebral discs Left crus: bodies of the first two lumbar vertebrae and the intervertebral disc Medial arcuate ligament: from body of the second lumbar vertebra to the tip of the transverse process of the first lumbar vertebra Lateral arcuate ligament: from the tip of the transverse process of the first lumbar vertebra to the lower border of the 12th rib median arcuate ligament Dr. Sara S.Elmegarhi /Anatomy Dr.Sara Elmegarhi &Embryology Dep. Anatomy Faculty of 41 43 Medicine/University of Tripoli The diaphragm is inserted into a central tendon, which is shaped like three leaves. The superior surface of the tendon is partially fused with the inferior surface of the fibrous pericardium. Some of the muscle fibers of the right crus pass up to the left and surround the esophageal orifice in a slinglike loop. These fibers appear to act as a sphincter and possibly assist in the prevention of regurgitation of the stomach contents into the thoracic part of the esophagus Dr.Sara Elmegarhi Anatomy 44  Diaphragm Nerve Supply: – Motor: right and left phrenic nerves (C3, 4, 5) – Sensory: Central surfaces: phrenic nerve Peripheral: lower six intercostal nerves Action: On contraction, the diaphragm pulls down its central tendon and increases the vertical diameter of the thorax. Functions – Muscle of inspiration – Muscle of abdominal straining (micturition, defecation, and parturition) – Weight-lifting muscle – Thoracoabdominal pump Dr. Sara S.Elmegarhi /Anatomy Dr.Sara Elmegarhi &Embryology Anatomy Dep. Faculty of 45 45 Medicine/University of Tripoli  Openings in the Diaphragm Aortic opening: Level of T12 between the crura – Aorta – Thoracic duct – Azygos vein Esophageal opening :Level of T10 in a sling of muscle fibers derived from the right crus – Esophagus – Right and left vagus nerves – Esophageal branches of the left gastric vessels – Lymphatics from the lower third of the esophagus. Caval opening: Level of T8 in the central tendon – Inferior vena cava – Terminal branches of the right phrenic nerve Dr. Sara S.Elmegarhi /Anatomy Dr.Sara Elmegarhi &Embryology Anatomy Dep. Faculty of 46 46 Medicine/University of Tripoli In Addition To The THREE MAIN Openings: I. The sympathetic splanchnc nerves pierce the crura. II. The sympathetic trunks pass posterior to the medial arcuate ligament on each side. III. The superior epigastric vessels pass between the sternal and costal origins of the diaphragm on each side. Dr. Sara S.Elmegarhi /Anatomy Dr.Sara Elmegarhi &Embryology Anatomy Dep. Faculty of 47 Medicine/University of Tripoli  Functions of the Diaphragm Muscle of inspiration: On contraction, the diaphragm pulls its central tendon down and increases the vertical diameter of the thorax. The diaphragm is the most important muscle used in inspiration. Muscle of abdominal straining: The contraction of the diaphragm assists the contraction of the muscles of the anterior abdominal wall in raising the intra- abdominal pressure for micturition, defecation, and parturition. Weight-lifting muscle: In a person taking a deep breath and holding it (fixing the diaphragm), the diaphragm assists the muscles of the anterior abdominal wall in raising the intra-abdominal pressure to such an extent that it helps support the vertebral column and prevent flexion. This greatly assists the postvertebral muscles in the lifting of heavy weights. Needless to say, it is important to have adequate sphincteric control of the bladder and anal canal under these circumstances. Thoracoabdominal pump: The descent of the diaphragm decreases the intrathoracic pressure and at the same time increases the intra-abdominal pressure. This pressure change compresses Dr. Sara S.Elmegarhithe blood in the inferior vena cava /Anatomy and forces it upward into theDr.Sara righ&EtmabElmegarhi trryoiluogmyDeopf.FtahcuAnatomy eltyhofeart. 48 42 Medicine/University of Tripoli  Clinical Notes Paralysis of half of the diaphragm (one dome or hemidiaphragm) because of injury to its motor supply from the phrenic nerve does not affect the other half because each dome has a separate nerve supply. One can detect paralysis of the diaphragm radiographically by noting its paradoxical movement. Dr.Sara Elmegarhi Anatomy 49  Intercostal Arteries and Veins Each intercostal space contains a large single posterior intercostal artery and two small anterior intercostal arteries. The posterior intercostal arteries of the first two spaces are branches from The Superior IntercostalArtery, a branch of the costocervical trunk of the Subclavian Artery  The posterior intercostal arteries of the lower nine spaces are branches of The Descending ThoracicAorta The anterior intercostal arteries of the first six spaces are branches of The Internal ThoracicArtery which arises from the first part of the subclavian artery. The anterior intercostal arteries of the lower spaces are branches of The Musculophrenic Artery, one of the terminal branches of the Internal thoracic Dr.Sara artery. Elmegarhi Anatomy 50 Venous drainage  posterior intercostal veins  Azygos  hemiazygos veins  anterior intercostal veins  Internal thoracic vein Dr. Sara S.Elmegarhi /Anatomy Dr.Sara Elmegarhi &Embryology Anatomy Dep. Faculty of 51 44 Medicine/University of Tripoli  The Internal Thoracic Artery (branch of the first part of the subclavian artery in the neck). it supplies the anterior wall of the body from the clavicle to the umbilicus. It descends vertically on the pleura behind the costal cartilages, a fingerbreadth lateral to the sternum, and ends in the sixth intercostal space by dividing into a) Superior Epigastric b) Musculophrenic Arteries. Branches of Internal thoracic artery: 1) Two anterior intercostal arteries for the upper six intercostal spaces 2) Perforating arteries, which accompany the terminal branches of the corresponding intercostal nerves 3) The pericardiacophrenic artery, which accompanies the phrenic nerve and supplies the pericardium 4) Mediastinal arteries to the contents of the anterior mediastinum (e.g., the thymus) 5) The superior epigastric artery. 6) The musculophrenic artery, which runs around the costal margin of the diaphragm and supplies the lower intercostal spaces and the diaphragm Dr.Sara Elmegarhi Anatomy 52  INTERCOSTAL VEINS Anterior Intercostal Veins: Drain into: 1) Internal thoracic vein or its venae comitantes 2) Venae comitantes of musculophrenic artery Right Posterior Intercostal Veins: 1st vein: to right brachiocephalic vein 2nd and 3rd veins: Form right superior intercostal vein, which ends into arch of azygos veins 4th- 11th veins: To azygos vein *Right Subcostal vein: Joins right ascending lumbar vein to form azygos vein Left Posterior Intercostal Veins: 1st vein: Left brachiocephalic vein 2nd and 3rd veins: Form left superior intercostal vein, ends into left brachiocephalic vein. 4th- 8th veins: Join superior hemiazygos Veins 9th- 11th: Join inferior hemiazygos *Left Subcostal vein: Joins left ascending lumbar vein to form inferior hemiazygos vein Dr.Sara Elmegarhi Anatomy 53 Dr.Sara Elmegarhi Anatomy 54 Endothoracic Fascia The endothoracic fascia is a thin layer of loose connective tissue that separates the parietal pleura from the thoracic wall. The suprapleural membrane is a thickening of this fascia  Suprapleural Membrane:  Tent-shaped fibrous sheet is attached laterally to the medial border of the 1st rib and costal cartilage. Attached at its apex to the tip of the transverse process of the C7 and medially to the fascia investing the structures passing from the thorax into the neck.  Protects the underlying cervical pleura and resists the changes in intrathoracic pressure occurring during respiratory movements. Dr. Sara S.Elmegarhi /Anatomy Dr.Sara Elmegarhi &Embryology Anatomy Dep. Faculty of 55 48 Medicine/University of Tripoli  Nerves of Thoracic Wall The 12 pairs of thoracic spinal nerves supply the thoracic wall. The anterior rami of nerves T1–T11 form the intercostal nerves that run along the intercostal spaces. The anterior ramus of nerve T12, coursing inferior to the 12th rib, is the subcostal nerve. The posterior rami of thoracic spinal nerves pass Dr.Sara Elmegarhi Anatomy 56 TYPICAL INTERCOSTAL NERVES The 3rd–6th intercostal nerves enter the posterior intercostal spaces, between the parietal pleura and the internal intercostal membrane.Near the angles of the ribs, the nerves pass between the internal intercostal and the innermost intercostal muscles. just inferior to the costal grooves, running inferior to the intercostal arteries (the neurovascular intercostals bundle runs as VAN order (vein, artery, nerve) from up to down under the costal groove). Dermatome: most thoracic spinal nerves (T2–T12) supply a strip-like dermatome of the trunk extending from the posterior median line to the anterior median line. Sympathetic nerve fibers are distributed through branches of all spinal nerves(anterior and posterior rami) to reach blood vessels, sweat glands, and smooth muscle of body wall and limbs. Rami communicantes, or communicating branches, that connect each intercostal nerve to the ipsilateral sympathetic trunk. Collateral branches that arise near the angles of the ribs and descend to course along the superior margin of the lower rib, helping supply intercostal muscles and parietal pleura. Lateral cutaneous branches that arise near the MAL, pierce the internal and external intercostal muscles, and divide in turn into anterior and posterior branches. supply the skin of the lateral thoracic and abdominal walls. Anterior cutaneous branches pierce the the intercostal space in the parasternal line and divide into medial and lateral branches. supply the skin on the anterior aspect of the thorax and abdomen. Muscular branches that supply the intercostal, subcostal, transversus thoracis, levatores cos4ta9 rum, and serratus posterior muscles. Dr.Sara Elmegarhi Anatomy 57  ATYPICAL INTERCOSTAL NERVES Although the anterior ramus of most thoracic spinal nerves is simply the intercostal nerve for that level, the anterior ramus of the 1st thoracic (T1) spinal nerve first divides into a large superior and a small inferior part. The superior part joins the brachial plexus, the nerve plexus supplying the upper limb, and the inferior part becomes the 1st intercostal nerve. Other atypical features of specific intercostal nerves include the following: The 1st and 2nd intercostal nerves course on the internal surface of the1st and 2nd ribs, instead of along the inferior margin in costal grooves. The 1st intercostal nerve has no anterior cutaneous branch and often no lateral cutaneous branch. When there is a lateral cutaneous branch, it supplies the skin of axilla and may communicate with the intercostobrachial nerve or the medial cutaneous nerve of the arm. The 2nd intercostal nerve gives rise to a large lateral cutaneous branch, the intercostobrachial nerve; it emerges from the 2nd intercostal space at the MAL, and enters the axilla and arm. The intercostobrachial nerve usually supplies the floor of the axilla and then communicates with the medial cutaneous nerve of the arm. The 7th–11th intercostal nerves, after giving rise to lateral cutaneous branches, cross the costal margin posteriorly and continue on to supply abdominal skin and muscles. No longer being between ribs (intercostal), they now become thoraco- abdominal nerves of the anterior abdominal wall. Their anterior cutaneous branches pierce the rectus sheath. Dr.Sara Elmegarhi Anatomy 58 ‫وصلى هللا وسلم وبارك على سيدنا محمد‬ ‫وعلى اله وصحبه أجمعين‬ ‫‪Dr.Sara Elmegarhi Anatomy‬‬ ‫‪& Embryology Department‬‬ ‫‪59‬‬